NCERT 7th Class (CBSE) Science: Nutrition in Plants

Question: What is nutrition? Answer: The process of taking in food by an organism and its utilization by the body is called nutrition. There are two types of nutrition: The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic nutrition. For example plants. The mode of nutrition in which organisms take in ready made food prepared by the plants called heterotrophic nutrition. For example animals Question: What are ‘stomata’? Where are thy normally found? Answer: Leaves take in carbon dioxide from the air through tiny poses called stomata. These poses are located on the underside of the leaves. Question: Write down the chemical equation for manufacture of food in green plants. Answer: Carbon dioxide+Water Chlorophil / sunlite Glucose+Oxygen. Question: What factors are essential for photosynthesis to take place? Answer: The factors that are essential for photosynthesis are water and chlorophyll, Carbon dioxide, sunlight. Questiona: How does an insectivorus plant absorb nutrients from an insect trapped by it? Answer: An insectivorus plant absorb nutrients from an insect by the calls of the plant secrete digestive juices to digest the insect. Question: Why are Nitrogenous fertilizers not added in soil in which leguminous plants are grown? Answer: Nitrogenous fertilizers are not added in soil in which leguminous plants are grown because a bacteria Rhizobium can take atmospheric Nitrogen and convert it into a soluble form that the plants can absorb. Question: Differentiate between Autotrophs and Heterotrophs, giving two examples of each. Answer: Difference between autotrophs and heterotrophs is as follows: Question: How will you test a leaf for starch? Mention any precaution you will take? Answer: Starch test: Pluck a leaf from a plants which has been exposed to sunlight. Boil it for about few minutes in water to soften it. Place it in a test tube containing alcohol. Place this test tube in a beaker of water and warm the water gently until the alcohol begins to boil. (caution: Do not allow the water in the beaker to boil). The alcohol will dissolve the chlorophyll and the leaf will lose its green color. Wash the leaf in the warm water to remove the alcohol. Now spread the leaf out on a white tile and pour iodine solution on it with water. Hold it up against the light. You will observe that parts of the leaf become blue black. These parts of the leaf have starch in them. Question: How do plants get Nitrogen to synthesize proteins? Answer: Though air contains large amounts of Nitrogen, plants cannot absorb Nitrogen directly. They get Nitrogen in two ways:- Soil contains certain bacteria called Rhizobium that can convert atmospheric Nitrogen into water – soluble compounds. Plants absorb these compounds along with water to get Nitrogen. Farmers add fertilizers rich in Nitrogen to the soil. These are absorbed by plants. Question: Explain the following with the help of an example for each. Answer: Parasitic nutrition: Some organisms live in or on other living organisms and derive their food from then. For example – dodder is a plant that sucks the food from other plants, these plants are known as parasites. These plants from which they get food is known as host. There are Partial Parasitic plants too – These parasites are green plants and can make their own food but they are dependent on the host plant for shelter and obtaining water and minerals for the food they make. For example Loranthus. Symbiosis: The association between plants which mutually benefit each other is called symbiosis. For example – Lichens in this the fungus supplies water and minerals to the cells of the algae while the algae supplies food to the fungus. Saprophytic nutrition: Some non green plants live on dead and decaying plants and animals and derive there food for them. Examples are mushrooms and other fungi and bacteria. They secrete digestive juices on the dead and decaying matter. This converts solid matter into liquid form. Question: Why are manures and fertilizers added to the soil in a form? Answer: Manures and fertilizers are added to the soil to enrich the soil with required nutrients and nitrogen, so that plants grow rapidly and nutrients get replenished in the soil. These fertilizers add nutrients like Nitrogen, Phosphorus, Potassium to the soil. Question: Distinguish between parasites and partial parasites in plants giving one examples of each. Answer: Difference between parasitic plants and partial parasitic plants is as follows: Question: Why do organism need to take food? Answer: Food is needed by all living organisms for four main purposes: An important function of food is to help a living organism to grow, if enough food is not given or it is not of right kind, growth will not be sufficient or healthy. Second important function of food is to provide energy. We need energy for doing physical work. We use more energy when we run than we walk and less energy when we sleep. Food is also needed by living beings for replacement and repairing their damaged body parts. Food gives us resistance against diseases and protects us from infections. Question: What is Nutrients? Answer: Food is essential for all living organisms. Carbohydrates, proteins, fats, vitamins and minerals are components of food. The chemical substance present in components of food is necessary for our body and is called nutrients. Question: How humans and animals are are directly or indirectly dependent on plants. Answer: 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. Question: Difference between a parasite and saprotroph. Answer: The difference is as follows: Question: Give a brief description of the process of synthesis of food in green plants. Answer: The process by which the green plants synthesize their own food in the presence of sunlight and chlorophyll by taking carbon dioxide from the atmosphere and water from the soil is known as photosynthesis. Green plants require four things to prepare their own food. These are : Carbon dioxide, absorbed from the atmosphere through stomata present on the leaf surface. Water, absorbed from the soil, through the root system. Chlorophyll, present in the leaf. Light, coming from the sun. During photosynthesis, food is synthesized. Oxygen is released in the process. Question: What is autotrophic nutrition? Answer: The mode of nutrition where an organism makes its own food by taking in simple substances present in their surroundings is called autotrophic nutrition. Question: What is heterotrophic nutrition? Answer: The mode of nutrition in which organisms cannot prepare their food and depend on other plants and animals is called heterotrophic nutrition. Question: What is the mode of nutrition in plants? Answer: The mode of nutrition in plants is autotrophic . Question: What is the mode of nutrition of human and other animals? Answer: Heterotrophic. Question: What are the food factories of plants? Answer: Leaves are the food factories of plants. Question: Define photosynthesis. Answer: The process by which green plants prepare their food using carbon dioxide and water in the presence of sunlight and chlorophyll is called photosynthesis. Question: what is chlorophyll? Answer: A green pigment presents in the leaves of green plants that traps sunlight is called chlorophyll. Question: What is the function of chlorophyll? Answer: Chlorophyll captures the energy of sunlight. Question: What are stomata? Answer: Minute openings present mostly on the under surface of leaves are called stomata. Question: What are the raw materials for photosynthesis? Answer: 1. Water, 2. Carbon dioxide, 3. Chlorophyll, 4. Sunlight. Question: What are the end products of photosynthesis? Answer: Carbohydrates(glucouse) and oxygen. Question: What is the mode of nutrition of cuscuta? Answer: Parasitic. Question: What are insectivorous plants? Answer: The plants which trap insects and digest them to get nitrogenous food are called insectivorous plants. Question: Give an example of insectivorous plant. Answer: Pitcher plant and Venus flytrap. Question: What are saprophytic plats? Answer: Saprophytic plants are non – green plants that derive their nutrients from dead and decaying organic matter. Question: Give to examples of saprophytic plants. Answer: Bread mould and mushroom are examples of saprophytic plants. Question: What are parasitic plants? Answer: parasitic plants are plant that obtain their nutrients plants from other plants. Question: What is symbiosis? Answer: The association between plants which mutually benefit each other is called symbiosis. Question: Give an example of symbiotic relationship? Answer: Lichens (relationship between an algae and fungus). Question: What type of plants do use in the experiment to prove that chlorophyll is necessary for photosynthesis? Answer: Destarched potted plants with variegated leaves, e.g. croton, money plants. Question: Name the bacteria which converts atmospheric nitrogen into a soluble form. Answer: Rhizobium bacteria. Question: Where dose rhizobium bacteria live? Answer: They live in the roots of legumes such as gram, peas and other pulses. Question: Name the form in which carbohydrates are stored in the plants? Answer: Starch. Question: Which gas is released during photosynthesis? Answer: Oxygen. Question: Name one plant each showing the following modes of nutrition : (a) Saprophytic, (b) Parasitic, (c) Insectivorous, (d) Symbiotic. Answer: (a) Saprophytic – Mushrooms (b) Parasitic – Cuscuta (c) Insectivorous – Pitcher (d) Symbiotic – Lichens Question: Why are leaves called the food factories of plants? Explain. Answer: Leaves are called the food factories of plants due to following functions: Green leaves have all the raw materials necessary to carry the process of photosynthesis. They have chlorophyll (green pigment) which captures the energy of sunlight. Leaves consist of tiny pores called stomata on their surface. Carbon dioxide from air is taken in through stomata. Water and minerals are absorbed by the roots from the soil and transported to the leaves by vessels. Question: What are stomata? What is their role? Answer: Stomata are the tiny pores present in the surface of leaves. Massive gaseous exchange takes place in the leaves through stomata for the purpose of photosynthesis and respiration. Question: In which form nitrogen is taken up by the plants? Answer: The nitrogen is taken either in form of inorganic nitrates or nitrates or organic compounds which have been prepared by bacteria form atmospheric nitrogen. Question: What do you understand by symbiotic relationship between organisms? Answer: Some organisms live together and share shelter and nutrients. This is called symbiotic relationship. For example, certain fungi live in the root 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 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. Question: Some plants are both parasite and saprophyte. Explain with examples. Answer: There are some plants which survive like parasites as well as saprophyte. For example, Lichen. In lichen algae which is green in colour and lives on the upper side of the plant in the sun and prepares its own food during photosynthesis. The lower part of lichen is fungus which is saprophyte in nature. Both live together in it. Question: What are the essential conditions in which photosynthesis takes place? Answer: The essential conditions for photosynthesis are: Green parts of the plants (i.e.,presence of chlorophyll). Presence of sunlight. Presence of carbon dioxide. Question: Is ‘nutrition’ a necessity for an organism? Discuss. Answer: Food is required for the following purposes: It provides energy for the various metabolic processes in the body. It is essential for the growth of new cells and repair or replace worn out cells. It is needed to develop resistance against various diseases. Question: What would happen if green plants disappear from earth? Answer: Green plants are the sources of energy for all organisms. If all green plants disappear from the earth, all the herbivores will die due to starvation and so will the carnivores. Question: How does the fungus get its nutrition? Answer: Fungus is a saprotroph. Its mode of nutrition is called saprotrophic mode of nutrition. It takes its food from dead and decaying matter. The digestive juice of fungus converts the dead materials into solution. Then it absorbs nutrients from it. Question: Why are Lichens considered symbionts? Answer: Lichen is made of fungus and an alga together. In lichen, alga (autotrophs) and fungus (saprophyte) depend on each other for their nutritional needs. The fungus supplies water and minerals to the alga. The alga being green and autotroph synthesis food by photosynthesis and supplies organic food to the fungus. Hence Lichens are considered symbionts. Question: How does a pitcher plants get its nutrition? Answer: In the pitcher plant, the leaf blade is modified into a long tubular pitcher to form a pitfall trap with sticky liquid inside. When an insect enters this pitcher, it gets trapped in a sticky liquid inside the pitcher. The insect then gets slowly digested by this sticky liquid. Question: Write the importance of Rhizobium bacteria for the farmers. Answer: Usually crops require a lot of nitrogen to make proteins. They cannot utilise the atmospheric nitrogen. They can use it in soluble from. The Rhizobium bacteria convert atmospheric nitrogen into soluble form. In this way Rhizobium plays an important role for the farmer because it helps to save fertilisers and manures. Question: Describe the factors affecting the process of photosynthesis. Answer: Factor affecting the process of photosynthesis: Light: It is essential for the process of photosynthesis. An increase in the intensity of light increases the rate of photosynthesis. carbon dioxide: It is the source of carbon for the synthesis of organic compounds formed in the plant. Water: It is also very important for the process of photosynthesis. Lack of water decreases the rate of photosynthesis. Temperature: The optimum temperature required by most of the plants for photosynthesis is 350°c. Chlorophyll: It is indispensable for the process of photosynthesis. Photosynthesis does not occur in the plants that lack chlorophyll. Question: How can nitrogen in the soil be replenished? Answer: (1) Plants get nitrogen in the form of soluble salts such as nitrates, urea and ammonium sulphate etc. from the soil through their root system. The nitrates formed are absorbed by plants as fertilizers which convert them into proteins. Plants are eaten by animals. A part of the plant proteins is used in making flesh and rest is excreted as urea in urine which goes back to the soil. Bacteria which are present in soil decompose urea to ammonia. They also decompose proteins of the dead animals into ammonia. Ammonia is partly converted into nitrates and the rest into nitrogen. (2) The atmospheric nitrogen cannot be utilised by plants as such. However, certain bacteria such as symbiotic bacteria present in the root nodules of the leguminous plants can convert atmospheric nitrogen into soluble salts of nitrogen e.g. nitrates. These nitrates being soluble, are absorbed by the plants through their root system. The denitrifying bacteria like pseudomonas convert some of the nitrates formed in the soil into free nitrogen gas which goes back into the atmosphere. Thus nitrogen in the soil can be replenished. Question: Whether food is made in all parts of a plant or only in certain parts? Answer: Only certain part plant like leaves having green pigment chlorophyll can make food, therefore leaves are called the food factories of plants. Besides leaves, photosynthesis also takes place in other green parts of the plant — 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. Question: Give reasons for the following: Fungi are saprotrophs: Because they do not have chlorophyll, they have to depend upon dead and decaying matter for nutrients. Lichens represent symbiotic relationship: Because lichens consist of algae and fungus. Algae provides the nutrition to fungus and which in return provides minerals and shelter to algae. After the harvest, the soil becomes deficient in nitrogen: Because the plants use up the nitrogenous component of soil for their growth. Symbiotic relationship of leguminous plants and bacteria Rhizobium is of great significance for the farmer: Rhizobium fixes nitrogen in soil naturally and farmers do not need to add any nitrogen fertilizers to the soil. Question: What is the role of stomata in photosynthesis? Answer: The role of stomata in photosynthesis is that it takes in carbon dioxide, which is necessary in photosynthesis. Question: How do leguminous plant replenish the soil? Answer: Leguminous plants replenish the soil by the presence of Rhizobium. These plants contain legumes and nodules which reside in the bacteria called rhizobium. These bacteria convert the atmospheric nitrogen into a soluble form that can be absorbed by roots. Question: How Pitcher plants get their nutrition? The pitcher plant has a pitcher-shaped structure filled with liquid. It has a flap-like-structure on its mouth. The edge of the opening of the pitcher is slippery. The insect that sits on it slips and fall into the pitcher, getting trapped inside with the closing of the lid. Question: Explain the mechanism of trapping insect in Venus flytrap. Answer: The leaves of the Venus flytrap have stiff hair-like projections on their edge and the entire leaf is divided into two parts, with the midrib acting as a hinge. When an insect sits on the leaf, it shuts tightly, trapping the insect inside it. Question: Write the functions of the following: Xylem: The root system in plants helps in the absorption of water and minerals from the soil. These are carried to the other parts of the plant through tubular structure called xylem. Phloem: Helps in the transportation of the food to the other parts of the plant. Chloroplast: These are the cells that contains chlorophyll. Question: Difference between Parasitic Relationship and Symbiotic Relationship. Answer: Difference is as follows:

Class Notes NCERT Solutions for CBSE Students

NCERT 7th Class (CBSE) Science: Nutrition in Plants

Question: Difference between Parasitic Relationship and Symbiotic Relationship.

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