General Science
8th Class
Chapter 1
Ecology
Questions
1. Encircle the correct option.
(i) The phenomenon which does not lead to global warming:
a. greenhouse effect b. ozone depletion c. deforestation d. photosynthesis
(ii) The feeding level of an organism in an ecosystem is called ________ .
a. tropic level b. secession level c. food chain d. food web
(iii) The graphical representation of trophic relationship of organisms in an ecosystem is called ________ .
a. food chain b. tropic level c. ecological pyramid d. predation
(iv) All the food chains are joined together to form _________ .
a. ecological pyramid b. food web c. tropic level d. none of these
(v) The energy of the Sun is trapped as chemical energy by ________ .
a. producers b. primary consumers c. secondary consumers d. tertiary consumers
(vi) Consumers that actively hunt other organisms are called ________ .
a. prey b. predator c. symbiont d. competitor
(vii) A relationship where two species live together closely is called _________ .
a. predation b. symbiosis c. competition d. none of these
(viii) We can solve environmental problems by:
a. reducing pollution b. plantation c. protection of endangered species d. all of these
(ix) Ecological imbalance is caused by:
a. migration b. overhunting c. over population d. all of these
2 Write short answers.
(i) What are ecological pyramids?
Ans.
The different feeding levels of organisms in an ecosystem are called trophic levels e.g., producers, herbivores, primary carnivores etc. Biologists express the trophic relationships by the diagram that take the shape of pyramids. This diagram is thus called ecological (or biological) pyramid. Diagram shows that at the base of the pyramid are producers or green plants. The upper levels are occupied by primary, secondary and tertiary consumers in according order. Usually primary consumers are herbivores and the rest are carnivores (or omnivores).
(ii) What is predation?
Ans.
Consumers that actively hurt other organisms are called predators. The organism upon which a predator feeds is called prey. This process is called predation. For example a frog that eats an insect is a predator. The insect is the prey. The frog itself is prey to other organisms such as snakes and storks.
(iii) Differentiate between:
(a) oxygen and carbon cycle (b) food chain and food web
Ans.
(a) oxygen and carbon cycle
The carbon dioxide and oxygen gases circulate between the constantly between the environment and living organisms in a cyclic way. When plants prepare food in photosynthesis, they take in carbon from the atmosphere in the form of carbon dioxide. In this process, they also release oxygen gas to the atmosphere.
All animals and plants respire to get energy. During respiration they take in oxygen from the atmosphere and release carbon dioxide to atmosphere.
Similarly, during decomposition and combustion of biomass (matter of dead bodies), the oxygen gas present in atmosphere is used and the carbon of biomass is released into the atmosphere in the form of carbon dioxide.
(b) food chain and food web
Production of food and the feeding relationship among organisms at different levels form a chain called food chain. whereas when all animals feed in more than one food chain, these food chains are joined together to make a food web.
(iv) Write any of the solution of environmental problems.
Ans.
Plantation:
There are many benefits of plants. Planting more trees can reduce the level of air pollution as plants absorb pollutants. It also maintains the temperature of an area at a lower level than an area that does not have trees. They are also the habitat for birds and birds and many other animals. Trees are also a source of fruits and flowers. Each and everyone of us have to plant trees and enhance the quality of life.
(v) Name some of the factors which can cause ecological imbalance.
Ans.
Introduction of new species in an ecosystem, overhunting, migration, etc. are the factors which can cause ecological imbalance.
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