KSEEB Solutions for Class 8 Science Chapter 2 Our Environments

Karnataka Board Class 8 Science Chapter 2 Our Environment

KSEEB Class 8 Science Chapter 2 Textual Questions & Answers

I. Four alternatives are given to each of the following incomplete statements. Choose the right answer.

Question 1.
Fill in the box with an 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:

Question 1.
The crust of the Earth is called ……….
Answer:
Lithosphere

Question 2.
The basic unit of study in the environment is ……….
Answer:
Organism

Question 3.
A group of individuals belonging to the same species is ……….
Answer:
Population

Question 4.
Different kinds of the ecosystem together constitute ………….
Answer:
Biosphere

Question 5.
In a parasitic food chain, the pyramid of the number will be ……….
Answer:
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 the life to exist on the earth are as follow

  1. The presence of water has some unique physical and chemical properties that are essential for supporting life’s existence.
  2. As the photosynthetic algae appeared on earth the oxygen concentration increased which is ideal for the other life forms.
  3. An atmosphere which is a mixture of gases water vapour to support and Sustain life.
  4. Lithosphere allows life to flourish unlike the barren surface of other plants.

Question 2.
Define the following
1. Lithosphere
2. Population
3. Biotic community
4. Food web
5.Tropic level

Answer:

  1. Lithosphere: The surface or crust of the earth is called the lithosphere. It accompanies the mountains, ocean floors, and the plane lands.
  2. Population:  A collection of individuals belonging to the same species occupying a given area at a given time is called population.
  3. Biotic community: The living components are called biotic components.
    Eg: plants, animals, bacteria, and fungi.
  4. Food web: Since most organisms feed on more than one kind of food item. Every organism at even tropic level becomes linked to several food chains at the same time. A complex network of interconnected food chains forming a food web.
  5. Tropic level: Representation of the different levels of feeding in the ecosystem is described as tropic levels.

Question 3.
What is an ecosystem?
Answer:
An interaction between living and non-living components is known as the ecosystem.

Question 4.
Why is the use of DDT not advisable.
Answer:
The indiscriminate use of DDT has resulted in biomagnification in the tropic level. A gradual increase in the concentration of DDT is 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 arc killed in a tern trial 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 be unstable.

Question 7.
In any food chain tropic level – 1 is occupied by green plants. Give reason.
Answer:
The first trophic level of the food chain is always occupied by green plants which are termed to be producers. This is because producers directly absorb sunlight, the abiotic factor, and fix it into the food chain. This energy is transferred to organisms in other trophic levels of the food chain.

KSEEB Class 8 Science Chapter 2 Additional Questions & Answers

Question 1.
Explain the formation of the earth.
Answer:
When the earth was formed about 4.8 billion of years ago. Earth was a hot revolving ball of gas. The extremely high temperature and the dry climate of the earliest earth would have made it impossible for the life to appear and exist. The first multicellular organisms appeared about 1.4 billion years ago. These organisms and the other forms of life which evolved from them could survive when the condition on earth began to stabilize gradually.

Question 2.
What is hydrosphere?
Answer:
The surface of the earth is covered by water. This part of the earth is called hydrosphere.

Question 3.
Water has some unique physical ‘and chemical properties seen in other substances. Which are essential for supporting life’s existence. What are they?
Answer:

  1. Water requires a considerable amount of energy to get heated up and also to get converted from a liquid state into a gaseous state. On a very hot day, water bodies help maintain atmosphere temperature cool by absorbing heat from the sun. When the sun” sets. The heat which water has absorbed is returned to the atmosphere, as water evaporates. Such regulation is crucial for the survival of living organisms.
  2. Water has a high resistance to sudden changes in temperature and this feature makes water an excellent habitat for most organisms.
  3. At 4° water can expand on cooling or heating this feature ensures that all the water in a water body will be close to 0° c before any freezing can occur.
  4. The high surface tension of water and its tendency to expand on freezing helps in the weathering of rocks. 1 ending to soil formation.

Question 4.
Explain How did friendly atmosphere evolve on the earth?
Answer:
Atmosphere of the earth at its beginning was rich in carbon dioxide and oxygen content was very less. As photosynthetic algae appeared on earth oxygen concentration increased resulting in a shift from reducing the 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 5.
What is Lithosphere?
Answer:
The Surface or crust of the earth is called the lithosphere.

Question 6.
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 7.
What is ecology?
Answer:
The Scientific studies which enable us to understand the totality and pattern of the relations between organisms and their environment is called ecology.

Question 8.
What are the basic laws of ecology?
Answer:
The basic laws of ecology are.

  1. We can never continue to do anything in nature.
  2. In nature, everything is connected to everything else.

Question 9.
Write the levels of organization in nature.
Answer:
The level of organization in nature is Species → Population → biotic community → ecosystem → biosphere.

Question 10.
Define the following terms.
1. Organism
2. Species
3. Population
4. Biotic components
5. Ecosystem
6. biotic components.
Answer:

  1. Organism:  Any form of life can be called an organism.
  2. Species: Species is a group of similar organisms sharing common genetic structure and capable of breeding among themselves.
  3. Population:  A collection of individuals belonging to the same species occupying a given area at a given time is called population.
  4. Biotic components:  The living components are called biotic components.
    Eg: plants, animals, bacteria, and fungi.
  5. Ecosystem:  An interaction between living and non-living components is known as the ecosystem.
  6. biotic component:  The non¬living components are called as biotic components.
    Eg: Air, water, land, sun, light

Question 11.
Name the types of ecosystems.
Answer:
Natural ecosystem can be broadly classified into two types. They are ;

  1. aquatic ecosystem
  2. terrestrial ecosystem.

Question 12.
List a few examples of the man-made ecosystem.
Answer:
Aquarium, Garden, Terrace Garden, zoological park.

Question 13.
What is meant by a food chain? write any two food chains.
Answer:
The kind of nutritional relationship where the food energy is getting transferred from one tropic level to another is called a food chain.
Eg:
1. Grass → Grasshopper → Frog → Snake.
2. Algae → Insect large → fishes → Aquatic birds.
3. Grass → Rabbit → Wolf.

Question 14.
What is meant by grazing or herbivorous food chain?
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.
Grass → Rabbit → wolf.

Question 15.
What is a detritivorous food chain? give example.
Answer:
The food chain in which, the primary consumers are a detrivore is called a detritivorous food chain.
Ex: Fallen leaves → termites → birds.

Question 16.
What is meant by the parasitic food chain? give 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 17.
Ants, termites are called detrivore why?
Answer:
Ants, termites, earthworms are called detrivores because they feed on detritus.

Question 18.
Define the food web? draw a simple food web.
Ans. A complex network of interconnected food chains forming a food web.
KSEEB Solutions for Class 8 Science Chapter 2 Our Environments 18

Question 19.
How does food become energy in an organism?
Answer:
Various organisms found in an ecosystem are constantly growing, reproducing, dying, and decaying. They need energy for all their activities. When organisms consume food the carbohydrates in their food become the source of energy. This energy their food becomes the source of energy. This energy is released as you are aware through a process called respiration. It makes the stored energy in the carbohydrates available for biological work.

Question 20.
Which is the main source of energy for all ecosystem?
Answer:
The main source of energy for all ecosystems is solar energy.

Question 21.
Draw a food chain with five tropic levels.
Answer:

KSEEB Solutions for Class 8 Science Chapter 2 Our Environments 21

Question 22.
Draw a picture of energy flow in nature.
Answer:

KSEEB Solutions for Class 8 Science Chapter 2 Our Environments 22

Question 23.
Define ecological pyramids?
Answer:
The graphical representation of the relationship between the energy number of individuals and their biomass at each tropic level in the form of a pyramid are called ecological pyramids.

Question 24.
Define the following.
1. Pyramid of numbers
2. Pyramid of biomass
3. Pyramid of energy
Answer:

  1. Pyramid of biomass: 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.
  2.  Pyramid of numbers: A Pyramid constructed based on the number of individuals occupying a given tropic level at a given period of time is called the pyramid of numbers.
  3.  Pyramid of energy: A Pyramid constructed on the basis of the amount of energy fixed at each level is called the pyramid of energy.

Question 25.
Draw a graphical representation of an upright pyramid of number
Answer:
KSEEB Solutions for Class 8 Science Chapter 2 Our Environments 25

Question 26.
Draw an Inverted pyramid of numbers.
Answer:
KSEEB Solutions for Class 8 Science Chapter 2 Our Environments 26

Question 27.
The pyramid of energy will be always upright. Give reason
Answer:
In any ecosystem. For any food chain, the pyramid of energy. Will be always upright because the amount of usable energy available at each trophic level is about 10% of the energy that was available at the previous tropic level.

Question 28.
What is meant by biomagnification?
Answer:
An increase in the concentration of a toxic substance or a pollutant, with every link in the food chain, is called biomagnification.

Question 29.
Why is the use of DDT not advisable?
Answer:
The indiscriminate use of DDT has resulted in biomagnification in the tropic level. A gradual increase in the concentration of DDT is 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. It is a non-biodegradable substance. DDT is chemically called Dichloro Diphenyl Trichloroethane

KSEEB Solutions for Class 8 Science

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