The process of getting rid of wastes by the living organisms is called excretion. It is a characteristic feature found in all living things. Unwanted or waste products are formed due to life processes such as digestion, respiration etc. Animals and human beings excrete waste in the form of urine and sweat. Plants excrete unwanted gases through the stomata present on the leaves.

Respiration is the process inhalation and exhalation of air in which energy is released from food during this process. The energy released by respiration is used for carrying out life processes such as growth and movement.

Breathing is the process of air moving in and out of the body. It is a part of respiration. It involves the exchange of gases such as oxygen and carbon dioxide. Human beings breathe through the nose, earthworm breathes through moist skin and plants breathe through stomata.

The organisms which cannot prepare their own food are called heterotroph. They depend on plants directly or indirectly to fulfil their food requirement. They are also called as consumers. Food is required for all living organisms for growth and development.