Chapter 12 : Interaction Between Biotic and Abiotic Factors in an EcoSystem - Frank Solutions for Class 9 Biology ICSE

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Chapter 12 - Interaction Between Biotic and Abiotic Factors in an EcoSystem Excercise 99

Question 1
Name the organisms that convert sun's energy into chemical or food energy.
Solution 1
Question 2
What are organisms that depend on others for food called?
Solution 2
Question 3
Name the climatic impacts that occur on ecosystems.
Solution 3
The climatic factors affecting ecosystem are sunlight, temperature, humidity, rainfall and wind.
Question 4
How do variations in temperatures affect plants and animals?
Solution 4
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.
Question 5
What do you understand by 'consumers of the first and second orders'?
Solution 5
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.
Question 6
How is water a limiting factor in the deserts?
Solution 6
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.
Question 7
Differentiate between biotic and abiotic components.
Solution 7
Question 8
Differentiate between primary and secondary producers and give examples of each.
Solution 8
Question 9
What role do vital atmospheric gases play in an ecosystem?
Solution 9
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.
Question 10
Explain, how do living organisms interact in an ecosystem.
Solution 10
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.
Question 11
How does energy move in an ecosystem?
Solution 11
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.
Question 12
What is a food chain?
Solution 12
The transfer of energy from autotrophs through a series of organisms that consume and are consumed is known as a food chain.
Question 13
Name two types of food chain.
Solution 13
The types of food chain are:
(i) Grazing food chain
(ii) Detritus food chain
(iii) Auxiliary food chain
(Write any two)
Question 14
What is food web?
Solution 14
Individual food chains interconnected in a complex way is called food web.
Question 15
What is an energy pyramid?
Solution 15
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.
Question 16
Why is pyramid of energy broader at the base and narrower at the top?
Solution 16
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.
Question 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
(ii) A food chain consists of
(a) producers
(b) consumers
(c) decomposers
(d) producers and consumers
(iii) Trophic levels in a food chain are formed by
(a) producers
(b) consumers
(c) decomposers
(d) all the above
(iv) A food chain always starts with
(a) photosynthesis
(b) respiration
(c) nitrogen fixation
(d) decay
(v) Primary consumers are
(a) green plants
(b) herbivores
(c) carnivores
(d) all the above
(vi) Primary consumers in detritus food chain are
(a) herbivores
(b) bacteria, fungi, etc.
(c) insect, larvae, nematodes
(d) all the above
(vii) An ecosystem is an interacting system of
(a) communities
(b) Communities and their physical environment
(c) populations
(d) individuals
(viii) The driving force for an ecosystem is
(a) biomas
(b) producers
(c) carbohydrates in producers
(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
(x) Trophical 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
Solution 17
(i) (a) unidirectional
(ii) (d) producers and consumers
(iii) (d) all the above
(iv) (a) photosynthesis    
(v) (b) herbivores
(vi) (b) bacteria, fungi, etc.
(vii) (b) Communities and their physical environment
(viii) (d) solar energy
(ix) (d) biotic and abiotic
(x) (d) high temperature and high rain