class 7 cbse nutrition in plants worksheets
Answers
Nutrition in plants
Question 3. Answer in one or two sentences.
1. What is nutrition?
ANSWER: Nutrition is defined as the process of obtaining food and utilising it by any organism.
Nutrition is one of the key processes of obtaining energy from food.
2. What are 'stomata'? Where are they normally found?
ANSWER: Stomata are the tiny pores on the leaves through which plants absorb atmospheric
carbon dioxide. They are normally found on the underside of the leaves.
3. Write down the chemical equation for manufacture of food in green plants.
ANSWER: The chemical equation representing the process of manufacturing food by green plants
(photosynthesis) is as follows
Carbon dioxide + Water →Chlorophyll Sunlight Glucose + Oxygen
4. What factors are essential for photosynthesis to take place?
ANSWER: Factors essential for photosynthesis are sunlight, water, carbon dioxide and chlorophyll
(green pigment present in the leaves).
5. How does an insectivorous plant absorb nutrients from an insect trapped by it?
ANSWER: Insectivorous plants secrete digestive juices to digest the insect trapped by them. These
plants then absorb the nutrients released from the digested insect.
6. How does a saprophyte digest its food?
ANSWER: A saprophyte secretes digestive juices on the dead and decaying matter to convert the
solid substances into liquid. The saprophyte then absorbs the nutrients from this liquid.
Question 4. Answer these questions.
1. Differentiate between autotrophs and heterotrophs, giving two examples of each.
Ans. Autotrophs Heterotrophs
Organisms which can make their own food from
simple substances are called autotrophs.
Organisms which can not make their own food and
obtain it directly or indirectly from green plants are
called heterotrophs.
They are producers. They are consumers.
For example, all green plants, cynobacteria, etc. For example, all animals like cow, lion and humans.
2. How will you test a leaf for starch? Mention any precautions you will take.
ANSWER: Test for starch:
* Pluck one of the green leaves that have been exposed to sunlight.
* Boil that leaf in water for 5 minutes to soften it.
* Then put the leaf in a test tube containing alcohol. Now, gently place this test tube in a beaker of
warm water till the alcohol starts boiling. The chlorophyll will slowly get dissolved in the alcohol
and the leaf will start losing its green colour.
* Now, remove the alcohol by washing the leaf with warm water. Then spread the leaf over a
white tile and add some iodine solution to it.
* Wash the leaf with water to remove the iodine solution and then hold it in light. The parts of leaf
which have starch will turn blue-black.
Precautions
*Do not allow the water in the beaker to boil.
3. How do plants get nitrogen to synthesize proteins?
ANSWER: Nitrogen is present in the atmosphere in large amounts, but plants can not absorb it
directly. There are two ways by which plants can absorb nitrogen. They are as follows:
The soil bacterium Rhizobium is able to fix the atmospheric nitrogen in water soluble compounds.
Plants absorb these compounds along with water in order to get nitrogen.
Plants can also get nitrogen from the nitrogen-rich fertilizers used by farmers to treat the soil.
4. Explain the following with the help of an example for each:
(a) parasitic nutrition
(b) symbiosis
(c) saprotrophic nutrition
ANSWER:
(a) Parasitic nutrition: Parasites feed on other living organisms to obtain nutrition. This mode of
nutrition is referred to as parasitic nutrition. For example, non green plants like dodder which can
not synthesise their own food, grows over other plants and sucks nutrition from them using their
root like structure.
(b) Symbiosis: The mutually beneficial relationship between two organisms is termed as symbiosis.
For example, lichens are association between alga and fungi. Alga supplies food to its fungal
partner, while fungi provides shelter to its algal partner.
c Saprotrophic nutrition: Organisms which feed on dead and decaying matter are called saprotrophs, and this mode of obtaining nutrition is called Saprotrophic nutrition. For example, mushrooms, fungi and bacteria
5 Why are manures and fertilizers added to the soil in a farm ?
ANSWER
Manures and fertilizers added to the soil in order to enrich it's organic composition and replenish the nutrients in it. The plants absorb most of the nutrients from the soil, leaving the soil deficient of these nutrients. Manures and fertilizers are rich in organic matter and nutrients like nitrogen, potassium and phosphorous. Thus, according the need of the plants, farmers add manures and fertilizers in the soil
Answer:
the process of taking in food and it's utilization by an organisms