Q1. Define nutrition.
Ans:
Nutrition is the mode of taking in food by an organism & its utilization by the body.
Q2. Define nutrients.
Ans:
Carbohydrates, proteins, fats, vitamins & minerals are components of food called nutrients.
Q3. What is the function of guard cells in photosynthesis:
Ans:
- Guard cells are kidney shaped cells that surround the stomata opening.
- They control the opening & closing of the stomata, allowing the exchange of oxygen & carbon dioxide during photosynthesis and respiration.
- They also regulate transpiration, the process of water vapor loss from the plant.
- By balancing gas exchange & water loss, guard cells help the plant maintain optimal internal conditions.
Q4. Sun is the ultimate source of energy for all living organisms. Explain
Ans:
- Chlorophyll the green pigment present in the leaves captures the energy of the sunlight.
- During photosynthesis, this energy is used to prepare food from carbon dioxide & water.
- Solar energy captured by the leaves as stored in the plant in the form of food.
- All other organisms are directly or indirectly dependent on the plants for food.
- Plants cannot make their food without sunlight.
- Hence, sun is the ultimate source of energy for all living organisms.
Q5. ''In the absence of photosynthesis, life would be impossible on the earth.'' What do you think about this statement?
Ans:
- There will be no life if there is no photosynthesis.
- Plants are autotrophs & prepare their own food during photosynthesis.
- All living organisms depend directly or indirectly on the food prepared by the plants.
- Oxygen which is released during photosynthesis is essential for survival of all living organisms.
- So an absence of photosynthesis, life would be impossible on earth.
Q6. Avni saw lichens on the rock. Help her by identifying the mode of nutrition of lichens.
Ans:
- Lichens have a symbiotic mode of nutrition.
- In symbiosis, organisms live together & help each other by mutually sharing shelter & nutrients.
- In lichens, an alga & fungus live together.
- The fungus provides the alga with shelter, water & minerals.
- The alga has chlorophyll, hence it prepares food & provides it to the fungus.
Q7. What would be the impact on the ecosystem if decomposers were remove from the environment?
Ans:
- Decomposers like fungi & bacteria feed on dead & decaying matter.
- Eliminating them would cause dead bodies of animals & plants to pile up.
- Thus there would leave no space for new organisms to survive.
- Decomposers release essential nutrients like nitrogen, phosphorus & potassium back into the soil by breaking down organic matter.
- Plants, being primary producers, rely on these nutrients recycled by decomposers for growth.
- This would cause all life forms to starve & die.
Q8. How do plants get carbon dioxide for photosynthesis?
Ans:
- The leaves surface contain tiny pores called as stomata.
- Carbon dioxide enters through these stomata opening.
Q9. Why are animals & humans called heterotrophs?
Ans:
- Heterotrophs are organisms that cannot prepare their own food.
- They depend on other organisms for their food.
- Animals & humans depend directly or indirectly on plants or other organisms for their food.
- Hence, they are called heterotrophs.
Q10. Why algae are green in colour?
Ans:
- Algae contain green pigment called as chlorophyll.
- Algae can prepare their own food & get the green colour due to the presence of this pigment. chlorophyll.
Q11. Rohan observed a greyish white thing which spoiled his school leather shoes during rainy season. What is this thing and why got did it spoil the shoes?
Ans:
- The greyish white thing on the shoes is fungi.
- The fungi are saprophytes i.e. organisms that grow & get their nutrition from dead & decaying matter.
- They usually grow in damp, moist & humid areas.
- In rainy season, the climate is moist & humid.
- Hence the fungi grow easily on leather shoes that are moist or not kept in proper ventilation.
- These fungi spoil a lot of things pickles, leather, clothes, etc. during rainy season.
Q12. Why gardeners use fertilizers & manures?
Ans:
- As plants absorb minerals & nutrients from the soil, they keep on declining .
- Hence, to enrich the soil fertilizers & manures containing nutrients such as nitrogen, potassium, phosphorous, etc. need to be added.
- This helps in growing healthy plants.
Q13. Benefits of rhizobium.
Ans:
- Crop plants cannot directly absorb the atmospheric nitrogen though it is present in abundance.
- The soil has certain bacteria like rhizobium, that convert gaseous nitrogen into soluble usable form.
- Also, when crop plants absorb nitrogen & the soil becomes deficient in nitrogen.
- Rhizobium convert atmospheric nitrogen to usable form & reduce the use of nitrogenous fertilizer.
Q14. There are three pots A, B, & C. Pots A & B have soil with nitrogen fertilizer. Pot C has soil with no fertilizer. A bean plant without root nodules is planted in pot A. In pot B & C bean plant with root nodules are planted. After few days plant in which pot will show highest yield and why?
Ans:
- The plant in pot A will show very low yield as without root nodules, it will not be able to use the nitrogen in the soil efficiently.
- The plant in pot B will give the highest yield as it has two sources of nitrogen which is an important nutrient for growth of crop plants. The plant benefits from both: the nitrogen fertilizer in the soil & the nitrogen fixed by the soil bacteria rhizobium present in its root nodules.
- The plant in pot C will show lower yield as it has less nitrogen due to absence of nitrogen fertilizers. It gets only nitrogen that is fixed by the soil bacteria rhizobium present in its root nodules.
Q15. Some leaves are not green in colour but can prepare their own food.
Ans:
- These plants have chlorophyll & so they can prepare their own food.
- Nut their leaves also have red, brown or other colour pigments.
- These pigments mask the green colour of the chlorophyll.
- Hence, some leaves are not green in colour but can prepare their own food.
