INTRODUCTION– Food is the basic requirement of living organisms. Food helps to carry out all life processes. The components of food like carbohydrate, protein, fats, vitamins and minerals essential for living organisms are called as nutrients. Any substance that provides nutrients is called food.
NUTRITION- The process of taking nutrients and using them for the growth, development and maintenance of the body is called nutrition. Nutrition can be categorized into two types-
1. Autotrophic Mode of Nutrition
2. Heterotrophic Mode of Nutrition
Autotrophic Mode of Nutrition–It is the mode of preparing food by own. Green plants prepare their own food by photosynthesis. Iron bacteria and Sulpher bacteria prepare their own food by chemicals, the process called chemo-synthesis. Such organisms which prepare their food by photosynthesis and chemo synthesis are called autographs. e.g.- Plants, Green Sulpher bacteria, Iron Bacteria etc. Organisms which prepare food by their own are called as autotrophs and such node of nutrition is called as autotrophic mode of nutrition.
Photosynthesis- The process by which living plants prepare their food from carbon dioxide, water, in presence of sunlight and chlorophylls is called photosynthesis. (Gr. Photo= Light; synthesis= to combine)
Photosynthesis is a biochemical reaction in which solar energy is converted into chemical energy by plants. The reaction of photosynthesis can be represented as-
Sunlight
Carbon dioxide + Water ——————-> Glucose + Oxygen + Water + Energy { Word Equation}
Chlorophylls
Or,
Sunlight
6 CO2 + 12 H2O ————-> C6 H12 O6 + 6O2 + 6H2 O + Energy(36 A.T.Ps) {Chemical Equation}
Chlorophylls
Glucose, a simple carbohydrate is the main product of photosynthesis. Glucose is changed into a complex carbohydrate ‘starch’. Due to formation of food the green plants are called as Producers. The chlorophylls are green pigments found in chloroplast of plant cells in leaves, flower and green stem. Chlorophylls trap solar energy. Carbon dioxide gas is absorbed by plants through tiny pores in leaves called ‘stomata’ (Singular- stoma).The opening and closing of stomata depends on intensity of sunlight. The number of stomata is more on lower surface of leaves than upper surface. Stomata are guarded by two guard cells that help in it’s opening and closing. The exchange of Oxygen and Carbon dioxide and loss of water vapours occur through stomata.
The water is absorbed by roots and water reaches to the leaves through special tissue called Xylem. The oxygen released as by-product in photosynthesis comes out from absorbed water. The green fleshy stem of Cactus, Cynobacteria (blue green algae)and green algae floating on water surface also prepare their food by photosynthesis. Beside carbohydrate plants also prepare proteins and lipids.
Heterotrophic Mode of Nutrition– It is the mode of obtaining food from others. Certain organisms cannot prepare their own food and get their food from other organisms. Such organisms are called heterotrophs and their mode of nutrition is called as hetero-tropism. Following are the types of hetero-tropism on the basis of their feeding habits-
1. Parasitic Nutrition
2. Saprophytic / Saprotrophic Nutrition
3. Insectivorous Nutrition
4. Symbiotic Nutrition
1. Parasitic Nutrition – Those organisms which live inside or on the body of other organism to get their food are called parasites and their mode of nutrition is called as parasitic nutrition. The organism from which parasites take their food is called as host.
e.g.- Cuscuta-(Amarbel-Hindi or Dodder-English)-It a golden yellow colored very thin parasitic plant. It sucks the food and water from host plants. Sometimes the host plant eventually dies due to excess growth of dodder.
e.g.- Mistletoe-This parasitic plant prepares it’s own food but absorbs water and minerals from host plant.
e.g.-Rafflesia, world’s largest flower is an example of parasitic plant.
Cuscuta/Doddar
Rafflesia
2. Saprophytic Nutrition– Fungi are different from plants. They grow in moist foods, wet leather shoes, belts, wood, plant and animal wastes, etc. They release enzymes outside their body for digestion of food. Then, they absorb the nutrients. Those organisms which take their foods from dead and decaying organic matters are called saprophytes or saprotrophes. Their mode of nutrition is called saprophytic or saprotrophic nutrition. The bacteria and fungi (Singular-fungus) decompose the dead plants and animals.
Fungi
Fungi
3. Insectivorous Nutrition– There are certain plants which grow in nutrient deficient soil especially nitrates, therefore, they entrap insects to fulfill nutrient requirements. They do photosynthesis as well as entrap insects. Therefore, insectivorous plants show partial parasitism. Nutrient may be for one particular nutrient or more. Those plants which entrap insects for their nutritional requirements are called insectivorous plants. e.g- Pitcher plant, Venus fly trap, Bladderwort, Sundew, Butterwort etc.
.
Pitcher Plant
Pitcher plants like Cobra lily and Monkey Cup grow in marshy areas where nitrates containing nitrogen (N) are lacking. Their leaves get modified into pitcher like structure; pitcher is usually half filled with water. Once insect falls into it, they are digested by the enzymes and nutrients are absorbed.
4. Symbiotic Nutrition-It is a mutual beneficial relationship between two organisms. e. g- Lichens, they are symbiotic association between an algae and fungi. Algae prepare the food by photosynthesis and fungi use the food. On the other hand, fungi increase the surface area and help in absorbing water and minerals. Lichens are indicators of pollution as they grow in pollution free areas mainly.
Algae + Fungi = Lichens
Mychorrhiza is a symbiotic association between fungi and roots of plants like maize, pine, tomato etc.
Rhizobium bacteria found in root nodules of leguminous plants are another example of symbiotic association. A detail of these bacteria is described further.
Replenishing Nutrients In the Soil– Plants require a number of essential nutrients for their growth and normal functioning. Nitrogen (N), Phosphorus (P), Potassium (K), Calcium, Magnesium, Zinc, Boron, Sulpher etc. are a few plant nutrients. Chemical fertilizers like Urea contain Nitrogen (N), Phosphorus (P), and Potassium (K).
When same kind of crop is grown in the same crop field, there will be lack of nutrients in that soil. To fulfill this lack of nutrients, chemical fertilizers and manures are added in crop fields. This is called replenishment of nutrients in the soil.
Another easy method of nutrient replenishment is growing of leguminous plants like Mustard, Pea, Beans, Pulses, etc. in that crop field. Such leguminous plants have Rhizobium bacteria present in their root nodules. The plants require nitrogen for protein synthesis, DNA, RNA, Enzymes, etc formation but they cannot take it directly from atmosphere. Rhizobium bacteria absorb atmospheric nitrogen and convert it into soluble form to be absorbed by plants. In turn, the bacteria get food from plants. So it is a symbiotic relation. Therefore, farmers should follow ‘crop rotation’ method in which a combination of crops including one leguminous crop is grown alternately in the crop field. e.g. Paddy (1st season) , Gram (2nd season) Wheat (Next Crop Season), Mustard (Another Next Crop Season) etc.
CHECK YOUR PROGRESS-
Select the correct option among the followings.
Q.1 Which one is not an autotroph?
(a) Blue Green Algae (Cynobacteria)
(b) Iron, Sulpher Bacteria
(c) Fungi
(d) Green Plants
Q.2 Which among these is not a heterotroph?
(a) Cuscuta
(b) Pitcher Plant
(c) Lichens
(d) Green Plants
Q.3 Host Parasite relationship is found in caused by which organism?
(a) Pitcher Plant
(b) Cuscuta
(c) Lichens
(d) Fungi
Q.4 To fulfill their deficiency of what, pitcher plants entrap insects?
(a) Nitrogen
(b) Phosphorus
(c) Calcium
(d) Iron
Q.5 Which among these is/are insectivorous plant?
(a) Venus Flytrap
(b) Sundew
(c) Pitcher plant
(d) All of these
Q 6. Fill in the blanks.
A. The raw materials for photosynthesis are……………… and ………………….
B. In Photosynthesis, the oxygen is released from………………………..
C. Lichens are symbiotic association between …………………… and ………………
D. Absorption of nutrients by external digestion is shown by…………………. mode of nutrition.
E. Replenishment of nutrients in soil is done by chemical fertilizers, manures and……… bacteria.
Q.7 What are stomata? Write their functions.
Q.8 Write differences between autotrophs and heterotrophs.
Q.9 What is photosynthesis? Write its equation. What are it’s products?
Q.10 What is symbiotic nutrition? Give two examples of it.
Q. 11 How nutrients are replenished in the soil?
NCERT QUESTIONS –SOLVED
Q.1 Why do organisms need to take food?
Ans-The nutrition is essential for organisms. Organisms take food to get energy and utilize the food for their growth, development and maintenance of their body.
Q.2Distinguish between a parasite and a saprotroph.
Ans-
|
Parasite
|
Saprotroph
|
|
Those organisms which live inside or on the body of other organism to get their food are called parasites. e.g- Cuscuta(Dodder), Mistletoe
|
Those organisms which take their food from dead and decaying organic matters are called saprophytes or saprotrophes. e.g- Bacteria and Fungi,
|
Q.3 How would you test the presence of starch in leaves?
Ans-A potted plant was taken and kept in dark room for 72 hours to destarch it. Then, the plant was kept in sunlight for 3-4 hours for starch formation. A leaf of that plant was plucked and boiled in water for 5 minutes. This boiled leaf was taken in a test tube filled with ethyl alcohol. Then, test tube containing leaf in alcohol was indirectly boiled in the water of a beaker. After sometime, green color of the boiled leaf mixed up with alcohol. The boiled leaf was washed in normal water and placed in Petri dish. A few drops of Iodine were poured over the leaf and leaf turned into bluish-black color. It confirmed the presence of starch in leaves.
Q.4 Give a brief description of the process of synthesis of food in green plants.
Ans- Plants prepare their food by the process of photosynthesis. Carbon dioxide is absorbed from atmosphere by tiny pores of the leaves called stomata. Water is absorbed from soil by the roots and reaches to leaves by xylem tissue. Carbon dioxide and water are the raw materials for photosynthesis. The chlorophylls of the leaves trap the sunlight. As a result the glucose (carbohydrate), oxygen, water vapours and energy (ATPs) is formed.
Sunlight
Carbon dioxide + Water ——————-> Glucose + Oxygen + Water + Energy
Chlorophylls
Q.5 Show with the help of a sketch that the plants are the ultimate source of food.
Ans- Plants are the ultimate source of energy on the earth as they convert solar energy into chemical energy by photosynthesis.
Q.6 Fill in the blanks.
(a) Green plants are called …………………………. since they synthesizes their own food.
(b) The food synthesized by the plants is stored as …………………………
(c) In photosynthesis solar energy is captured by the pigments called ……………………
(d) During photosynthesis plants take in ………………….. and release ………………………..
Ans- (a) autotrophs (b) carbohydrate or starch (c) chlorophylls (d) carbon dioxide, oxygen
Q.7 Name the following:
(i) A parasitic plant with yellow, slender and tubular stem.
(ii) A plant that has both autotrophic and heterotrophic mode of nutrition.
(iii) The pores through which leaves exchange gases.
Ans- (i) Cuscuta/ Amarbel/ Dodder (ii) Pitcher plant (iii) Stomata
Q.8 Tick the correct answer:
(a) Amarbel is an example of-
(i) Autotroph (ii) Parasite (iii) Saprotroph (iv) Host
(b) The plant which traps and feed on insects is-
(i) Cuscuta (ii) China rose (iii) Pitcher plant (iv) Rose
Ans- (a) (ii) Parasite (b) (iii) Pitcher plant
Q.9 Match the items given in column I with those in column II
Column I Column II
(a) Chlorophyll (i) Bacteria
(b) Nitrogen (ii) Heterotrophs
(c) Amarbel (iii) Pitcher plant
(d) Animals (iv)Leaf
(e) Insects (v) Parasite
Ans- (a) iv (b) I (c) v (d) ii (e) iii
Q.10 Mark ‘T’ if the statement is true and ‘F’ if it is false:
(i) Carbon dioxide is released during photosynthesis.
(ii) Plants which synthesis their food themselves are called saprotrophes.
(iii) The product of photosynthesis is not a protein.
(iv) Solar energy is converted into chemical energy during photosynthesis.
Ans- (i)F (ii) F (iii) T (iv) T Q.11 Choose the correct option from the following: Which part of the plant gets carbon dioxide from the air for photosynthesis.
(i) Root hair (ii) Stomata (iii) Leaf Veins (iv) Sepals
Ans- Stomata
Q.12 Choose the correct option from the following: Plants take carbon dioxide from the atmosphere mainly through their-
(i) Roots (ii) Stem (iii) Flowers (iv) Leaves
Ans- Leaves
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