Category : 7th Class
Nutrition in Plants
All living things need food to survive. Food gives energy to grow, reproduce, move and to work.
Nutrition is the process by which an organism obtains its food and utilize them. The nutrition can be categorised mainly into two types namely autotrophic and heterotrophic nutrition.
Green plants, algae and some bacteria can produce their own food by the process of photosynthesis. The process of photosynthesis occurs only when plants or algae or some bacteria have green pigment, called chlorophyll in their cells. In the process of photosynthesis, the leaves of plants convert water and carbon dioxide into glucose or sugar and oxygen with the help of energy from the sun. Plants take in carbon dioxide from air and water from the soil.
The plants which do not contain chlorophyll obtain their food by heterotrophic mode of nutrition. There are mainly three types of plants which obtain their food by heterotrophic nutrition. These plants are:
Saprophytes are the non-green plants that feed on dead and decaying organic matters derived from plants and animals. These organisms break down the organic matters by secreting digestive juices into it. For example, mushrooms and toadstool, etc.
Some non-green plants live inside or on other organisms and derive nutrition from them. Such plants are called parasites and the organisms on which the parasite lives are called hosts. For example, dodder is a parasitic plant that winds its yellowish and threadlike stems around other plants and draw nutrition from them.
Some plants obtain a part of their food from insects. For example pitcher plants trap the insects in their modified leaf, kill them and digest them to obtain nutrients. In fact insectivorous plants grow in the soil which is not very rich in nutrients. So they get essential nutrients by eating insects.
Nutrition in Animals
Animals cannot make their own food because they do not have green pigment named chlorophyll. Animals depend on plants or other animals for their food.
Nutrition in Animals involve Five Steps
Ingestion: Intake of food inside the body is called ingestion.
Digestion: Breaking down of large food molecules to smaller one is called digestion.
Absorption: The digested food is absorbed into blood stream through intestinal wall. This process is known as absorption.
Assimilation: The process of utilizing absorbed food by body cells for various metabolic processes is called assimilation.
Egestion: The process of removing undigested food out of body is called egestion.
Nutrition in Amoeba
Amoeba is a unicellular organism living in pond water. Amoeba has finger like projections called pseudopodia. Pseudopodia are false feet which is used by amoeba for catching and engulfing tiny food particles. The food is stored and digested into food vacuoles. The digested food is absorbed into cytoplasm and utilized for the metabolic procedures. The undigested food is expelled out of the body by rupturing cell membrane.
Human Digestive System
Human digestive system consists of many organs. These are mouth, oesophagus, stomach, small intestine, large intestine, liver, pancreas, gall bladder, rectum and anus.
Food is taken inside the body through the mouth. Mouth contains teeth, tongue and salivary glands. Food enters the mouth and gets chewed by the teeth and mixes up with the saliva. Saliva helps in digesting starch present in the food. The partially digested food is swollen down to oesophagus.
Oesophagus is a tube which carries partially digested food from mouth to stomach. Oesophagus is also known as food pipe.
Stomach is a bag like structure which receives slightly digested food from oesophagus. Wall of stomach secretes mucus, hydrochloric acid and digestive juices. The digestive juices break down the proteins into simpler substances. Now the food is sent to the small intestine.
It is a very long tube which is arranged in the form of a coil. Small intestine receives bile secreted by liver, pancreatic juice secreted by pancreas and intestinal juice secreted by its own wall. Here food is completely digested and absorbed by blood vessels present in the walls of small intestine. The undigested food is sent to the large intestine.
It is a long and wide tube where most of the water from undigested food is absorbed and the waste is stored in the rectum. The waste is removed out of body through anus.
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