Nutrition in Plants Question Answers: NCERT Class 7 Science

The organisms take food to build their bodies, to grow, to repair damaged parts of their bodies and provide the energy to carry out life process like respiration, reproduction, digestion, nutrition, transportation, excretion and circulation of blood etc. To perform all these life process the organisms requires energy and mineral nutrients.

  FOOD THAT HELPS IN OUR BODY METABOLISM

• The energy that is taken by the organisms is supplied through food.
• The intake of food helps to perform all the activities and also develops the immunity by making antibodies to fight against infectious diseases.
• The vital nutrients absorbed by blood from food also plays important role in healing the wound and curing the diseases or the attack of the pathogens on the organism.
• Food is a basic vital or essential ingredient which plays a superior role in maintaining, functioning and developing of the organisms. Thus, organisms needs to consume food.

Parasitic: The living organisms which take their nutrition and lives in body of other or on the host's body, those organisms are called parasites. There are three main categories of parasites that can cause disease in humans: protozoa, helminths and ectoparasites. Entamoeba histolytica is a anaerobic protozoan which infects human. A microscope is necessary to see this parasite, we cannot see it with naked eyes because they are so small.

Saprotrophs: The living organisms which take their nutrition from dead organisms and decaying matter. Most saprotrophs are bacteria and fungi wich feeds on decaying matter. Saprotrophs are important in food chains as they feeds on decay and release nutrients for the growth of their own.

The presence of starch in leaves can be tested or prooved by the Iodine test. Remove chlorophyll from the leaf by boiling it in alcohol and then put two drops of iodine solution, then if its colour changes to blue, indicates the presence of starch.

Process of Photosynthesis: Green plants are autotrophs which synthesise their own food by the process of photosynthesis. The green plants make their own food from simple inorganic substances like carbon dioxide and water in the presence of sunlight or by taking solar energy. The plants use the energy from sunlight to prepare food in the presence of a green colouring matter called ‘chlorophyll’ present in the leaves of a green plant .

The process by which green plants make their own food such as glucose from carbon dioxide and water by using sunlight energy in the presence of chlorophyll is called photosynthesis.

Chlorophyll is present in the green leaves and the process of photosynthesis takes place in the leaves of a plant. Oxygen gas is produced during photosynthesis which is important for the survival of living beings.  

1. Carnivores: Those organisms which eats mostly meat, or the flesh of other animals are carnivores. carnivores are also called as predators which feeds on prey. Examples of carnivores: lion, Tiger (they both are top predators or carnivores), Wolf etc.

2. Herbivore: Those organisms which feeds only on plants are called herbivores. Many herbivores have special digestive systems that let them to digest almost all kinds of plants, including grasses which contains very hard part to digest like cellulose. Examples of herbivores: Cow, Deer, Buffalo etc.

3. Decomposers: Those organisms which depends on dead organisms. They helps in the decomposition to the organic material. For examples: Bacteria, Fungi.

4. Solar Energy: Solar power is energy from the sun that converts thermal energy to the electrical energy.

(a) Autotrophs
The mode of nutrition in which organisms make their food themselves from simple substances is called autotrophic nutrition. Hence, the plants that makes their own food are called autotrophs. There is a green pigment that are found in leaves of plants are called chlorophyll, which helps plants to capture sunlight and this energy is used to synthsis food from carbon dioxide and water.

(b) Starch
During photosynthesis oxygen gets released and the food is stored in leaves. Starch is a carbohydrate. The presence of starch in leaves indicates the occurrence of photosynthesis which can also be prooved by the iodine test.

(c) Chlorophyll
The green pigment present in the surface of the leaves is known as chlorophyll. It helps leaves to capture to the sunlight which can then be used to prepare food.

(d) CO₂ , O₂
During photosynthesis plants take CO₂ and release O₂ gas.

(i) Cuscuta: Cuscuta has lost its chlorophyll and leaves during evolution and thus it derives its nutrition from host plant thus it is a parasitic plant.

(ii) Insectivorous Plant: Some examples are algae, bacteria and some plants. Insectivorous plants are not complete autotrophs but are partially autotrophs. They digest insects but still produce their own source of energy with light and water.

(iii) Stomata: Stomata are the tiny pores present on the epidermis of leaves. We can see stomata under the light microscope. In some of the plants, stomata are present on stems and other parts of plants. Stomata play an important role in gaseous exchange and photosynthesis; this also helps in the transpiration process.

(a) (ii) Parasite
An example of parasite plant is Cuscuta which is also known as Amar bail. Cuscuta plant does not contains chlorophyll that is why it is not green in colour. We can see Cuscuta plant a yellow, oragne tubular structure twining around the stems and branches of a tree. It cannot synthesise its own food because of lacking of chlorophyll. Cuscuta plant takes readymade food from the tree on which it climbs. 

(b) (iv) Pitcher plant
It is a different carnivores plant which can trap insects and digest them. The pitcher-like or jug-like structure is the modified part of leaf also known as pitfall traps. The leaf's apex forms a lid which are able to open and close the mouth of the plant. Inside the pitcher there are hair which are directed downwards and inwards. When an insect falls in the pitcher, the lid get closed and the trapped insect gets entangled into the hair. The insect is then digested by the digestive juices that are secreted in the pitcher and its nutrients are absorbed. These insect-eating plants are called insectivorous plants.

Column I                              Column II
Chlorophyll                       Leaf
Nitrogen                            Bacteria
Amarbel                            Parasite
Animals                            Heterotrophs
Insects                              Pitcher plant

Chlorophyll is present in the leaves which traps the sunlight and synthesis own food. Cascuta is yellow, orange and parasitic plant which is also known as Amar bail. Heterotrophs are those which cannot synthesis their food by their own and feeds on other organism like animals. Pitcher plant are the carnivores plants that modifies their leaf which are known as pitfall traps (a prey trapping mechanisms usually for insects with the deep dig with the digestive liquid). 

(i) False                                                                                                                                                                                                                                          During photosynthesis oxygen is released and intake of carbon dioxide occurs.

(ii) False                                                                                                                                                                                                                                              The living organism which take their nutrition from dead or decaying matter is called Saprotrophs.

(iii) True                                                                                                                                                                                                                                    Sunlight, water and carbon dioxide are three main components that are necessary for photosynthesis process, which gives end result as oxygen and glucose. The final result of photosynthesis is, therefore is glucose and oxygen, not a protein.

(iv) True                                                                                                                                                                                                                                            In photosynthesis, solar energy is used and converted to chemical energy in the form of glucose by using water and carbon dioxide. Oxygen is released as a end product.

(ii) Stomata
For photosynthesis process, green plants take carbon dioxide from the air and releases oxygen at day time. The carbon dioxide enters the leaves of the plant through the stomata present on their surface. Stomata are the tiny pores that helps in the transpiration and exchange of gases.  

(iv) Leaves
Plants take carbon dioxide from the atmosphere mainly through their leaves in which stomata is present which helps in the gaseous exchange. Stomata are small pores that are present on the surface of the leaves.