Excretion

• The process of removal of chemical wastes (mainly nitrogenous wastes) from the body is known as 'excretion' (ex: out, crete: flow).
• Excretion is the process of removal of harmful and unwanted nitrogenous waste products from the body.
• Excretion is defined as the process by which organisms expel metabolic waste products and other toxic substances from the body.

Organs which are concerned with the formation, storage and elimination of urine constitute the 'excretory system'.

Excretion is the process by which living organisms remove harmful and waste substances, such as urea, uric acid, and ammonia, from their bodies. These substances are produced as by-products of metabolic activities. If not eliminated, they can accumulate in the body and cause severe harm, even leading to death. Therefore, excretion is essential for the survival and health of all living organisms.

Methods of Excretion:

1. Unicellular Organisms: In simple organisms like amoebas, waste materials are directly eliminated through the cell surface via diffusion.
2. Multicellular Organisms: In more complex organisms, excretion involves specialised systems.

For example:

• Humans use organs like the kidneys to filter waste (urea) from the blood and expel it as urine.
• The skin removes waste through sweat, and the lungs excrete carbon dioxide produced during respiration.

1. Aim: To observe the excretion of water in plants through a process called transpiration.

2. Requirement: transparent plastic bag and plant with leaves.

3. Procedure

• Select a healthy leaf from the plant.
• Tie a transparent plastic bag over the leaf, ensuring it is sealed.
• Leave the setup undisturbed for 6 to 7 hours.

4. Observation: After that time, droplets of water are seen collecting inside the bag.

5. Conclusion: The droplets indicate that plants excrete water in the form of vapour, confirming excretion as a characteristic of living things.

Excretion on the leaves of a plant