12th Class Biology Organisms and population Death

Definition : Death may be defined as the permanent cessation of all the vital function in an organism.

Characteristics

(1) It is the last event in the degenerative processes of ageing.

(2) Death of an organism involves the death of the body cells. But all the cells of the body do not die at the same rate e.g., ciliated cells lining the respiratory tract of mammals continue to beat their cilia for a long time even after animal's death. Brain cells of body are last to die.

(3) There is no natural death in the protozoans e.g., Amoeba.

(4) Death involves widespread cell breakdown and cell death.

(5) It usually occurs due to lack of oxygen supply to body tissues.

Causes of death : Causes of death are many. These can be separated into following main categories :

(1) The weakening of the body tissues and of vital organs like heart, lungs, liver, kidneys, etc. which cause physiological and metabolic disorders of permanent nature leading to death. Death, in some cases, occurs due to sudden stoppage of the circulation of blood, food and oxygen to heart and brain leading to immediate death.

(2) The immune system (A system that provide resistance against disease - causing microbes) of the body is gradually impaired with advancing age. This increases the chances of infection in old age. Many old persons die of infectious diseases.

(3) Sudden blockage in the circulation of blood to heart, lungs and brain. This causes instantaneous death.

Brain or cerebral death : In the presence of cardiac activity, the permanent loss of cerebral functions, manifested clinically by absence of responses to external stimuli, lack of breath, and absence of cerebral reflexes is called brain death.

The only truth of life : The death is an inevitable reality of life, and should be gladly accepted. It is a biological necessity for the maintenance of the balance of nature. Old organisms must make room for new ones.

Habit that influence life span : Life-style habits can influence life span considerably. Although a healthful diet does not guarantee immortality, regular exercise and avoiding of alcohol, smoking and drugs, contentment and freedom from stress can make a person's last years more pleasant.

Significance : Death is an essential and inescapable biological phenomenon which helps in maintaining ecological balance or homeostasis in nature. It prevents overcrowding of the members of a specific species and justifies the ‘continuity of life’ on earth.