1. Plants are the only organisms which can make their own food by using simple substances like water (H2O) and carbon-dioxide (CO2).
2. Nutrition is mode of taking food by an organism and utilizing nutrients from food by body.
3. Some organisms make their own food, and these organisms are called Autotrophs (Auto=self and trophos=nutrition). They are also called the producers in the food chain.
4. Plants are Autotrophs and make their own food by photosynthesis. Animals and most of the other animals indirectly or directly depend on plants for food. These organisms are called Heterotrophs (hetero=other and trophos=nutrition)
5. As we know plants make their food by photosynthesis (photo=light and synthesis=to combine) and use some simple substances like Carbon-dioxide (CO2), water (H2O) and many minerals which are present in soil.
6. The roots absorb the water and minerals from soil and they are transported to leaves through stem.
7. The stem transports minerals and nutrients from the roots to the leaves by small pipes called vessels, in dessert plants photosynthesis is done by the stem.
8. The leaves have small pores in them; these are called stomata and are surrounded by guard cells. They take carbon-dioxide from air.
9. The cells of a leaf have a green pigment present in them, this green pigment is called chlorophyll, and it helps the leaves to capture Sun’s energy to make the food.
10. The word equation for photosynthesis is-
Carbon dioxide + Oxygen chlorophyll sunlight
= Carbohydrate + Oxygen.
11. If a plant’s leaves contain starch it indicates the occurrence of photosynthesis. Starch is also a type of carbohydrate.
12. You may have seen leaves of colours other than green, they also contain chlorophyll. There is just a masking of red, brown or other colour pigments which mask the green colour.
13. Algae are also an autotroph they also contain chlorophyll, and it also make food through photosynthesis.
14. Carbohydrates as its name are made with carbon, hydrogen and oxygen; these are also used to synthesize proteins, vitamins and fats.
15. But proteins are nitrogenous substances which contain nitrogen. As we know there is almost 78% nitrogen, but plants cannot use this atmospheric nitrogen.
16. So, there is a special kind of bacteria which converts this atmospheric nitrogen to a usable form for plants and plants absorb this with water and minerals.
17. Farmers also spray some special type of fertilizer which contains nitrogen, to make soil rich in nitrogen.
18. Like buildings are made with bricks, our body is also made up of cells; we can say that they are building blocks of our body.
19. Some organisms are made up of only one cell; they are called single celled organisms. You can read our ‘Animal World’ series to know more about these.
20. But some organisms are complex and have a lot of cells in them, so let us know more about cell and let’s know its structure.
21. So let’s start with the cell membrane; each cell is enclosed with a thin boundary which is called cell membrane.
22. Then we have the nucleus. In each cell there is a distinct, centrally located spherical shape nucleus. The nucleus is surrounded with a jelly-like substance called cytoplasm.
23. Some plants do not have chlorophyll, so they cannot synthesize their own food. They use heterotrophic nutrition to fulfill their demand of food.
24. Parasites are organisms which use a heterotrophic mode of nutrition and collect food from their host; sometimes parasites are harmful for the host too.
25. Mosquito is also a parasite, but you will read about it later. In this chapter we will read about a parasite which feeds on the plants.
26. Amarbel or Cuscuta does not have chlorophyll; it takes readymade food from the plant it is climbing.
27. Plants which feed on insects are called insectivorous plants. It has a pitcher/jug like part which is a modified leaf.
28. The leaf forms a lid which opens and closes as per the requirement. Inside the mouth of the pitcher there are hairs which are directing downwards.
29. When an insect land the lid closes and the insect get trapped in the hair and get digested through digestive juices secreted by the plant.
30. The fungi absorb the nutrients from the food.
31. Saprotrophic nutrition is the mode of nutrition in which organisms absorb the nutrients from dead or decaying matter like rotten bread.
32. Such organisms which use Saprotrophic nutrition are called Saprotrophs. The fungal spores are present in the air and when they land on wet and warm place they germinate very rapidly.
33. Some organisms live together and share the shelter and nutrients. This relationship is called symbiosis.
E.g. certain fungus lives in the roots of the plant. The plant provides nutrients to fungus and in return fungus provide the plant with water and some nutrients.
34. In lichens there is an organism called alga, which contains chlorophyll and can perform photosynthesis lives with fungus which provides alga shelter, water and nutrients; and in return alga provides the fungus with food.
35. Ever thought why do farmers spray fertilizers in the soil? The fertilizers and manures which farmers put in their crop give the plants some essential nutrients like potassium, phosphorus. Etc.
36. These nutrients are added to the soil after a period of time as the plants absorb the nutrients present in the soil, and soil becomes deficient of nitrogen and nutrients.
37. But there is a bacterium called Rhizobium, it can make atmospheric nitrogen to a usable form for the plants.
38. As we know fruits and vegetables are rich source of vitamins, and vitamins are also nitrogenous food, so they also need nitrogen, and that’s another reason why farmers spray fertilizers.
39. The bacterium Rhizobium can’t make its own food but it lives in a symbiosis or symbiotic relation with the plant.
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