Frank Solutions for Chapter 12 Interaction between Biotic and Abiotic Factors in an Ecosystem Class 9 Biology ICSE
Exercises
1. Name the organisms that convert sun's energy into chemical or food energy.
Answer
Answer
Producers
2. What are organisms that depend on others for food called?
Answer
Consumers
Consumers
3. Name the climatic impacts that occur on ecosystems.
Answer
Answer
The climatic factors affecting ecosystem are sunlight, temperature, humidity, rainfall and wind.
4. How do variations in temperatures affect plants and animals?
Answer
Low and high temperatures restrict the growth of plants and existence of animal species.
Changes in temperature patterns will impact plant life which in turn will influence the animal life, since animals depend directly or indirectly on it for food. During extreme cold and hot conditions, animals either migrate to favourable places, some may hibernate or some may aestivate.
5. What do you understand by 'consumers of the first and second orders'?
Answer
Answer
Consumers which eat only plants are called consumers of the first order. Consumers that eat herbivores like deer, goats, grasshoppers, etc. are called consumers of the second order.
6. How is water a limiting factor in the deserts?
Answer
Deserts have scanty water, either because there is little rainfall, or because the water evaporates very fast in deserts. Desert species are adapted to less amounts of water and they are capable of surviving for long periods of time in the scarcity of water. The growth of plants and animals and their vital functions are dependent on water intake. Hence water is a vital limiting factor in deserts due to the scant availability of this important resource.
7. Differentiate between biotic and abiotic components.
Answer
Difference between biotic and abiotic components
| Abiotic components | Biotic components |
| These are the non-living factors affecting the organisms of an ecosystem | These are the living organisms present in an ecosystem |
| Examples are Water, sunlight, temperature etc. | Examples are Plants, animals, microbes etc. |
8. Differentiate between primary and secondary producers and give examples of each.
Answer
Answer
Difference between primary and secondary producers
| Primary producers | Secondary producers |
| These are autotrophic plants | These are heterotrophic organisms |
| They use sun's energy, water, air and chlorophyll to produce their own food. | They consume food and produce new types of organic substances while digesting their food. |
| Examples - Green plants | Examples - Fungi, animals |
9. What role do vital atmospheric gases play in an ecosystem?
Answer
Vital atmospheric gases are oxygen, carbon dioxide and nitrogen. Oxygen availability seldom becomes a limiting factor for land animals unless they live in soil or invade high altitudes. Plants release oxygen into the air which is used by animals for respiration. During respiration, animals release carbon dioxide which is required by plants for photosynthesis. Nitrogen is an essential gas which is vital for the growth and sustenance of organisms.
10. Explain, how do living organisms interact in an ecosystem.
Answer
Answer
In a natural ecosystem, green plants capture solar energy and convert it into chemical forms. The energy is then passed onto herbivores when they feed on green plants. From herbivores, the energy moves into carnivores that eat them. Some animals like lion and vultures are not eaten by other organisms. All the organisms ultimately pass on energy to the decomposers. Energy thus flows continuously through the ecosystem from plant to animals and from prey to predator.
11. How does energy move in an ecosystem?
Answer
Answer
Energy passes through the ecosystem in a one-way path. Energy goes through each trophic level, one at a time. As it goes from one level to another, it is lost due to metabolism and in the form of heat.
For example – The energy ingested by producers is used by the producers for carrying out various life activities and some amount of energy is lost as heat, so that the entire energy does not pass completely to the consumers. The energy lost as heat cannot be used anymore.
12. What is a food chain?
Answer
Answer
The transfer of energy from autotrophs through a series of organisms that consume and are consumed is known as a food chain.
13. Name two types of food chain.
Answer
Answer
The types of food chain are:
- Grazing food chain
- Detritus food chain
- Auxiliary food chain
14. What is food web?
Answer
Answer
Individual food chains interconnected in a complex way is called food web.
15. What is an energy pyramid?
Answer
Answer
An energy pyramid is a graphical representation of the flow of energy from the producers through the various consumers. It shows the amount of energy available and the loss of useful energy at each step of the food chain in an ecosystem.
16. Why is pyramid of energy broader at the base and narrower at the top?
Answer
As the energy gets transferred from lower trophic level to the higher one, there is a loss of large amount of energy due to metabolism and as heat. As a result very little energy (i.e. 10%) gets transferred to the next level. So the trophic level at the base has maximum energy and that at the top has the least amount of energy. Hence energy pyramid is broader at the base and narrower at the top.
17. Each question has four options. Choose the correct answer.
(i) Energy flow in an ecosystem is
(a) unidirectional
(b) bidirectional
(c) multidirectional
(d) all the above
(a) unidirectional
(b) bidirectional
(c) multidirectional
(d) all the above
Answer
(a) unidirectional
(a) unidirectional
(ii) A food chain consists of
(a) producers
(b) consumers
(c) decomposers
(d) producers and consumers
(a) producers
(b) consumers
(c) decomposers
(d) producers and consumers
Answer
(d) producers and consumers
(d) producers and consumers
(iii) Trophic levels in a food chain are formed by
(a) producers
(b) consumers
(c) decomposers
(d) all the above
(a) producers
(b) consumers
(c) decomposers
(d) all the above
Answer
(d) all the above
(d) all the above
(iv) A food chain always starts with
(a) photosynthesis
(b) respiration
(c) nitrogen fixation
(d) decay
(a) photosynthesis
(b) respiration
(c) nitrogen fixation
(d) decay
Answer
(a) photosynthesis
(a) photosynthesis
(v) Primary consumers are
(a) green plants
(b) herbivores
(c) carnivores
(d) all the above
(a) green plants
(b) herbivores
(c) carnivores
(d) all the above
Answer
(b) herbivores
(b) herbivores
(vi) Primary consumers in detritus food chain are
(a) herbivores
(b) bacteria, fungi, etc.
(c) insect, larvae, nematodes
(d) all the above
(a) herbivores
(b) bacteria, fungi, etc.
(c) insect, larvae, nematodes
(d) all the above
Answer
(b) bacteria, fungi, etc.
(b) bacteria, fungi, etc.
(vii) An ecosystem is an interacting system of
(a) communities
(b) Communities and their physical environment
(c) populations
(d) individuals
(a) communities
(b) Communities and their physical environment
(c) populations
(d) individuals
Answer
(b) Communities and their physical environment
(b) Communities and their physical environment
(viii) The driving force for an ecosystem is
(a) biomas
(b) producers
(c) carbohydrates in producers
(d) solar energy
(a) biomas
(b) producers
(c) carbohydrates in producers
(d) solar energy
Answer
(d) solar energy
(d) solar energy
(ix) The two components of an ecosystem are
(a) plants and animals
(b) weeds, trees, animals and man
(c) energy flow and mineral cycling
(d) biotic and abiotic
(a) plants and animals
(b) weeds, trees, animals and man
(c) energy flow and mineral cycling
(d) biotic and abiotic
Answer
(d) biotic and abiotic
(d) biotic and abiotic
(x) Tropical forests are denser due to
(a) wild animals
(b) high temperature and less rainfall
(c) low temperature and excess rain
(d) high temperature and high rain
(a) wild animals
(b) high temperature and less rainfall
(c) low temperature and excess rain
(d) high temperature and high rain
Answer
(d) high temperature and high rain
(d) high temperature and high rain