Chapter 29 Natural Environment Textbook Solutions

NIOS Class 10 Science Chapter 29 Question Answers

INTEXT QUESTIONS 29.1

1. Sunlight forms the abiotic component of ecosystem. Name one biotic component.

Ans: Plants, animals, and microorganisms (any one).

2. Why are plants called producers? Which trophic level do they occupy in an ecosystem?

Ans: They produce the food for all the animals either directly or indirectly; first trophic level

3. Give one reason in support of the statement that “food web is a jumble of food chains”.

Ans: Animals eat more than one kind of food to meet their food and energy requirements

4. Construct one food chain and one food web from the following :

Tiger, grains, vulture, frog, snake, grass, cat, sheep, peacock, wolf, rabbit, phytoplankton, small fish, rat, large fish.

Ans: Food chain

Food Web

INTEXT QUESTIONS 29.2

1. Name any two ways which are responsible for adding carbon dioxide in the atmosphere.

Ans: Factories, vehicles, burning wood, living organisms (respiration) (any two)

2. Name the bacteria which live in the roots of the leguminous plants and are responsible for nitrogen fixation.

Ans: Rhizobium

3. What is the process of conversion of free atmospheric nitrogen into nitrites and nitrates called?

Ans: Ammonification

4. What is the role played by denitrifying bacteria and nitrifying bacteria in the nitrogen cycle? Give the name of one denitrifying bacteria and one for nitrifying bacteria.

Ans:

Denitrifying bacteria reduce nitrate to nitrogen.Example: denitrifying bacteria – Pseudomonas, Clostridium (any one)
Nitrifying bacteria convert ammonia to nitrate. Eg., Nitrosobactor, Nitrosomonas

5. Mention any one role that you play in the (i) nitrogen cycle and (ii) carbon cycle.

Ans: (i)Release/excrete N2 as nitrogen compounds in the urine/excreta) ( ii) Release CO2 to the atmosphere

6. Nitrogen is an essential component of the proteins and nucleic acids in living beings. Mention any one way by which you obtain nitrogen for your growth.

Ans: As food/as vegetables/meat (Any other)

7. Mention one way in which increasing deforestation by humans is influencing the carbon cycle.

Ans: Leads to an increase in the level of atmospheric carbon dioxide

INTEXT QUESTIONS 29.3

1. Why are leaves of water lily coated with wax on the upper surface?

Ans: Wax acts as a water repellent.

2. Name two tree dwellers.

Ans: Flying squirrel/flying lizard/ tree frogs/lemurs/monkeys (any two)

3. Enumerate the adaptations of birds that enable them to fly so easily (Any two).

Ans: Streamlined body, hollow bones, strong flight muscles, wings covered with feathers, forelimbs modified into wings.

4. How are penguins able to survive in the extreme cold conditions?(Any two adaptations)

Ans: The Presence of a thick layer of densely packed feathers, flippers, and legs is adapted to reduce heat loss.

5. Why do the desert plants have fewer stomata?

Ans: To reduce water loss.

6. Humans are not adapted for aquatic life. List any two challenges that you would face when you go for swimming in a pond/lake, and the ways by which you would overcome them and become an effective swimmer.

Ans: Challenges: Keeping afloat, breathing, eyes getting affected (Any two)

How to overcome: Try to move hands and feet to swim/keep the nose above water to breathe air; wear a water mask (any two)

INTEXT QUESTIONS 29.4

1. How is the sucker fish benefitted by attaching itself to the shark’s body? What type of association is it?

Ans: It is protected from its predators; can be widely dispersed. Commensalism

2. If alga provides food to the fungus that lives on it, what does the fungus do for the alga?

Ans: Fungus provides water, shelter, and minerals to the alga.

INTEXT QUESTIONS 29.5

1. When does the population density increase?

Ans: When the birth rate is more than the death rate.

2. What is the difference between Emigration and Immigration?

Ans: Emigration

(i) It is the permanent outward movement of the organisms from a given population.
(ii) Decrease the size of the population.

Immigration

(i) It is the permanent inward movement of the organisms from outside into a given population.
(ii) Increases the size of the local population.

3. What is lag phase?

Ans: When the individuals enter a previously unoccupied area, the growth is slow at first

as it adapts to the new conditions and establishes itself.

TERMINAL EXERCISES

1. What is an ecosystem? Name the various components of an ecosystem.

Ans: An ecosystem may be defined as “a biological environment consisting of all organisms living in a particular area, as well as the non-living physical components of the environment with which the organisms interact”.

Both non-living and living things constitute an ecosystem. Accordingly, they are termed as abiotic and biotic components.

Abiotic components are the non-living physical and chemical factors in the environment of an ecosystem.
Biotic components are the organisms that include plants, animals, and microorganisms in an ecosystem.

2. Is detritus a biotic component or is it an abiotic component of an ecosystem?

Ans: The Detritus food chain starts from dead organic matter of once living beings. So it may be included as a biotic component of an ecosystem. The dead organic matter is broken down into simple nutrients by microorganisms like fungi and bacteria. These simple nutrients and decomposers are then consumed by smaller carnivores, which in turn become food for larger carnivores.

3. What is the function of Nitrosomonas in nitrogen cycle?

Ans: Nitrosomonas is a nitrifying bacterium that converts ammonia into nitrate, which is later taken up by plants for their nutrition. Nitrification is an important step in the nitrogen cycle, and Nitrosomonas helps with this process.

4. With the help of suitable examples differentiate between the detritus and grazing food chain.

Ans: Detritus food chain.

Grazing food chain.

5. What is the significance of food chain and food web?

Ans: Significance of food chain and food web:

They help to maintain ecological balance.
They help in understanding the feeding relations among organisms.
Energy flow and nutrient cycle take place through them.

6. Why does the energy decrease as we go along the food chain from producers to tertiary consumers?

Ans: In a food chain, the energy flow is unidirectional, i.e., the energy that is transferred from one trophic level to the next does not come back. As it passes from one trophic level to the next, only a fraction of the energy is passed on; the rest of the energy is lost as heat or is used up by the organism to carry out its life processes. The same process happens in each level. Because of the large amount of energy that is lost at each link, the amount of energy that is transferred gets less and less as we go up the food chain

7. What will happen if all the animals are removed from a pond?

Ans: Removal of all animals from a pond will completely disturb the energy flow of the pond. It will result in the overpopulation of algae and other aquatic plants, which in turn will affect the nutrient cycle, which will affect the water quality. The dip in water quality affects the sustenance of other aquatic plants and eventually, the ecosystem will collapse.

8. Why is the number of trophic level restricted to four or five in a food chain?

Ans: The number of trophic levels is restricted to four or five in a food chain because only a fraction of the energy is passed on; the rest of the energy is lost as heat or is used up by the organism to carry out its life processes. Thus, the higher trophic levels receive less energy and will be insufficient for their sustenance if there are more than five trophic levels.

9. What is the difference between energy flow and biogeochemical cycle in an ecosystem?

Ans: Energy flow in an ecosystem is unidirectional. It means the energy that is transferred from one trophic level to the next does not come back. In the biochemical cycle, the elements that pass from one stage to the next are not lost but replenished cyclically.

10. How are camels able to survive in extreme heat?

Ans:

Camels have a hump to store fat.
A camel can drink very large amounts of water in one day or survive for a relatively long time without drinking any water.
They can excrete concentrated urine when water is scarce and thus reducing water loss.

11. Why do polar bear have thick fur over their body?

Ans:

They have very thick fur over the body to trap air and insulate it.
They also have a layer of stored fat under the skin to give additional insulation.
The body shape and size of many cold-climate mammals are well-adapted to the cold climate.
They are round and bulky with short legs, ears, and a tail.
These adaptations help to conserve heat.

12. Compare the S-shaped pattern of population growth with the J-shaped pattern of population growth.

Ans:

S-Shaped Growth Curve

Initially, the growth is slow.
Next comes the lag phase, when the natality and mortality are small but constant.
Gradually, growth becomes rapid when the natality rate increases and mortality remains low.
Later, the natality and mortality rates become equal, and the growth curve enters the stable phase.

J-Shaped Growth Curve

A J-shaped growth curve is where the population growth is exponential until the environmental resistance becomes effective. When there is stiff competition for survival, the growth rate stops abruptly with a sudden increase in mortality.

13. What is population dispersal? What are the two types of population dispersal?

Ans: Population dispersal is the movement of individuals or groups of living organisms by which they expand the space or range within which they live. Population dispersal can be of two types:

Emigration: It is the permanent outward movement of organisms from a given
population. It decreases the size of the local population.
Immigration: It is the permanent inward movement of organisms from outside into a given population. It increases the size of the local population.

14. What is the main cause of population explosion?

Ans: The main cause of population explosion is the huge difference between the birth rate, natality, and death rate, mortality. When the birthrate is much higher than the death rate, population growth explodes.

15. Do you think population remains static? Support your answer with suitable explanation.

Ans: The Population of any species does not remain static. It changes. Population growth is the change in the number of individuals of any species in a population at a given time. The size of the population depends upon the density, natality (birth rate), mortality (death rate), population dispersal, age distribution, and environmental resistance that the population has to face.

16. Try to complete the table given below

Ans:

	Feature	How is this feature advantageous to the organism?	Name of the plant/animal it is found in
1	Nostrils positioned near the top of the head allow animals	Nostrils close when the animal goes under the water	Whales
2	Leaves and stems are absent	To store water	Cacti
3	Loss of water by excreting uric acid in water.	This ensures very little wastage of water.	Camel
4	Hollow bone	To make them light to fly	Birds
5	Birds have wings that are covered with feathers	Trap air to keep the body warm and help the bird fly	Birds
6	Presence of flippers and legs	For swimming	Whales
7	Thin and broad leaves with a large number of stomata on the undersides of leaves.	Reduce transpiration and prevent water loss	Mesophytes
8	The broad upper surface is coated with wax	Acts as a water repellent and allows them to remain afloat on the surface of water	Water lily

17. Extensive poaching and hunting have reduced the tiger population in Asia to a dangerous level.

(a) What are they hunted for (2 points)

(b) Draw a food web with tiger as the top-level carnivore (At least 2 food chains to be shown)

(c) What effect will removal of the tiger have on (i) the herbivore, (ii) producer?

Ans:

(a) Tigers are hunted for the wildlife trade and for making traditional medicine.
(b) Grass 🠖 Rabbit 🠖 Tiger OR Plants 🠖 Deer 🠖 Tiger.
(c) The removal of the tiger will affect
- Herbivore: The number of herbivores will increase exponentially.
- Producer: The number of producers would decline as the herbivores are larger in population.