1. Choose the correct option.
a. In the process of photosynthesis, the gas given out by green leaves is ______
i. oxygen
ii. carbon dioxide
iii. nitrogen
iv. ozone
Answer: i. oxygen
b. To test for the presence of starch using iodine, the green leaf is first boiled in alcohol to
i. remove starch
ii. dissolve chlorophyll
iii. make the leaf soft
iv. make the leaf transparent
Answer: ii. dissolve chlorophyll
c. Which of the following is an insectivorous plant?
i. Cuscuta
ii. Croton
iii. Lichen
iv. Sundew
Answer: iv. Sundew
d. The mode of nutrition shown by coral root is ______
i. myco-heterotrophic
ii. parasitic
iii. saprotrophic
iv. autotrophic
Answer: i. myco-heterotrophic
2. Assertion-Reasoning questions.
(i) Assertion (A): All plants are not autotrophic.
Reason (R): Insectivorous plants cannot synthesise their own food.
(d) Assertion (A) is true, but Reason (R) is false.
Explanation: The Assertion is true because some plants, like Cuscuta and mushrooms, are heterotrophic. However, the Reason is false because insectivorous plants are autotrophic and can perform photosynthesis; they trap insects only to get nutrients like nitrogen.
(ii) Assertion (A): Plants convert light energy into chemical energy during the process of photosynthesis.
Reason (R): Sugar produced from photosynthesis by plants is used by human beings as a source of energy.
(b) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
Explanation: Both statements are correct. The Reason correctly explains the Assertion by stating what the “chemical energy” (sugar) is used for, demonstrating the energy conversion.
3. Answer the following questions in one sentence.
a. Organism on which a parasite lives
- Host
b. Organisms that break down organic matter to release nutrients.
- Decomposers
c. Modified succulent roots in parasitic plants.
- Haustoria
d. A relationship between two organisms in which both are benefited.
- Symbiosis
e. Cells that regulate the opening and closing of stomata.
- Guard cells
4. Answer the following questions in 2-3 sentences.
a. Explain the term autotrophic nutrition.
Answer. Autotrophic nutrition is the mode of nutrition where organisms can make their own food. They use simple inorganic substances like carbon dioxide and water in the presence of sunlight to synthesize complex food, such as glucose. Green plants are autotrophs.
b. What is crop rotation?
Answer. Crop rotation is a farming practice of growing different types of crops on the same piece of land in a sequential season. This helps in replenishing soil nutrients naturally, especially nitrogen, by growing leguminous plants like peas or beans.
c. What is a lichen?
Answer. A lichen is a symbiotic association between a fungus and an alga. The fungus provides shelter and water, while the alga prepares food through photosynthesis. It is a classic example of a mutualistic relationship.
5. Answer the following questions in 3-4 sentences.
a. Explain total parasites with an example.
Answer. Total parasites are plants that depend completely on the host plant for all their needs, including water, minerals, and food. They lack chlorophyll and therefore cannot perform photosynthesis. A common example is Cuscuta (dodder), which is a yellow thread-like plant that winds around the host and derives its nutrition through special roots called haustoria.
b. What are decomposers? Explain the two types of decomposers with examples.
Answer. Decomposers are organisms that break down dead and decaying organic matter into simpler inorganic substances, thus recycling nutrients in the ecosystem. The two main types are:
1. Saprotrophs: They secrete digestive enzymes onto the dead matter and absorb the digested food. Example: Fungi like Mushrooms.
2. Detritivores: They ingest (eat) the dead matter and then digest it inside their body. Example: Earthworms.
6. Complete the table to compare the modes of nutrition.
| Plant | Autotroph or Heterotroph | Site of photosynthesis if an autotroph | Mode of nutrition if heterotroph |
| Apple tree | |||
| Cuscuta | |||
| Lichen | |||
| Mushroom | |||
| Mistletoe |
| Plant | Autotroph or Heterotroph | Site of photosynthesis if autotroph | Mode of nutrition if heterotroph |
| Apple tree | Autotroph | Leaves | – |
| Cuscuta | Heterotroph | – | Parasitic |
| Lichen | Autotroph | Algal partner | – |
| Mushroom | Heterotroph | – | Saprotrophic |
| Mistletoe | Heterotroph | – | Parasitic |