Excretion: Excretion
13.1 Excretion
Definition
- Excretion = removal of toxic materials and waste products of metabolism from organisms.
Main Excretory Products
- Carbon dioxide (CO₂) → from respiration, excreted via lungs.
- Urea → formed in liver from breakdown of excess amino acids, excreted in urine.
- Salts, water → excess removed by kidneys and skin (sweat).
Excretion vs Egestion
- Excretion: removal of metabolic waste (COâ‚‚, urea).
- Egestion: removal of undigested food via anus.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course
Organs Of Excretion
| Organ | Excretory Product |
|---|---|
| Lungs | Carbon dioxide, water vapour |
| Kidneys | Urea, excess salts, water |
| Skin | Water, salts, urea (in sweat) |
Why Excretion Is Important
- Prevents accumulation of harmful substances.
- Maintains constant internal environment.
- Example: Too much CO₂ → lowers blood pH, affects enzyme activity.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course