Chapter 1: Nutrition in Plants - Important Questions & Answers
I. Very Short Answer Type Questions (1-2 Marks)
Define nutrition.
Answer:
Nutrition is the mode of taking food by an organism and its utilisation by the body.
What are autotrophs? Give an example.
Answer:
Organisms that can prepare their own food from simple inorganic substances like carbon dioxide and water are called autotrophs. Example: Green plants.
What are heterotrophs? Give an example.
Answer:
Organisms that depend on other organisms for their food are called heterotrophs. Example: Animals, humans, fungi.
Name the green pigment present in leaves.
Answer:
Chlorophyll.
What are stomata?
Answer:
Stomata are tiny pores present on the surface of leaves, mainly on the lower surface, through which plants exchange gases (carbon dioxide and oxygen) with the atmosphere.
Name the raw materials required for photosynthesis.
Answer:
Carbon dioxide, water, sunlight, and chlorophyll.
What is the end product of photosynthesis?
Answer:
Carbohydrates (glucose/starch) and oxygen.
Name a parasitic plant.
Answer:
Cuscuta
(
Amarbel
).
Name an insectivorous plant.
Answer:
Pitcher plant, Venus flytrap.
What is the mode of nutrition in fungi?
Answer:
Saprotrophic nutrition.
II. Short Answer Type Questions (2-3 Marks)
Why do organisms need to take food?
Answer:
All organisms need to take food to get energy for their growth, to repair damaged parts of their bodies, and to carry out various life processes.
Differentiate between a parasite and a saprophyte.
Answer:
Parasite:
An organism that lives on or in another living organism (host) and derives its nutrition from the host, often harming it. (e.g.,
Cuscuta
)
Saprophyte:
An organism that obtains nutrients from dead and decaying organic matter. (e.g., Fungi like mushrooms, bread mould)
Explain the process of photosynthesis.
Answer:
Photosynthesis is the process by which green plants synthesize their own food (carbohydrates) from carbon dioxide and water in the presence of sunlight and chlorophyll. Oxygen is released as a
byproduct
. The process can be represented by the equation: Carbon
dioxide+WaterSunlight
, Chlorophyll
Carbohydrates+Oxygen
How are water and minerals transported to the leaves of a plant?
Answer:
Water and minerals absorbed by the roots from the soil are transported to the leaves through specialized vessel-like structures that form a continuous network throughout the root, stem, branches, and leaves. These vessels are called xylem.
Why are leaves called the "food factories" of plants?
Answer:
Leaves are called the food factories of plants because the process of photosynthesis, where food is synthesized, primarily occurs in the leaves. They contain chlorophyll, which captures sunlight, and have stomata for the intake of carbon dioxide.
Why do some plants trap insects, even though they are green and perform photosynthesis?
Answer:
Insectivorous plants, like the pitcher plant, trap insects because they grow in soil that is deficient in certain nutrients, particularly nitrogen. While they perform photosynthesis for carbohydrates, they digest insects to
fulfill
their nitrogen requirements.
What is a symbiotic relationship? Give an example.
Answer:
A symbiotic relationship is an association between two different organisms where both organisms benefit from each other.
Example:
Lichens are a symbiotic association between an alga and a fungus. The alga provides food (through photosynthesis) to the fungus, and in return, the fungus provides shelter, water, and minerals to the alga. Another example is Rhizobium bacteria living in the root nodules of leguminous plants, providing nitrogen to the plant and getting food and shelter in return.
III. Long Answer Type Questions (3-5 Marks)
How would you test the presence of starch in leaves? Explain with an experiment.
Answer:
To test the presence of starch in leaves (Iodine test):
Procedure:
Take two potted plants of the same kind.
Keep one plant in a dark room for 72 hours (3 days) to remove any pre-existing starch from its leaves.
Keep the other plant in sunlight.
Take a leaf from each plant.
Boil each leaf in water for a few minutes to soften it.
Then, immerse each leaf in a beaker containing alcohol and carefully heat it over a water bath (alcohol is
flammable, so direct heating is avoided). This removes the green chlorophyll.
Wash the decolorized leaves with water.
Add a few drops of iodine solution to each leaf.
Observation:
The leaf from the plant kept in sunlight will turn blue-black, indicating the presence of starch. The leaf from the plant kept in the dark will not show a blue-black colour, indicating the absence of starch.
Conclusion:
This experiment demonstrates that sunlight is necessary for photosynthesis and the formation of starch in leaves.
Show with the help of a sketch that plants are the ultimate source of food.
Answer:
(For this question, students should draw a diagram. A description of the diagram is provided below.)
Sketch components:
Sun:
The primary source of energy.
Green Plant:
Depict a plant synthesizing food using sunlight. Label it as "Producer."
Herbivore:
Show an animal (e.g., goat, deer, rabbit) eating the plant. Label it as "Primary Consumer."
Carnivore:
Show an animal (e.g., tiger, lion, human) eating the herbivore. Label it as "Secondary Consumer."
Omnivore (optional):
Show an animal (e.g., human) eating both plants and animals.
Decomposers (optional):
Show fungi/bacteria acting on dead plants and animals, returning nutrients to the soil.
Explanation:
The sketch illustrates a food chain, starting from the sun providing energy for plants to make their own food. Herbivores directly consume plants, and carnivores consume herbivores. Thus, all living organisms, directly or indirectly, depend on plants for their food and energy.
How are nutrients replenished in the soil? Explain both natural and artificial methods.
Answer:
Plants continuously absorb nutrients from the soil, leading to their depletion. Nutrients are replenished in the soil by:
Natural Methods:
Decomposition:
Decomposers (bacteria and fungi) break down dead organic matter (plants and animals), releasing nutrients back into the soil.
Nitrogen Fixation:
Atmospheric nitrogen, which plants cannot directly use, is converted into usable forms (like nitrates) by certain bacteria (e.g., Rhizobium) present in the root nodules of leguminous plants (e.g., peas, beans). This enriches the soil with nitrogen.
Rain and weathering:
Rainwater can leach nutrients from rocks, and weathering of rocks also releases minerals into the soil.
Artificial Methods:
Adding Manure and Fertilizers:
Farmers add organic manure (composed of decomposed plant and animal waste) and chemical fertilizers (rich in specific nutrients like nitrogen, phosphorus, and potassium) to the soil. These replenish the nutrient content and maintain soil fertility.
IV. Higher Order Thinking Skills (HOTS) Questions
If a few leaves of a potted plant are coated with a thin layer of Vaseline or oil, what effect would it have on the leaves and the plant as a whole?
Answer:
Coating leaves with Vaseline or oil would block the stomata (tiny pores) on their surface. This would severely hinder:
Photosynthesis:
Carbon dioxide would not be able to enter the leaves, stopping food production.
Transpiration:
The loss of water vapor from leaves would be prevented, which can lead to overheating of the plant and disrupt water uptake from the roots. Ultimately, this would lead to the wilting and eventual death of the affected leaves and potentially the entire plant due to lack of food and disrupted water balance.
Farmers often rotate crops, for example, growing leguminous plants (like pulses) after cereal crops (like wheat or rice). Why is this practice beneficial?
Answer:
This practice is beneficial because leguminous plants have a symbiotic relationship with Rhizobium bacteria in their root nodules. These bacteria fix atmospheric nitrogen into a usable form for plants. When leguminous plants are grown, they enrich the soil with nitrogen, which is a crucial nutrient for plant growth. This reduces the need for artificial nitrogenous fertilizers for the subsequent cereal crop, making the soil more fertile naturally and promoting sustainable agriculture.
Can we survive only on raw, leafy vegetables/grass? Discuss.
Answer:
No, humans cannot survive only on raw, leafy vegetables or grass. While these provide some nutrients, human digestive systems are not equipped to efficiently break down the cellulose present in large quantities in grass and many raw leafy vegetables. Ruminant animals (like cows) have specialized digestive systems and bacteria to digest cellulose. Humans need a balanced diet consisting of carbohydrates, proteins, fats, vitamins, and minerals from various sources for proper growth, energy, and body functions.
V. Multiple Choice Questions (MCQs)
Which of the following is an example of an autotroph? a) Mushroom b)
Cuscuta
c) Green plant d) Human
Answer:
c) Green plant
The gas released during photosynthesis is: a) Carbon dioxide b) Nitrogen c) Oxygen d) Hydrogen
Answer:
c) Oxygen
The term used for the mode of nutrition in yeast, mushroom, and bread mould is: a) Autotrophic b) Insectivorous c) Saprophytic d) Parasitic
Answer:
c) Saprophytic
Cuscuta
is an example of a: a) Autotroph b) Parasite c) Saprotroph d) Host
Answer:
b) Parasite
The plant which traps and feeds on insects is: a) Rose b) China rose c) Pitcher plant d) Mango tree
Answer:
c) Pitcher plant
In the absence of which of the following will photosynthesis not occur in leaves? a) Guard cells b) Chlorophyll c) Vacuole d) Space between cells
Answer:
b) Chlorophyll
The tiny pores on the surface of leaves through which gases are exchanged are called: a) Xylem b) Phloem c) Stomata d) Guard cells
Answer:
c) Stomata
Solar energy is converted into chemical energy during: a) Respiration b) Transpiration c) Photosynthesis d) Digestion
Answer:
c) Photosynthesis
