INTEXT QUESTIONS 29.1
1. Sunlight forms the abiotic component of ecosystem, name one biotic component.
Answer: A biotic component of an ecosystem is plants (animals and microorganisms).
2. Why are plants called producers? Which trophic level do they occupy in an ecosystem?
Answer: Plants are called producers because they are the only organisms that can convert inorganic substances like carbon dioxide, water, and minerals into organic food such as carbohydrates, using sunlight energy through the process of photosynthesis. They produce food for all other living organisms in the ecosystem.
Plants occupy the first trophic level in an ecosystem.
3. Give one reason in support of the statement that “food web is a jumble of food chains”.
Answer: A food web is a jumble of food chains because an organism occupies more than one trophic level and feeds on multiple sources. Since animals eat varied food to meet energy needs, interconnected food chains form a complex, tangled web rather than a simple linear path.
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.
Answer: Food chain : Grass → Rabbit → Tiger
Food Web: Grass → Rabbit → Tiger
Grass → Sheep → Wolf
Grains → Rat → Snake → Peacock
Grains → Rat → Cat
Phytoplankton → Small Fish → Large Fish → Vulture.
INTEXT QUESTIONS 29.2
1. Name any two ways which are responsible for adding carbon dioxide in the atmosphere.
Answer: Two ways responsible for adding carbon dioxide to the atmosphere are:
(i) Factories (ii) Vehicles
2. Name the bacteria which live in the roots of the leguminous plants and are responsible for nitrogen fixation.
Answer: The bacteria that live in the roots of leguminous plants and are responsible for nitrogen fixation are called rhizobium .
3. What is the process of conversion of free atmospheric nitrogen into nitrites and nitrates called?
Answer: The conversion of free atmospheric nitrogen into nitrites and nitrates is called nitrogen fixation.
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.
Answer: Role of denitrifying bacteria: Reduces nitrate to nitrogen .
Examples:
Denitrifying bacteria – Pseudomonas (or Clostridium)
Role of nitrifying bacteria: Converts ammonia to nitrate .
Examples:
Nitrifying bacteria – Nitrosomonas (or Nitrobacter)
5. Mention any one role that you play in the (i) nitrogen cycle and (ii) carbon cycle.
Answer: i) Role in the nitrogen cycle: We release nitrogen compounds into the soil through our urine and excreta.
(ii) Role in the carbon cycle: We release carbon dioxide (CO₂) into the atmosphere through respiration.
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.
Answer: We obtain nitrogen from the food we eat, such as vegetables, pulses, milk, eggs, or meat, which contain proteins.
7. Mention one way in which increasing deforestation by humans is influencing the carbon cycle.
Answer: Increasing deforestation increases the level of carbon dioxide (CO₂) in the atmosphere, as fewer trees are available to absorb CO₂ during photosynthesis.
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