Excretion In Animals
Key Notes :
1. What is Excretion?
- Excretion is the process by which animals remove waste products and harmful substances from their bodies.
- These waste products are generated during metabolism (the breakdown of food and energy).
- Excretion helps maintain the internal balance (homeostasis) of the body.
2. Importance of Excretion
- Removes toxic substances (e.g., ammonia, urea).
- Regulates water and salt balance in the body.
- Helps in maintaining proper blood pressure and overall health.
3. Excretory Organs in Animals
- Humans: The primary excretory organs are the kidneys, which filter waste from the blood and produce urine.
- Fish: Excrete ammonia through gills, which dissolves in water.
- Amphibians: Excrete urea through kidneys and skin.
- Birds: Excrete uric acid as a paste to conserve water.
- Insects: Excrete uric acid through specialized structures called Malpighian tubules.
4. Excretory System in Humans
- Kidneys: Filter the blood, remove waste, and produce urine.
- Ureters: Tubes that carry urine from the kidneys to the bladder.
- Bladder: Stores urine until it is excreted.
- Urethra: The tube through which urine is expelled from the body.
5. Types of Excretion in Animals
- Ammonotelic: Animals like fish excrete ammonia, which is highly toxic but soluble in water.
- Ureotelic: Animals like mammals excrete urea, which is less toxic and requires more energy to produce.
- Uricotelic: Animals like birds and reptiles excrete uric acid, which conserves water and is less toxic.
6. Excretion in Different Animals
- Invertebrates: Many invertebrates like insects and worms excrete waste through specialized cells or organs.
- Fish: Excrete waste via gills and kidneys.
- Amphibians: Excrete waste via kidneys and skin.
- Birds: Excrete solid uric acid to conserve water.
7. Role of Excretion in Homeostasis
- Helps maintain the balance of essential substances such as water, salts, and pH in the body.
- Controls the concentration of substances in the blood, like sodium, potassium, and urea.
8. Excretion and Adaptation
- Desert Animals: Animals in dry environments (e.g., camels) excrete minimal urine to conserve water.
- Aquatic Animals: Excrete large amounts of waste dissolved in water due to the availability of water.
9. Diseases Related to Excretion
- Kidney Disease: When kidneys fail to properly filter waste, it leads to conditions like kidney stones, infections, or kidney failure.
- Uremia: A condition caused by the accumulation of urea in the blood when kidneys fail.
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