Life Processes such as Nutrition, Respiration, Circulation and Excretion are necessary for the survival of living beings. Energy is needed for running life processes.
Solar energy is trapped by plants to produce sugar (glucose) from CO2 and H2O in the presence of chlorophyll. This is called photosynthesis. Water is picked up by roots and reaches leaves through xylem where photosynthesis occurs. CO2 reaches leaves from atmosphere through stomata. Plants are autotrophs. Sugar reaches other parts of the plant from leaves through phloem.
Animals feed on plants and other animals to get energy. They are heterotrophs. Animal nutrition involves ingestion, digestion, absorption, assimilation and egestion. Digested food is transported to cells by blood.
Oxygen also reaches cells through blood. Oxygen obtained through respiration helps to get energy from food. Carbon dioxide is produced after food is oxidised by oxygen. It is removed from body during respiration.
Ammonia, uric acid and urea are produced when proteins are broken down for utilisation by the body. These substances reach the kidney for removal as harmful wastes from the body by means of blood. This is called excretion.
Nervous system (NS) and endocrine system together ensure that all the parts of the body work in a controlled and coordinated manner. NS includes brain, spinal cord, sense organs and nerves. Endocrine glands secrete hormones directly into the blood.