14-ECOSYSTEM

CHAPTER NO.14 ECOSYSTEM

A154

INTRODUCTION

The ecosystem is the structural and functional unit of ecology where the

living organisms interact with each other and the surrounding environment. In other words, an ecosystem is a chain of interaction

between organisms and their environment. The term “Ecosystem” was first coined by A.G.Tansley, an English botanist, in 1935.

Types of Ecosystem

There are two types of ecosystem

1.) Terrestrial Ecosystems: They are exclusively land based

ecosystems. They are as follows:

Forest Ecosystems

Grassland Ecosystems

Tundra Ecosystems

Desert Ecosystem

2.) Aquatic Ecosystem

Aquatic ecosystems are ecosystems present in a body of water. These can be further divided into two types, namely:

Freshwater Ecosystem

Marine Ecosystem

Structure of the Ecosystem

The structure of an ecosystem is characterised by the organisation of both

biotic and abiotic components. This includes the distribution of energy in our environment. It also includes the climatic conditions prevailing in that particular environment.The structure of an ecosystem can be split into two main components,namely:

Biotic Components

Abiotic Components

The biotic and abiotic components are interrelated in an ecosystem. It is

an open system where the energy and components can flow throughout the boundaries.

Biotic Components

Biotic components refer to all life in an ecosystem. Based on nutrition,biotic components can be categorised into autotrophs, heterotrophs and saprotrophs (or decomposers).

Producers include all autotrophs such as plants. They are called autotrophs as they can produce food through the process of

photosynthesis. Consequently, all other organisms higher up on the food chain rely on producers for food.

Consumers or heterotrophs are organisms that depend on other organisms for food. Consumers are further classified into primary

consumers, secondary consumers and tertiary consumers.

Primary consumers are always herbivores that they rely on producers for food.

Secondary consumers depend on primary consumers for energy. They can either be a carnivore or an omnivore.

Tertiary consumers are organisms that depend on secondary consumers for food. Tertiary consumers can also be an omnivore.

Quaternary consumers are present in some food chains.These organisms prey on tertiary consumers for energy.Furthermore, they are usually at the top of a food chain as they

have no natural predators.

Decomposers include saprophytes such as fungi and bacteria. They directly thrive on the dead and decaying organic matter. Decomposers are essential for the ecosystem as they help in recycling nutrients to be reused by plants.

Abiotic Components

Abiotic components are the non-living component of an ecosystem. It includes air, water, soil, minerals, sunlight, temperature, nutrients, wind,altitude, turbidity, etc.

Functions of Ecosystem

The functions of the ecosystem are as follows:

1. It regulates the essential ecological processes, supports life systems and renders stability.

2. It is also responsible for the cycling of nutrients between biotic and abiotic components.

3. It maintains a balance among the various trophic levels in the ecosystem.

4. It cycles the minerals through the biosphere.

5. The abiotic components help in the synthesis of organic components that involves the exchange of energy.

Size of Ecosystem

As you know an ecosystem may be as small and as simple as a cow dung pad or as complex and large as an ocean or the biosphere itself,

comprising a wide variety of species. An interesting point to observe is that

ecosystems occur within ecosystem. To take an example, cow dung ecosystem may be contained in a forest ecosystem which is contained in

the biosphere.In some cases, like a pond ecosystem, the boundaries are well defined. In These ecosystems often are separated, from adjacent ecosystems by a transition zone or a diffused boundary zone called ecotone. Organisms of adjacent ecosystems intermingle in the ecotone zone; consequently they

may have greater diversity of species than the neighbouring ecosystems

the case of forests, grasslands and deserts there are no sharp boundaries.

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PART A

MULTIPLE CHOICE QUESTIONS:

1.Ecosystem may be defined as

a) A species along with environment

b) Plants found in water

c) Plant found on land

d) All plants and animal species along with environment

2.The most important organism for an ecosystem are

a) Herbivorous

b) Carnivorous

c) Green plants

d) Protozoa

3.Primary consumer are

a) Green plants\

b) Herbivorous

c) Carnivorous

d) All the above

4.Biome is

a) The fauna of an ocean

b) The flora of land

c) Communities of organisms interacting with one another

d) Part of earth and its atmosphere which is inhibited by living organism

5.Energy flow in an ecosystem is

a) Unidirectional

b) Bidirectional

c) Multidirectional

d) All the above

(B) TRUE AND FALSE

a) Ecosystem is composed of biotic components.

b) The global quantity of carbon is 71% found dissolved in oceans.

c) The term microcosm is also used for ecosystem\

(C) FILLIN THE BLANKS

a) Plants are called as because they fix carbon dioxide.

b) In aquatic ecosystem, the limiting factors for the productivity is.

ANSWER KEY

PART A

MCQ:

1. d) All plants and animal species along with environment: The ecosystem

is the structural and functional unit of ecology where the living organisms

interact with each other and the surrounding environment.

2. c) Green plants: They are the producers

3. b) Herbivorous

4. c) Communities of organisms interacting with one another

5. a) Unidirectional: Energy flows from sunlight to earth

(C) TRUE AND FALSE

(a) False : Ecosystem is composed of biotic and abiotic components

(b) True

(C) FILL IN THE BLANKS

(a)producers or autotrophs (b) light

PART B: SHORT ASNWER TYPE QUESTION

1. Define an ecosystem.

2. What are two basic categories of ecosystem? Give two examples of

each.

3.Give an account of energy flow in an ecosystem.

PART C: LONG ANSWER TYPE QUESTION

1.Explain biotic and abiotic components of ecosystem with examples.

A155

INTRODUCTION

Stratification in the field of ecology refers to the vertical layering of a habitat. Its the arrangement of vegetation in layers. It classifies layers of vegetation largely according to different heights to which plants grow.

Community structure can become stratified both vertically and horizontally during the process of succession as species become

adapted to their habitat.

Vertical stratification refers to vertical distribution of organisms in a community. Vertical stratification occurs in forest community, grassland community and aquatic. Eg; Forest community

Horizontal stratification refers to the distribution of individuals on a horizontal plane in a community.

Significance. Stratification increases the number of habitats which reduces the interspecific competition.Stratification in a forest community A forest community is a typical example of terrestrial stratification

because here a number of strata both above and below the soil can be recognised.

A forest bears an over story stratum. This stratum is composed of trees which are forty or more feet in height. These trees often form a canopy.Relative proximity of the trees determines whether the canopy will be open

or thick-set.

Below this lies the understory stratum extending from twenty feet in height to a little below the over- story. The trees of this stratum are usually shade-tolerant and never grow to the height of the over story.

Below this stratum lies the transgressive stratum extending from four feet in height to a short distance below the understory stratum. The trees of this stratum are also shade-tolerant and have the potentiality to grow to increase the density or to replace those species making up the over story

or understory strata.

A seedling stratum ranges between the soil level and the lower limit of the transgressive stratum. These seedlings are hardwood species.

Finally, there is a herbaceous stratum containing non-woody plants Animals residing in the wood are also stratified but the stratification is not so rigid because of the mobility of the animals. Animals move from

one stratum to another stratum in search of food or in response to other abiotic

factors. Insects, birds, squirrels and many other animals travel between seedling to upper strata.

Stratification in a pond ecosystem

A pond ecosystem is a freshwater ecosystem that can either be temporary or permanent and consists of a wide variety of aquatic plants and animals interacting with each other and with the surrounding aquatic conditions.

The pond ecosystem falls under the category of a lentic ecosystem because the water remains stagnant for a longer period.

Different factors such as distance from the shore, penetration of light,depthof water, plant and animal species etc determine the following zones found in pond ecosystem

Littoral zone: It is the zone closer to the shore. It contains shallow water and allows easy penetration of light. It is occupied by rooted plant species. Animal species include reeds, crawfish, snails,insects, etc.

Limnetic zone: The limnetic zone refers to the open water of the pond with an effective penetration of light. This zone is dominated

by phytoplankton. Animal species mainly include small fishes and insects.

Profundal zone: The region of a pond below the limnetic zone is called a profound zone with no effective light penetration. It is

occupied by some amphibians, small turtles.

Benthic zone: The bottom zone of a pond is termed benthic and is occupied by a community of organisms called decomposers. The decomposers are called benthos.

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Multiple choice questions

1.Choose the correct combination of labeling of the zones in water in a lake.

(a) a-Littoral zone, b-Profundal zone, c-Benthic zone, d-Limnetic zone

(b) a-Limnetic zone, b-Littoral zone, c-Benthic zone, d-Profundal zone

(d) a-Littoral zone, b-Benthic zone, c-Profundal zone, d-Limnetic zone

(e) a-Limnetic zone, b-Profundal zone, c-Littoral zone, d-Benthic zone

2. Which of the following is not starata of grassland Community

(a) Subterranean stratum

(b) Floor stratum

(d) overstory stratum

3. Presence of plants arrange into well define vertical layers depending on their height can be seen in

(a) Tempelate forest

(b) Tropical savannah

(d) Grassland

4.The zone at the edge of the lake which alternatively exposed to air and immersed in water is called

(a) pelagic zone

(b) benthic zone

(d) lentic zone

5. Understory stratum represented by tree height

(a) 20-40 feet

(b) 4-20 feet

(d) 2-3 meter

True/ False

1.Understory stratum is represented by 4-20 feet.

2.Littroal zone includes rooted plants.

Fill In The Blanks

1. Biotic communities are generally arranged or stratified.

2. Overstory stratum represented by trees more than ____ feet in height.

3.Stratification the number of habitats which the interspecific competition.

VERY SHORT QUESTION ANSWERS

1.Define Stratification.

2.Give the significance of Stratification.

3.Name the ecosystem with maximum stratification.

Long Questions

1.Explain community stratification.

2. Explain pond or lake community

MCQs

1. (C)

2. (d) (In the grassland community no trees are present)

3. (C) (In the Forest community five vertical strata are represent example:- tropical rainforest)

4. (c) (Littoral Zone represented by shallow water having rotten plants. It includes rooted plants.)

5. (a) (Understory stratum represented by trees 20 - 40 feet in height.)

True/False

1.False (Understory stratum represented by trees 20 - 40 feet in height.)

2.True.(Littoral zone represented by shallow water having rotten plants.It includes rooted plants. )

Fill In The Blanks

1.Vertically

2.40 feet

3.Increase, Reduces

Very Short Questions

1.The term stratification refers to the arrangement of different animalsand plants in different vertical layers of the ecosystem

2. Stratification increases the number of habitats which reduces the interspecific competition.

3.Tropical Rainforest

A156

INTRODUCTION

Pond represents a self-regulatory and self-sustainable freshwater ecosystem.The salient features of a pond are abundant vegetation, large number of microorganism and plants but relatively small animals.There are two types of components in the pond ecosystem.

1. Abiotic components

2. Biotic components

1. Abiotic components: Abiotic components of pond ecosystem includes inorganic substances such as water, carbon dioxide, oxygen, nitrogen,calcium, phosphorus etc and organic substances such as amino acids,humus etc. Only small amount of nutrients are found in the water, the rest of the nutrients are present in the residue at the bottom. The quantity of light penetrating the water and the temperature regulate the rate of

functioning of pond ecosystem.

2. Biotic components: Biotic components of a pond ecosystem comprise the producers and variety of consumers.

PRODUCERS:-

phytoplanktons such as Chlamydomonas, Oscillatoria, Anabaena,Volvox etc.

Filamentous algae such as Spirogyra, Chara, Oedogonium etc.

Submerged plants such as Potamogeton and Vallisneria etc.

Some surface floating plants such as Eichhornia, Wolffia, Pistia.

Some emergent plants such as lpomea, Typha and Phragmites.

CONSUMERS:-

Zooplanktons such as Paramecium, Daphnia, Cyclops and Mysids.

Bottom dwelling such as Molluscans and annelids.

Insect larvae. (Primary consumers)

Small fishes and water beetles. (Secondary consumers)

Large fishes and crayfishes. (Tertiary consumers)

DECOMPOSERS:--

Decomposers or micro consumers such as bacteria, fungi and flagellates which decompose the organic excreta of animals and

dead bodies of plants and animals. The decomposers are also called saprotrophs or reducers.

Thus, there is a cyclic exchange of materials between the living community and non-living components of the ecosystem.

LET US KNOW WHAT WE HAVE LEARNT!

PART: AVERY SHORT ANSWER TYPE QUESTIONS:

1. MCQs:

1. Phytoplankton consists of

(a) Spirogyra and Chara

(b) Chlamydomonas and Oscillatoria

(d) Potamogeton and Vallisneria

2. Biotic components of a pond ecosystem comprises

(a) All the living organisms

(b) Plants and animals

(d) None of above

3. Zooplanktons present in the pond ecosystem consists of

(a) Insect larvae

(b) Paramecium, Daphnia and Cyclops

(d) none of above

4. Phytoplankton and zooplanktons are related to:

(a) Plants and animals

(b) animal and plants

(d) none of the above

5. Ultimate source of energy of pond ecosystem comes from:

(a) Water

(b) Sun

(d) Animals

2. TRUE/FALSE:

1. Fishes and water beetles are the secondary consumers in pond ecosystem.

2. There is cyclic exchange of materials between the abiotic and biotic components in the pond ecosystem.

3. Pond ecosystem is the self-regulatory and self-sustainable freshwater

ecosystem.

3. FILL IN THE BLANKS:

1. Some surface floating plants of pond ecosystem are .

2. Large fishes and crayfishes are the consumers of pond ecosystem.

ANSWER KEY: PART —-A

1. MCQs:

1. — (b) Chlamydomonas and Oscillatoria

2. — (a) All the living organisms

3. — (b) Paramecium, Daphnia and Cyclops

4. — (a) Plants and animals

5. — (b) Sun

2. TRUE/FALSE:

1. — True

2. — True

3. — True

3. FILL IN THE BLANKS:

1. —Eichhornia and Wolffia

2. — Tertiary consumers

3. — Bacteria and fungi.

PART: B SHORT ANSWER TYPE QUESTIONS:

1. Write any two examples of micro consumers.

2. Explain the process of cyclic exchange of materials.

3. Define fresh water pond ecosystem.

PART: C LONG ANSWER TYPE QUESTIONS:

1. Explain the different functional steps of pond ecosystem.

A157

INTRODUCTION

ECOSYSTEM IS A FUNCTIONAL UNIT OF NATURE, WHERE LIVING ORGANISMS INTERACT AMONG THEMSELVES AND ALSO WITH ENVIRNMENT.

ECOSYSTEM TERM WAS GIVEN BY TRANSLY.

PRODUCTIVITY THE RATE OF BIOMASS PRODUCTION IN AN ECOSYSTEM IS CALLED PRODUCTIVITY (DRY WEIGHT).IT IS EXPRESSED IN TERM OF weight g/m? /yr or energy Kceal/m? /yr

Primary productivity is defined as biomass or organic matter produced per unit area over a time period by plants during photosynthesis.

It’s expressed in terms of weight g/m? or energy Kcal/m? It is of two types:-

Gross primary productivity (G.P.P.}- It is total production of organic matter produced during photosynthesis (including the organic matter used up in respiration).

Net primary productivity (N.P.P} :- It is the amount of stored organic matter in plant tissues after respiratory utilisation.

NPP is the available biomass for the consumption to heterotrophs

SECONDARY PRODUCTIVITY:-

It is defined as the rate of formation of new organic matter by consumers.

NOTE: Net community productivity or Net productivity The rate of storage of organic matter not used by the heterotrophs

NCP =N.P.P.-—HR (HR= Heterotroph use or heterotrophic respiration)(Individual note counted, community counted)

FACTORS AFFECTING ECOSYSTEM:

1. CHEMICAL COMPOSITON OF DETRITUS :

In a particular climate condition, decomposition rate is slower if detritus is

rich in lignin and chitin.It is quicker, if detritus is rich in nitrogen and water soluble substances like sugars.

2. CLIMATIC FACTORS :

a) TEMPERATURE: Temperature is measured by the thermometer and under water by thermistor.

BERGMANN RULE: Birds and mammals attain greater body size in cold region and lesser in warm region.

ALLENS RULE: Mammals from colder climates generally have shorter ears and limbs to minimise heat loss.

EURYTHERMAL ORGANISMS :

The can function at a wide range of ambient temperature.e.g. Goat, man, cat, tiger, dog, cow etc.

STENO THERMAL ORGANISMS:The can function in a thin range of temperature. e.g.Penguin, python, crocodile, etc.

(b)LIGHT: Light is measured by luxmeter or photometer. It is electromagnetic spectrum.

SOLAR CONSTANT: Solar radiation before entering the atmosphere carries energy at a constant rate i.e., 2 cal cm min’ known as the solar constant.Visible spectrum of light is 400-700 nm. It is called

photosynthetically active radiation (PAR).

THE U.V. radiation distinguished in

U.V. —C --- (0.100 to 0.280 um)

U.V. —B --- (0.280 to 0.320 ~um)

U.V. —A --- (0.320 to 0.400 ~m)

ALBIDO VALUE: ability of a surface to reflect the incoming radiation is called albido value (AV).

It is 80% for fresh snow.

20%-30% for sand.

5-10% for the forest

Sun is the only source of energy for all eco system on earth.Of the incident solar radiation (ISR) less than 50% of it is

PAR.

Plants capture only 2-10% of the PAR and this small amount of energy sustains the entire living world.

a) SOIL: The uppermost layer of earth formed by weathering of rocks. It is mixture of living and non-living materials.

SOIL MINERAL MATTER:

As a result of weathering the mineral particles of different size are formed. The soil is divided into following types on the basis of SIZE OF SOIL PARTICLES.

b) OTHER COMPONENTS:

1. WATER: Water is the most important factor influencing the life of organisms. For aquatic organisms the quality (chemical composition,pH) of water becomes important.

The salt concentration (measured as salinity in parts per thousand), is less than 5 PPT in inland waters, 30-35 PPT the sea and more than 100 PPT in some hypersaline lagoons.Some organisms are tolerant of a wide range of salinities (euryhaline)but others are restricted to a narrow range (stenohaline) many fresh water animals cannot live for long in sea water and vice versa because

of the osmotic problems, they would face.

2. TOPOGRAPHY: It includes the physical features of the earth like altitude,

slope, exposure, mountain chains, and valleys plants. It affects distribution of organism by influencing the climatic factor like light,wind, rainfall etc.

LET US KNOW WHAT WE HAVE LEARNT!

PART: AVERY SHORT ANSWER TYPE QUESTIONS:

A. MCQs:

1. On, Earth in per unit area maximum productivity occur in:

1. Tropical rain forest

2. Ocean

3. Temperate deciduous forest

4. Marsh

2. A majority of organisms which are restricted to a narrow range of temperature are called as:

1. Stenothermal

2. Endothermal

3. Homeothermal

4. Eurythermal

B. FILL IN THE BLANKS:

1. The rate of formation of new organic matter by rabbit ina grassland is called productivity.

2. GPP = +R (R= respiration)

ANSWER KEY: PART —-A

A. MCQs:

1. 1 (Tropical rain forest)

2. 1 (Stenothermal)

B. FILL IN THE BLANKS:

1. Secondary

2. NPP (Net Primary Productivity)

PART: B SHORT ANSWER TYPE QUESTIONS:

1. What do you mean by NPP? (Net Primary Productivity)

2. What is PAR?

3. Differentiate between Eurythermal and Stenothermal animals.

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INTRODUCTION

DECOMPOSITION

It is physical and chemical breakdown of complex organic remains with the help of organisms called decomposers.Complex organic matter is breakdown into inorganic substances like carbon dioxide, water and nutrients.

Dead plant remains such as leaves, bark, flowers and dead remains of animals

including faecal matter constitute detritus. It is the raw material for decomposition.

Microbes then process this detritus which are collectively known as saprophytes.

MECHANISM OF DECOMPOSITION

The important steps in the process of decomposition are -

FRAGMENTATION - Detrivores (e.g., Earthworm, Termites, Carrion beetles) break down detritus into smaller particles. This process is called fragmentation.

LEACHING - By the process of leaching, water soluble inorganic nutrients go down into soil horizon, get precipitated as unavailable salts.

CATABOLISM - Decomposers (e.g., bacteria, fungi) secrete digestive enzymes over the detritus. It changes complex organic substance into simple inorganic substances. This process is called catabolism.

HUMIFICATION - All the above steps in decomposition occur simultaneously on the detritus. Decomposition process give rise to two products- humus and inorganic nutrients (minerals). The processes involved in their formation are called humification and mineralisation respectively. Humification leads to accumulation of a dark colour

amorphous substance called humus. It is resistant to microbial action and

undergoes decomposition at an extremely slow rate. It is colloidal in nature.So, it serves as a reservoir of nutrients which are released slowly.

MINERALISATION - It is release of inorganic substance from organic matter. Mineralisation occurs from humus which is further degraded by some microbes.

FACTORS AFFECTING DECOMPOSITION

Decomposition is largely an oxygen requiring process. The rate of decomposition is controlled by several factors like —

1) CHEMICAL COMPOSITION OF DETRITUS — In a particular climatic condition, decomposition rate is slower if detritus is rich in

lignin and chitin. It is quicker, if detritus is rich in nitrogen and water-soluble substances like sugar.

2) CLIMATIC FACTORS -

TEMPERATURE - A soil temperature of 20 degree Celsius and more hastens decomposition. A low temperature of less than 10 degree Celsius reduces rate of decomposition.

MOISTURE - Itis essential for decomposition. Decomposition rate is very low in tropical deserts although there is high temperature.

Excessive moisture also lowers decomposition due to anaerobiosis.

pH — Neutral and slightly alkaline soils are rich in detrivores (earthworm) and decomposer microbes. Acidity decreases the number of detrivores.

Aerobiosis — Decomposition is oxygen requiring process. So aerobic conditions are essential for activity of decomposer

organisms because decomposition is oxygen requiring process.

Low temperature and anaerobiosis inhibit decomposition resulting in build-up of organic material.

SIGNIFICANCES OF DECOMPOSITION -

During the process of decomposition, the decomposers provide food for themselves by extracting chemicals from the dead bodies

or organic wastes; using these to produce energy. Decomposers will then produce waste of their own. In turn, this will also

decompose, eventually returning nutrients to the soil.

These nutrients can then be taken up by the roots of living plants enabling them to grow and develop, so that organic material is

naturally recycled. Virtually nothing goes to waste in nature. When an animal dies and decomposes, usually only the bones remain,

but even these will decompose over a much longer period of time.It is not just on a forest floor that decomposition is important. Death and decomposition are an essential part of all life cycles on earth.To enable successful birth and growth of young plants and animals,older specimens must die and decompose. This limits the composition for resources and provides a fresh source of essential nutrients for new generations of life.

LET US KNOW WHAT WE LEARN?

PART A VERY SHORT ANSWER TYPE QUESTIONS: -

a) MULTIPLE CHOICE QUESTIONS:

Q-1 The organisms responsible for the breakdown of complex organic matter into inorganic substances:

(a) Decomposers

(b) Producers

(d) Herbivores

Q-2 The complex organic remains of dead plants and faecal matter:

(a) Humus

(b) Mucus

(d) Detritus

Q-3. Which of the following is an example of detrivorous animal?

(a) Monkey

(b) Termites

(d) Flatworm

Q-4 ‘The process of formation of a dark coloured amorphous substance is called:

(a) Leaching

(b) Catabolism

(d) Humification

Q-5 Which of the following substances are formed along with humus due to the process of decomposition?

(a) Organic substances

(b) Minerals

(d) Fragments

b) TRUE / FALSE:

Q-1 Earthworms breakdown detritus into small particles. This process is known as Fragmentation.

Q-2 Decomposition rate is higher, if detritus is rich in lignin and chitin.

Q-3 Low temperature and anaerobiosis inhibit decomposition.

c) FILL IN THE BLANKS:

Q-1 Decomposers (e.g., Bacteria and Fungi) secrete over the detritus. It changes complex organic substances into simple inorganic

substances.

Q-2 Very low temperature reduces the rate of ;

ANSWER KEY (PART - A)

MULTIPLE CHOICE QUESTIONS:

ANS-1 (a) Decomposers.

ANS-2 (d) Detritus.

ANS-3 (b) Termites.

ANS-4 (d) Humification.

ANS-5 (c) Inorganic substance.

TRUE / FALSE:

ANS-1 TRUE

ANS -2 FALSE (Decomposition rate is slower)

ANS-3 TRUE

FILL IN THE BLANKS:

ANS-1 Digestive enzyme.

ANS -2 Decomposition.

PART-B SHORT ANSWER TYPE QUESTIONS: -

Q-1 Write the main steps of decomposition.

Q-2 Whatis catabolism?

Q-3 How climatic factors effect on decomposition?

PART —C LONG ANSWER TYPE QUESTIONS: -

Q-1 Define decomposition. Describe the process of decomposition and write

products of decomposition.

A159

INTRODUCTION

HOMEOSTASIS IN ECOSYSTEM

Homeostasis, also called Ecological Balance, is a peculiar property by which a functional balance or state of equilibrium is maintained between different components of ecosystem.

Odum(1971) described that an ecosystem is formed by two major components:

A. Biotic (living) components

B. Abiotic (non-living) components

Ecosystem is not static but it is dynamic and is achieved through following controls:

1. Carrying capacity of environment.

2. Material cycling in ecosystem.

3.Self-regulation through interactions between biotic potential and environmental resistance.

4.Feedback interactions between the prey and

predator populations.

TROPHIC LEVELS:Organisms occupy a place in a community according to their feeding relationship with other organisms. Th

organisms deriving their energy from the same source}or obtaining their nourishment from the sun by the same number of steps are said to belong to the same trophic levels.

FIRST TROPHIC LEVEL (T1-level) - The producers which derive their energy from sun belong to first trophic level.

SECOND TROPHIC LEVEL (T2-level) - All the

herbivorous animals or primary consumers derive energy from the producers belong to secondary trophic level.

THIRD TROPHIC LEVEL (T3-level) - All the primary carnivores or secondary consumers belongs to third trophic level.

FOURTH TROPHIC LEVEL (T4-level) – The secondary carnivores or tertiary consumers belongs to fourth trophic level.

FIFTH TROPHIC LEVEL (T5- level) - Quaternary

consumers generally belong to T5 trophic level.

SIXTH TROPHIC LEVEL (T6- level) Detritus trophic level. Decomposers form the last or detritus trophic level.

An ecosystem has only a few trophic levels

because:

There is loss of food energy at each transfer which follows 10 percent law.

Food is not completely utilized by an organism of a trophic level. Some part of food materials goes waste.

Large amount of energy available is used in

respiration to provide energy to maintain metabolic functions of

ENERGY FLOW:

Energy flow is sequential process of the movement of energy in an ecosystem through a_ series of organisms. Sun is the only source of energy for all ecosystems on earth (except for deep sea hydrothermal ecosystem). Flow of incident energy is shown below:

SOURCE OF ENERGY:

Of the incident solar radiation less than 50% of it is Photosynthetically Active Radiation (PAR). Plant capture only 2-10%of PAR or 1-5% of incident sola radiation in synthesis of organic matter.Energy does not remain trapped permanent in any organisms. It is either passed on to the higher trophic level or becomes available to detrivores o

decomposers after the organism dies. Herbivores feed on producers. Part of energy is wasted in digestion and assimilation. Some of the assimilated food is broken down to release energy for performing body

activities. A very small proportion becomes part of the body of herbivore. Herbivores are eaten by primary carnivores, latter by secondary carnivores and so on.So, energy flow in an ecosystem is always unidirectional or one way i.e.

Solar radiation m Producemp Herbivores prnivores.Thus, the energy passes from autotrophic plants to the herbivores does not pass back to the autotrophs.

ENERGY FLOW FOLLOWS LAWS OF THERMODYNAMICS:

This large expenditure of energy in the ecosystem is based on two basic laws of thermodynamics:

FIRST LAW OF THERMODYNAMICS: It states that

“energy is neither created nor destroyed but can be transformed from one state to another” Energy of sunlight can be transformed into energy of food and heat.

SECOND LAW OF THERMODYNAMICS: It states

that “no transfer of energy occurs unless and until it is accompanied by degradation or dissipation of energy from concentrated to disperse form.” The transfer of

energy from one organism to another is accompanied by degradation and loss of major part of food energy as heat.

TEN PERCENT LAW OF ENERGY TRANSFER:

The law was proposed by Linderman in 1942.The

transfer of energy from one trophic level to another trophic level is accompanied by loss of energy at each level.

ECOLOGICAL EFFICIENCIES:

Ecological efficiencies are the percentage ratios between energy flow at different trophic levels of a food chain.

These include a number of ratios which indicate the ratios between energy transfer e.g.

1. Trophic level energy intake efficiency: It is the most important kind of ecological efficiency. It is the percentage ratio between the amounts of energy assimilated at two successive trophic levels. It is also called Lindeman’s efficiency and varies from

1- percent for producers and 10-20 percent for highe trophic levels.

2.Trophic level assimilation efficiency: It is the percentage ratio between the net production and food energy ingested at a particular trophic level. It varies

from 10 to 50 percent.

3. Photosynthetic efficiency: It is percentage ratio between total photosynthesis (or Gross primary productivity) and incident total solar radiation. On average, it varies from 1 to 5 percent.

3. Net production efficiency. It is percentage ratic betwseen net primary productivity and gross priman productivity. It is about 50 percent.

“LET US KNOW WHAT WE HAVE LEARNT!”

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

A. MCQs:

1. The first trophic level in an ecosystem consists of:

(a)Primary producers

(b)Primary consumers

(c)Secondary producers

(d)Secondary consumer

2. Which of the following is not a producer?

(a)Spirogyra

(b)Agaricus

(c)Volvex

(d)Nostoc

3. Maximum CO: fixation is done by:

(a)Green plants

(b)Phytoplankton

(c)Parasitism

(d)Predator

4.The loss of energy as one proceeds from one trophic level to the next trophic level is approximately:

(a) 30%

(b) 40%

(d) 90%

5. Which of the following is tertiary consumers:

(a) Zooplankton

(b) Rabbit

(d) Wolf

B. TRUE / FALSE:

1. Energy and materials follow unidirectional flow.

2. The energy flow in an ecosystem is

unidirectional.

3. Breakdown of organic molecules is carried out by producers.

C. FILL UPS:

1. Plants are called as because they can

fix carbon dioxide.

2. Each step in a food chain is called as .

3. The amount of food energy produced or stored by a particular trophic level per unit area in a unit time is .

ANSWER KEY: PART-A

A. MCQs:

1- (a) Primary producers

2- (b) Agaricus

3- (b) Phytoplanktons

4-(d) 90%

5- (d) Wolfs

B. TRUE/FALSE:

1- False

2- True

3- False

C. FILL UPs:

1- Producers (autotrophs)

2- Trophic level

3- Biomass

PART: B SHORT ANSWER TYPE QUESTIONS:

1. What is trophic level?

2. What is the ultimate source of energy for the ecosystem?

3. Which type of organisms belong to T1 and T2 trophic level of food chain.

4. Define ecological efficiency.

PART: C LONG ANSWER TYPE QUESTIONS:

1. Flow of energy through various levels in an ecosystem is unidirectional and non-cyclic.Explain it?

A160

INTRODUCTION

FOOD CHAIN:-It is a series of groups of organisms called trophic levels in which there is repeated eating and eaten by so as to transmit the food energy.

CHARACTERISTICS OF FOOD CHAIN:-

1. Food chain involved a nutritive interaction between the biotic components.

2. Food chain is unidirectional flow of energy from sun to producers and to

consumers.

3. Usually 90% of potential energy is lost as heat at each transfer.

4. Shorter food chains will provide greater available energy.

5. Omnivores occupy more than one trophic level in a food chain.

TROPHIC LEVELS:-

First trophic level (Producer level):- It includes Green plants or producer.

Second trophic level (Primary consumer):-It includes plant eater.

Third trophic level (Secondary consumer):- It includes flesh eater.

TYPES OF FOOD CHAINS:-

1. Grazing food chains (GFC):- In this green plants constitute first step.The plant biomass eaten by the herbivores. The grazing food chain directly depends upon solar radiations. Green plants manufacture their food with the help of solar radiations by the process of photosynthesis.From the energy point of view grazing food chains are very important.

2. Detritus food chains (DFC):- In this dead organic matter either in the form of fallen leaves or dead animal bodies. These are not directly depending upon solar energy. The dead organic matter is first eaten by decomposers,e.g., bacteria, fungi and protozoans. These decomposers organisms have

saprotrophic mode of feeding as primary consumer, these are also called as

detritivores. Detritivores release inorganic elements in the ecosystem by decomposing dead organic matter. In a terrestrial ecosystem detritus food chains are more important than GFCs for energy flow.A food chain having consumers in it is called predator food chain.Producers are also called energy transducers as they change the radiant

energy of sun into chemical energy stored in organic compound.

SIGNIFICANCE OF FOOD CHAINS:

1. These helps to study the feeding relationship between organisms.

2. These inform us about amount of energy we gain by consuming which food.

3. These inform about the energy flow from one trophic level to another trophic level.

ECOLOGICAL PRINCIPLES DERIVED FROM FOOD CHAIN:

1. A food chain must get energy from outside to keep going.

2. The shorter a food chain, the more efficient it is.

3. The size of the population is ultimately determined by the number of trophic levels in the food chain.

4. In any food chain, the successive members are larger in size though fewer in number.

5. An organism cannot always be assigned to just one trophic level.

LET’S KNOW WHAT WE HAVE LEARNT!!

PART — A VERY SHORT ANSWER TYPE QUESTIONS:

01-MCQs:

1. Which of the following is primary consumer?

a. Lion

b. Bird

c. Grasshopper

d. Wolf

2. Detritus food chain begins with:

a. Primary producers’

b. Primary consumers

c. Secondary consumers.

d. Dead organic matter

3. In grazing food chain, carnivores may be referred to as :

a. Primary producer

b. Secondary producers

c. Decomposer

d. detritus

4. The flow of energy among various trophic levels of an ecosystem is:

a. Unidirectional

b. Bidirectional

c. Multidirectional

d. Circular

5. Detritus food chain starts from:

a. Algae

b. Bacteria

c. Protozoa

d. Virus

02- FILL IN THE BLANKS:

1. Each step in a food chain represents a ...........

2. A........18 a series of trophic levels in which there is repeated “eating and

eaten by” to transfer the food energy.

3. In aquatic ecosystem ........food chain are more important for energy flow

detritus food chain starts from ............ matter.

4. Complete the food chain:

Grass—...........frog—snake—predatory bird

03- TRUE / FALSE:

1. Usually there occur one or two levels in the food chain.

2. GFC stands for grazing food chain.

3. DFC Stands for decompose food chain.

4. Decomposing organism have autotrophic mode of feeding.

5. Crop — Rat Owl

ANSWER KEY: PART-A

01- MCQs:

01 — c (grasshopper is herbivorous)

02 — d (detritus are saprophytic organisms)

03 — b (carnivores depend on herbivores which are primary consumers)

04 — a (Flow of energy in ecosystem is unidirectional)

05 -— b (Detritus food chain starts from bacteria)

02-FILL IN THE BLANKS:

01 -- Trophic level

02 - Food chain

03 -- Grass

04 - Bacteria

05 — Grasshopper

03-TRUE / FALSE:

01. False (usually there are a minimum of four levels in food chain)

02. True

03. False (DFC stands for detritus food chain)

04. False (Decomposing organisms have saprophytic mode of feeding)

05. True

PART: B SHORT ANSWER TYPE QUESTIONS:

1. Define food chain.

2. How many types of food chains? Define briefly.

3. What is the importance of food chain?

PART: C_ VERY LONG ANSWER TYPE QUESTION:

1. Broadly explain food chains.

A161

INTRODUCTION

Dear students we have discussed about food chain in our previous assignment that

food chain is a linear sequence of organisms which starts from producer and ends

with decomposers and show that how energy flow from one trophic level to another

trophic level. In an ecosystem in nature food chain do not operate in isolation. In

fact these are interconnected forming a sort of interlocking pattern.

Now in this assignment, we will discuss about interlocking pattern, food web.

FOOD WEB

Food web is a network of food chains which become interconnected at various

trophic levels so as to form a number of feeding connections among different

organisms of a biotic community.

Unlike food chains, food webs are never straight. Interlocking pattern in a food

web is promoted by the fact that a single living organism may participate at

different trophic levels in different food chains. In grassland ecosystem, the

grass may be eaten by the grazing cattle. In the absence of grazing cattle in the biotic community, grass may be eaten by a rabbit or in the absence of both, rat or mouse may consume the grass. Rat or mouse may be eaten by predatory birds or snakes. Snakes may also be eaten by Predatory birds.To sum up, alternatives are available in nature which results in a sort of interlocking pattern or the food web.

CHARACTERISTICS OF FOOD WEB:-

1. Unlike food chains food webs are never straight.

2. Food web is formed by interlinking of food chains.

3. Food web provides alternative pathways of food availability.For example, if a particular species of producer is destroyed by a disease in the ecosystem, the herbivores of that area can feed on other species of producers.

4. In food web, greater are the alternative pathways more stable is the ecosystem.

5. Food webs also help in checking the over population of highly fecundive species of organisms both animals and plants.

6. Food webs also help in ecosystem development.

There can be three types of food chains in a food web —

1. Predator chains that begin with plants and proceeds from small to large animals.

3. Saprophytic chains proceeds from dead animals to microorganisms.

SIGNIFICANCE OF FOOD WEB:-

Food webs provide stability to the ecosystem. Most animals are polyphagous, that is, feed on more than one kind of organisms. If the

population of species decreases to an endangered level, its Predators shift to

another prey and the endangered species may get a chance to recover its population. Even a loss of a particular type of organisms would not produce large fluctuations in the populations of other organisms which use it as food because they would have alternative food organisms.

LET US KNOW WHAT WE HAVE LEARNT!

PART: A - VERY SHORT ANSWER TYPE QUESTIONS:

(A). Multiple Choice Questions:

1. Food Chains

a. operate in isolation

b. do not operate in isolation

c. both a and b

d. none of these

2. Saprophyte food chain starts from:

a. dead organic matter

b. herbivores

c. carnivores

d. green plants

3. Interlocking system of food chains is known as:

a) This interlocking pattern is known as food web.

b) This interlocking pattern is known as web chain.

c) This interlocking pattern is known as web.

d). None of these

4. What checks the over population of highly fecundate species?

a. food chain

b. parasitic food chain

c. food web

d. none of these

5. The food chain in which microorganisms break down the food formed by primary producers is:

a. parasitic food chain

b. detritus food chain

c. consumer food chain

d. predator food chain

(B). True/False:

1. Food chains deals with one animal dependent on another while in food

web if one animal become extinct predators still have other source of food.

2. Greater are the alternative path ways more stable is the eco system.

3. Like food chain, food webs are also straight.

(C). Fill in the blanks:

1. All of the interconnected and over lapping food chains in an eco-system make up a .

2. Food Web provides the of food availability.

ANSWER KEY: PART -A

(A). Multiple Choice Questions:-

1. b. do not operate in isolation

2. a.dead organic matter

3. a. This interlocking pattern is known as food web.

4. c.food web

5. b.detritus food chain

(B). True/False:-

1. True

2. True

3. False Food Web is interconnected of Food Chains

(C). Fill in the blanks:-

1. All of the interconnected and over lapping food chains in an eco-system

make up a__ Food Web_.

2. Food Web provides the _alternative path ways _ of food availability.

PART: B_ SHORT ANSWER TYPE QUESTIONS:

1. Write three types of food chains in food web.

2. Write the significance of food web.

3. Label the diagram given below:

PART -C: LONG ANSWER TYPE QUESTIONS:

1. Define Food Web? Describe Different Characters of Food Web.

A162

INTRODUCTION

Except for the deep sea hydro-thermal ecosystems, sun is the only source

of energy for all ecosystems on earth. Different ecosystems receive different amounts of energy depending upon the latitude, slope, cloud formation and atmospheric pollutants.

The conservation and use of energy in the Eco - System is based on two laws of thermodynamics:

First law of thermodynamics :- Energy cannot be created or destroyed but can be transferred from one state to another.

Thus energy of sunlight is changed into chemical energy of food and heat.As food, energy is passes from one trophic level to the next.

Second law of thermodynamics :- No energy transformation occurs spontaneously unless energy is dissipated from a concentrated to a

dispersed from.

Energy of food is in concentrated form while it is highly dispersed form in heat. The transfer of food energy form one trophic level or organism to another is accompanied by degradation and loss of major part of food

energy. Roughly 10% is stored as biomass.

Thus, ecosystem needs a constant supply of energy to synthesize the molecules they require, to counteract the universal tendency toward increasing disorderliness.

(i) Plants capture only 2-10% of PAR (Photo synthetically Active Radiations) and this energy sustains the entire living world.

(ii) Energy flow is one way process i.e. It is always unidirectional e.g.

Solar radiation ==» Producers ==» Herbivores=—=» Carnivores

(iii) Amount of energy flow decreases with successive trophic levels.

(iv) Energy requirement for maintenance of body is 20% of gross productivity in producers 30% of assimilated energy in carnivores.

(v) Length of food chain is generally limited to 3-4 trophic levels.

Ten percent law _:- (Lindeman, 1942) :- The passage of about 10% of energy from one trophic level to the next is called Ten percent law e.g. if 1000 Kg biomass is present in grass, only 10% of it (100 kg) will go to deer and so on.

TROPHIC LEVELS :- These are the different levels at which organisms obtain their food in a food chain.

The number of trophic levels is equal to the number of steps in the food chain. The basic trophic levels are producers and consumers. Each trophic level uses a part of food in body building while the major part is liberated in the form of energy through respiration.

LET US KNOW WHAT WE HAVE LEARNT!!

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

A. MCQs:

Q:1 Which of the following is example of man-made ecosystem?

(a)Herbarium

(b) Crop fields

(d) both B and C

Q:2 Vertical distribution of different species occupying different levels

is called?

(a)Enumeration

(b) Stratification

(d) None of these

Q:3 Which one of the following is not an abiotic component?

(a) Temperature

(b) Decomposers

(d) Soil

Q:4 In an ecosystem abiotic components includes which of the following?

(a)Flow of energy

(b) cycling of materials

(d) Both (a) and (b)

Q: 5 Which of the following is not a producers?

(a)Agaricus

(b) Nostoc

(d) Spirogyra

Q: 6 Energy flow in ecosystem is:

(a)Unidirectional

(b) Multidirectional

(d)None of These

B. FILL INTHE BLANKS:

1. Phosphorus cyle is type of cycle.

2. Each higher trophic level in a food chain can utilize only of energy.

3. The pyramid of is always upright

4. Plants are called as because they fix carbon dioxide.

5. In an ecosystem dominated by trees, the pyramid is of type.

6.A is a series of trophic levels in which there is repeated eating and being eaten by to transfer the food energy.

7. The major reservoir of carbon on earth is

8. The amount of food energy produced or obtained or stored by a particular trophic level per unit area in a unit time is .

C. TRUE FALSE:

1. Biotic factors include sunlight, soil, temperature and water.

2. An ecosystem consists of all the biotic and abiotic factors in an area and

their interactions.

3. Herbivores are a necessary link between producers and other

consumers

4. Dung beetles eat animal faces.

5. Autotrophs make their own food.

ANSWER KEY: PART -A

A.MCQs:

Ans :1. (D) herbarium and aquarium are artificial ecosystems.

Ans : 2. (B) stratification is vertical distribution of different species .

Ans : 3. (B) Decomposers are the biotic component.

Ans: 4. (D) In an ecosystem abiotic components includes both energy flow

and cycling of materials.

Ans: 5. (A) Agaricus is a fungus (a decomposer) and doesn’t contain

chlorophyll

Ans: 6. (A) Energy flow in an ecosystem is unidirectional.

B. FILL IN THE BLANKS:

Ans:1. Sedimentary

Ans:2. Ten Percent

Ans.3. Energy

Ans. 4. Autotrophs.

Ans.5. Inverted

Ans. 6. Food Chain

Ans.7. Ocean Water

Ans. 8. Biomass

C. TRUE FALSE:

Ans:1 False (Abiotic factors include sunlight,soil,temperature and water)

Ans:2 True

Ans:3 True

Ans.4 True

Ans.5 True

PART: B VERY SHORT ANSWER TYPE QUESTIONS:

Q.1 Give an example of a secondary carnivore found in an aquatic ecosystem.

Q.2 The base tier of the ecological pyramid indicates?

Q.3 Pick an omnivore that appears in both the decomposer and grazing food chain.

Q.4 List two entities which are formed in more than one trophic level in an ecosystem?

Q.5 In an ecosystem which is the ultimate source of energy.

Q.6 Is the edible mushroom a heterotroph or an autotroph?

Q.7 What is self-sustainability?

Q.8 Which metabolic process causes a reduction in the gross primary roductivity?

Q.9 Name any two man-made ecosystem?

Q.10 What is 10% law?

PART: C LONG ANSWER TYPE QUESTIONS:

Q.1. Write a note on the flow of energy in the eco system.

A163

INTRODUCTION

An ecological pyramid may be defined as a graphical representation of the numbers or biomass or status of accumulated energy at different tropic levels in a food chain in an ecosystem.

The idea of ecological pyramids was developed by Charles Elton,so the ecological pyramids are also called Eltonian Pyramids. It may be

Upright, Inverted or spindle-shaped

We must be familiar with the shape of a Pyramids. The base of a pyramids is

broad and it narrows down at the apex.one gets a similar shape,whether weexpress the food or energy relationship between oanisms at different trophics level.Thus relationship is expressed in terms of Number,Biomass or

Energy. The base of each pyramids represents the Producers or the firsttrophic

level while apex represents tertiary or Top level Consumer.The three Ecological Pyramids that are usually studied are:

1 PYRAMID OF NUMBER

2 PYRAMIDS OF BIOMASS

3 PYRAMIDS OF ENERGY

1. PYRAMID OF NUMBER:It is the pictorial representation showing the arrangement of

number of individuals of different trophic levels in a food chain in an ecosystem. The Pyramid of number in a pond ecosystem

is always upright, showing the number of individual organisms at each level. In a pond, the producers, which are mainly

phytoplanktons, are always maximum in number.

In a predatory food chain in grassland ecosystem or a pond ecosystem,Pyramid of number is always upright, showing the

number of individual organisms ateach level.

Here thesize of organisms increases from the Producer level to the Top Carnivores while their Number decreases in a food chain(from

grasslandto predatory Birdsin grassland ecosystem and from Phytoplanktons to large Fish in Pond ecosystem) so producers are

smallest sized but maximum in number while the tol carnivores are the largest in size but the least in number so they can not be used as prey by another species

UPRIGHT_IN POND ECOSYSTEM:The ecological pyramids such as pyramids of number and pyramids of biomass in the pond ecosystem are always inverted because, in the ponds

the number and biomass of the consumers are more in number than the producers.

The pyramid of biomass is inverted in a pond ecosystem because the biomass of fish is higher as compared to producers.

INVERTED IN PARASITIC FOOD CHAIN :An Oak-Tree pyramid of Number, in which a single Oak tree (Producers)support a large number of fruit eating Birds which in turn support a still

larger number of parasites like lice and bugs, Hyper parasites like Bacteria,

fungi etc. are greatest number and occupy the top of inverted pyramid of

number.

SPINDLE SHAPE IN TREE ECOSYSTEM:A Tree-Dominated Ecosystem single large sized tree(T:) is attacked by numerous minute plant-eating insects(T2) preyed upon by fewer spiders and carnivores insets(T3) which are further preyed upon by a lesser number of

small-sized bird(T.4) which finally preyed upon by only a few large sized birds

of prey(Ts),The ecosystem is Spindle —shaped.Simmialrly the pyramid of number in forest ecosystem is spindle shaped.

2. PYRAMIDS OF BIOMASS:The Biomass Pyramids show the amount of biomass (living or organic

matter present in an organism) present per unit area at each trophic level.It is drawn with the producers at the base and the top camivores at the tip.Pyramid of biomass is generally ascertained by gathering all organisms occupying each trophic level separately and measuring their dry weight.

Each trophic level has a certain mass of living material at a particular time

called standing crop, which is measured as the mass of living organisms (biomass) or the number in a unit area.

UPRIGHT PYRAMID OF BIOMASS : Ecosystems found on land mostly have pyramids of biomass with large base of primary producers with smaller trophic level perched on top, hence the upright pyramid of biomass.it also shows there sharp decrease in biomass at higher Trophic levels e.g. top carnivores having only

1.5kg/m? biomass while producers having biomass of 809kg/m?.

But in Aquatic Habitats (Marine) Pyramid of Biomass is inverted. Producers are

more in number and biomass than the herbivores, and herbivores are more in

number and biomass than the camivores so all the pyramids, of number, of energy

and biomass are upright.The pyramid of biomass in sea is also generally inverted because the biomass of fishes far exceeds that of phytoplankton.

3. PYRAMIDS OF ENERGY:It is a graphical representation of amount of energy trapped per unit time and area in different trophic levels of a food chain with Producers forming

the base and Top carnivores at the top.The unit of measurement of energy is Kcal/m?/year. According to Second Law of Thermodynamics,there is gradual decrease in energy at successive trophics levels.

Because at each transfer 80-90% of energy available at lower trophics level is used to overcome its entropy and perform metabolic activities and only 10 % (in herbivores) to 20% (in Carmivores) is available to next

trophics levels.

So Pyramid of Energy is always Upright can never be inverted, because when energy flow one level to next trophic level, some energy is always lost as heat at each step. The Law governing the retaining of only 10% of

Chemical Energy at each trophic level is called 10 percent Law proposed by Lindemann.

LIMITATIONS OF ECOLOGICAL PYRAMIDS:

1) It does not take into account the same species belonging to two or more

trophic levels on the basis of their feeding relationship with others e.g.Sparrow is said to be primary consumer when it eats seeds, fruits, peas, etc.while it is referred as secondary consumer when it eats insects and worms.

2) It assumes a simple food chain, something that almost never exists in nature

3) It does not accommodate a food web.

4) Saprophytes are not given any place in ecological pyramids. Saprophytes

play important role in the material cycling in an ecosystem.

LET US KNOW WHAT WE HAVE LEARNT!!

PART: A- VERY SHORT ANSWER TYPE QUESTIONS :

A. MULTIPLE CHOICE QUESTIONS:

1) Which of following is the first trophic level of ecosystem?

a) Animals

b) Plants

c) Bothaandb

d) none of above

2) Which ecological pyramid is always straight/upright?

a) Pyramid of energy

b) Pyramid of biomass

c) Pyramid of Number

d) None of above

3) Secondary producers are:

a) Herbivores

b) Producers

c) Carnivores

d) None of above

4) In a pyramid of number, in a grassland ecosystem, the largest population

is that of:

a) Producers

b) Tertiary consumers

c) Secondary consumers

d) Primary producers

5) Pyramid of number in a grassland ecosystem is:

a) Upright

b) Inverted

c) Spindle -shaped

d) None of above

B. TRUE/FALSE:

1. Eltonian Pyramids may be upright or Inverted or Spindle shaped.

2. Pyramids of Number always upright.

3. Saprophytes are not given any place in ecological pyramids even though

they play a vital role in the ecosystem.

C. FILL IN THE BLANKS:

1. ... ...pyramids idea was first developed by Charles Elton.

2. Plants are called... .......because they fix carbon dioxide.

3. The amount of food energy produced or obtained or stored by a particular

trophic level per unit area in a unit time is...

ANSWER KEY: PART-A

(A) MULTIPLE CHOICE QUESTIONS :

1. b) Plants (Plants are first trophic level of ecosystem as they are producers)

2. a) Pyramid of energy (it is always upright)

3. a) Herbivores (herbivores consume plants which are primary producers, hence they become secondary producers)

4. a) Producers (pyramid of number starts with max no. of producers)

5. a) Upright (pyramid of no. is upright)

(B) TRUE/FALSE:

1. TRUE

2. FALSE because Pyramids of Number Inverted In Parasitic Food Chain e.g.an

Oak-Tree pyramid of Number,in which a single Oak tree (Producers) support a large number of fruit eating Birds which in turn support a still larger number of parasites like lice,bugs,Hyperparasites like Bacteria,fungi etc.are greatest number and occupy the top of inverted pyramid of number.

3. TRUE

(C) FILL IN THE BLANKS :

1. Ecological

2. Producers

3. Biomass

PART: B_ SHORT ANSWER TYPES QUESTIONS:-

1. Explain the concept of pyramid of biomass.

2. What is 10 percent Law of Energy Flow?

3. Explain briefly the ecological pyramid which is always upright?

4. What does the base tier of the ecological pyramid represent ?producers

PART: C LONG ANSWER TYPES QUESTIONS:

1. Define Ecological Pyramid. And describe its types with examples.

A164

INTRODUCTION

ECOLOGICAL SUCCESSION: It is the natural development of a series of biotic communities called SERES one after the other; in the same areatill a permanent climax community is established.

CHARACTERISTICS:

1. It starts with small plants and starts towards large long lived plants.

2. It leads from less to very complex diversity of life.

3. It slowly changes simple food chains to complex food webs.

4. There is not only a charge in the species of organisms present but,

also on increase in the number of species.

The first community to inhabit on an area is called: Pioneer Community.The last and stable community is called: Climax Community.

The intermediate communities between PIONEER and CLIMAX community are called Transitional or Seral Communities.

TYPES OF SUCCESSION: These are basically of two types:

a) Primary Succession: It starts from primitive substratum, where there was no previously any sort of living matter. It may take many years.

b) Secondary Succession: It starts from previously built up substrata with already existing matter. It has organic matter such as lands,cut-forests.

On the basis of nature of environment where the process has begun, It is of following types:

Hydrosere: Starting in regions where water is in plenty.

Mesarch: Where adequate moisture conditions are present.

Xerosere or Xerarch: Where moisture is minimum such as dry deserts, rocks etc.

It may be further of different kinds:

Lithosere: Initiating on rocks.

Psammosere: On sand.

Halosere: On saline water or soil.

HYDROSERE: It is the ecological succession in pond or lake.

Stages of Hydrosere:

a) Plankton Stage: It is the pioneer community and is formed by the germination of spores. These are phytoplanktons such as algae,diatoms etc. These are followed by zooplanktons which feed on phytoplanktons. Dead phytoplankton mix with bottom mud.

b) Rooted Submerged Stage: It is formed of the rooted submerged hydrophytes like Hydrilla, vallisenaria, utricularia etc. Due to their death and decay bottom level rises.

c) Rooted Floating Stage: It is formed of rooted hydrophytes such as trapa, monochoria etc. There may be free floating species. Their death and decay also adds to the bottom.

d) Reed-swamp stage: It is the amphibious stage. It includes plants like sagittaria, typha etc. The organic matter added by them also raises the substratum.

e) Sedge-Meadow Stage: It is formed of plants species like carex,juncus, Catha, polygonum etc. These form mat like vegetation towards the centre of the pond with the help of their branched rhizomes.

f) Wood land Stage: Some shrubby plants occupy the peripheral area.These can tolerate sunlight as well as water logged condition for example cornus, button brush etc. These build up more soil.

g) Forest Stage: It is the climax community. It depends upon the climate condition for example tropical deciduous or monsoon

forests in region of moderate rain fall, tropical rain forests in areas with heavy rain fall.

LITHOSERE (XEROSERE): It involves the ecological succession on bare rock surfaces.

Stages in Lithosere:

a) Crustose Lichen Stage: It forms the pioneer community and is represented by lichen species like graphis, rhizo carpus lacarosa etc.These can tolerate desiccation. These produce organic acids which cause weathering of rocks and release mineral ions.

b) EFoliose Lichen Stage: It includes lichens like parmellia which are large sized. There are able to accumulate dust which helps in the formation of substratum.

c) Moss Stage: It is characterized by extensive growth of mosses like polytrichum, Torula etc. Their death and decomposition add organic matter, so thickness of soil increases.

d) Herbs Stage: The mat formed by mosses on rock becomes suitable for handy grasses which have sand binding properties. Their death and

decomposition accumulates more soil.

e) Shrub Stage: The accumulated soil becomes suitable for the growth of shrubs like Rhus, Zizyphus caparis etc. Their roots penetrate deep into the soil causing more soil formation.

f) Forest Stage: It is the climax community and is formed of many hardy trees. Those add more humus content. The vegetation finally becomes mesophytic.

LET US KNOW WHAT WE HAVE LEARNT!!

MULTIPLE CHOICE QUESTIONS:

1. Which one of the following statement is correct for secondary succession:

a) It begins on a barren rock.

b) It occurs on a deforested site.

Cc) It follows primary succession.

d) It is similar to primary succession except that has a relatively fast pace.

2. Correct sequence of SERAL stages in hydro sere is:

a) Plankton, submerged, floating, seed swamp, sedge meadow,woodland

b) Plankton, floating, submerged, reed swamp, sedge meadow,woodland

c) Plankton, submerged, floating, sedge meadow, reed swamp,woodland

d) Plankton, submerged, floating, sedge meadow, woodland, reed swamp.

3. In primary succession on rocks the pioneer species are usually:

a) Algae

b) Fungi

c) Lichens

d) Bryophytes

4. Identify the plant belonging to amphibious stages in hydrosere:

a) Juncus

b) Sagittaria

c) Salix

d) Trapa

5. There are two statements written as assertion reason while answering, choose any one of these for response:

a) If both assertion and reason are true and reason is the correct explanation.

b) If both assertion and reason are true but reason is not the correct explanation.

c) If assertion is true but reason is false.

d) If both assertion and reason are false.

Assertion: In lichen stage by corroding action soil formation occurs but their action is slow.Reason: Crustose lichens produce carbonic acid which corrodes the

rocks.

a) b) c) d)

ll. FILL IN THE BLANKS:

1. Ecological succession on the sand is called

2. Intermediate community between pioneer and climax community is called

3. The final and stable community of the succession is the

ill. TRUE/FALSE:

1. The ecological succession taking place in water is called xerosere.

2. The introduction of new life form in bare areas is initiated by the act of migration.

3. Ecological succession starts with small plants having small life span and progresses towards large, long lived plants.

ANSWER KEY: PART A

A) MULTIPLE CHOICE QUESTIONS:

1. a) Secondary succession begins in area where natural biotic communities have been destroyed as in abandoned farm lands, burnt

or cut forest, flooded lands.

2. a) Plankton, submerged, floating, seed swamp, sedge meadow,woodland

3. c) Various Lichens for example Graphis, Lacanora etc. come first.These can tolerate desiccation, then produce acids which cause

weathering of rocks.

4. b) Sagittaria plant has well developed rhizomes. The organic matter added (by them raises the substratum)

5. a) Organic acids cause weathering of rocks and release mineral ions for proper growth of lichens.

B) FILLIN THE BLANKS:

1. Psammosere

2. Seral or Transitional community

3. Climax community

C) TRUE/ FALSE:

1. False (The ecological succession taking place in water is called hydro sere)

2. True

3. True

1. What is pioneer community?

2. What are transitional communities?

3. What are primary and secondary successions?

1. What is hydro sere? Explain different Seral communities occupying in a hydro sere?

2. What is Xero sere? Mention its types. Explain ecological succession on a barren rock.

A165

HYDROSERE or HYDRARCH

The ecological succession can be broadly classified into two kinds on the basis of thenature of habitat:

1. Hydrach (Hydrosere)

2. Xerarch ( Exerosere)

HYDROSERE:A Hydrosere is a plant succession which occurs in an area of fresh GEE such as a pond, lakes and marshes.Hydrosere is the primary succession which develops in aquatic environment such as lakes and ponds. It results in conversion of water body and its

community into a landcommunity. In time, area of open _ freshwater will naturally dry out, ultimately becoming woodland. During this change, a range of different land types such as swamp and marsh will succeed each other.

Such a succession does not necessarily lead the aquatic communities towardsthe development of land communities. If the water body is large and very deep or strong wave action and other powerful physical forces

are at work, the succession results in a stable aquatic community in which any

considerable further change is hardly recognizable.

If the hydrarch succession starts from a comparatively small water body such as pond, lakes etc. there is always a high probability for the formation of a terrestrial climax community.

IMPORTANT CHARACTERISTICS OF HYDROSERE ARE:-

Hydrosere usually starts from a pond.

Phytoplankton's are the pioneer community.

A forest or a grassland will be the climax community.It includes several seral stages of plant and animal communities.Seral communities of plants are more obvious than animals.

STAGES OF HYDROSERE:The various stages in a hydrosere are well studied in ponds,

pools or lakes. Hydrosere, originating in a pond, starts with the colonisation

by the pioneers like phytoplanktons and finally terminates into a forest, which is

a climax community. Successive changes in hydrosere takes place both in plants as well as animals life. But the changes are more obvious in plants than animal; it looks as it is a succession of plant only. Hydrosere completed through a sequence of several seral stages (seral communities). The various

stageswith their chief components of plant species of a hydrosere are as follows:-

SERAL STAGES OF HYDROSERE:

Phyto-plankton Stage.

Rooted Submerged Stage.

Rooted Floating Stage.

Reed-swamp Stage.

Sedge-Meadow Stage.

Woodland Stage.

Forest Stage.

PHYTO-PLANKTON STAGE:In this initial, the pond water is poor in nutrient and devoid of much life. At this stage, phytoplanktons consisting of microscopic blue green algae, green algae,diatoms and bacteria etc are the first organism to colonise the primitive medium of the pond. They constitute the pioneer community. Phytoplankton are followed

by zooplankton. All these organisms add large amount of organic matter and nutrients due to their various life activities and after their death, they settle at the bottom of pond to form a layer of muck.

ROOT SUBMERGED STAGE: As a result of death and decomposition of phytoplanktons, and their mixing with slits, brought from the surrounding land by rain waters, a soft mud atthe bottom of pond develops. The new habitat which is now shallower and richer in nutrients, and where light is available upto a certain depth becomes suitable for the growth of rootedsubmerged hydrophytes like,

Hydrilla, Potamogeton, Vallisneria, Utricularia and Ceratophyllum. These

plants bring about further buildup of the substratum as a result of their death and

decay. The water level also decreases making the pond more shallower.

ROOTED FLOATING STAGE: Now the water depth is almost 2-5 feet. At this stage the pond is colonised by the plant species which are rooted in mud with their large leaves floating onthe water surface. These are species of Nymphaea, Trapa, Monochoria etc. Some freefloating species as Azolla,

Lemma, Wolffia, Pistia, Salvia etc, also become associated with the rooted

plants. The water level by now becomes very much decreased, making the pond more swallowers. The decomposing organic matter formed due to death of these plants brings further buildup of the substratum. Floating species sooner or later disappear from the area.

REED-SWAMP STAGE:This stage is also called the "Amphibious Stage", as the plants of the community are rooted but most parts of their shoots remain exposed to air. Species of Typha, Sagittaria and Phragmites etc, are the chief plants of this stage. Plants in this stage have well- developed rhizomes and form dense vegetation over the area and this will prevent the light penetration to the lower

portion. At this condition, the remaining rooted floating or free floating or

submerged plants of the previous seral stage disappears.

SEDGE MARSH OR MEADOW STAGE:- Due to successive decrease in water level and further changes in the substratum, species of some Cyperaceae and Gramineae, such as Carex, Juncus, Cyperus and Eleocharis colonize the

area. They form a mat like vegetation with the help of their much branched rhizomatous system. As a result of high rate of transpiration, there is much rapid

loss of water, and sooner or later, the mud is exposed to air. Once the soil is

exposed to the air, the nutrients such as ammonia, sulphides etc, become oxidized to nitrates and sulphates. The condition in the area gradually changes from marshy to mesic and marshy vegetation disappears gradually and gradually.

WOODLAND STAGE: Disappearance of marshy vegetation, soil becomes drier for most of the time and become suitable for development of wet woodland. This rea is now invaded by the terrestrial plants, which are some shrubs (Salix,fungi and other. Thus mineralization of the soil favours the arrival of new tree

species in the area leading to the climax stages.

FOREST STAGE (CLIMAX STAGE): Forest stage is the climax community in hydrarch succession. The woodland community is invaded by a variety of large tree forms which soon develops into climax community. The nature of the climax community (forest) is dependent upon the climate of the region. In

tropical climates with heavy rainfall, tropical rain forestdevelop, whereas in

temperate regions mixed forests of Ulmus, Acer and Quercus develop. In region of moderate rainfall, there develop tropical deciduous forest or monsoon forest.

There are also changes in the animal life, but these are not be as obvious as those in the plant communities. Thus with the ageing of a pond and the development of the marshes, the animal life also undergoes changes. These are as follows:

The protozoans like Paramecium, Amoeba, Euglena etc are the pioneers. When the planktonic growth forms are very rich, other animal life form as blue gill fish, sun fish,largemouth bass etc., start appearing. Some caddis flies are also found. In the next, submerged stage the caddis flies are

replaced by other animals that may creep over the submerged vegetation.Thus dragon flies, mayflies and some crustaceans inhibit the pond at this stage.

At the floating stage, the animal life is chiefly represented by Hydra spp.,gill breathing snails, frog, salamander diving beetles and other insects. Some turtles and snakes also appear. At the reed swap stages, the pond becomes shallower, and the bottom starts to be exposed. The floating animals are replaced by different species of mayflies and dragon flies, whose nymphs remain

attached to submerged parts of the vegetation, and adults present on the

surface of emergent parts. Gill breathing animals like snails are replaced by

Finally, at the woodland stage, under terrestrial condition most of the

terrestrial forms of animal life appear in the area.

“LET US KNOW WHAT WE HAVE LEARNT!!!”

PART: (A) VERY SHORT ANSWER TYPE QUESTIONS:

(1). Multiple choice questions:

1. When the ecological succession occurs in the water it is termed as:

a) Psammosere.

b) Lithosere

c) Exerosere.

d) Hydrosere

2. Pioneer community shows:

a) very little biodiversity.

b) very high biodiversity

c) medium biodiversity.

d) No biodiversity

3. During biotic succession, the first community to inhabit an area is called:

a) climax community.

b) pioneer community

c) serial community.

d) Transition community

4. What is a climax community in a hydrarch succession?

a) Root submerged plants.

b) Free floating Angiosperms

c) Forest.

d) Scrub

5. Who replaces the free floating plants in a hydrarch succession?

a) Root submerged plants.

b) The Reed swamp

c) Free floating Angiosperms.

d) Phytoplankton

2). Fill in the blanks:

1. The succession that takes place in the water is called..................

2. In Hydro sere, after phytoplankton the next stage is...............

3. In primary succession of water, what does the water body convert to................2

4. The first community to establish in an barren area is called climax community.

ANSWER KEY - PART (A)

(1). Multiple choice questions:

1. d (Hydrosere)

2. a (very little biodiversity)

3. b (pioneer community)

4. c (forest)

5. b (the reed swamp)

(2). Fill in the blanks:

1. Hydrach

2. Submerged stage

3. Land

(3). True/False:

1. False (maximum diversity found in climax community)

2. False (it is pioneer community)

PART: (B) SHORT ANSWER TYPE QUESTIONS:

(1) Define Hydro sere.

(2) What is the difference between pioneer community and climax community?

(3) Give summary of Hydrarch succession.

PART (C) LONG ANSWER TYPE QUESTIONS:

(1) Describe in detail Hydrarch succession.

A166

INTRODUCTION

LITHOSERE:-The sequence of successional stages on a bare rock is called Lithosere.

There are seven main stages of lithosere in plants.The stages are:-

1. CRUSTOSE LICHEN STAGE

2. FOLIOSE LICHEN STAGE

3. MOSS STAGE

4. HERB STAGE

5. SHRUB STAGE

6. TREES STAGE

7. CLIMAX STAGE

1. CRUSTOSE LICHEN STAGE:A barren rock consists of solid surface very large boulders and there is no place for rooting plants to colonize.Lichen species like graphisrhizocarpan, rinodina and lecanora forms are the pioneer community in alethosere,as they can tolerate desert or extreme hot conditions.

Crustose lichens can adhere to the surface of rock and absorb moisture from atmosphere therefore these colonize the barren surface of rock first.

The propagules of these lichens are brought by air from the surrounding area.

Organic acids produced by lichens leach the rock surface and release minerals for proper growth of lichens.= When these lichens die there thalli are decomposed and add humus.

This promotes soil formation and the environment becomes suitable for growth of foliose fruticose type of lichens.

2. FOLIOSE AND FRUTICOSE LICHEN STAGE:

As the soil formation proceed It leads to the growth of foliose lichens like parmelia, physcia etc.

Foliose and Fruticose lichens are attached to the substratum at one point only therefore do not cover the soil completely.

Foliose lichen retains more water and accumulates more soil particles helping

in the development of a fine layer of soil on the rock surface. They can absorb and retain more water and are able to accumulate more dust particles.

Their dead remains are decomposed to humus which maxes with soil particles and help building substratum and improving soil moisture contents further.

The shallow depressions in the rocks and crevices become filled with soil and

topsoil layer increase further.

3. MOSS STAGE:The spores of xerophytes mosses such as Polytrichum, Tortula and Grimmia are brought to the rock where they succeed lichens.

POLYTRICHUM

Accumulation of soil and humus leads to the growth of mosses such Polytrichum and Grimmia.

After some times as a lot of soil and organic matter accumulates that favour the growth of moisture loving mosses like hypnum, bryum etc.

Their rhizoids penetrate soil on the rocks.

As mosses develop in patches they catch soil particle from the air and help increase the amount of substratum.

The bodies of mosses are rich in organic andinorganic compounds.When these die they add these compounds to the soil increasing the fertility of the soil.

The changing environment leads to invasion of herbaceous vegetation that can out compete mosses.

4. HERB STAGE:Deathand decay of mosses produce a mat of organic moss rich in organic

soil that help the germination to reach of hardy grasses like:Eleusin, Aristida etc.

Further decomposition of these annual grasses promotes the growth of perennial grasses like Cymbopogon, Heteropogon etc.

Their roots are penetrates deep down, secrete acids and enhance the process of weathering.

Leaf litter and death of herbs add humus to the soil.

Shading of soil results in decrease in evaporation and maintains soil moisture and slightly increases in temperature.

Asa result the xeric conditions begin to change and biennial and perennial herbs and xeric grasses survive.

These climatic conditions favour growth of bacterial and fungal population resulting in increase in decomposition activity.

5. SHRUB STAGE

The herb and grass vegetation is replaced by shrub species, such as Rhus and Phytocarpus.

The soil formation continues and its moisture content increase.

Further weathering of rocks and death of herbs make the habitat more suitable for the growth of shrubs like RHUS, CAPARIS and ZIZIPHUS etc.

Since the roots of shrubs penetrate more deeply in the rocky substratum causes more weathering and soil formation.

6. TREE STAGE:Change in environment favours colonization of tree species among the

shrubs. The kind of tree species inhabiting ta area depends upon the nature of the soil

The tree form canopy and shades the area.

Shade loving shrubs continue to grow as secondary vegetation.

Leaf litter and decaying roots weather the soil further and add humus to it.

Mosses and ferns make their appearance and fungi population growth abundantly.

7. CLIMAX STAGE:The succession culminates in a climax community the forest.

Many intermediate tree stages develop prior to establishment of a climax community.

The forest type of depends upon climatic condition.

Vegetation finally becomes mesophytic.

A steady state is reached between the environment and the biotic community

Let us know what we have learnt!!

PART- A: VERY SHORT ANSWER TYPE QUESTIONS:

A: MULTIPLE CHOICE QUESTIONS:

1. Which one of the following statements is correct for secondry succession:

(a)it begains on a bare rock

(b)it occurs on a deforested site

(c)it follows primary succession

(d)it is similar to primary succession except that it has a relatitvely fast pace

2. The final stable community of ecological succession is called:

(a)Final Community

(b) Ultimate Community

(c)Climax Community

(d)Seral Community

3. In ecological succession the inter mediate developmental phase is known as:

(a)Acess

(b)Climax

(c)Nudation

(d)Sere

4. Which of the following is a pioneer community in Lithosere:

(a)Phytoplankton

(b)Foliose Lichen

(c)Crustose Lichen

(d)Moss

B: TRUE/ FALSE:

1. The ecological succession in dry area is known as Xerarch.

2. It is possible to predict the direction of succession.

3. Plant communities are always stable.

4. The introduction of new life forms in bare areas is initiated by act of

migration.

C: FILL IN THE BLANKS:

1. The serial changes in previously sterile or totally barren area is called

2. Intermediate community between the pioneer and climax community is called

ANSWER KEY: PART -A

A: MULTIPLE CHOICE QUESTIONS:

1. b) It occurs on a deforested site

2. c) Climax Community

3. d) Sere

4. c) Crustose Lichen

B: TRUE/ FALSE:

1. True

2. True

3. False (Plant communities are not always stable)

4. True

C: FILL IN THE BLANKS:

1. Primary Succession

2. Seral Communities

PART-B: SHORT ANSWER TYPE QUESTIONS:

Q .1 Write a short note on ecological succession on a bare rocks.

Q . 2 State the main difference between primary and secondary succession.Provide one example of each.

PART- C: LONG ANSWER TYPE QUESTIONS:

Q. 1 Whatis lithosere? Explain the stages of lithosere with suitable example?

A167

INTRODUCTION

BIOGEO CHEMICAL CYCLING or NUTRIENT CYCLING:

Energy flow and nutrient circulation are the major functions of the ecosystem.

Energy is lost as heat forever in terms of the usefulness of the system. On the

other hand, nutrients of food matter never get used up. They can be recycled again and again indefinitely.

Carbon, hydrogen, oxygen, nitrogen and phosphorus as elements and compounds makeup 97% of the mass of our bodies and are more than 95% of the mass of all living organisms.

In addition to these, about 15 to 25 other elements are needed in some form for

the survival and good health of plants and animals.

These elements or mineral nutrients are always in circulation moving from non-

living to living and then back to the non-living components of the ecosystem in a

more or less circular fashion.

This circular fashion is known as biogeochemical cycling (bio for living; geo for atmosphere).

Among the most important nutrient cycles are the carbon nutrient cycle and the nitrogen nutrient cycle.

There are many other nutrient cycles that are important in ecology, including a large number of trace mineral nutrient cycles.

OF NUTRIENT CYCLES:Many biogeochemical cycles affect our daily lives in many ways. A prime example of one of these cycles is the water cycle. The constant changing states of water

and how it interacts with our environment (gas, ice, and liquid states). Some key

words with the water cycle include condensation, precipitation, and evaporation.

‘Ne eT

Another great example in our everyday lives is the flow of oxygen and carbon

dioxide. The constant respiration from animals and photosynthesis from plants

creates a constant cycle which has been continuing for millions of years.

Based on the replacement period, a nutrient cycle is referred to as Perfect or Imperfect cycle.

A perfect nutrient cycle is one in which nutrients are replaced as fast as they are utilized.

Most gaseous cycles are generally considered as perfect cycles.

In contrast sedimentary cycles are considered relatively imperfect, as some nutrients are lost from the cycle and get locked into sediments and so become unavailable for immediate cycling.

Based on the nature of the reservoir, a nutrient cycle is referred to as Gaseous or

Sedimentary cycle

Gaseous Cycle: the reservoir is the atmosphere or the hydrosphere —water cycle, carbon cycle, nitrogen cycle, etc.

Sedimentary Cycle: the reservoir is the earth’s crust (soluble elements mostly found in earth's crust) — phosphorous cycle, sulphur cycle,calcium cycle, magnesium cycle etc.

DEFINITION OF BIOGEOCHEMICAL CYCLE:

“Biogeochemical cycles mainly refer to the movement of nutrients and other elements between biotic and abiotic factors.”

The term biogeochemical is derived from “bio”means biosphere, “geo” means the

geological components and “chemical”means the elements that moved through a cycle.

The matter on Earth is conserved and present in the form of atoms. Since matter

can neither be created nor destroyed, it is recycled in the earth's system in various

forms.

The earth obtains energy from the sun which is radiated back as heat, rest all other

elements are present in a closed system.

The major elements include:

Carbon

Hydrogen

Nitrogen

Oxygen

Phosphorus

Sulphur

These elements are recycled through the BIOTIC and ABIOTIC components of

the ECOSYSTEM. The atmosphere, hydrosphere and lithosphere are the abiotic components of the ecosystem.

PHOSPHORUS CYCLE:Phosphorus is an important element for all living organisms. It forms a significant part of the structural framework of DNA and RNA. They are also an important

component of ATP Adenosine Tri Phosphate. Humans contain 80% of phosphorus

in teeth and bones.Phosphorus cycle is a very slow process. Various weather processes help to wash the phosphorus present in the rocks into the soil. Phosphorus is absorbed by the

organic matter in the soil which is used for various biological processes.Since phosphorus and phosphorus-containing compounds are present only on land, atmosphere plays no significant role in the phosphorus cycle.

Phosphorous is a crucial nutrient for plants and animals. For instance, it forms an

integral component of genes and also plays a significant role in the Adenosine

Triphosphate (ATP) energy cycle. Without phosphorous, you wouldn't be able to

contract your muscles.The phosphorus cycle refers to the biogeochemical cycle by which phosphorous moves through the biosphere, hydrosphere, and lithosphere.The atmosphere doesn't play a substantial role in the cycling of phosphorous. This is because phosphorous and phosphorous-based compounds cannot be found in the air in the gas state.

PHOSPHORUS CYCLE DEFINITION;“Phosphorus cycle is a biogeochemical process that involves the movement of phosphorus through the

lithosphere, hydrosphere and biosphere.”

STEPS OF PHOSPHORUS CYCLE:Following are the important steps of phosphorus cycle:

1. Weathering

2. Absorption by Plants

3. Absorption by Animals

4. Return to the Environment through Decomposition

1. WEATHERING Phosphorus is found in the rocks in abundance. That is why the phosphorus cycle starts in the earth's crust. The phosphate salts are broken down from the rocks.These salts are washed away into the ground where they mix in the soil.

2. ABSORPTION BY PLANTS The phosphate salts dissolved in water are absorbed by the plants. However, the amount of phosphorus present in the soil is very less. That is why the farmers apply phosphate fertilizers on agricultural land.The aquatic plants absorb inorganic phosphorus from lower layers of water bodies.Since phosphate salts do not dissolve in water properly, they affect plant growth in aquatic ecosystems.

3. ABSORPTION BY ANIMALS The animals absorb phosphorus from the plants or by consuming plant-eating animals. The rate of the phosphorus cycle is faster in plants and animals when compared to rocks.

4. RETURN OF PHOSPHORUS BACK TO THE ECOSYSTEM

When the plants and animals die, they are decomposed by microorganisms During

this process, the organic form of phosphorus is converted into the inorganic form,

which is recycled to soil and water.

Soil and water will end up in sediments and rocks, which will again release phosphorus by weathering. Thus, the phosphorus cycle starts over.

HUMAN IMPACT ON PHOSPHORUS CYCLE:A number of human activities, use of fertilizers, artificial eutrophication, etc. has a

great impact on the phosphorus cycle.

The phosphorus fertilizers increase the level of phosphorus in the soil. Overuse of

these fertilizers reduces the fertility of the soil and is also harmful to the

microorganisms present in the soil. When these are washed away into the nearby

water bodies, they are hazardous to aquatic life.During the shipping of food from farms to cities, the amount of phosphorus that is

washed away in water causes eutrophication. This leads to the growth of algae.These form algal blooms or die, which is toxic to the aquatic ecosystem.

SUMMARY OF PHOSPHORUS CYCLE:In this biogeochemical cycle, phosphorus moves through the hydrosphere,lithosphere and biosphere. Phosphorus is extracted by the weathering of rocks.Due to rains and erosion phosphorus is washed away in the soil and water bodies.Plants and animals obtain this phosphorus through the soil and water and grow.Microorganisms also require phosphorus for their growth. When the plants and

animals die, they decompose, and the stored phosphorus is returned to the soil and

water bodies which are again consumed by plants and animals and the cycle

continues.

(i) Phosphorus is a major constituent of biological membranes, nucleic acids and

cellular energy transfer systems.

(ii) Many animals also need phosphorus to make shells, bones and teeth.

(iii)The natural reservoir is rock, which contains phosphorus in the form of

phosphates.

(iv)When rocks are weathered, minute amounts of these phosphates dissolve in soil solution and are absorbed by the roots of the plants.

(v)Herbivores and other animals obtain this element from plants.

(vi)Organic waste products and the dead organisms are decomposed by the

phosphate solubilizing bacteria releasing phosphorus.

LET US KNOW WHAT WE HAVE LEARNT!!

PART: A VERY SHORT ANSWER TYPE QUESTIONS: -

a) MULTIPLE CHOICE QUESTIONS:

1) Phosphorus is difficult for plants and animals to access in nature because:

a. It reacts quickly with other elements, like oxygen.

b. Most phosphorus in the environment is bound to carbon, nitrogen, and

hydrogen.

c. It is typically found as a phosphate.

d. Most phosphorus in the environment is stored in reservoirs.

2) Dr. Schindler and his team of researchers at the Experimental Lakes Area noticed a significant growth in algae when they added fertilizer heavy in to the water.

a. phosphorus

b. carbon

c. nitrogen

d. Both a andc

3) Without phosphorus, living beings cannot grow, reproduce, or move.This is because phosphorus:

a. Forms part of the structure of DNA and RNA.

b. Provides structure to cell membranes.

c. Is needed for energy transport in cells.

d. all of the choices

4) Phosphorus does NOT travel through which of the following spheres?

a. lithosphere

b. atmosphere

c. biosphere

d. geosphere

5). Which one of the following is a major constituent of biological membranes, nucleic acids, and cellular energy transfer systems?

a) Potassium

b) Phosphorous

c) Selenium

d) Cobalt

b) TRUE/FALSE:

1. The reservoir of gaseous type of Bio geochemical cycle exists in Lithosphere.

2. The process of Mineralization by microorganisms heips in the release of

inorganic nutrients from the humus.

3. The process of breakdown of detritus by Deritivores is called Mineralization.

c) FILL UPs:

1. Humus serve as the reservoir Of...............0...0.

2. The dead plant parts and animal remains are called...............

ANSWER KEY: PART -A

a) MULTIPLE CHOICE QUESTIONS:

1) (d); most phosphorus in the environment is stored in reservoirs.

2) (d); Bothaandc

3) (d);All of the above

4) (b);Atmosphere

5) (b); Phosphorus

b) TRUE/FALSE:

1. False: The reservoir of gaseous type of Bio geochemical cycle exists in Atmosphere.

2. True

3. False: The process of breakdown of detritus by Deritivores is called

Fragmentation.

c) FILL UPs:

1. Nutrients

2. Detritus

PART: B SHORT ANSWER TYPE QUESTIONS:

1) Define biogeochemical cycle.

2) How does phosphorus return to atmosphere?

PART: C LONG ANSWER TYPE QUESTIONS:

1) Describe various steps of phosphorus cycle.

A168

INTRODUCTION

The carbon cycle is the phenomenon where in carbon compounds one interchanged amongst the geosphere, biosphere, atmosphere and hydrosphere of earth. This cycle depicts the movement of carbon in combined and elemental

states on earth. It is found in the gaseous state in the atmosphere as carbon dioxide, graphite and diamond in the elemental form and as carbonates in minerals in the combined state.

The carbon cycle is most easily studied as two interconnected sub-cycles:

1. One dealing with rapid carbon exchange among living organisms.

2. One dealing with long term cycling of carbon through geographical Processes.

Although we will look at them separately, it’s important to realize. These cycles are

linked. For instance the same pools of atmospheric and oceanic cog .That are

utilized by organisms are also fed and depleted by geological processes.

The Biological Carbon Cycle:Carbon enters all food webs both terrestrial and aquatic through autotrophs or self-feeders. Almost all of these autotrophs are photo synthesizers, such as plant or algae Autotrophs capture carbon dioxide from the air or bicarbonate ions from the water and use them to make organic compounds such as glucose. In Heterotrophs and other Carbon enters all food webs both terrestrial and

aquatic through autotrophs or self-feeders. Almost all of these autotrophs are photo synthesizers, such as plant or algae. Autotropns capture carbon dioxide from the air or bicarbonate ions from the water and use them make organic compounds such as glucose. Heterotrophs and other feeders such as humans,consume the organic modules and the organic carbon is passed through food

chains and webs.

The Geological Carbon cycle:The geological pathway of the carbon cycle takes much longer than the biological pathway describe above. In fact it usually takes a millions of years for carbon to cycle through the geological pathway. Carbon may be stored for long periods of time in the atmosphere , bodies of liquid water mostly oceans-ocean sediment

,Soil, rock , fossil fuels and earth’s interior .

Human impact on the Carbon cycle

Global demand for Earth's limited fossil fuel reserves has risen since the beginning of the Industrial Revolution. Fossil fuels are considered a renewable resource because they are being used up much faster than they can be produced by geological processes. When fossil fuels are burned, carbon dioxide is released into air. Increasing use of fossil fuels has led to elevated levels of atmospheric COz.

DEFORESTATION- The cutting down of forest is also a major contributes to

increasing CO.

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

(A) MULTIPLE CHOICE QUESTIONS:

Q1. The source of carbon to plant in the carbon cycle is:

a) Fossil fuels

b) Carbonate rocks

c) Atmospheric carbon dioxide

d) All of the above

Q2. The role of Bacteria in the carbon cycle is:

a) Breakdown of organic compound

b) Chemosynthesis

c) Photosynthesis

d) Assimilation of nitrogen compound

Q3. The radioactive and very rare carbon isotope is:

a) Carbon -11

b) Carbon -12

c) Carbon -13

d) Carbon-14

B. FILL IN THE BLANKS:

a) In the carbon cycle the human body returns carbon to the atmosphere through b) The most abundant compound found in living organism is is produced by respiration in all living organisms.

C. TRUE AND FALSE:

a) Cellular respiration provides energy for living things.

b) Most of the global warming is due to the perturbation of global carbon

cycle.

ANSWERS KEY: PART-A

A. MULTIPLECHOICEQUESTIONS:

1. (c) The source of carbon to plant in the carbon cycle is atmospheric CO2

2. (a) The role of Bacteria in the carbon cycle is breakdown of organic

compound.

3. (d) Carbon-14 isotope is radioactive and very rare.

B. FILL IN THE BLANKS:

1. Cellular Respiration

2. Water

3. CO,

C. TRUE/FALSE:

1. TRUE

2. TRUE

PART: B SHORTANSWERTYPEQUESTIONS:

Q.1 How can human activities affect a nutrient cycle?

Q.2 Where are short terms carbon stores found?

PART: C LONGANSWERTYPEQUESTIONS:

Q.1 Why do the carbon dioxide level cycle up and down over the Years?

A169

INTRODUCTION

ECOSYSTEM SERVICES:The products of ecosystem processes beneficial to the environment are

termed as ecosystem services.Healthy ecosystems are the base for a wide range of economic, environmental and aesthetic goods and services.The important components of ecosystem services are:

a) Purification of air and water by healthy forest ecosystem.

b) Mitigation of droughts and floods.

c) Cycling of nutrients.

d) Generate fertile soils.

e) Provide wildlife habitat.

f) Maintain biodiversity.

g) Pollinate crops by bees and insects, etc.

h) Carbon-fixation — CO2 is removed naturally and fixed by plants by photosynthesis. All consumers depend upon the energy produced by this process.

i) Release of oxygen by the producers as a by-product in the process of photosynthesis, improves the air quality and supports life on earth.

j) Dispersal of seeds by various abiotic and biotic components of ecosystem.

k} Provide aesthetic, cultural and spiritual values.

1) Grazing of cattle in wild areas reduce pressure on crop plants.

m) Forests provide shelter to the tribal.

n) Control pests by natural predators.

0) Prevent floods.

Robert Constanza and his colleagues have tried to put price tag on nature's life

support services. Researchers have estimated the price to be 33 trillion US dollars a year, while global gross production is only 18 trillion US dollars.

Out of the cost of various ecosystems services, the soil formation accounts for

about 50% and contribution of other services like recreation and nutrient cycling

are less than 10% each.

The cost of climate regulation and habitat for wild life are about 6% each.

LET US KNOW WHAT WE HAVE LEARNT!!

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

(A) MULTIPLE CHOICE QUESTIONS:

1) Cycling of elements in an ecosystem is known as:

a) Geological Cycling

b) Geo-chemical Cycling

c) Bio-geological Cycling

d) Nutrient Cycling

2) Which is not recycled in ecosystem?

a) Nitrogen

b) Water

c) Energy

d) Oxygen

3) Source of maximum sulphur is:

a)Ocean

b)Lakes

c) Land

d) Rocks

4) The cost of ecosystem services is nearly:

a) Twice the value of global gross national product.

b) Half the value of the global GNP.

c) Twice the value GPP

d) Twice the value of NPP

5) Who have tried to put price tag on nature’s life support services?

a) Robert Constanza et al

b) Nile perch et al

c) Herbert Boyer et al

d) RamdeoMisra et al

(B) FILL IN THE BLANKS:

1. Plants are called as because they fix carbon dioxide.

2. In an ecosystem dominated by trees, the pyramid is type.

3. In aquatic ecosystems, the limiting factor for the productivity is

4. Common detritivores ecosystems are .

5. The major reservoir of carbon on earth is

(C) TRUE/FALSE:

1. Robert Constanza and his colleagues put price tag on nature's life

support services.

2. Out of total costs of various ecosystems services , soil formation forms about 50 percent.

ANSWER KEY: PART -A

(A) MULTIPLE CHOICE QUESTIONS:

1.d) Nutrient cycling involves cycling of elements.

2.c) Energy never recycled in an ecosystem.

3. d) Rocks are reservoir of sulphur

4. a) The cost of ecosystem services is twice the value of GNP.

5. a) Robert Constanza et al put price tag on nature's life support services.

(B) FILL IN THE BLANKS:

1. Producers

2. Spindle

3. Light

4. Earthworm

5. Ocean

(C) TRUE/FALSE:

1. True

2. True

PART: B- SHORT ANSWER TYPE QUESTIONS:

1. Write short note on price tag on ecosystem services.

2. What contributions have been made by Robert Constanza?

PART: C- LONG ANSWER TYPE QUESTIONS:

1. Write down services of a healthy forest ecosystem.

A170

INTRODUCTION

Dear students we have studied the whole chapter no.14; ecosystem, in our previous Daily doses starting from DD154 to 169.

Now let us do the NCERT questions of this chapter in this assignment.

1. Fill in the blanks:

(a) Plants are called as.............because they fix carbon dioxide.

(b) In an ecosystem dominated by trees, the pyramid (of numbers)

is.......... type.

IS........e

(d) Common detritivores in our ecosystem are................

(e) The major reservoir of carbon on earth is...............

Ans: (a) Autotrophs

(b) inverted

(d) Earthworms

(e) Oceans

2. Which one of the following has the largest population in a food chain?

(a) Producers

(b) Primary consumers

(d) Decomposers

Ans: (d) Decomposers form the largest population in food chain. They include microbes such as fungi and bacteria.

3. The second trophic level in a lake is-

(a) Phytoplankton

(b) Zooplankton

(d) Fishes

Ans: (b) Zooplankton forms the second trophic level in a lake as they are the primary consumers in food chain that is aquatic, feeding upon phytoplankton. Hence, they hold the second level.

4. Secondary producers are

(a) Herbivores

(b) Producers

(d) None of the above

Ans: (d) There are no secondary producers. Plants are the only producers.They are autotrophs and synthesize their own food through the process of photosynthesis.

5. What is the percentage of photo synthetically act., radiation (PAR), in the incident solar radiation?

(a) 100%

(b) 50 %

(d) 2-10%

Ans: (b)Photosynthetically active radiation or PAR constitutes about 50% of the total incident solar radiation.

6. Distinguish between:

Ans: (a) Grazing food chain and detritus food chain

7. Describe the components of an ecosystem.

Ans: The components of an ecosystem are as follows :

1. Abiotic components or non living components : These include inorganic substances or minerals (standing state or standing quality), organic substances and different climatic conditions like temperature, pH, light, etc.

2. Biotic components or living components :

(a) Autotrophs or producers which have capacity to manufacture their own

food or which can fix radiant energy of sun into chemical energy, e.g.,green plants and photosynthetic bacteria.

(b) Heterotrophs or consumers which are unable to manufacture their own food and depend upon other organisms for their food. These are of following types:

Primary consumers or herbivores which depend upon producers or green plants for their food.

Secondary consumers or carnivores which live upon herbivores.

Top consumers or top carnivores which live upon secondary consumers.

(c) Decomposers or microconsumers decompose dead organic substances of producers and consumers into simple substances and thus continue mineral cycles, e.g., bacteria, fungi, actinomycetes etc.

Figure: Components of ecosystem

8. Define ecological pyramids and describe with examples, pyramids of number and biomass.

Ans: An ecological pyramid is a graphical representation of the relationship

between the different living organisms at different trophic levels.The importance of ecological pyramid can be explained in the following points:

1. They show the feeding of different organisms in different ecosystems.

2. It shows the efficiency of energy transfer.

3. The condition of the ecosystem can be monitored, and any further damage can be prevented.Three types of ecological pyramid exist.

They are as follows:Pyramid of Numbers

In this type of ecological pyramid, the number of organisms in each trophic

level is considered as a level in the pyramid. The pyramid of numbers is

usually upright except for some situations like that of the detritus food chain,

where many organisms feed on one dead plant or animal.Pyramid of Biomass

In this particular type of ecological pyramid, each level takes into account the

amount of biomass produced by each trophic level. The pyramid of biomass is also upright except for that observed in oceans where large numbers of Zooplanktons depend on a relatively smaller number of phytoplanktons.

PYRAMID OF ENERGY:

Pyramid of energy is the only type of ecological pyramid, which is always upright as the energy flow in a food chain is always unidirectional. Also, with

every increasing trophic level, some energy is lost into the environment.

9. What is primary productivity? Give brief description of factors that affect primary productivity.

Ans: Primary productivity of an ecosystem is the amount of energy fixed or biomass synthesized by primary producers or green plants per unit area per unit time during photosynthesis. Factors affecting primary productivity are —

Plant species inhabiting a particular area

Sunlight

Temperature

Soil water

Nutrients

lit deserts, sunlight is abundant but water is scarce or nutrients are lacking.Therefore, in such areas, water & nutrients supply become the limiting factors.

10. Define decomposition and describe the processes and products of decomposition.

Ans: The process by which decomposers break down complex organic remains (dead plants, animal remains and excretions) into inorganic substances like carbon dioxide, water and nutrients is called decomposition.The important steps in the process of decomposition are fragmentation, leaching,

catabolism, humification and mineralisation.

1. Detritivores (e.g., earthworm) break down detritus into smaller particles. This

process is called fragmentation.

2. By the process of leaching, water-soluble inorganic nutrients go down into the

soil horizon and get precipitated as unavailable salts.

3. Bacterial and fungal enzymes degrade detritus into simpler inorganic

substances. The process is called as catabolism.All the above steps in decomposition operate simultaneously on the detritus.

4. Humification and mineralisation occur during decomposition in the soil.Humification leads to accumulation of a dark coloured amorphous substance called humus that is highly resistant to microbial action and undergoes decomposition at an extremely slow rate. Being colloidal in nature it serves as a reservoir of nutrients.

5. The humus is further degraded by some microbes and release of inorganic

nutrients occur by the process known as mineralisation.

11. Give an account of energy flow in an ecosystem.

Ans: Flow of energy in an ecosystem is unidirectional. The ultimate source of

energy is sun. The solar energy is captured by the green plants which utilize it in

synthesizing their own food. The energy fixed by the green plants is transferred

to herbivores which feed on them. The energy is then transferred to higher trophic levels (carnivores). At every step, considerable amount of energy is lost.According to 10% law, only 10% of total energy stored in a trophic level is transferred to the next trophic level of a food chain.

12. Write important features of a sedimentary cycle in an ecosystem.

Ans: The movement of nutrient elements through various components of an

ecosystem takes place by a biogeochemical cycle. It is of 2 types — gaseous and

sedimentary. A nutrient that does not enter the atmosphere easily is said to have

a sedimentary cycle. Sedimentary cycle involve cycling of sulphur, phosphorus

etc. which are located in earth's crust.

Phosphorus is a very important element as it is present in various substances

found in living beings. The cycling of phosphorus in an ecosystem occurs in such

a way that plants obtain it from soil or rocks. The animals or primary consumers

obtain it from plants. Secondary consumers or carnivores take it from herbivores

while omnivores (like man) receive it both from plants and animals. Phosphorus

present in organisms is also released during decomposition.

13. Outline salient features of carbon cycling in an ecosystem.

Ans: Carbon is an important constituent of living matter. Green plants take it in

the form of C02 from atmosphere and fix it as carbohydrates. Carbon which is also present in proteins, fats etc. is transferred to the organisms of other trophic levels. Apart from being released in atmosphere as C02 during respiration,carbon is also released in atmosphere through burning of wood, fossil fuel and decomposition of organic matter by microbes.

A171

INTRODUCTION

The ecosystem is the structural and functional unit of ecology where the living

organisms interact with each other and the surrounding environment.In other words, an ecosystem is a chain of interaction between organisms and their environment.

The term “Ecosystem” was first coined by:

A.G.Tansley, an English botanist, in 1935.

TYPES OF ECOSYSTEM

There are two types of ecosystem

1.) TERRESTRIAL ECOSYSTEMS:

They are exclusively land based ecosystems. They are as follows:

Forest Ecosystems

Grassland Ecosystems

Tundra Ecosystems

Desert Ecosystem

2.) AQUATIC ECOSYSTEM

Aquatic ecosystems are ecosystems present in a body of water. These can be further divided into two types, namely:

Freshwater Ecosystem

Marine Ecosystem

STRUCTURE OF THE ECOSYSTEM

The structure of an ecosystem is characterized by the organization of both biotic and abiotic components. This includes the distribution of energy in our environment.It also includes the climatic conditions prevailing in that particular environment.The structure of an ecosystem can be split into two main components, namely:

Biotic Components

Abiotic Components

The biotic and abiotic components are interrelated in an ecosystem. It is an

open system where the energy and components can flow throughout the boundaries.

FUNCTIONS OF ECOSYSTEM

The functions of the ecosystem are as follows:

1. It regulates the essential ecological processes, supports life systems and renders

stability.

2. It is also responsible for the cycling of nutrients between biotic and abiotic

components.

3. It maintains a balance among the various trophic levels in the ecosystem.

4. It cycles the minerals through the biosphere.

5. The abiotic components help in the synthesis of organic components that involves

the exchange of energy.

PRODUCTIVITY

THE RATE OF BIOMASS PRODUCTION IN AN ECOSYSTEM IS CALLED PRODUCTIVITY (DRY WEIGHT).ITIS EXPRESSED IN TERM OF weight g/m?/yr or energy Keal/m? /yr THERE ARE TWO TYPES OF PRODUCTIVITY:

PRIMARY PRODUCTIVITY:-

Primary productivity is defined as biomass or organic matter produced per unit area over a time period by plants during photosynthesis.

It's expressed in terms of weight g/m? or energy Kcal/m?

It is of two types:-

GROSS PRIMARY PRODUCTIVITY (G.P.P.) :-

It is total production of organic matter produced during photosynthesis (including the organic matter used up in respiration).

NET PRIMARY PRODUCTIVITY (N.P.P) :-It is the amount of stored organic matter in plant tissues after respiratory utilisation.

NET PRIMARY PRODUCTIVITY:

NPP is the available biomass for the consumption to heterotrophs.

SECONDARY PRODUCTIVITY:- It is defined as the rate of formation of new organic matter by

consumers.

DECOMPOSITION:It is physical and chemical breakdown of complex organic remains with the help of organisms called decomposers. Complex organic matter is breakdown into inorganic substances like carbon dioxide, water and nutrients.Dead plant remains such as leaves, bark, flowers and dead remains of animals

including faecal matter constitute detritus. It is the raw material for decomposition.

Microbes then process this detritus which are collectively Known as” saprophytes”.

MECHANISM OF DECOMPOSITION:The important steps in the process of decomposition are

FRAGMENTATION - Detrivores (e.g., Earthworm, Termites, Carrion beetles) break down detritus into smaller particles. This process is called fragmentation.

LEACHING - By the process of leaching, water soluble inorganic nutrients go down into soil horizon, get precipitated as unavailable salts.

CATABOLISM - Decomposers (e.g., bacteria, fungi) secrete digestive enzymes over the detritus. It changes complex organic substance into simple inorganic substances. This process is called catabolism.

HUMIFICATION — Decomposition process give rise to two products-humus and inorganic nutrients (minerals). The processes involved in their formation are called humification and mineralisation respectively.Humification leads to accumulation of a dark colour amorphous substance called humus. It is resistant to microbial action and undergoes decomposition at an extremely slow rate. It is colloidal in nature. So, it serves as a reservoir of nutrients which are released slowly.

MINERALISATION - Itis release of inorganic substance from organic matter. Mineralisation occurs from humus which is further degraded by some microbes.

FACTORS AFFECTING DECOMPOSITION:Decomposition is largely an oxygen requiring process. The rate of decomposition is controlled by several factors like —

CHEMICAL COMPOSITION OF DETRITUS - Ina particular climatic condition, decomposition rate is slower if detritus is rich in lignin and chitin. It is quicker, if detritus is rich in nitrogen and water-soluble substances like sugar.

CLIMATIC FACTORS -

TEMPERATURE

MOISTURE

AEROBIOSIS

SIGNIFICANCES OF DECOMPOSITION:These nutrients can then be taken up by the roots of living plants enabling them to grow and develop, so that organic material is naturally recycled. Virtually nothing goes to waste in nature. Death and decomposition are an essential part of all life cycles on earth. To enable successful birth and growth of young plants and animals, older specimens must die and decompose.

ELOW OF ENERGY IN AN ECOSYTEMExcept for the deep sea hydro-thermal ecosystem, sun is the only source of energy for all ecosystems on Earth. Of the incident solar radiation less than 50 per cent of it is Photosynthetically Active Radiation (PAR). We know that plants and photosynthetic bacteria (autotrophs), fix

Sun’s radiant energy to make food from simple inorganic materials. Plants capture

only 2-10 per cent of the PAR and this small amount of energy sustains the entire

living world. So, it is very important to know how the solar energy captured by plants

flows through different organisms of an ecosystem. All organisms are dependent for

their food on producers, either directly or indirectly. So you find unidirectional flow of energy from the sun to producers and then to consumers.The energy is then

transferred to higher trophic levels (carnivores). At every step, considerable amount of energy is lost. According to 10% law, only 10% of total energy stored in a trophic level is transferred to the next trophic level of a food chain.

Number of individuals at each trophic level is shown in pyramid. The pyramid of

number (for example of grassland) is upright. In this there is a decrease in the

number of organisms.

ECOLOGICAL PYRAMIDS:An ecological pyramid is a graphical representation of the relationship between the different living organisms at different trophic levels.

The importance of ecological pyramid can be explained in the following points:

1. They show the feeding of different organisms in different ecosystems.

2. It shows the efficiency of energy transfer.

3. The condition of the ecosystem can be monitored, and any further damage can be prevented.

Pyramid of Numbers:Number of individuals at each trophic level is shown in pyramid. The pyramid of number (for example of grassland) is upright. In this there is a decrease in the number of organisms starting from primary producers (plants) to top consumers

(carnivores).

In this type of ecological pyramid, the number of organisms in each trophic level is considered as a level in the pyramid.

Pyramid of numbers is “partly” upright sometimes. In this ecosystem, the

producers are large-sized trees, which sit at the base of the number pyramid. The

herbivores, such as elephants and fruit-eating birds, make the primary consumers. They are more in number than the producers. Afterward, the number of individual organisms reduces at each successive trophic level.

The pyramid of numbers is usually upright except for some situations like that of

the detritus food chain, where many organisms feed on one dead plant or animal.An inverted number pyramid is found in parasitic food chains. In these food chains, there’s normally one producer supporting numerous parasites.

Pyramid of energy is the only type of ecological pyramid, which is always upright as the energy flow in a food chain is always unidirectional. Also, with every

increasing trophic level, some energy is lost into the environment.

ECOLOGICAL SUCCESSION:The gradual and predictable changes in the species composition of a given area are collectively called ecological succession. Some species colonise an area during succession, and their populations become more numerous, whereas

populations of other species decline and even disappear.

TYPES OF SUCCESSION:

(a) PRIMARY SUCCESSION:It starts in a barren area, never having vegetation of any type where no living organism ever existed. Some bare primary areas are the newly exposed

seafloor, igneous rocks, sand dunes, new cooled lava sediments, newly submerged areas, etc. As there is no soil and the conditions are too hostile to sustain life thus, the succession is slower. It usually takes several hundred to thousand years for establishing a biotic community depending upon the substratum and the climate.

(b) SECONDARY SUCCESSION:It starts in areas that somehow lost all the living organisms that existed there.Since some soil or sediment is present, succession is faster. Destruction of the previous community can occur due to forest fire, flooded lands, landslides,earthquakes, drought, overgrazed areas, storms, etc. Following such

destruction, the process of succession will occur again from the new environmental conditions.

STAGES OF SUCCESSION: This process involves the following stages, which are as follows:

1. Nudation: Development of bare area or nudation without any form of life. It

may be caused due to several factors like volcanic eruptions, landslides, floods,

erosion, earthquake, forest fire, the spread of disease, etc.

2. Invasion: It is the successful establishment of a species in a barren area.

The arrival of reproductive bodies or propagules of various species and their

settlement in the new or bare area occurs by air, water, etc., known as migration. Adjustment of establishing species with the prevailing conditions is known as ecesis. Then the individual species are multiplied by

reproduction and increase their numbers; this is called aggregation.

3. Competition and coaction: After ggregation, the individuals of a species compete with other organisms for food, space and other resources.The intraspecific and interspecific competition takes place along with interaction with the environment. New invasion by plants and animals takes place.

4. Reaction: The modification of the environment through the influence of

living organisms on it is called reaction.

5. Stabilisation (Climax): The stage at which the final or climax community becomes more or less stabilised for a longer time in that particular environment is known as stabilisation.

TYPES OF SUCCESSIONAL COMMUNITIES:There are three main types of successional communities:

(a) Pioneer community:It is the one that sets first in a barren area. Examples include lichens on rock,phytoplankton and Zooplanktons in ponds. They survive in the most hostile environment.

(b) Climax community:It is the last community in biotic succession, which is relatively stable and is in near equilibrium with the environment of that area called a climax community. Example:forests.

These are the ones that follow the pioneer community. Examples include bryophytes, herbs, shrubs in xerosere, submerged, floating etc., in ponds.They contribute maximum to the formation of a stable community.

The entire series of communities occurring in biotic succession is called sere.

Seral stages or seral communities are individual transitional communities.

BIOGEO CHEMICAL CYCLING or NUTRIENT CYCLING:

The cyclic movement of the nutrients between biotic and abiotic components of the ecosystem is called nutrient cycle.

Organisms need a constant supply of nutrients to grow, reproduce and regulate various body functions.

Nutrient cycling is also referred as biogeochemical cycle.Nutrient cycles are of two types-

Gaseous

Sedimentary

Gaseous cycle is the cycling of carbon, nitrogen etc.Sedimentary cycle is the cycling of sulphur, phosphorous etc.The key difference between gaseous and sedimentary biogeochemical cycles is their main reservoir of the element.In gaseous biogeochemical cycles, the main reservoir of the element is the air or ocean.But, the main reservoir of the element is the Earth crust in sedimentary

biogeochemical cycles.

CARBON CYCLE:

1. Carbon constitutes 49% of dry weight of an organism, 71% of carbon is found in the ocean and 1% of global carbon is in atmosphere.

2. Fossil fuel is also a reservoir of carbon.

3. Some carbon dioxide returns to atmosphere therough respiratory activities of producers and decomposers.

4. Burning of wood, forest fires, combustion of organic matter and fossil fuel, volcanic activity , add carbon dioxide to atmosphere.

5. Deforestation, fossil fuel burning - increase carbon dioxide in atmosphere.

PHOSPHOROUS CYCLE:

1. Phosphorous is a component of biological membrane, nucleic acid and cell energy like ATP.

2. In animals, P is in shells, bone, teeth etc.

3. Rock is a natural reservoir as PO,.

LET US KNOW WHAT WE HAVE LEARNT!!

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

A.MULTIPLE CHOICE QUESTIONS:

1. Ultimate source of energy for living beings is:

a) Carbohydrates

b) Proteins

c) Solar energy

d) ATP

2. Natural reservoir of phosphorous is:

a) Sea water

b) Animal bones

c) Rock

d) Fossils

3. Energy flowin an ecosystem is:

a) Unidirectional

b) Bidirectional

c) All round

d) None of these

4. This entity will be the first one to colonize a bare rock

a) Herbs and shrubs

b) Annual plants

c) Lichens

d) Perennial plants

5. Detritus food chain starts with

a) Algae

b) Bacteria

c) Protozoans

d) Dead organic matter

6. During ecological succession

a) types and numbers of animals remain constant

b) establishment of a new biotic community is fast in its primary phase

c) predictable and gradual changes in species composition take place in a given area

d) changes lead to a community that is in near equilibrium with the environment and is referred to as pioneer community

7. At the producer level, if 20J of energy is trapped, then how much energy will be available to a peacock as food in the subsequent chain?

Plant -> Mice -> Snake -> Peacock

a) 0.2 J

b) 0.02 J

c) 0.002 J

d) 0.0002 J

8. The pyramid of energy is

a) always upright

b) always inverted

c) both upright and inverted

d) none of the above

9. The organisms at the base of food chain are

a) herbivores

b) photosynthetic plants

c) saprophytic plants

d) Carnivores

10. There is no difference between the following

a) trophic level 1 and herbivores

b) primary consumers and herbivores

c) primary consumers and trophic level Il

d) secondary consumers and herbivores

11. Generally the food chain has how many trophic levels?

a)1

b)2

c)4 or more

d)3

12.Zooplanktons forms are

a) primary consumers

b) secondary consumers

c) carnivores

d) primary producers

13.What is the percentage of photo synthetically act., radiation (PAR), in

the incident solar radiation?

a) 100%

b) 50 %

c) 1-5%

d) 2-10%

B. FILL INTHE BLANKS:

1. Vertical distribution of different species occupying different levels in an ecosystem, is called .

2. The rate of production of biomass is termed as .

3. The degradation of humus by some microbes to release the inorganic nutrients, is called

4. of organisms is the beginning of the detritus food chain.

5. is the saprotrophs (heterotrophs) which meet their energy requirements by degrading the detritus.

6. The amount of energy at successive trophic levels.

7. The is measured as biomass or number per unit area.

8. Plants are called as.............because they fix carbon dioxide.

9. In an ecosystem dominated by trees, the pyramid (of numbers)is.......... type.

10. In aquatic ecosystems, the limiting factor for the productivity IS..........

11. Common detrivores in our ecosystem are................

12. The major reservoir of carbon on earth is...............

C. TRUE/FALSE:

1. Birds and animals are the examples of abiotic environment.

2. In an ecosystem; the example of producer is green plant,example of consumer is animal, and example of decomposer is fungi.

3. Coral reefs are the examples of fresh water ecosystem.

4. Aquarium is not a natural ecosystem.

5. The reservoir of gaseous type of Bio geochemical cycle exists in Lithosphere.

6. The process of Mineralization by microorganisms helps in the release of inorganic nutrients from the humus.

7. The process of breakdown of detritus by Deritivores is called Mineralization.

ANSWER KEY: PART-A

A.MULTIPLE CHOICE QUESTIONS:

1. c) Solar energy

2. c) Rock

3. a) Unidirectional

4. c) Lichens

5. d) Dead organic matter

6. d) changes lead to a community that is in near equilibrium with the environment and is referred to as pioneer community

7. b) 0.02 J

8. a) always upright

9. b) photosynthetic plants

10.b) primary consumers and herbivores

11.d) 3

12.a) primary consumers

13.b) 50 %

B. FILL IN THE BLANKS:

1. Stratification

2. Productivity

3. Mineralization

4. Death

5. Decomposers

6. Decreases

7. Standing crop

8. Autotrophs

9. Inverted

10. Sunlight

11. Earthworms

12. Oceans

C.TRUE/FALSE:

1. False: birds and animals are examples of biotic environment. All living organisms constitute biotic environment and non-living

components are together called abiotic components.

2. True

3. False: coral reefs are examples of marine ecosystem

4. True: Aquarium is an artificial ecosystem

5. False: The reservoir of gaseous type of Bio geochemical cycle exists in Atmosphere.

6. True

7. False: The process of breakdown of detritus by Detrivores is called

Fragmentation.

PART: B SHORT ANSWER TYPE QUESTIONS:

1. Describe the components of an ecosystem.

2. Differentiate between primary and secondary productivity.

3. Why the pyramid of energy is always upright?

4. What is the difference between a food chain and food web?

5. What is humification?

6. What is ecological succession? Write various events that occur during ecological succession.

PART: C LONG ANSWER TYPE QUESTIONS:

1. Give an account of energy flow in an ecosystem.

2. Outline salient features of carbon cycling in an ecosystem.

Plus Two

Saturday 30 January 2021

Chapter 14 Ecosystem

Chapter 14 Ecosystem

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