Excretion objective revision questions

Excretion is the process by which organisms remove waste products from their bodies to maintain homeostasis. It is an essential function that helps regulate the internal environment of living organisms.

1. Purpose of Excretion:
- Elimination of metabolic waste: Cells produce waste products as a result of their normal metabolic processes. Excretion removes these waste substances, such as carbon dioxide, urea, and excess ions like ammonia, to prevent their accumulation and toxicity.
- Maintenance of osmotic balance: Many organisms excrete excess water and salts to maintain proper osmotic balance within their bodies. This helps prevent dehydration or electrolyte imbalances.

2. Organs and Systems involved in Excretion:
- Kidneys: In most vertebrates, including humans, kidneys play a key role in excretion. They filter blood, remove waste products, regulate water and electrolyte balance, and produce urine.
- Lungs: In humans and many other organisms, the lungs excrete carbon dioxide and water vapor during the process of breathing.
- Skin: Sweating helps remove water, salts, and some nitrogenous wastes like urea from the body.
- Liver: The liver is involved in the excretion of certain waste products, like bilirubin and some drugs, as part of its detoxification functions.

3. Excretion in Plants:
- Plants excrete waste products through various mechanisms, including the shedding of leaves, bark, and fruit.
- Some plants also excrete excess salts through salt glands in leaves.

4. Excretion in Single-celled Organisms:
- Single-celled organisms, like bacteria and protists, excrete waste products directly into their environment.
- Amoebas, for example, excrete metabolic wastes through the cell membrane.

5. Importance of Excretion:
- Eliminating waste products helps maintain proper internal balance and prevent toxic buildup.
- Rebalancing water and ion levels is crucial for cellular functioning and overall homeostasis.

In summary, excretion is the process by which organisms eliminate waste products. It involves various organs and systems, including kidneys, lungs, skin, and liver. Excretion is important for maintaining internal balance and preventing toxin buildup in organisms.