Free Nutrition in Plants Subjective Test 02 Practice Test - 7th grade
Question 1
Name a bacterium responsible for fixing atmospheric nitrogen. [1 MARK]
SOLUTION
Solution :Rhizobium bacteria thriving in the root nodules of leguminous plants are capable of nitrogen fixation. They are able to convert atmospheric nitrogen to the form usable by plants.
Question 2
Name a parasitic plant which has a yellow slender tubular stem? What is its special root called? [2 MARKS]
SOLUTION
Solution :Name of plant: 1 Mark
Name of root: 1 Mark
Cuscuta is the parasitic plant with a yellow slender tubular stem.
The special roots that penetrate deep into host plant tissues and absorb the nutrients from them are called haustoria.
Question 3
"All the plants in the world are autotrophs."
Is this statement true or false? Explain your answer. [2 MARKS]
SOLUTION
Solution :Statement: 1 Mark
Explanation: 1 Mark
This statement is false.
Autotrophs only account for the green plants in the world. Since there are so many non-green plants in the world, it would be wrong to say that all plants are autotrophs.
Many plants like the pitcher plant and Venus flytrap are partly autotrophic and partly heterotrophic. Since they grow in nitrogen-deficient soil they trap and digest insects to meet their nitrogen requirements. Some plants alike Cuscuta are completely non-green and are parasitic in nature.
Question 4
What is holozoic mode of nutrition? Give some examples of organisms exhibiting this mode of nutrition. [2 MARKS]
SOLUTION
Solution : Definition: 1 Mark
Examples: 1 Mark
The mode of nutrition in which organisms take in food and digest it inside the body is called holozoic nutrition.
Examples: Humans, Amoeba, etc.
Question 5
Name the products and byproducts produced during photosynthesis? What are they used for? [2 MARKS]
SOLUTION
Solution :Nutrients: 1 Mark
Use: 1 Mark
Simple sugars like glucose is produced during photosynthesis. Oxygen is produced as a byproduct.
The glucose is used by plants to generate energy for its metabolic activities. A very small portion of the oxygen produced is used by the plants for cellular respiration while the rest is released into the atmosphere. This oxygen released into the atmosphere is used by other organisms.
Question 6
Distinguish between a parasite and a saprophyte. Give examples for each. [3 MARKS]
SOLUTION
Solution : Differences: 1 Mark each
Examples: 1 Mark
S.No Parasites Saprophytes 1. They grow on other
organisms and derive their nutrients from
them.They obtain their
nutrition from
dead and decaying
organic matter.2. They take readymade
food from the host
plant.They release digestive enzymes
into the surroundings and absorb the
digested food.Examples Cuscuta, orchids Fungi, some bacteria
Question 7
"Autotrophs are the ultimate source of food". Do you agree with the statement? Why or why not? Justify with a diagram [3 MARKS]
SOLUTION
Solution : Statement: 1 Mark
Justification: 1 Mark
Diagram: 1 Mark
The statement is correct, autotrophs are the ultimate source of food.
Only autotrophs like plants and algae can produce food on their own and all the other organisms are either directly or indirectly dependent on them.
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Question 8
Name the following: [3 MARKS]
1. Organisms that live together and get mutually benefited.
2. Example of a plant having both autotrophic and heterotrophic mode of nutrition.
3. The pores through which leaves exchange gases.
SOLUTION
Solution : Each part: 1 Mark
1. Organisms that live together and get mutually benefited - Symbionts.
2. Pitcher plant has both autotrophic and heterotrophic mode of nutrition.
3. Stomata are the pores through which leaves exchange gases.
Question 9
What are the basic components required for photosynthesis? Mention where these components are used. [3 MARKS]
SOLUTION
Solution : Requirements: 1 Mark
Uses in photosynthesis: 2 Marks
For performing photosynthesis, plants require the following basic components:
1. Carbon dioxide and water
2. Chlorophyll
3. Sunlight
Carbon dioxide acts as the carbon source for sugar formation.
Water provides electrons and hydrogen.
Chlorophyll is the green pigment which helps the plant to harness light energy.
Sunlight is very important as it provides the high energy required to break the hydrogen and oxygen bonds in water.
Question 10
Why are carnivorous plants dependent on insects for their nutritional requirements? Give two examples. [3 MARKS]
SOLUTION
Solution :Explanation: 2 Marks
Examples: 1 Mark
Carnivorous plants derive some or most of the nutrients (but not energy) by trapping small animals and insects. They are adapted to grow in places where the soil is poor in nutrients, especially nitrogen. So, to obtain this nitrogen, they depend on other organisms.
Examples: Venus flytrap, Pitcher plant etc.
Question 11
Can green plants be heterotrophic? Explain any two types of heterotrophs. [3 MARKS]
SOLUTION
Solution : Statement: 1 Mark
Types of heterotrophs: 1 Mark each
Green plants can sometimes be heterotrophic.
The different types of heterotrophs are parasites, symbionts, saprophytes, and insectivores.
Any two:
1. Parasitic plants obtain their nourishment from other living organisms. Example: mistletoe.
2. Symbiotic plants develop a special relationship with certain other organisms to obtain nourishment. This type of arrangement is beneficial to both the organisms involved. Example: lichens.
3. Saprophytic plants which feed on dead or decaying organic matter. They secrete digestive juices onto dead and decaying matter to break it and then absorb nutrients from it. Example: coral roots.
4. Insectivorous plants have leaves that are modified into special structures which have the ability to trap small organisms like insects. The plant then derives the nutrition from the insect by slowly digesting it. Example: Venus flytrap.
Question 12
Give a detailed note on symbiosis. How is it beneficial for organisms? Explain with the help of examples. [3 MARKS]
SOLUTION
Solution :Explanation: 1 Mark
Examples: 1 Mark each
Symbiosis is the relationship between two organisms in which both organisms get benefited from each other.
For example, certain fungi live in the roots of trees. The tree provides nutrients to the fungus and, in return, receives help from it to take up water and nutrients from the soil. This association is very important for the tree.
In organisms called lichens, a chlorophyll-containing partner, which is algae and a fungus lives together. The fungus provides shelter, water, and minerals to the algae.
In return, the algae provide food which it prepares by photosynthesis.
Question 13
Is chlorophyll necessary for photosynthesis? How do we prove it with an experiment? [5 MARKS]
SOLUTION
Solution : Experiment steps: 1 Mark each
Inference: 1 MarkChlorophyll is extremely important to perform photosynthesis since it is the compound responsible for harnessing sun's energy.
To prove the importance of photosynthesis, the following steps are performed in a sequential order.
Step-1: Take a beaker with boiling water and drop a croton leaf into it. Let it boil for 2 minutes (A croton leaf is a variegated leaf with white and green patches)
Step-2: Take the leaf out of the beaker and place it in a test tube with alcohol. Place this test tube in a hot water bath for 10 minutes. Alcohol decolourises the leaf by removing chlorophyll from it by the process of bleaching.
Step-3: Remove the leaf from alcohol and wash it with warm water. Place it on a tile for further test.
Step-4: Add 2 drops of iodine onto the leaf. The portions which were green i.e. contained chlorophyll turn into bluish-black colour indicating a positive test for starch. The portions which did not contain chlorophyll and did not participate in photosynthesis turns brown because of the iodine solution indicating a negative test for starch.
This experiment proves that food, or starch, is made only in the places of the leaves which are green, or in other words, have chlorophyll in them. So we can conclude that chlorophyll is necessary to perform photosynthesis.
Question 14
Explain with an experiment how light is necessary for photosynthesis. [5 MARKS]
SOLUTION
Solution : Experiment steps: 1 Mark each
Inference: 1 Mark
1) A plant is selected and destarched by keeping it in darkness for 3 days. Pick a leaf and test it with iodine to confirm that the plant is starch free. It won't turn blue-black, which means it did not perform photosynthesis in the darkness and all the starch is used up by the plant.
2) Cover one leaf with black paper.
3) Expose the plant to sunlight for a day.
4) After a day, test the leaf covered with black paper using iodine. It will not turn blue-black as it has not synthesised starch, while the other uncovered leaves will now turn black-blue on the addition of iodine.
Inference: Photosynthesis did not occur in the leaf covered with black paper confirming the essentiality of light for the synthesis of starch.
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Question 15
Prove with the help of an experiment that carbon dioxide is necessary for photosynthesis. [5 MARKS]
SOLUTION
Solution : Experiment steps: 1 Mark each
Inference: 1 Mark
For proving the necessity of carbon dioxide for photosynthesis, the following steps are performed:
1) A potted plant is taken and placed in complete darkness for 24 to 72 hours to destarch it.
2) Take potassium hydroxide in a conical flask stoppered with a rubber cork. Insert one leaf (still attached to parent plant) through a hole in the rubber cork. Potassium hydroxide absorbs all the left-over carbon dioxide from the flask.
3) The entire arrangement is exposed to sunlight for 6 hours.
4) The leaf placed in the conical flask with potassium hydroxide solution is tested with iodine solution. This does not turn blue-black.
Inference: The leaf trapped inside the conical flask did not perform photosynthesis as it did not receive any carbon dioxide. This is the reason why it did not answer a positive test for starch.
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