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Karnataka State Syllabus Class 8 Science Chapter 2 Our Environment
KSEEB Class 8 Science Our Environment Textbook Exercise Questions and Answers
I. Four alternatives are given to each of the following incomplete statements/questions. Choose the right answer
Question 1.
Fill in the box with the appropriate organism.
Grass → ___________ → Frog → Snake → Eagle
(a) deer
(b) lizard
(c) grasshopper
(d) rat
Answer:
(c) grasshopper
Question 2.
One of these is a decomposer
(a) fungi
(b) algae
(c) protozoa
(d) insect
Answer:
(a) fungi
II. Fill in the blanks with suitable words:
1. The crust of the Earth is called …………………….
2. The basic unit of study in the environment is …………………….
3. A group of individuals belonging to the same species is …………………….
4. Different kinds of ecosystems together constitute …………………….
5. In a parasitic food chain, the pyramid of the number will be …………………….
Answer:
1. lithosphere,
2. ecosystem,
3. population,
4 biosphere,
5. inverted
III. Answer the following:
Question 1.
List the factors which have made life to exist on the earth.
Answer:
The factors which have made life to exist on the earth are
- The presence of water has some unique physical and chemical properties that are essential for supporting life’s existence.
- An atmosphere which is a mixture of gases, water vapor to support and sustain life.
- As the photosynthetic algae appeared on earth, the oxygen concentration increased which is ideal for the other life forms.
- Lithosphere allows life to flourish ‘ unlike the barren surface of other planets.
Question 2.
Define the following
1. Lithosphere
2. Population
3. Biotic community
4. Food web
5. Tropic level
Answer:
1. Lithosphere: The outer layer of the earth comprising the crust and the upper part of the mantle. (The lithosphere is about sixty miles thick)
2. Population: A population is the number of all the organisms of the same group or species, which live in a particular geographical area
3. Biotic community is the living thing that shape an ecosystem. Usually, they include producers, ie autotrophs. Eg: plants.
4. Food web: A network of food chains or feeding relationships by which energy and nutrients are passed on from one species of living organisms to another
5. Trophic level: The trophic level of an organism is the position it occupies in a food chain the word trophic is derived from the Greek (trophy) referring to food or feeding. A food chain represents a succession of organisms that eat other organisms and areas, in turn, themselves has eaten by others.
Question 3.
What is an ecosystem?
Answer:
A unit in nature where there is an interaction between living and non-living components is known as an ecosystem.
Question 4.
Why is the use of DDT not advisable?
Answer:
The indiscriminate use of DDT has resulted in biomagnification in tropic levels. A gradual increase in the concentration of DDT has been detected in the tissues of small fishes; predatory birds and also in mother’s milk. Therefore it is not advisable to use DDT.
Question 5.
Construct a simple food chain.
Answer:
grass → deer → tiger
Question 6.
What may happen if all herbivores are killed in a terrestrial ecosystem?
Answer:
If all the herbivores are killed, the number of producers will increase and the secondary and tertiary consumers will die of starvation. Thus the nutritional relationship ‘eating and being eaten will become unstable.
Question 7.
In any food chain, trophic level-1 is occupied by green plants. Give reason.
Answer:
Plants are the food for a variety of organisms i.e., Primary consumers. Most of the primary consumers depend on plants for their food. Hence tropic level 1 is occupied by green plants.
KSEEB Class 8 Science Our Environment Additional Questions and Answers
Question 1.
Water has some unique physical and chemical properties, not seen in other substances, which are essential! for supporting life’s existence. What are they?
Answer:
(a) Water requires a considerable amount of energy to get heated up and also to get converted from a liquid state into a gaseous state. Therefore, on a very hot day, water bodies help to maintain atmospheric temperature cool by absorbing heat from the Sun. When the Sun sets the heat which was absorbed is returned to the atmosphere. Such regulation is crucial for the survival of living organisms.
(b) Water has a high resistance to sudden changes in temperature and this feature makes water an excellent habitat for most organisms.
(c) At 4° C, water can expand on cooling or heating. This feature ensures that all the water in the water body will be close to 0° C before any freezing can occur.
(d) The high surface tension of water and its tendency to. expand on freezing helps in the weathering of rocks, leading to soil formation.
Question 2.
How did a friendly atmosphere evolve on the earth?
Answer:
The atmosphere of the earth at its beginning was riel) in carbon dioxide and oxygen content was very less. As photosynthetic algae appeared on earth, oxygen concentration increased resulting in a shift from reducing type of atmosphere to an oxidizing type. Gradually atmosphere reached its present composition, which is ideally suited for humans and other forms of life.
Question 3.
What is the biosphere?
Answer:
The hydrosphere, atmosphere, and lithosphere of the earth together constitute the biosphere. It is the sum total of all organisms and their places of living.
Question 4.
What is ecology?
Answer:
The scientific studies which enable as to understand the totality and pattern of the relations between the organisms and their environment is called ecology. lt are also known as environmental science.
Question 5.
Write the two basic laws of ecology.
Answer:
The two basic laws of ecology are
(1) We can never continue to do anything in nature.
(2) In nature, everything is connected with everything else
Question 6.
Mention the levels of the organization.
Answer:
The levels of the organization are species population biotic community ecosystem biosphere
Question 7.
What is a species?
Answer:
A species is a group of similar organisms sharing common genetic structure and capable of breeding among themselves.
Question 8.
What is the population?
Answer:
A collection of individuals belonging to the same species occupying a given area at a given time is called population.
Question 9.
What are abiotic components?
Answer:
The non-living components are called abiotic components. They represent the physical, chemical, and climatic conditions operating in the environment. Physical factors are light, temperature, soil, and water. Chemical factors are organic and inorganic substances required or not required by the living organism. Climate factors represent rainfall and humidity.
Question 10.
What are the biotic components?
Answer:
The living components are called biotic components. They are represented by plants, animals, bacteria, and fungi.
Question 11.
What is meant by a food chain?
Answer: The kind of nutritional relationship where the food energy is getting transferred from one tropic level to another is called a food chain.
Ex. grasshopper frog snake eagle
Question 12.
What is meant by grazing or herbivorous food chain? Give an example.
Answer:
The food chain in which the primary consumers are plant-eating animals is called grazing or herbivorous food chain. This is also called a predatory food chain. Ex. grass deer tiger
Question 13.
What is meant by Detritivourous food, the chain? Give an example.
Answer:
The food chain in which the primary consumer is a detritivore is called as a Detritivorous food chain.
Ex. fallen leaves termites birds
Question 14.
What is meant by the parasitic food chain? Give an example.
Answer:
The food chain in which the transfer of food energy occurs through a series of parasites at each trophic level is called the parasitic food chain. Ex. Tree birds lice protozoans
Question 15.
Ants, termites are called as detrivores. Give reason.
Answer:
Ants, termites, earthworms, etc., are called detrivores because they feed on detritus.
Question 16.
What is the food web?
Answer:
A complex network of interconnected food chains is called a food web.
Question 17.
What are the ecological pyramids?
Answer:
The graphical representations of the relationship between the energy, number of individuals, and their biomass at each trophic level in the form of pyramids are called ecological pyramids.
Question 18.
What is meant by a pyramid of numbers?
Answer:
A pyramid constructed based on the number of individuals occupying a given trophic level at a given period of time is called the pyramid of numbers.
Question 19.
What is meant by the pyramid of biomass?
Answer:
A pyramid constructed in the view of biomass, which is the dry weight of all the matter in the organisms at a tropic level is called the pyramid of biomass.
Question 20.
The pyramid of energy will be always upright. Why?
Answer:
In any ecosystem, for any food chain, the pyramid of energy will be always upright because of the amount of usable energy available at each, the tropic level is about 10% of the energy that was available at the previous tropic level.
Question 21.
What MI meant by the pyramid of energy?
Answer:
A pyramid constructed on the basis of the amount of energy fixed at each level is called the pyramid of energy.
Question 22.
What is meant by biomagnifications?
Answer:
An increase in the concentration of a toxic substance or a pollutant, with every link in the food chain is called biomagnification.
II. Fill in the blanks.
- The surface of the earth is called _____________
- 78% of the atmosphere is ______________
- Any form of life can be called as _________________
- All human beings belong to the species __________________
- The Binomial Nomenclature of dog is ____________________
- The Binomial Nomenclature of pea is ____________________
- The basic unit of classification is ___________________
- Closely related species are grouped to form ________________
- The functional unit in the biosphere is _________________
- The aquarium is an example for an _____________ aquatic ecosystem.
- The non-living components are called as _____________
- The living components of an ecosystem are called _____________
- Plants are described as ______________
- Animals are described as ______________
- The flow of energy is __________________
Answers:
- lithosphere,
- nitrogen,
- organism,
- sapiens,
- Canis familiaris,
- Pisum sativum,
- species,
- genera,
- ecosystem,
- man-made,
- abiotic components,
- biotic compounds
- autotrophs,
- heterotrophs,
- unidirectional.
III. Only one of them is best suited. Circle its correct answer.
Question 1.
The unique planet in the solar system is
(a) Venus
(b) Earth
(c) Mars
(d) Jupiter
Answer:
(b) Earth
Question 2.
The only planet where life exists is
(a) Mars
(b) Saturn
(c) Pluto
(d) Earth
Answer:
(d) Earth
Question 3.
The gaseous component of the Earth is
(a) Atmosphere
(b) Hydrosphere
(c) Biosphere
(d) Lithosphere
Answer:
(a) Atmosphere
Question 4.
The water bodies on earth is called as
(a) Lithosphere
(b) Atmosphere
(c) Biosphere
(d) Hydrosphere
Answer:
(d) Hydrosphere
Question 5.
A unit in nature where there is an interaction between the living and non-living is called
(a) Biome
(b) Community
(c) Ecosystem
(d) Population
Answer:
(c) Ecosystem
Question 6.
Herbivores are
(a) Producers
(b) Decomposers
(c) Primary consumers
(d) Secondary consumers
Answer:
(c) Primary consumers
Question 7.
A secondary consumer from the following is
(a) snake
(b) insect
(c) Rabbit
(d) Frog
Answer:
(d) Frog
Question 8.
The functional stability of any ecosystem depends on continuous
(a) Production
(b) Consumption
(c) Decomposition
(d) All of the above
Answer:
(d) All of the above
Question 9.
The flow of energy in the ecosystem is
(a) Unidirectional
(b) Cyclic
(c) Poly directional
(d) Non-cyclic
Answer:
(a) Unidirectional
Question 10.
The movement of materials in an ecosystem is
(a) Unidirectional
(b) Cyclic
(c) Poly directional
(d) Non-cyclic
Answer:
(b) Cyclic
Question 11.
The first tropic level in every ecosystem is
(a) Herbivorous
(b) Producer
(c) Consumer
(d) Decomposer
Answer:
(b) Producer
Question 12.
Pyramid of energy is
(a) Always upright
(b) Always inverted
(c) Can be upright or inverted
(d) None of the above
Answer:
(a) Always upright
Question 13.
Pyramid of biomass in the parasitic food chain is
(a) upright
(b) inverted
(c) both a & b
(d) neither a nor b
Answer:
(a) upright
Question 14.
Pyramid of biomass in an herbivorous food chain is
(a) upright
(b) inverted
(c) both a & b
(d) neither a nor b
Answer:
(b) inverted
Question 15.
Pyramid of number in an herbivorous food chain is
(a) upright
(b) inverted
(c) both a & b
(d) neither a nor b
Answer:
(a) upright
Question 16.
Pyramid of number in the parasitic food chain is
(a) upright
(b) inverted
(c) both a & b
(d) neither a nor b
Answer:
(b) inverted
IV. Match the following:
A – B
1. Tree [] Birds [] Bird lice [] Protozoans – a. biomagnification
2. Fallen leaves [] Earthworm [] Birds – b. Herbivorous food chain
3. Grass [] deer [] Tiger – c. Detritivorous food chain
4. Water containing insecticide [] zooplankton [] small fish [] large fish [] Human being – d. Parasitic food chain
Answers
1. d:
2. c
3. c
4. a