Notes on Various steps of nutrition
Answers
Nutrition in Animals
Animals are heterotrophs and hence they depend on other organisms (plants and other animals) for their food.
All the animals can be divided into three groups on the basis of their food habits. These are:
Herbivores
Carnivores
Omnivores
Herbivores: Those animals which eat only plants are called herbivores. Examples are Goat, Cow, and Deer etc.
Carnivores: Those animals which eat only other animals as food are called carnivores. Examples are Lion, Tiger, and Lizard etc.
Omnivores: Those animals which eat both, plants and animals are called omnivores. Examples are Man, Dog and Crow etc.
It is the energy of sun which provides food for plants, and animals.
Different steps in the process of nutrition in animals
There are five steps in the process of nutrition in animals.
Ingestion: The process of taking food into the body is called ingestion.
Digestion: the process in which the food containing large, insoluble molecules is broken down into small, water soluble molecules is called digestion.
Absorption: The process in which the digested food passes through the intestinal wall into blood stream is called absorption.
Assimilation: The process in which the absorbed food is taken in by the body cells and used for energy, growth and repair is called assimilation.
Egestion: The process in which the undigested food is removed from the body is called egestion.
Nutrition in Simple Animals:
Amoeba and paramecium are two very simple unicellular animals. In unicellular animals, all the processes of nutrition are performed by the single cell.
Nutrition in Amoeba:
Amoeba eats tiny plants and animals as food which floats in water in which it lives.
The mode of nutrition in Amoeba is holozoic.
The process of obtaining food by Amoeba is called phagocytosis.
Steps involved in the nutrition of Amoeba:
Ingestion:
Amoeba ingests food by forming temporary finger-like projections called pseudopodia around it.
The food is engulfed with a little surrounding water to form a food vacuole (‘temporary stomach’) inside the Amoeba.
Digestion:
In Amoeba, food is digested in the food vacuole by digestive enzymes which break down the food into small and soluble molecules by chemical reactions.
Absorption:
The digested simple and soluble substances pass out of food vacuole into the surrounding environment.
Assimilation:
The absorbed food materials are used to obtain energy through respiration and make the parts of Amoeba cell which leads to the growth of Amoeba.
Egestion:
The remaining undigested material is moved to the surface of the cell and thrown out of the body of Amoeba.
Nutrition in Paramecium:
Paramecium is also a tiny unicellular animal which lives in water.
Ingestion:
Paramecium uses its hair like structures called cilia to sweep the food particles from water and put them into mouth.
Ingestion is followed by other steps such as digestion, absorption, assimilation and egestion. (as written in Amoeba)
Nutrition in Human Beings (Complex Multicellular Animal):
The various organs of the human digestive system in sequence are: Mouth, Oesophagus (Food pipe), Stomach, Small intestine and Large intestine.
The glands which are associated with the human digestive system are: Salivary glands, Liver and Pancreas.
The various steps of nutrition in human beings are as follows:
Ingestion:
In human beings, food is ingested through the mouth. The food is put into the mouth with the help of hands.
Digestion:
The digestion of food begins in the mouth itself.
The teeth cut the food into small pieces, chew and grind it. (Physical digestion)
The salivary glands in our mouth produce saliva (watery liquid) which contains an enzyme salivary amylase which digests the starch (carbohydrate) present in the food into sugar. (Chemical digestion)
Our tongue helps in mixing this saliva with food.
The digestion of food remains incomplete in mouth.
Oesophagus:
The slightly digested food in the mouth is swallowed by the tongue and goes down the food pipe called oesophagus.
When the slightly digested food enters the food pipe, the walls of food pipe start contraction and expansion movements called as peristaltic movement.
This peristaltic movement of food pipe pushes the slightly digested into the stomach.
