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SUB–TOPIC 2: EXCRETION
Definition: Excretion is defined as the process by which living things eliminate waste products or toxic substances from their body through their excretory organs.
Excretory System of some organisms
| ORGANISM | EXCRETORY SYSTEM |
| Some unicellular organism | Contractile Vacuole |
| Flatworms | Flame cells |
| Annelids (e.g. earthworm) | Nephridia |
| Insects | Malpighian tubules |
| Vertebrates | Kidneys, lungs, skin, and liver. |
| Plants | Stomata and Linticels |
EXCRETORY ORGANS AND SUBSTANCES THEY EXCRETE IN VERTEBRATES
IN ANIMAL
- Lungs: Carbon (iv) oxide, and water vapour.
- Skin: Sweats, Salts and nitrogenous waste.
- Kidney: Urea, excess water, excess salts, ammonium compounds, and acids.
- Liver: Bile Pigments.
IN PLANTS
- Stomata: Oxygen, Carbon (iv) oxide and water vapour.
- Bark: Tannins, resins and latex.
- Leaves: Crystals of calcium oxalate, calcium carbonate and anthocyanin pigments which give red, blue, and violet colours to many flowers.
- Lenticels: Oxygen, Carbon (IV) oxide and vapour.
EVALUATION
- Define the term excretion
- List some organs of excretion and the organism concerned.
- Outline some waste products in animals and plants and organs responsible.
OBJECTIVE TEST:
- One of these is a micronutrient (a) cobalt (b) nitrogen (c) potassium (d) magnesium (e) calcium.
- The compound (NADH) coenzyme is reduced by ———— (a) hydrogen compound (b) hydrogen ion (c) carboxylic acid (d) hydroxyl ion (e) hydroxyl group.
- The kidney excretes all these except—– (a) acids (b) excess water (c) excess salts (d) Oxygen (e) ammonium compound.
ASSIGNMENT
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