Important Main Point In Class 7 Science Chapter 1
1. Mode Of Nutrition In Plants
In this part of the content gives you a fundamental idea about modes of nutrition which is usually required by different organisms. As we know, food is essential for all living organisms. The food contains some nutrients like, Carbohydrate, Proteins, Fats, Vitamins and Minerals which are required by our body for the growth and development, called nutrition. We get food from plants and animals, as you know. But how do plants get their food? Remember, plants can make their food themselves, but humans and animals cannot. Autotrophs are the mode of nutrition in which organisms make their own food. That means plants are autotrophs. Here, we cannot make our food; we are dependent on plants for the readymade form of food. So, we are known as тАШHeterotrophsтАЩ. Therefore, it is clear that the plant uses the autotrophic mode of nutrition for their growth and development.┬аNutrition in Animals┬аand most of the other organisms is heterotrophic mode of nutrition for growth and development.
2. Photosynthesis тАУ Food Making Process In Plants
In this part of the content focuses on the process of photosynthesis which is essential for the survival of all living organisms. Plants are the only organisms that can prepare food by using sunlight, water, carbon dioxide and minerals. You are surprised to know that leaves are the food factories of plants. Therefore, all the raw materials must reach there. The leaves have a green pigment called chlorophyll which captures the energy of the sunlight. This light energy is used to prepare food. So, this process is known as тАШPhotosynthesisтАЩ. The raw material, i.e. carbon dioxide taken from the air through the tiny pores of leaves, called stomata. Water and minerals present in the┬аsoil┬аare absorbed by the roots and transported to the leaves. The food produced by the process of photosynthesis is mainly carbohydrate which later gets converted into starch. During the process of photosynthesis, oxygen is released in the atmosphere. Thus, you can see how photosynthesis is essential for the survival of all living organisms.
3. Other Modes Of Nutrition In Plants
There are some plants which do not contain chlorophyll in them and thus cannot prepare their food. They depend on other plants or organisms for food. Therefore, they are known as a parasite. You will be surprised to know that there are some plants which can trap insects and digest them. Such insect-eating plants are called insectivorous plants.
4. Saprotrophs
This part of the content introduces some other modes of nutrition which is usually essential for different organisms. You might have seen cotton-like threads spread on the rotten or wet piece of bread. These organisms are often known as fungi. The way they take their nutrients from dead or decaying matter called тАШSaprotrophsтАЩ. Remember, the mode of nutrition in which organisms take their nutrients from decaying matter called saprotrophic nutrition. Sometimes, two plants of different species live together and help each other in obtaining food and shelter. This association is called symbiosis, and such plants are called symbiotic plants. The association is significant for both of their survival.
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5. How Nutrients Replenished In The Soil
You learnt that plants absorb nutrients from the soil. Crops require much nitrogen to make protein. After the harvest, the soil becomes deficient in nitrogen. Plants cannot use the nitrogen gas available in the atmosphere directly. The action of┬аrhizobium bacteria can convert this nitrogen┬аinto a soluble form but that bacteria cannot make its own food. In return, leguminous plants provide food and shelter to the rhizobium bacteria. Thus, they have a symbiotic relationship as you learn before. This association is significant for the farmer, as they do not need to add nitrogen fertilizers to the soil in which leguminous plants are grown. In this way, you can see that every living organization needs some energy and nutrient materials to ensure that the life-processes go on smoothly.
Important Questions In Class 6 Science Chapter 1
1. The term that is used for the mode of nutrition in yeast, mushroom and bread-mould is
(a) autotrophic
(b) insectivorous
(c) saprophytic
(d) parasitic
2. Organisms which prepare food for themselves using simple naturally available raw materials are referred to as
(a) heterotrophs
(b) autotrophs
(c) parasites
(d) saprophytes
3. When we observe the lower surface of a leaf through a magnifying lens we see numerous small openings. Which of the following is the term given to such openings?
(a) Stomata
(b) Lamina
(c) Midrib
(d) Veins
4. 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
5. Two organisms are good friends and live together. One provides shelter, water, and nutrients while the other prepares and provides food. Such an association of organisms is termed as
(a) saprophyte
(b) parasite
(c) autotroph
(d) symbiosis
6. Which of the following statements is/are correct?
(i) All green plants can prepare their own food.
(ii) Most animals are autotrophs.
(iii) Carbon dioxide is not required for photosynthesis.
(iv) Oxygen is liberated during photosynthesis.
Choose the correct answer from the options below:
(a) (i) and (iv) (b) (ii) only (c) (ii) and (iii) (d) (i) and (ii)
7. Which of the following raw material is available in the air for photosynthesis?
(a) Oxygen
(b) Carbon dioxide
(c) Nitrogen
(d) Hydrogen
8. Pitcher plant traps insects because it
(a) is a heterotroph.
(b) grows in soils which lack in nitrogen.
(c) does not have chlorophyll.
(d) has a digestive system like human beings.
9. A goat eats away all the leaves of a small plant (balsam). However, in a few days, new leaves could be seen sprouting in the plant again. How did the plant survive without leaves?
10. Nitrogen is an essential nutrient for plant growth. But farmers who cultivate pulse crops like green gram, bengal gram, black gram, etc. do not apply nitrogenous fertilizers during cultivation. Why?
Answers Of Important Questions
1 (c)
2 (b)
3 (a)
4 (b)
5 (d)
6 (a)
7 (b)
8 (b)
9. The plant survived on the food stored in the stem and roots.
10. Roots of pulses (leguminous plants) have a symbiotic association with a bacterium called Rhizobium which fixes nitrogen. Hence, farmers need not use nitrogenous fertilizers.
Important NCERT Questions Class 7 Science Chapter 1
Keep the plant in a dark room for three days so that all the starch gets used up.
Now select a leaf cover its portion with a black strip paper and keep the plant in sunlight for about six hours.
Pluck the leaf from the plant. Mark the uncovered area in it and trace them on a sheet of paper.
Dip the leaf in boiling water for a few minutes.
After this, immerse it in a beaker containing alcohol.
Carefully place the above beaker in a water-bath and heat till the alcohol begins to boil.
Now dip the leaf in a dilute solution of iodine for a few minutes.
Take out the leaf and rinse off the iodine solution.
You observe that the presence of starch in various areas of the leaf which was uncovered.
7th Science Chapter 1 Important Questions Set тАУ 1
What Do You Mean By Nutrients?
Food is essential for all living organisms. Carbohydrates, proteins, fats, vitamins and minerals are components of food. These components of food are necessary for our body and are called nutrients.
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How Do Plants And Animals Get Their Food?
All living organisms require food. Plants can make their food themselves but animals including humans cannot. They get it from plants or animals that eat plants. Thus, humans and animals are directly or indirectly dependent on plants.
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Name The Raw Materials Which Are Required By Plants For The Preparation Of Food?
Plants are the only organisms that can prepare food for themselves by using sunlight, water, carbon dioxide and minerals. The raw materials are present in their surroundings.
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What Is Nutrition? How Does It Help For All Living Organisms?
Nutrition is the mode of taking food by an organism and its utilisation by the body.
The nutrients enable living organisms to build their bodies, to grow, to repair damaged parts of their bodies and provide the energy to carry out life processes.
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Autotrophic Nutrition
The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic (auto = self; trophos = nourishment) nutrition.
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7th Science Chapter 1 Important Questions Set тАУ 2
Whom Do You Call Autotrophs And Heterotrophs?
The mode of nutrition in which organisms make food themselves, called autotrophs. Such as Plants.
Animals and most other organisms take in ready-made food prepared by the plants. They are called heterotrophs (heteros = other).
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What Do You Understand By Stomata?
Plants takes carbon dioxide from air through the tiny pores present on the surface of the leaves. These pores are surrounded by тАШguard cellsтАЩ. Such pores are called stomata.
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How Do Plants Get Their Raw Materials?
Plants are the only organisms that can prepare food for themselves by using sunlight, water, carbon dioxide and minerals. Water and minerals present in the soil are absorbed by the roots and transported to the leaves. Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. And the solar energy is captured by the leaves.
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Explain Why Leaves Are Termed As Food Factories Of Plants?
Leaves are known as food factories of plants because leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This energy is used to synthesise (prepare) food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight.
Besides leaves, photosynthesis also takes place in other green parts of the plant тАФ in green stems and green branches. The desert plants have scale- or spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.
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Algae
The green patches in ponds or in other stagnant water bodies. These are generally formed by the growth of organisms called algae
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7th Science Chapter 1 Important Questions Set тАУ 3
What Happens If Photosynthesis Do Not Occur In Plants?
In the absence of photosynthesis there would not be any food. The survival of almost all living organisms directly or indirectly depends upon the food made by the plants. Besides, oxygen which is essential for the survival of all living organisms is produced during photosynthesis. In the absence of photosynthesis, life would be impossible on the earth.
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How Does Some Plant Get Their Nitrogenous Compound From Soil?
Nitrogen is present in abundance in gaseous form in the air. However, plants cannot absorb nitrogen in this form. Soil has certain bacteria that convert gaseous nitrogen into a usable form and release it into the soil. These soluble forms are absorbed by the plants along with water.
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There Are Some Plants Which Do Not Have ChlorophyllтАЭ тАУ How Do They Survive?
There are some plants which do not have chlorophyll but they can survive. They cannot synthesise their food. Like humans and animals such plants depend on the food produced by other plants. They use the heterotrophic mode of nutrition. A yellow tubular structures twining around the stem and branches of many trees. This is a plant called Cuscuta (Amarbel). It does not have chlorophyll. It takes readymade food from the plant on which it is climbing. Since, it deprives the valuable nutrients, as parasite.
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What Is Saprotrophic Nutrition?
The mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition.
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The Characteristics Of Pitcher Plant
The pitcher plant has the special structure that is modified part of the leaf. The apex of the leaf forms a lid which can open and close the mouth of the pitcher. Inside the pitcher there are hair which are directed downwards. When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair. The insect is digested by the digestive juices secreted in the pitcher. Such insect-eating plants are called insectivorous plants.
7th Science Chapter 1 Important Questions Set тАУ 4
How Do Fungi Get Their Food?
Fungi have a different mode of nutrition. They secrete digestive juices on the dead and decaying matter and convert it into a solution. Then they absorb the nutrients from it. This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition. Plants which use saprotrophic mode of nutrition are called saprotrophs.
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How Does Fungi Germinate And Grow?
The fungal spores are generally present in the air. When they land on wet and warm things they germinate and grow. Fungi grow on pickles, leather, clothes and other articles that are left in hot and humid weather for long time. During the rainy season they spoil many things.
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What Do You Mean By Symbiotic Relationship?
Some of the organisms live together and share shelter and nutrients. This is called symbiotic relationship. 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.
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Explain With Examples Of Symbiotic Relationship.
Some of the organisms live together and share shelter and nutrients. This is called symbiotic relationship.
In organisms called lichens, a chlorophyll-containing partner, which is an alga, and a fungus live together. The fungus provides shelter, water and minerals to the alga and, in return, the alga provides food which it prepares by photosynthesis.
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The Process Of Food In Green Plants
Leaves are the food factories of plants. The synthesis of food in plants occur in leaves. Therefore, all the raw materials (water, carbon dioxide and sunlight) must reach there. Water and Minerals are transported to the leaves by the vessels which run like pipes throughout the route, the stem, the branches and the leaves. The leaves have a green pigment called chlorophyll which helps leave to capture the energy of the sunlight. The energy is used to synthesis (prepare) food from carbon dioxide and water.
7th Science Chapter 1 Important Questions Set тАУ 5
How Nutrients Are Replenished Into The Soil?
Usually crops require a lot of nitrogen to make proteins. After the harvest, the soil becomes deficient in nitrogen. Nitrogen gas is available in plenty in the air, plants cannot use it in the manner they can use carbon dioxide. They need nitrogen in a soluble form. The bacterium called Rhizobium can take atmospheric nitrogen and convert it into a soluble form. But Rhizobium cannot make its own food. So, it lives in the roots of gram, peas, moong, beans and other legumes and provides them with nitrogen. Most of the pulses (dals) are obtained from leguminous plants. In return, the plants provide food and shelter to the bacteria.
Thus, they have a symbiotic relationship. This association is of great significance for the farmers. They do not need to add nitrogen fertiliser to the soil in which leguminous plants are grown.
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How Nutrients Are Replenished Into The Soil?
Nitrogen Is An Essential Nutrient For Plant Growth. But Farmers Who Cultivate Pulses As Crops Like Green Gram, Bengal Gram, Black Gram Etc. Do Not Apply Nitrogenous Fertilizers During Cultivation. Why?
The plants such as gram, peas, pulses are called тАШLeguminous plantтАЩ. This plants have root nodules in them which have a symbiotic association with bacteria such as rhizobium. This bacteria convert gaseous nitrogen of air into water soluble nitrogen compounds like nitrates. Some of these nitrogen compounds are used by the leguminous plants for their growth. Hence, farmer do not need to apply nitrogenous fertilisers in the fields during cultivation.
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Distinguish Between A Parasite And A Saprotroph.
Parasite:
i). The organisms derive nutrition from the body of other living organisms host are parasites.
ii). Example: Cuscuta (Amar bel)
Saprotroph:
i). The plants which derive nutrition from dead and decaying organisms are called saprotrophs.
ii). Example: Mushrooms.
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Wheat Dough If Left In An Open, After Few Days, Starts To Emit A Foul Smell And Become Unfit For Use. Give Reason.
Carbohydrates in wheat dough encourage the growth of yeast and other saprophytic fungi. They breakdown carbohydrates into simpler compounds like CO2 and alcohol that leads to a foul smell.
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The Presence of Starch in Leaves
Take a potted plant with variegated leaves тАУ for example, money plant or crotons.
Keep the plant in a dark room for 3 days so that all the starch gets used up.
Now select a leaf cover its portion with black strip paper and keep the plant in sunlight for about 6 hours.
Pluck the leaf from the plant. Mark the uncovered area in it and trace them on a sheet of paper.
Dip the leaf in boiling water for a few minutes.
After this immerse it in a beaker containing alcohol.
Carefully place the above beaker in a water bath and heat till the alcohol begins to boil.
Now dip the leaf in the dilute solution of iodine for a few minutes.
Take out the leaf and rinse off the iodine solution.
You observed that the presence of starch in various areas of the leaf which was uncovered.