LIFE PROCESS

Introduction

• All the plants and animals are alive or living things.
• The most important criterion to decide whether something is alive or not is the movement.
• The movements in animals are fast and can be observed easily but the movements in plants are slow and observed with difficulty.
• Animals can move from one place to another or they can move their body parts.
• The plants can only move parts of their body such as leaves, flowers, roots and shoots.

Life Processes

The basic functions performed by living organisms to maintain their life on this earth are called life processes.

Basic life processes common to all living organisms are:

• All the living organisms need energy to perform various life processes. They get this energy from food. Food is a kind of fuel which provides energy to all the living organisms.

Nutrition

• Food is an organic substance. The simplest food is glucose also called simple sugar.
• A more complex food is starch. It is made from glucose.
• The general name of substances like glucose and starch is ‘carbohydrates’.

Nutrient: A nutrient can be defined as a substance which an organism obtains from its surroundings and uses it as a source of energy or for the biosynthesis of its body constituents.

Example: carbohydrates and fats are the nutrients which are used by the organism mainly as a source of energy.

Proteins and mineral salts are nutrients used by organism for the biosynthesis of its body constituents like skin, blood, etc.

Nutrition:

Nutrition is the process of intake of nutrients (like carbohydrates, fats, proteins, minerals, vitamins and water) by an organism as well as the utilization of these nutrients by the organism.

Mode of Nutrition:

Mode of nutrition means method of obtaining food by an organism. There are mainly two modes of nutrition:

1. Autotrophic mode of nutrition
2. Heterotrophic mode of nutrition

Autotrophic mode of nutrition: 

• Autotrophic nutrition is that mode of nutrition in which an organism makes (or synthesizes) its own food from the simple inorganic materials like carbon dioxide and water present in the surroundings (with the help of sunlight energy).
• Those organisms which can make their own food from carbon dioxide and water are called autotrophs.
• Example: all green plants, autotrophic bacteria.
• Autotrophs make their food by photosynthesis.

Heterotrophic mode of nutrition: 

• Heterotrophic nutrition is that mode of nutrition in which an organism cannot make (or synthesizes) its own food from simple inorganic materials like carbon dioxide and water, and depends on other organisms for its food.
• Those organisms which cannot make their own food from inorganic substances like carbon dioxide and water, and depends on other organisms for their food are called heterotrophs.
• Example: all the animals (man, dog, cat, lion, etc.), most bacteria and fungi.

Types of Heterotrophic Nutrition:

 Heterotrophic mode of nutrition is of three types:

1. Saprotrophic (saprophytic) nutrition
2. Parasitic nutrition
3. Holozoic nutrition

Saprotrophic nutrition:

• Saprotrophic nutrition is that nutrition in which an organism obtains its food from decaying organic matter of dead plants, dead animals and rotten bread, etc.
• The organisms having saprotrophic mode of nutrition are called saprophytes.
• Saprophytes are the organisms which obtain food from dead plants (like rotten leaves), dead and decaying animal bodies, and other decaying organic matter.
• Example: Fungi (liker bread moulds, mushrooms), and many bacteria.

Parasitic nutrition:

• The parasitic nutrition is that nutrition in which an organism derives its food from the body of another living organisms without killing it.
• A parasite is an organism (plant or animal) which feed on another living organism called its host.
• Example: some animals like Plasmodium and roundworms, a few plants like Cuscuta (amarbel) and several fungi and bacteria.

Holozoic nutrition:

• The holozoic nutrition is that nutrition in which an organism takes the complex organic food materials into its body by the process of ingestion, the ingested food is digested and then absorbed into the body cells of the organism.
• Example: human beings and most of the animal.

  Nutrition in plants:

  • Green plants are autotrophic and synthesize their own food by the process of photosynthesis.
  • The process, by which green plants make their own food from carbon dioxide and water by using sunlight energy in the presence of chlorophyll, is called photosynthesis.
  • Oxygen is released during photosynthesis.

  The process of photosynthesis can be represented as:

  • The process of photosynthesis takes place in the green leaves of a plant.
  • The food is prepared by the green leaves of a plant in the form of a simple sugar called glucose.
  • The extra glucose is changed into another food called starch. This starch is stored in the leaves of the plant.
  • The green plants convert sunlight energy into chemical energy by making carbohydrates.

  The photosynthesis takes place in the following three steps:

  1. Absorption of sunlight energy by chlorophyll.
  2. Conversion of light energy into chemical energy, and splitting of water into hydrogen and oxygen by light energy.
  3. Reduction of carbon dioxide by hydrogen to form carbohydrate like glucose by utilizing the chemical energy.

  Conditions necessary for photosynthesis:

  The conditions necessary for photosynthesis to take place are:

  1. Sunlight
  2. Chlorophyll
  3. Carbon dioxide
  4. water
  • Green leaves make starch as food. Starch gives a blue black color with iodine solution.

  Raw materials for photosynthesis:

  The raw materials for photosynthesis are:

  1. Carbon dioxide
  2. Water

  How the plants obtain carbon dioxide?

  • There are a large number of tiny pores called stomata on the surface of the leaves of plants.
  • The carbon dioxide gas enters the leaves of the plant through the stomata present on their surface.
  • Each stomatal pore is surrounded by a pair of guard cells. The opening and closing of stomatal pores is controlled by the guard cells.
  • When water flows into the guard cells, they swell, become curved and cause the pore to open.
  • On the other hand, when guard cells lose water, they shrink, become straight and close the stomatal pores.

  How the plants obtain water for photosynthesis:

  • The water required by the plants for photosynthesis is absorbed by the root of the plants from the soil through the process of osmosis.
  • The water absorbed by the roots of the plants is transported upward through the xylem vessels to the leaves where it reaches the photosynthetic cells.
  1. The plants also need other raw materials such as nitrogen, phosphorus, iron and magnesium, etc., for building their body.
  2. The plants take these materials from the soil.
  3. Nitrogen is essential element used by the plants to make proteins and other compound.

  Site of photosynthesis: Chloroplasts

  • The site of photosynthesis in a cell of the leaf are chloroplasts which contain chlorophyll.
  • Chloroplasts are present in the photosynthetic cells (mesophyll cells) of green plants. These cells contain more chlorophyll than other plant cells. 

    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:
    1. Herbivores
    2. Carnivores
    3. 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.

    1. Ingestion: The process of taking food into the body is called ingestion.
    2. Digestion: the process in which the food containing large, insoluble molecules is broken down into small, water soluble molecules is called digestion.
    3. Absorption: The process in which the digested food passes through the intestinal wall into blood stream is called absorption.
    4. 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.
    5. 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.

     

    Stomach:

    • The stomach is a J-shaped organ present on the left side of the abdomen.
    • The stomach walls contain s three tubular glands in it walls which secrete gastric juice.
    • The gastric juice contains three substances: Hydrochloric acid, the enzyme pepsin and mucus.
    • The hydrochloric creates an acidic medium which facilitates the action of the enzyme pepsin i.e. digestion of protein.
    • The mucus helps to protect the stomach wall from its own secretions of hydrochloric acid.
    • The partially digested food then goes from the stomach into the small intestine.

     

    Small intestine:

    • From the stomach