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NIOS Class 10 Science and Technology Chapter 29 Natural Environment
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Natural Environment
Chapter: 29
INTEXT QUESTIONS 29.1
1. Sunlight forms the abiotic component of the 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 in order 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: Refer to text.
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 reduces nitrate to nitrogen.
(i) Nitrifying bacteria converts ammonia to nitrate.
(ii) Example: denitrifying bacteria – Pseudomonas, Clostridium (any one).
(iii) Nitrifying bacteria Nitrobacter, Nitrosomonas.
5. Mention any one role that you play in the
(i) nitrogen cycle. and
(ii) carbon cycle.
(a) (i) Nitrogen cycle.
Ans: Release/excrete N2 as nitrogen compounds in the urine/excreta).
(ii) carbon cycle.
(b) 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: Lead to 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: Presence of thick layer of densely packed feathers, flippers and legs are 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: Do yourself.
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 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 the 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 is a community of organisms and their physical environment interacting together. Environment involves both living organisms and the non-living physical conditions. These two are inseparable but interrelated. The living and physical components are linked together through nutrient cycles and energy flows.
It consists of two major components, biotic or living components and non biotic or nonliving components. Biotic components include plants, animals, decomposers. Nonliving components include air, water, land.
2. Is detritus a biotic component or is it an abiotic component of an ecosystem?
Ans: Detritus refers to the dead remains of living organisms such as barks, flowers, leaves, and even faeces. It is a biotic component of the ecosystem because it contains the dead remains of organisms.
3. What is the function of Nitrosomonas in the nitrogen cycle?
Ans: The function of nitrogen cycle are mentioned below:
(i) Nitrosomonas is a nitrifying bacteria which converts the nitrogen from ammonia in soil.
(ii) oxidises ammonia to nitrite.
4. With the help of suitable examples differentiate between the detritus and grazing food chain.
Ans: The grazing food chain is different from the detritus food chain as in detritus food chain starts from the dead organ to animal and in grazing starts from the producer which produce food from sunlight.
5. What is the significance of food chain and food web?
Ans: A food chain outlines who eats whom. A food web is all of the food chains in an ecosystem. Each organism in an ecosystem occupies a specific trophic level or position in the food chain or web. Producers, who make their own food using photosynthesis or chemosynthesis, make up the bottom of the trophic pyramid.
6. Why does the energy decrease as we go along the food chain from producers to tertiary consumers?
Ans: As from the food chain it is clear that the primary substance in ecosystem present in more number and gradually this decrease in ordered to the upper category.
7 What will happen if all the animals are removed from a pond?
Ans: If all the animal are removed from the water of pond, then there will be an increase in the number of plants in the pond and because of that oxygen shortage will happen.
8. Why is the number of trophic levels restricted to four or five in a food chain?
Ans: On average only 10 percent of the food available to a trophic level is transferred to next tropic level. Since the amount of available energy becomes as we move to higher tropic levels so very little usable energy remains after four trophic levels. That’s why the food chain has only 3 to 4 tropic levels.
9. What is the difference between energy flow and biogeochemical cycle in an ecosystem?
Ans: Flow takes place in a single direction but the biogeochemical is circular in nature. The process of transfer energy through various trophic levels of the chain is known as the flow of energy and the cycling of the nutrients in the biosphere is called the biogeochemical or nutrient cycle.
10. How are camels able to survive in extreme heat?
Ans: Camels are adapted to live in extreme environments, both hot and cold. Unlike a lot of other mammals, most of a camel’s fat is stored in its humps, which allows for better thermoregulation. It makes it easier for them to release heat from their bodies in hot weather.
11. Why do polar bears have thick fur over their body?
Ans: The polar bear has thick fur in its body. This fur helps the polar bear body warm in the very cold condition in all the season in the polar region.
12. Compare the S-shaped pattern of population growth with the J-shaped pattern of population growth.
Ans: Do yourself.
13. What is population dispersal? What are the two types of population dispersal?
Ans: Population dispersion is the pattern in which organisms in the population live in relation to each other. It is important to note that a population is made up of organisms of the same species in the same area and that dispersion patterns relate to a single species at a time.
Dispersion patterns are the spatial pattern of individuals within a population after the individuals have dispersed. There are three types of population dispersion patterns: uniform, random, and clumped.
14. What is the main cause of population explosion?
Ans: The main causes are high birth rate, lack of reproductive education and family planning, poverty, increase in lifespan due to better health facilities, decrease in death rate, lack of employment opportunities, and improvements in agriculture.
15. Do you think population remains static? Support your answer with suitable explanation.
Ans: Decreased death rates: Advances in medicine, sanitation, and nutrition have led to people living longer, which means more people reach reproductive age. High birth rates: In some parts of the world, cultural norms or lack of access to family planning resources can contribute to larger families.
It’s important to note that population growth rates are slowing down globally, and some regions are even experiencing population decline.
16. Try to complete the table given below.
Ans:
| Feature | How is the feature advantageous to the organism? | Name of the plant/animal if is found | |
| 1 | Nostrils positioned near the top of the head of animals | For breathing | Dolphin’s |
| 2 | In sponge or root | To store water | Cacti |
| 3 | Loss of water by excreting uric acid in water | For Secretion of unwanted substance | In animal. |
| 4 | Hollow bone | oxygen intake during flying | Birds |
| 5 | Feathers in the surface of the body | Trap air to keep the body warm and help the bird to fly | Birds |
| 6 | Presence of flippers and legs | Foe the movement | Dolphin |
| 7 | Thin, bread leaves with alarge number of stomata on the underside of leaves | For the photosynthesis process | In plants leaf |
| 8 | Bladder present in body or swimblade | acts as a water repellentand allows them to remainafloat on the surface ofwater | Water lily |
17. Extensive poaching and hunting has reduced the tiger population in Asia to a dangerous level.
(a) What are they hunted for 2 points.
Ans: The hunted for the skin and the teeth of the tiger while poaching from Asian region.
(b) Draw a food web with tiger as the top level carnivore (At least 2 food chain to be shown)
Ans: DO yourself.
(c) What effect will removal of the tiger have on
(i) The herbivore.
Ans: Herbivores might consume plants faster than they can grow back, leading to a decline in plant diversity and overall food availability.
(ii) Producer?
Ans: Reduced Plant Diversity: With increased pressure from herbivores, some plant species might be preferentially eaten, leading to a decline in their populations and a less diverse plant community.
