A life process is an activity that an organism must carry out in order to remain alive.  For instance: growing, feeding, breathing, excreting, responding, moving and reproducing.

Growth

This means irreversible or permanent increase in size.  It usually involves formation of different body parts (tissues) - a process called differentiation.

In plants, growth takes place throughout the lifetime of the plant but only in certain parts of the plant for example the terminal end of the shoot and the tip of the root.  Such a type of growth is called apical growth.

In animals, growth takes place throughout the body of the animal but only for a certain period of time then ceases.  Such a type of growth is called Intercalary growth.

Nutrition

This refers to the method of feeding. In plants, simple inorganic substances like carbon dioxide and water are built up to form complex organic compounds like starch.  Such a type of nutrition is called Autotrophic nutrition or Holophytic nutrition.

In animals, complex organic compounds are broken down to simpler substances.  Such a type of nutrition is called Heterotrophic nutrition.

Human beings need better nutrition in order to generate energy for wrestling

Respiration

This is the taking in of oxygen to oxidize food to release energy and carbondioxide and water are given out as waste products.

The taking in of oxygen and out of carbondioxide takes place between the organisms and the environment (atmosphere or water) and is called external respiration or breathing or gaseous exchange.

The oxidizing of food to release energy takes place in the tissues and is called internal respiration or tissue respiration.

The main aim of respiration is thus to release energy. Where energy is released by the use of oxygen, then aerobic respiration has taken place.

In some bacteria and yeasts, energy can be released from food without the use of oxygen i.e. anaerobic respiration.

Excretion

This is the elimination from the body of waste products that have been manufactured in the body and have taken part in body reactions (metabolism); which if they accumulated, could become toxic (poisonous).

In plants, waste products are converted to less harmful compounds and are used or stored for example tannins.

In animals, toxic waste products like ammonia are converted to less harmful compounds like urea and are expelled.  This conversion of toxic substances to less harmful compounds is called detoxication and in man it is carried out by the liver.

Excretion must not be confused with secretion which, is the production of useful fluids to the body for example saliva, mucus, tears, etc.

Excretion must also not be confused with egestion, which is the elimination of the part of our food, which is indigestible (faeces).

Faeces are not excretory waste products because they are not manufactured in the body; and they do not take part in body cell metabolism.

Faeces, however, contain excretory bile pigments, which are a waste product.

Nitrogenous waste products include urea, uric acid and ammonia.

Other waste products include carbon dioxide, excess water, excess heat, excess salt and oxygen from plants during daytime.

The major excretory organs in man are the liver, the lungs, kidneys and the skin.

Irritability

This is the ability to perceive changes in the environment and respond to them.  The ability to perceive is called sensitivity and the action taken thereafter is called the response; the change in the environment is called a stimulus.

The part of the organism that perceives the change in the environment is called the receptor for example eyes, ears, etc.

The part of the organisms that affects the response is called the effector for example muscles and glands.

In animals, response is immediately after a stimulus has been applied; but in plants, response is after a long time and that is if the stimulus persists.

If the response is such that the whole organism moves towards or away from the stimulus, then that is a tactic response or taxism.

If the response is such that only part of the organism grows towards or away from the stimulus, that is a tropic response or a tropism.

If the response has no particular direction in relation to the stimulus but is only a change in development pattern, then that is a nastic response or nastism.

Locomotion

This refers to change in position of an organism. Generally, only unicellular plants carry out locomotion; higher plants only move by growing. Most animals carry out locomotion.

Reasons for locomotion include:

Looking for food and water, escaping from enemies, looking for favourable conditions; and Looking for sex partners.

Structures used in locomotion include:

 

For locomotion to take place in higher animals there must be:

Contractile tissue for example muscles;

A rigid framework for example skeleton;

A resisting medium for example land, water or air.

 

Reproduction

This is the producing of offspring that resemble the parent. Although reproduction is one of the life processes, an organism can go on living without reproduction.

Although reproduction is not essential for the existence of an individual organism, it is essential for the existence of the species as whole.

Reproduction where there is fusing (joining) of reproductive cells (gametes) is called sexual reproduction. Reproduction where there is no fusing of gametes is called asexual reproduction.