Lesson 15 : Our Environment

 Lesson: Our Environment

Question: 1

Which of the following groups contain only biodegradable items?

(a) Grass, flowers and leather

(b) Grass, wood and plastic

(c) Fruit-peels, cake and lime-juice

(d) Cake, wood and grass

Solution:

c and d

Question: 2

Which of the following constitute a food chain?

(a) Grass, wheat and mango

(b) Grass, goat and human

(c) Goat, cow and elephant

(d) Grass, fish and goat

Solution:

b

Question: 3

Which of the following are environment-friendly practices?

(a) Carrying cloth-bags to put purchases in while shopping

(b) Switching off unnecessary lights and fans

(c) Walking to school instead of getting your mother to drop you on her scooter

(d) All of the above

Solution:

d

Question: 4

What will happen if we kill all the organisms in one trophic level?

Solution:

If we kill all the organisms of one trophic level, it will disturb the ecosystem and an imbalance will be created there.

Example: Let’s consider a food chain:

 Grass → Deer → Tiger

If all the tigers are killed, then the population of deer will increase. This will cause over-grazing. Over-grazing will lead to deforestation followed by soil erosion, loss of fertility of the land and so on.

Question: 5

Will the impact of removing all the organisms in a trophic level be different for

different trophic levels?

Can the organisms of any trophic level be removed without causing any damage to the ecosystem?

Solution:

The impact of removing all the organisms in a trophic level will be different for

different trophic levels. For example, if the primary producers are removed, then the primary and secondary consumers too will not survive.

However, if the secondary consumers were removed, then the impact on the primary producers and primary consumer would be initially less.

However, it needs to be understood that there is long-term impact of removing any tropic level, as it would disturb the entire ecosystem.

Question: 6

What is biological magnification?

Will the levels of this magnification be different at different levels of the ecosystem?

Solution:

The phenomena of accumulation or increase in the concentration of some toxic substances at each trophic level are known as biological magnification.

The level of biological magnification is different at different trophic levels. This can be understood by an example:

A pesticide is sprayed in the field to protect the plants from the pests. The pesticide is a non-biodegradable substance. The plant absorbs this pesticide.

When herbivorous animals eat the plant food, the pesticide gets in their bodies.

Human beings are omnivores; they eat the plant food as well as the herbivores. Therefore, he gets the pesticide both from the plant food as well as from the animals. Thus, the concentration of the pesticide becomes more in the higher tropic level.

Question: 7

What are the problems caused by the non-biodegradable wastes that we generate?

Solution:

The problems caused by non-biodegradable wastes are:

a)   Increase in pollution

b)   Increase in disease

c)   Inability of many organisms to survive

d)   Biological magnification

Question: 8

If all the waste we generate is biodegradable, will this have no impact on the

environment?

Solution:

If all the waste generated is biodegradable, the amount of waste would be more as compared to what the decomposers can break down. Therefore, less waste would be decomposed. Flies will breed on the wastes and would lead to the spread of diseases. The foul smell from the wastes will be unbearable for people living nearby.

Question: 9

Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this damage?

Solution:

The ozone layer is very important for us as this layer absorbs most of the harmful ultraviolet radiations and protects us from the harmful effects of ultraviolet rays which cause skin cancer and cataracts.

The depletion of ozone layer will allow the ultra violet rays to pass through the earth’s atmosphere and reach us. The depletion of ozone layer is caused by chemicals called chlorofluorocarbons.

To limit the damage, the release of CFCs should be controlled.

Following steps should be taken to prevent the damage of the ozone layer:

v  Use unleaded gasoline in vehicles.

v  Reduce the use of private vehicles in favour of public transport.

v  Use eco-friendly household cleaning products.

v  Avoid using pesticides.

v  Develop stringent regulations for rocket launches.

v  Ban the use of dangerous nitrous oxide.

v  Replace CFCs with HCFCs.

v  Improve the containment of chemicals to prevent leaks, evaporation and emissions of unintended by-products from factories.

Lesson: Our Environment

Question: 1

Which one of the following is an artificial ecosystem?

(a) Pond

(b) Crop field

(c) Lake

(d) Forest

Solution:

b

Question: 2

In a food chain, the third trophic level is always occupied by:

(a) Carnivores

(b) Herbivores

(c) Decomposers

(d) Producers

Solution:

a

Question: 3

An ecosystem includes:

(a) All living organisms

(b) Non-living objects

(c) Both living organisms and non-living objects

(d) Sometimes living organisms and sometimes non-living objects

Solution:

c

Question: 4

In the given food chain, suppose the amount of energy at fourth trophic level is 5 kJ, what will be the energy available at the producer level?

Grass → Grasshopper → Frog → Snake → Hawk

(a) 5 k J

(b) 50 k J

(c) 500 k J

(d) 5000 k J

Solution:

d

Question: 5

Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as:

(a) Eutrophication

(b) Pollution

(c) Bio magnification

(d) Accumulation

Solution:

c

Question: 6

Depletion of ozone is mainly due to:

(a) Chlorofluorocarbon compounds

(b) Carbon monoxide

(c) Methane

(d) Pesticides

Solution:

a

Question: 7

Organisms which synthesise carbohydrates from inorganic compounds using radiant energy are called:

(a) Decomposers

(b) Producers

(c) Herbivores

(d) Carnivores

Solution:

b

Question: 8

In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in the form of:

(a) Heat energy

(b) Light energy

(c) Chemical energy

(d) Mechanical energy

Solution:

c

Question: 9

Organisms of a higher trophic level which feed on several types of organisms belonging to a lower trophic level constitute the:

(a) Food web

(b) Ecological pyramid

(c) Ecosystem

(d) Food chain

Solution:

a

Question: 10

Flow of energy in an ecosystem is always:

(a) Unidirectional

(b) Bidirectional

(c) Multi directional

(d) No specific direction

Solution:

a

Question: 11

Excessive exposure of humans to UV-rays results in:

(a) Damage to immune system

(b) Damage to lungs

(c) Skin cancer

(d) Peptic ulcers

(a) (i) and (ii)

(b) (ii) and (iv)

(c) (i) and (iii)

(d) (iii) and (iv)

Solution:

c

Question: 12

In the following groups of materials, which group(s) contains only non-biodegradable items?

(a) Wood, paper, leather

(b) Polythene, detergent, PVC

(c) Plastic, detergent, grass

(d) Plastic, bakelite, DDT

(a) (iii)

(b) (iv)

(c) (i) and (iii)

(d) (ii) and (iv)

Solution:

d

Question: 13

Which of the following limits the number of trophic levels in a food chain?

(a) Decrease in energy at higher trophic levels

(b) Sufficient food supply

(c) Polluted air

(d) Water

Solution:

a

Question: 14

Which of the statement is incorrect?

(a) All green plants and blue green algae are producers

(b) Green plants get their food from organic compounds

(c) Producers prepare their own food from inorganic compounds

(d) Plants convert solar energy into chemical energy

Solution:

b

Question: 15

Which group of organisms are not constituents of a food chain?

        I.             Grass, lion, rabbit, wolf

     II.             Plankton, man, fish, grasshopper

  III.             Wolf, grass, snake, tiger

  IV.             Frog, snake, eagle, grass, grasshopper

(a) (i) and (iii)

(b) (iii) and (iv)

(c) (ii) and (iii)

(d) (i) and (iv)

Solution:

c

Question: 16

The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about:

(a) 1 %

(b) 5 %

(c) 8 %

(d) 10 %

Solution:

a

Question: 17

In the given figure the various trophic levels are shown in a pyramid.

At which trophic level is maximum energy available?

(a) T4

(b) T2

(c) T1

(d) T3

Solution:

c

Question: 18

What will happen if deer is missing in the food chain given below?

Grass → Deer → Tiger

(a) The population of tiger increases

(b) The population of grass decreases

(c) Tiger will start eating grass

(d) The population of tiger decreases and the population of grass increases

Solution:

d

Question: 19

The decomposers in an ecosystem

(a) Convert inorganic material, to simpler forms

(b) Convert organic material to inorganic forms

(c) Convert inorganic materials into organic compounds

(d) Do not breakdown organic compounds

Solution:

b

Question: 20

If a grass hopper is eaten by a frog, then the energy transfer will be from

(a) Producer to decomposer

(b) Producer to primary consumer

(c) Primary consumer to secondary consumer

(d) Secondary consumer to primary consumer

Solution:

c

Question: 21

Disposable plastic plates should not be used because

(a) They are made of materials with light weight

(b) They are made of toxic materials

(c) They are made of bio-degradable materials

(d) They are made of non-biodegradable materials

Solution:

d

Short Answer Questions

Question: 22

Why is improper disposal of waste a curse to environment?

Solution:

Waste materials produced by various activities of human beings can be categorised as biodegradable waste and non- biodegradable waste.

Accumulated biodegradable waste causes intolerable smell during the process of decomposition. Such wastes, if allowed to decompose in populated area or near water bodies may result in epidemic.

There is a need to dispose non-biodegrade resources properly. For example, improper disposal of plastics may prevent seepage of underground water.

Therefore, any improper disposal of waste in an area affects the living beings living around that area.

Question: 23

Write the common food chain of a pond ecosystem.

Solution:

A common food chain in a pond ecosystem can be:

Algae---------Protozoa-------Small fish---------Large fish/animals

Question: 24

What are the advantages of cloth bags over plastic bags during shopping?

Solution:

The advantages of cloth bags over plastic bags during shopping are given below:

(a)   Cloth bags are made up of biodegradable materials.

(b)   Cloth bags can carry more materials.

(c)   Cloth bags do not pollute environment.

(d)   Cloth bags can be reused.

Question: 25

Why are crop fields known as artificial ecosystems?

Solution:

All the biotic and abiotic components of the ecosystem in a crop field are controlled by the famer. A farmer decides:

·         which plant to grow,

·         how much to grow,

·         when to harvest,

·         which pesticides to use, etc.

Therefore, crop fields are examples of an artificial ecosystem.

Question: 26

Differentiate between biodegradable and non-biodegradable substances. Cite examples.

Solution:

Substances that can be broken down into simpler substances by biological processes are said to be biodegradable. Examples, wood, paper, food scrapes, egg shell, etc. These substances can be recycled.

Substances that cannot be broken down into simpler ones by biological processes are said to be non-biodegradable. Examples, plastic, DDT, silver foil, rubber, aluminium, polythene bags, etc. These substances cannot be recycled.

Question: 27

Suggest one word for each of the following statements/definitions

(a) The physical and biological world where we live in

(b) Each level of food chain where transfer of energy takes place

(c) The physical factors like temperature, rainfall, wind and soil of an ecosystem

(d) Organisms which depend on the producers either directly or indirectly for

food

Solution:

(a) Biosphere

(b) Trophic level

(c) Abiotic factors

(d) Consumers or heterotrophs

Question: 28

Explain the role of decomposers in the environment?

Solution:

The decomposers help in decomposing dead bodies of animals and plants. This not only helps in cleaning the environment but also plays an important role in recycling nutrients in the soil.

Question: 29

Select the mis-matched pair in the following and correct it.

(a) Biomagnification —$$ Accumulation of chemicals at the successive trophic

levels of a food chain

(b) Ecosystem —$$ Biotic components of environment

(c) Aquarium —$$ A man-made ecosystem

(d) Parasites —$$ Organisms which obtain food from other living organisms

Solution:

(b) Correction: Ecosystem consists of both biotic and abiotic components of the environment

Question: 30

We do not clean ponds or lakes, but an aquarium needs to be cleaned. Why?

Solution:

An aquarium is an artificial ecosystem which needs to be maintained by us. A pond or a lake is a natural ecosystem which is self-sustaining.

Long Answer Questions (8)

Question: 31

Indicate the flow of energy in an ecosystem. Why is it unidirectional?

Justify.

Solution:

Generally, the flow of energy is:

Sun → primary producer → primary consumer (herbivore) → secondary consumer (carnivore) →Tertiary consumer (carnivores)

Energy is transferred along food chains from one tropic level to another. It does not revert back. The amount of available energy decreases from one stage to the next. Thus, it is unlikely for the energy to flow in the reverse direction.

Hence, it is said to be unidirectional.

Question: 32

What are decomposers? What will be the consequence of their absence in an ecosystem?

Solution:

Decomposers are non-green microorganisms. The decomposers help in decomposing dead bodies of animals and plants. They clean the environment and recycle nutrients in the soil.

In the absence of decomposers not only will the garbage of wastes pile up, there will be increase in pollution and there will be no natural replenishment of soil.

Question: 33

Suggest any four activities in daily life which are eco-friendly.

Solution:

Any four activities in daily life which are eco-friendly are:

a)   Use of paper bag/cloth bag instead of plastic /polythene bag

b)   Plantation of trees

c)   Switching of lights/fans when not in use

d)   Avoiding waste of water through taps, leakage in pipes, etc.

Question: 34

Give two differences between food chain and food web.

Solution:

Food chain	Food Web
A food chain is a series of living organisms that depend on the others in the chain for their sources of nutrients and energy.	A food web shows how different food chains are connected to each other and how the energy flows through an ecosystem.
It is a simple chain of organisms at different tropic levels.	It is a complex chain of many interlinked food chains.

Question: 35

Name the wastes which are generated in your house daily. What measures would you take for their disposal?

Solution:

Some of the wastes generated in our house and measures taken for their disposal:

Wastes	Measures to dispose
Kitchen waste	Preparing a compost pit for kitchen waste
Paper wastes like newspaper, bags etc.	Separating biodegradable and non-biodegradable wastes and disposing them accordingly. Paper wastes should be given for recycling.
Vegetable/fruit peels	These should be disposed near plants/trees for decomposition.
Leakage of water through pipes and taps.	Repair of pipes and taps on a regular basis should be done.

Question: 36

Suggest suitable mechanism(s) for waste management in fertiliser industries.

Solution:

Sewages and harmful gases are the main wastes produced in a fertilizer factory.

Some of the steps that can be taken for the waste management are:

Using catalytic converter: Catalytic converters should be fitted in the chimneys for reducing the amount of gaseous pollutants.

Treatment of sewage: Sewage from the factory should be sent to effluent treatment plant. Once effluent is treated, the clean water can then be sent to the nearest water bodies and the sludge can be allowed to decompose.

Question: 37

What are the by-products of fertiliser industries? How do they affect the environment?

Solution:

The by-products of fertiliser industries are gases like SO₂ and NO. These are harmful to us. They cause air pollution and are responsible for acid rain.

Question: 38

Explain some harmful effects of agricultural practices on the environment.

Solution:

Modern agricultural practices include use of fertilisers and chemicals for increasing agricultural outputs. This has a negative impact on the environment. Some of these impacts are:

(a) Excessive use of fertilizers changes the soil composition. As a result, many useful microbes are disappearing from the soil.

(b) Too much use of non-biodegradable chemical pesticides has resulted in the biological magnification.

(c) The soil loses its fertility when only one type of crop is being grown for a number of years.

(d) Excessive use of ground water has impacted the survival of living organisms depending on the water.

(e) Use of pesticides has resulted in the extinction of many insects and plants that were found in the field.

Lesson: Our Environment

Question: 1

Why are some substances biodegradable and some non-biodegradable?

Solution:

Substances that can be broken into simpler soluble forms or decomposed by microorganism are biodegradable substances whereas substances that cannot be decomposed to simpler substances are non-biodegradable substances.

So, whether a substance can be decomposed or not make it biodegradable or non-biodegradable.

Question: 2

Give any two ways in which biodegradable substances would affect the environment.

Solution:

(a) Biodegradable substances such as, plant parts, kitchen wastes, etc. can be used as humus after composting to enhance the fertility of the soil.

(b) Carbon is an important constituent of the biodegradable substances. Carbon is released into the atmosphere after the substances are decomposed.

Question: 3

Give any two ways in which non-biodegradable substances would affect the environment.

Solution:

(a) Non-biodegradable wastes like plastic articles, glass articles, etc. are major pollutants of the environment.

(b) Non-biodegradable wastes like DDT, can pass from plants to animals and finally to human beings along the food chain.

Question: 4

What are trophic levels? Give an example of a food chain and state the different trophic levels in it.

Solution:

The trophic level of an organism in a food chain is the number of steps it is away from the beginning of the chain. Typically, plants are at trophic level 1, the primary consumers form the second trophic level, the secondary consumers form the third, and the tertiary consumers form the fourth trophic level.

In the given image, grass is the producer. It is eaten by the grasshopper. So, the grasshopper is the primary consumer. Then the grasshopper is eaten by the frog, so the frog is the secondary consumer and lastly the frog is eaten up by the snake. Hence, the snake is the tertiary consumer.

Question: 5

What is the role of decomposers in the ecosystem?

Solution:

The decomposers break down the biodegradable substances into simpler forms. This helps cleaning the environment and bringing nutrients back to the soil.

Question: 6

What is ozone and how does it affect any ecosystem?

Solution:

Ozone is a gas molecule made up of three oxygen atoms. The ozone layer is a layer of gas present in the stratosphere. The layer is only three to five millimetres thick and protects us from the harmful effects of the ultraviolet rays which cause skin cancer and cataracts.

Question: 7

How can you help in reducing the problem of waste disposal? Give any two methods.

Solution:

(a) Using catalytic converter: Catalytic converters should be fitted in the chimneys for reducing the amount of gaseous pollutants coming from the factories.

(b) Treatment of sewage: Sewage from the factories should be sent to the effluent treatment plants. Once the effluent is treated, the clean water can then be sent to the nearest water bodies and the sludge can be allowed to decompose.

Questions

Q1	What are the two components of an ecosystem?

Q2	Give two examples of biodegradable materials we get from animals.

Q3	Give two examples of biodegradable materials we get from plants.

Q4	Why should biological magnification be avoided?

Q5	A housing society is an artificial ecosystem. Why?

Q6	In which tropic level is the 10% law of energy transfer not applicable?

Q7	Why should we avoid ozone layer depletion?

Q8	Give an example of food chain in grassland.

Q9	Why are the decomposers an important part of our ecosystem?

Q10	How can the restricted use of fertilisers most likely prevent acid rains?

Q11	What is an ecosystem?

Q12	Why should we avoid the use of substances like silver foil, ball point refill, iron nails?

Q13	Mention the different of types of wastes produced.

Q14	How ozone is formed at the higher levels of the atmosphere?

Q15	A school introduces jute bags for the students, replacing the plastic bags. Why should the school be lauded?

Q16	A food web is considered to be a complex chain of interlinked food chain. Justify the statement.

Q17	What are autotrophs and heterotrophs?

Q18	Give an example to illustrate that the flow of energy from one trophic level to another is always unidirectional in an ecosystem.

Q19	Given below is a list of substances. Aluminum cans, Jute, Grass, Fruit, Flowers, Cakes Cottons, Synthetic fibre, Silver foils. Categorise the substances as biodegradable and non-biodegradable. How are these two categories different?

Q20	Why should food web, not food chain be used to show the energy flow between various components?

Questions

Q1	What are the two components of an ecosystem?

A1	Biotic component and abiotic component

Q2	Give two examples of biodegradable materials we get from animals.

A2	(a) Animal bone (b) Leather

Q3	Give two examples of biodegradable materials we get from plants.

A3	(a) Cotton (b) Jute

Q4	Why should biological magnification be avoided?

A4	Accumulation of poisonous substances to the consumers at higher level in the food chain is called biological magnification. These poisonous substances are non-biodegradable and are harmful.

Q5	A housing society is an artificial ecosystem. Why?

A5	A housing society is created and maintained by people. In these, biotic and abiotic components are manually created. Hence, they are called as artificial ecosystems.

Q6	In which tropic level is the 10% law of energy transfer not applicable?

A6	The various levels in the food chain at which the transfer of energy and food takes place are called the trophic levels. The energy that is being transferred from one to another level is decreased by 10%. In the first tropic level, only 1% of the energy available is utilized.

Q7	Why should we avoid ozone layer depletion?

A7

Ozone is a triatomic molecule which contains three oxygen atoms. This ozone gas forms the ozone layer in the stratosphere above the earth which protects human beings and plants from the harmful UV radiation. Depletion of the ozone layer will lead to leakage of harmful UV radiation to the earth’s surface. This has a long term effect on human and other living beings.

Q8	Give an example of food chain in grassland.

A8

Q9	Why are the decomposers an important part of our ecosystem?

A9	Decomposers break down the complex organic compounds present in dead organisms like dead plants and animals and their products like faces, urine, etc. into simpler substances. They make these available for reuse by the plants. They act as cleansing agents and help soil recover its nutrients.

Q10	How can the restricted use of fertilisers most likely prevent acid rains?

A10	Most of the fertilizers are NPK (Nitrogen, Phosphate, and Potassium) based. The harmful by-products of these types of fertilizers are gases such as SO2 and NO. They cause extensive air pollution and are responsible for acid rain. Restricted or no use of fertilisers may help in preventing acid rain.

Q11	What is an ecosystem?

A11	An ecosystem is the community in which living organisms live together and interact with each other and also with other non-living constituents of the environment. The living organisms are called the biotic components and the non- living or physical factors are the abiotic components.

Q12	Why should we avoid the use of substances like silver foil, ball point refill, iron nails?

A12	Silver foil, ball point refill, iron nails are non-biodegradable substances. Non bio-degradable substances are man-made and are not easily broken down by natural way. These substances cause pollution, kill animals, create imbalance in the ecosystem and form bio-magnifications.

Q13	Mention the different of types of wastes produced.

A13

Wastes are produced at various places. They are: a. Hospital wastes – Human tissue, cotton, syringes, needles and plastic bottles b. Household and kitchen wastes – Rotten vegetables, spoiled foods, fruit peels, paper, plastic and paper bags, etc. c. Industrial wastes – Untreated chemicals, dyes, poisonous gases, etc.

Q14	How ozone is formed at the higher levels of the atmosphere?

A14

Q15	A school introduces jute bags for the students, replacing the plastic bags. Why should the school be lauded?

A15

Jute bags are biodegradable whereas plastic bags are non-biodegradable. A comparison of two is given below:   Jute bags Plastic bags Do not pollute environment Pollute environment Reusable Non-reusable From here it is clear that the school is environment friendly and promotes conservation of resources.

Q16	A food web is considered to be a complex chain of interlinked food chain. Justify the statement.

A16

The statement can be explained with an example. Given below is a food web. It consists of a number of food chains like: a. Plant------grasshopper------hawk b. Plant---------grasshopper--------spider-----hawk c. Plant---------grasshopper--------spider-----shrew------hawk d. Plant---------grasshopper--------spider-----shrew---------owl It is clear from the example that a food web is considered to be a complex chain of interlinked food chain.

Q17	What are autotrophs and heterotrophs?

A17

Producers are called autotrophs. Producers belong to the first trophic level in the food chain. Examples of producers are plants, trees, blue green algae, etc. Consumers are called heterotrophs. Consumers are further classified as primary, secondary and tertiary consumers according the trophic level that they belong to in the food chain.

Q18	Give an example to illustrate that the flow of energy from one trophic level to another is always unidirectional in an ecosystem.

A18

Consider the food chain. Flower → caterpillar → frog → snake → owl The flow of energy is always decided by who eats whom. It is clear that the caterpillars eat flowers but flowers do not eat caterpillars. In the same way the organism at the third tropic level (frog) eats the organism at the second tropic level (caterpillar) and so on. Therefore, it can be concluded that: i. Flow of energy is from the lower trophic level to the higher trophic level and not vice versa. ii. Availability of energy at one trophic level decreases in the higher tropic level making it impossible to flow in the reverse direction. Thus, the flow of energy from one trophic level to another is always unidirectional in an ecosystem.

Q19	Given below is a list of substances. Aluminum cans, Jute, Grass, Fruit, Flowers, Cakes Cottons, Synthetic fibre, Silver foils. Categorise the substances as biodegradable and non-biodegradable. How are these two categories different?

A19

Biodegradable substances: jute, grass, fruit, flowers, cakes and cottons. Non-biodegradable substances: synthetic fibre, aluminium cans and silver foils.   Biodegradable substances Non-Biodegradable substances 1.      Decomposed by microorganisms Cannot be decomposed by microorganisms. 2.      Environment friendly Pollutes and harms the environment.

Q20	Why should food web, not food chain be used to show the energy flow between various components?

A20

Energy is transferred from one tropic level to the other through the food being eaten by living beings. a. The green plants convert about 1% of the energy of sunlight that falls on their leaves and convert it into food energy. b. Just 10% of this energy is available to the next tropic level, i.e. primary consumers.   At each subsequent level, only 10% of the energy entering a particular tropic level is available for the next level. Since a little energy is available for the next level of consumers, food chains generally consist of only three or four steps. In an ecosystem, there are larger numbers of individuals at the lower trophic levels. The greatest number of individuals are the producers. Each organism is generally eaten up by two or more other kinds of organisms in an ecosystem. This complex relationship cannot be shown just by one food chain. We require a food web to represent the complexities associated with the transfer of energy from tropic level to another.