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Class VII - science: Nutrition In Plants
One Word Answer Questions:
Q) The process of utilisation of food by an organism is called?
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Q) Animals which directly take food made by the plants are called?
    
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Q) Name a parasitic plant with yellow, slender and tubular stem?
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Q) Name a plant that has both autotrophic and heterotrophic mode of nutrition?
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Q) The pores through which leaves exchange gases are called?
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Q) Air enters a plant through the stomata on its?
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Q) In what form is extra food stored in plants?
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Q) Name the part of a cactus plant that prepares food for the plants?
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Short Answer Questions:
Q) Define autotrophs and heterotrophs with examples?
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Q) What is the importance of nutrients in our body?
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Q) What are insectivorous plants? Give an example?
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Q) What is a symbiotic relationship? Explain with an example?
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Q) Explain the process of photosynthesis in green plants?
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Q) Distinguish between a parasite and a saprotroph?
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Q) How do plants without chlorophyll survive? Explain?
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Q) What do green leaves need to produce food?
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Q) From where do leaves get energy for preparing food? Explain briefly?
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Q) Leaves of croton appear dark red. Do these leaves have chlorophyll?
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Q) How would you show that a green leaf has starch in it?
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Q) A balance between plants and animals is essential.why?
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Q) Write the functions of the stomata?
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Long Answer Questions:
Q) Explain briefly the importance of nutrients in the soil?
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Introduction
  • Food is the most important and basic thing for life. Carbohydrates, proteins, fats, vitamins and minerals are the components of food. These components are necessary for all living beings.
  • All plants and animals require food for their growth and getting energy. The process of utilization of food by an animal to obtain energy for growth and development is known as nutrition.
  • Plants make their food themselves but animals cannot. Hence, animals depend directly or indirectly on the plant.
Mode of Nutrition in Plants
Autotrophic Nutrition:
  • Auto means self and trophos means nourishment. Plants are called autotrophs because they make their food themselves. The making of food for themselves is called the Autotrophic nutrition. Autotrophic nutrition is found in green plants.
Heterotrophic Nutrition:
  • The word Heterotrophic is the combination of two words i.e. Hetero + Trophos. Hetero means ‘others’ and ‘trophos’ means nourishment. If organisms depend on others for their food, it is called the Heterotrophic Nutrition.
  • Animals cannot make their food themselves. They depend for food upon plants. Therefore, nutrition in animals is called Heterotrophic Nutrition. Animals are known as Heterotrophs.
Saprotrophic Nutrition:
  • The taking of nutrients by organism from dead and decaying matter in the form of solution is called the saprotrophic nutrition. The organisms which use saprotrophic mode of nutrition are called saprotrophs. For example: fungi.
Photosynthesis–Food Making Process in Plants
  • “The process of making of food by green plants in the presence of sunlight and chlorophyll is known as photosynthesis”.
  • Nutrition in Plants
  • Photosynthesis is the combination of two words.
  • Photo + Synthesis. ‘Photo’ means light and ‘Synthesis’ means to make.
Process of food making in green plants:
  • Green plants make their food themselves. Green leaves make food from Carbon dioxide and water in the presence of sunlight and chlorophyll.
  • Hence, for taking place of photosynthesis carbon dioxide, water and sunlight must be reached at the green leaves in addition to presence of chlorophyll.
  • Leaves have several tiny pores like structure on its lower surface.
  • This is called stomata, through which leaves absorb carbon dioxide from air.
Nutrition in Plants
  • Water is transported to the leaves through hair like pipelines from the roots. These pipelines are present throughout the plant, i.e. from roots to branches and leaves. These pipelines are known as Xylem.
  • Xylem is a type of tissues. Chlorophyll, a green pigment, is found in green leaves. Chlorophyll absorbs sunlight and gives energy. Chlorophyll absorbs sunlight, carbon dioxide and water and converts them to carbohydrate and oxygen. Carbohydrate is used as food and oxygen is emitted out to atmosphere.
  • This whole process of making food by plants is called photosynthesis.
  • The reaction takes place in the process of photosynthesis can be written as:
  • Carbon dioxide + Water Nutrition in Plants Carbohydrate + Oxygen
  • Carbohydrate which is produced in the process of photosynthesis is ultimately converted into starch and stored into leaves. From leaves it is transported to the parts of plants. Starch is a type of carbohydrate. The oxygen so produced is released into atmosphere through the stomata. Leaves are known as the kitchen or food factories of the plants because photosynthesis takes place in leaves. Leaves look green because of the presence of chlorophyll.
  • Besides leaves, photosynthesis takes place in other green parts of the plant also, such as in green stems. Chlorophyll is necessary for photosynthesis, hence photosynthesis takes place only in green plants.
  • The leaves of plants that grow in desert areas are modified in spine like structure or scales to reduce the loss of water in the course of transpiration. In such plants photosynthesis takes place in green stems.
  • The leaves other than green also have chlorophyll. The large amount of red, brown and other pigments mask the green colour. Photosynthesis takes place in these leaves also.
Nutrition in Plants
  • The photosynthesis helps to maintain a balance between oxygen and carbon dioxide in the atmosphere as it absorbs carbon dioxide and release oxygen.
  • Sunlight is necessary for photosynthesis. Thus sun is the ultimate source of energy for all living organism.
  • Our earth is the only unique planet, where photosynthesis takes place. In the absence of photosynthesis life would not be possible on earth.
  • Following are necessary for photosynthesis to be taken place:
  • Presence of sunlight
  • Presence of Chlorophyll
  • Presence of Water
  • Presence of carbon dioxide
Photosynthesis in Algae
  • Green patches in ponds or near the stagnant water can be seen easily. These green patches are living organism called algae. Algae are plants. Often algae grow near the shallow waterlogged areas such as near tube-wells, taps, etc.
  • One may slip over it. Algae look green because of presence of Chlorophyll. Algae prepare their own food by the process of photosynthesis.
Nutrition in Plants
Synthesis of plant food other than carbohydrates
  • Plants need proteins and fats besides the carbohydrate. Proteins are nitrogenous substances which contain nitrogen.
  • Although nitrogen is present in abundance in atmosphere, but plant cannot absorb atmospheric nitrogen. Plant gets nitrogen from soil.
  • Certain types of bacteria called rhizobium are present in soil. They convert gaseous nitrogen into usable form and release it into the soil. Plants absorb these soluble forms of nitrogen along with water and other minerals through their roots.
  • Sometimes farmers add nitrogenous fertilizer to their field to fulfill the need of nitrogen. In this way plants gets fulfillment of nitrogen along with other nutrients. After the fulfillment of all nutrients plants synthesize proteins and fats.
Modes of Nutrition in non–Green Plants
Heterotrophic Mode of Nutrition in Plants:
  • Some plants do not have the chlorophyll. Hence, they cannot synthesise their food by themselves. Such plants are known as non-green plants. They depend on other organisms for food. Such plants use the heterotrophic mode of nutrition. Some of them are called parasite.
  • A parasite is an organism which lives on or inside the body of another organism and takes shelter and food from that organism. The host, in this case, is always at loss.
  • Plants that do not have chlorophyll are called non-green plants. Plants, which live on other plants for food, are called parasitic plants.
Parasite (Parasitic Plant):
  • Plants that get their food from other plants by living on them are called parasite. Example: Cuscuta, mistletoe.
  • Cuscuta is a vine like plant with yellowish stem. It twines around big trees, like banyan tree. Cuscuta gets nutrition from the tree on which it lives. The tree upon which it climbs and lives is called the host. Here, banyan is the host and cuscuta is the parasite.
  • Nutrition in Plants
    Cuscuta (Amarbel) On Host plant
  • Some plants are total parasite while some are partial parasite.
  • A total parasite fully depends on other plants for their nutrition.
  • For example: Cuscuta.
Partial parasite:
  • Partial parasite is a parasite that receives a part of its nutrients from host. For example: mistletoe bears green leaves. It synthesises its own food, but receives water and mineral from host plant.
Nutrition in Plants
Mistletoe
Insectivorous plant
  • Some plants eat insects. Such plants are called insectivorous plants. They trap and digest the insects.
  • Pitcher plant is the example of an insectivorous plant. In pitcher plant the leaf is modified to form a pitcher like structure. The bright colour of the pitcher makes it very attractive to insects.
  • Inside the pitcher, there are several hair-like structures. These hairs direct the trapped insects downwards. When an insect sits on the pitcher of the plant, the lid closes and the insects get trapped inside the pitcher. The insect is then digested by the enzymes secreted by the cells of the plants.
Nutrition in Plants
Pitcher Plant Leaf With A Lid
Cause of eating of insects by plants:
  • The soil of marshy land is deficient in nitrogen. Plants living in marshy areas do not get nitrogen from the soil. Their nitrogen need is fulfilled by sucking the juice of insects. Venus flytrap, utricularia, drosera and Rafflesia are the other examples of insectivorous plants.
Saprotrophs
  • Saprtrophs are non-green plants.
  • Example: Agaricus (Mushroom) fungi, yeasts and bacteria. Saprotrophs get their food from dead or decaying organic matters. They grow on decaying organic matters such as cow-dung, wood, bread, etc.
  • Saprotrophs secrete digestive juice over the decaying materials and absorb nutrients from them. This is called Saprotrophic Mode of Nutrition. Such plants are called saprotrophs.
Nutrition in Plants
Mushroom Growing On Decaying Material
Symbiosis or mutualism:
  • Symbiosis is the combination of two Greek words ‘Sym’ means ‘with’ and ‘biosis’ means ‘living’, which means living together.
  • In symbiosis or mutualism two different types of organisms live and work together for their mutual benefit from each other. They share shelter and nutrients.
  • This is called “Symbiotic relationship”.
  • Example: Lichens.
  • Lichens are composite organisms composed of fungus and alga. Fungus is a saprophyte and alga is an autotroph. The Fungus supplies water and minerals to the cells of the alga while the alga supplies food, prepared by photosynthesis.
    Nutrition in Plants
    Leafy Lichen On A Branch Of Tree
  • A bird sitting on the back of a rhino is an example of symbiosis. The bird gets worms to eat, while the rhino gets rid of those worms.
Replenishment of Nutrients in the Soil
  • Some fungus lives in the roots of the plants. Roots of the plants provide shelter and food to the fungus while fungus provides important nutrients to the plants.
  • Because of continuous farming nutrients keep declining in the soil. Hence, to replenish those nutrients fertilizers are added to the soil.
  • Plants require a lot of nitrogen to grow and to be healthy. Although, a lot of nitrogen is available in the atmosphere, but plants cannot absorb nitrogen in gaseous form.
  • There is a bacterium called Rhizobium, which lives in the root nodules of legumes, such as gram, moong, etc.
  • These bacteria can absorb nitrogen from the atmosphere and make it available for the plants. Rhizobium cannot make its food, hence, it provides nitrogen to the legumes and in return legumes provide them food and shelter. This is an example of symbiotic relationship. This has great importance for farmers.
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