SS1 Biology Lesson Note on Excretion

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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

1. Define the term excretion
2. List some organs of excretion and the organism concerned.
3. Outline some waste products in animals and plants and organs responsible.

OBJECTIVE TEST:

1. One of these is a micronutrient (a) cobalt (b) nitrogen (c) potassium (d) magnesium (e) calcium.
2. The compound (NADH) coenzyme is reduced by ———— (a) hydrogen compound (b) hydrogen ion (c) carboxylic acid (d) hydroxyl ion (e) hydroxyl group.
3. The kidney excretes all these except—– (a) acids (b) excess water (c) excess salts (d) Oxygen (e) ammonium compound.

ASSIGNMENT

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