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Chapter 5

Ecosystems

Class 8 - Living Science Biology Ratna Sagar


Think and answer

Question 1

Decomposers are also called nature's scavengers. Why?

Answer

Decomposers are known as nature's scavengers because they help to clean the environment by decomposing the dead remains of the plants and animals.

Check your progress

Question 1

Green plants are called producers or ............... .

Answer

Green plants are called producers or autotrophs.

Question 2

Human beings and cockroaches are ............... .

Answer

Human beings and cockroaches are Omnivores.

Question 3

............... are also called nature's scavengers.

Answer

Decomposers are also called nature's scavengers.

Tick the most appropriate answer

Question 1

The study of the interaction between living organisms and their environment is called

  1. physiology
  2. zoology
  3. environment
  4. ecology

Answer

ecology

Reason — The study of the interaction between living organisms and their environment is called ecology.

Question 2

Which of the following are producers?

  1. carnivores
  2. herbivores
  3. green plants
  4. omnivores

Answer

green plants

Reason — Only green plants can trap energy from the sun and make their own food in the presence of sunlight using water, minerals and carbon dioxide. Thus, green plants are called producers or autotrophs.

Question 3

They break down the complex organic compounds present in the remains of dead plants and animals into simpler substances.

  1. producers
  2. primary consumers
  3. decomposers
  4. herbivores

Answer

decomposers

Reason — Decomposers are the nature's scavengers as they break down the complex organic compounds present in the remains of dead plants and animals into simpler substances.

Question 4

A series of organisms that are linked to each other through a process of eating and being eaten form a

  1. food net
  2. food chain
  3. food web
  4. none of these

Answer

food chain

Reason — A series of organisms that are linked to each other through a process of eating and being eaten form a food chain.

Question 5

The plants or the producers which fix the solar energy constitute the

  1. second trophic level
  2. third trophic level
  3. fourth trophic level
  4. first trophic level

Answer

first trophic level

Reason — All food chains start with plants as only green plants can trap energy from the sun and convert it into chemical energy present in food. Hence, they constitute first trophic level of any food chain.

Question 6

Animals depend on plants for

  1. food alone
  2. shelter alone
  3. carbon dioxide
  4. food and oxygen

Answer

food and oxygen

Reason — Animals depend on plants and trees for food, oxygen and shelter.

Question 7

Animals that are active at night are called

  1. diurnal animals
  2. nocturnal animal
  3. aquatic animals
  4. terrestrial animals

Answer

nocturnal animal

Reason — Animals that are active at night are called nocturnal animals.

Question 8

Which of these is not a terrestrial ecosystem

  1. pond
  2. grassland
  3. desert
  4. mountain

Answer

pond

Reason — Pond is an aquatic ecosystem.

Fill in the blanks

Question 1

The term ecology was first used by a German scientist named ............... .

Answer

The term ecology was first used by a German scientist named Ernst Haeckel.

Question 2

Plants, animals and microorganisms constitute the ............... components of an environment.

Answer

Plants, animals and microorganisms constitute the biotic components of an environment.

Question 3

Temperature, light, air and water are the ............... components of the environment.

Answer

Temperature, light, air and water are the abiotic components of the environment.

Question 4

Green plants which make their own food are called ............... .

Answer

Green plants which make their own food are called producers or autotrophs.

Question 5

Living organisms that cannot make their own food are called ...............or ............... .

Answer

Living organisms that cannot make their own food are called consumers or heterotrophs.

Question 6

............... are carnivores that feed on dead animals.

Answer

Scavengers are carnivores that feed on dead animals.

Question 7

............... eat both plants and animals.

Answer

Omnivores eat both plants and animals.

Question 8

An interaction in which one organism captures and eats another organism is called ............... .

Answer

An interaction in which one organism captures and eats another organism is called predation.

Differentiate between

Question 1

environment and ecosystem

Answer

Sl.
No.
EnvironmentEcosystem
1.Environment refers to the variety of living and non-living things present around an organism.All the interacting organisms in an area together with its non-living components constitute an ecosystem.
2.The environment refers to surrounding.The ecosystem refers to community of living organisms and their interaction with biotic and abiotic components of environment.

Question 2

producers and consumers

Answer

Sl.
No.
ProducerConsumer
1.The green plants that make their own food in the presence of sunlight, water and carbon dioxide are called producers.Living organisms that cannot make their own food but consume either plants or other animals are called consumers.
2.They are called Autotrophs.They are called Heterotrophs.
3.They constitute the first trophic level.They constitute the second, third or fourth trophic levels.
4.Example: Green plants, AlgaeExample: Cow, Lion

Question 3

Consumers and decomposers

Answer

Sl.
No.
ConsumersDecomposers
1.The organisms that cannot make their own food but consume either plants or animals are called consumers.Microscopic organisms that feed on the dead bodies of organism and decaying organic matter are called decomposers.
2.They get energy by eating other organisms.They derive their energy by breaking down the complex organic compounds present in the dead plants and animals.
3.They maintain the ecological balance.They help to maintain the nutrient cycle by recycling of the nutrients.
4.They are called heterotrophs.They are called nature's scavengers.

Question 4

Food chain and food web

Answer

Sl.
No.
Food ChainFood Web
1.A series of organisms that are linked to each other through a process of eating and being eaten form a food chain.Several food chains are interconnected to form a food web.
2.It is basic chain showing flow of energy.It is a complex network showing flow of energy at different trophic levels in different food chains.

Define these terms

Question 1

Ecosystem

Answer

Ecosystem — All the living organisms in a given area that interact with each other, as well as with biotic components and abiotic components of the environment constitute an ecosystem.

Question 2

Food chain

Answer

Food chain — A series of organisms linked by the process of eating and being eaten which shows linear flow of energy through different trophic levels is called Food chain.

Question 3

Food web

Answer

Food web — A network of various interconnected food chains which show complex feeding relationships is called food web.

Question 4

Trophic level

Answer

Trophic level — The various steps representing organisms in a food chain at which transfer of food and energy takes place are called trophic levels.

Question 5

Symbiosis

Answer

Symbiosis — Symbiosis is a close, long-term relationship between two organisms in which both the interacting organisms benefit.

Question 6

Parasitism

Answer

Parasitism — Parasitism is a relationship where an organism called the parasite lives in or on other organism called the host and derives food from its host. In such interaction, the parasite benefits and the host is harmed.

Find the odd one out. Give reasons

Question 1

lion, cow, leopard, tiger

Answer

Cow

Reason — Cow is herbivores but all others are carnivores.

Question 2

deer, goat, vulture, horse

Answer

vulture

Reason — Vulture is scavenger while others are herbivores.

Question 3

bear, cow, crow, human being

Answer

Cow

Reason — Cow is herbivore but others are omnivores.

Question 4

fungus, bacterium, cow, worm

Answer

cow

Reason — Cow is a herbivore while others are not.

Answer the following in short

Question 1

What are the main components of an ecosystem?

Answer

The main components of an ecosystem are Biotic (living) and abiotic (non-living).

Question 2

Give two examples of omnivores.

Answer

Two examples of omnivores are

  1. Human beings
  2. Crow

Question 3

Give an example of a food chain.

Answer

A food chain operating in a grassland ecosystem is :

Corn → Rat → Snake → Eagle

Question 4

Are carnivores primary or secondary consumers?

Answer

Carnivores are secondary consumers.

Question 5

What kinds of organisms are first level consumers?

Answer

The herbivores that feed on the green plants (producers) are first level consumers.

Question 6

Define predation.

Answer

An interaction in which one organism (predator) captures and eats another organism (prey) is known as predation.

Question 7

Give two examples of man-made ecosystem.

Answer

Two examples of man-made ecosystem are:

  1. Parks
  2. Crop-Fields

Answer the following in detail

Question 1

Write a short note on biotic components of the environment.

Answer

All the living organisms in an ecosystem, namely, plants, animals and microorganisms form its biotic components. Depending on how they obtain their food, living organisms can be divided into three groups, namely, producers, consumers and decomposers.

Producers — Green plants make their own food in the presence of sunlight using water, minerals and carbon dioxide. Thus, green plants are called producers or autotrophs.

Consumers — Living organisms that cannot make their own food but consume either plants or other animals, are called consumers or heterotrophs. They are either herbivores, carnivores or omnivores.

Decomposers — The microorganisms that feed on the dead bodies of organisms and decaying organic matter are called Decomposers.

Question 2

Explain unidirectional flow of energy.

Answer

There is unidirectional flow of energy in an ecosystem from the sun to producers to consumers and finally to decomposers. As per scientists, only 10 percent of the energy stored by producers is passed on to primary consumers. Similarly, a secondary consumer that eats primary consumer absorbs only 10 percent of its energy. Thus, the amount of energy that is transferred decreases at each level and the flow of energy is always in one direction only.

Question 3

How does light influence plant life?

Answer

The light affect plants in a number of ways. The green plants make food in the presence of light, light influences the closing and opening of stomata, germination of seeds and so on. The intensity of light affects the rate of photosynthesis. The amount of sunlight in a particular area has a direct influence on the types of plants.

Question 4

Explain the flow of energy in a food chain with the help of a diagram.

Answer

Green plants convert solar energy into chemical energy present in food. Some energy gets stored in plants while the rest is used up by them. When the plants are eaten by herbivores, the energy stored in them is transferred to herbivores. Herbivores use some of the energy for their activities and store a part of it in their body. This stored energy is further transferred to carnivores when they eat herbivores. Thus, as one organism eats the other, energy passes on from producers to herbivores and then to carnivores. The given diagram shows the flow of energy in a food chain:

Explain the flow of energy in a food chain with the help of a diagram. Ecosystems, Living Science Biology Ratna Sagar Solutions ICSE Class 8.

Question 5

Write a short note on the dependence of animals on plants.

Answer

The animals depend upon the plants in many ways like for food, shelter and and most importantly for oxygen. Dependence of animals on plants can be explained as follows:

  1. Animals (herbivores) depend upon plants for food.
  2. Animals such as birds, squirrels and monkeys depend upon plants for their shelter. Birds also use plant materials to make their nests. Insects like ants, bee and beetles etc. also live on trees.
  3. Animals also use Oxygen given out by plants for respiration.

Question 6

What are the different types of terrestrial ecosystems and what are the organisms found in the forest ecosystem?

Answer

The different types of terrestrial ecosystems are deserts, grasslands and forests.

The organisms found in the forest ecosystem are:

  1. Producers like herbs, shrubs, trees and climbers etc. A wide variety of grasses, ferns, creepers, berries etc. are found in a forest.
  2. The consumers in a forest ecosystem include:
    1. Herbivores such as deer, nilgai, elephants, leaf hoppers, bugs, beetles and so on.
    2. Carnivores such as tigers, lions and foxes. There are also a large number of predatory birds like eagle and kite. Omnivores like bear, crow, etc. are also present.
  3. Decomposers like bacteria and fungi are also found in the forest ecosystem.

Question 7

Write about biotic and abiotic components of a forest ecosystem.

Answer

Biotic component of forest ecosystem — The biotic components of a forest includes :

  1. Producers like herbs, shrubs and trees. A wide variety of grasses, ferns, creepers, berries etc. are found in a forest. The trees in a forest are home to thousand of birds and animals.
  2. Consumers like herbivores(deer,nilgai, elephants, leaf hoppers and bugs), Carnivores(tiger, lion, eagle kite) and Omnivores (bear, crow) are found in forest ecosystem.
  3. Decomposers like bacteria and fungi are also found in the forest ecosystem. They derive their nutrition from dead and decaying organisms.

Abiotic component of forest ecosystem — The abiotic components of a forest ecosystem include air rich in oxygen, water in several water bodies, organic and inorganic compounds in trees and soil as well as in the dead remains of plants and animals. Climatic factors such as sunlight, temperature, rainfall and humidity play a great role in determining the flora and fauna in a forest ecosystem.

Number the organisms

Question 1

Number the organisms in the correct sequence to complete the food chain.

Number the organisms in the correct sequence to complete the food chain. Ecosystems, Living Science Biology Ratna Sagar Solutions ICSE Class 8.

Answer

The correct sequence of the food chain is numbered in the below figure:

Number the organisms in the correct sequence to complete the food chain. Ecosystems, Living Science Biology Ratna Sagar Solutions ICSE Class 8.

Make three food chains

Question 1

Make three food chain using the following organism

grasshopper, frog, snake, vulture, grass, rat, deer, lion

Answer

Following three food chains can be made:

  1. grass → deer → lion

  2. grass → grasshopper → frog → snake → vulture

  3. grass → rat → snake → vulture

Think and Answer

Question 1

A plant or an animal may belong to several food chains. How?

Answer

Most of the consumers have more than one source of food. For example, frogs eat caterpillars besides grasshopper, snakes eat rabbits as well as lizards, mice and rats. Thus, a plant or an animal may belong to several food chains.

Question 2

Consumers depend on producers in a food chain. How?

Answer

Any food chain starts with producers because only producers can trap energy from the sun and convert it into chemical energy present in food. Producers i.e., green plants make their own food in the presence of sunlight using water, minerals and carbon dioxide. Consumers cannot make their own food and they depend directly or indirectly on producers for energy.

Question 3

Scavengers and decomposers are important for the environment. Why

Answer

Scavengers and decomposers are important for the environment because they help to clean the environment by breaking down the complex organic compounds present in the remains of dead plants and animals into simpler substances. They are useful in releasing the nutrients from dead, decaying organisms back into the environment. These nutrients are reused by plants. Thus, they help in recycling of nutrients.

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