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INTRODUCTION

Living beings are the organisms which show all the characteristics of life i.e growth, movement, reproduction, respiration etc.

Fig. Growth, reproduction

Living beings are made up of cells, which form tissues, tissues form organs and organs form organ systems which ultimately form a living body and this organization should be maintained by movement of molecules around all the time as all the structures are made up of molecules.

Cell------>Group of cells--------->Tissue----->Group of Tissue------->ORGAN----------->Group of Organ----->Organ system---->BODY

Life processes are the maintenance functions which take place even when the organisms are in rest to keep the living organisms alive.

Nutrition, respiration, transportation, excretion are all basic life processes in order to remain alive.

NUTRITION

Nutrition is the process of intake of source of energy i.e.food from outside the body in order to grow, develop and synthesize proteins
.
Nutrition in different organisms is fulfilled in different ways.
Some organisms use simple food material in the form of carbon dioxide and water and some use complex food materials which is first broken down in to simpler ones and is then used by the body.
Enzymes are the biocatalysts which help in the breaking down of complex substances into simpler ones.
The method of obtaining food is different in different organisms.
Mode of nutrition can be classified into autotrophic and heterotrophic nutrition based on the method of obtaining food.
Autotrophic organisms prepare their own food by the process of photosynthesis.Example--plants
Heterotrophic organisms depends on autotrophic organism for food.
Example-Human beings
AUTOTROPHIC NUTRITION

The nutrition in which organisms prepare their own food from inorganic raw materials like carbon di oxide and water is called autotrophic nutrition.

Fig. autotrophs

Green plants produce their food by the process of photosynthesis.

Fig. plants prepare their own food by photosynthesis

Photosynthesis is the process of production of food from carbon dioxide and water in the presence of sunlight and chlorophyll.

Events of photosynthesis-
1. [1]-Chlorophyll absorbs light energy,
2. Light energy is converted to chemical energy.
[2]-Water molecules splits into hydrogen and oxygen

[3]-Carbon dioxide reduces to carbohydrates

NOTE-Green dots present in some cells of leaves are called Chloroplasts which contain chlorophyll.

Fig. chloroplast

'The site of photosynthesis in a cell of the leaf is chloroplasts'.

[1]-The plants obtain carbon dioxide by tiny pores called as stomata present on the surface of the leaves of plants.

[2]-The carbon dioxide gas enters into the leaves through the stomata.

NOTES--Stomatal pores are surrounded by a pair of guard cells and guard cells regulate opening and closing of stomata.

Fig. opening and closing of stomata

[3]-Water can be lost through stomatal hence the pores are closed when not needed for photosynthesis.

[4]-When water flows into guard cells these swell causing the stomatal pores to open and the pores close if the guard cells shrink.

[5]-The raw materials such as water,nitrogen,phosphorous etc.used in photosynthesis are also taken up by the plants from different sources..

[6]-Water is absorbed by the plants from the soil by the roots in terrestrial plants.

Nitrogen, phosphorous, iron, magnesium is taken up from soil.

Nitrogen is either taken in the form of inorganic nitrates or as organic compounds prepared by bacteria from atmospheric nitrogen.

Nitrogen is used in the synthesis of proteins.

Fig. roots absorb nutrients and water from soil
HETEROTROPHIC NUTRITION

Heterotrophic nutrition is the mode of nutrition in which an organism depends on other living organisms for food.

Depending on the type of food, heterotrophs can be divided into 3 types-
1. Carnivores- Organism which eat only animals.
2. Example- lion, snake.
4. Herbivores- Organism which eat only plants.
5. Example-Rabbit,elephant.
Omnivores- Organisms which eat both plants and animals

Some organisms break down the food material outside the body and then absorb it. Example- yeast and mushrooms.

Fig. Mushroom

Some other animals break the food inside the body before absorbing. Example- human, cat.

Fig. A cat

Some organisms derive their food from the body of other organisms without killing them. Example- ticks, leeches.

Fig. A leech
Example- crow ,dog.
NUTRITION IN UNICELLULAR ORGANISMS

In unicellular organisms, the food is taken by the entire surface.

Amoeba, is an unicellular organism which takes in food using temporary finger like projections of the cell which fuse over the food particle to form a food vacuole and the food is broken down inside the food vacuole and diffuse into cytoplasm.

Fig. Amoeba (Drawn by ~~MANOJ MISHRA~~ )

The undigested food is taken to the cell surface and excreted.

Paramecium, another unicellular organism has a definite spot in the body to take in food.

Food is moved to the spot by the movement of hair like structure called cilia in the body of paramecium.

Fig. Paramecium