This question was attempted by many candidates and their performance was fair. In part (a) (i) candidates defined excretion partially by saying is the removal of waste product but candidates failed to say metabolic wastes product however in part (a)(ii) candidates listed excretory organs in humans. In part (a)(iii) candidates could list one substance excreted by each organ listed in (a)(ii) above. In part (b) candidates could not list skin diseases. Candidates mixed up skin diseases with respiratory diseases and digestive diseases. In part (c) candidates could not state the function of the following skin parts:
- Cornified layer:
- Blood vessels;
- Malphigian layer;
- Sebaceous gland.
In part (d) candidates could state functions of the human skeleton correctly.
The expected answer were as follows:
(a) (i) Excretion
- it is the removal/getting rid of metabolic waste products
from the body/tissues/cells
(ii) Excretory organs in human
(iii) Substances excreted by organs
- skin - sweat/water/urea/salt
- kidney - urea/salts/water/urine
- liver - excess cholesterol/bilirubin/breakdown products of red blood cell
- lungs - carbon dioxide/water vapour.
(b) Skin Diseases
- tinea/ringworn/athlete’s foot
- chicken pox.
(c) Functions of cornified layers, blood vessel, malphigian layer and sebaceous gland
- Functions of cornified layer
- prevents entry of microbes/bacteria
- reduces the rate of water loss from the body/evaporation
- protects the body against mechanical injury.
- Functions of blood vessels
- supply nutrients/oxygen to the skin
- transport excess water to the sweat glands
- help in regulating body temperature
- carry blood/nutrients/oxygen/to all parts of the body.
- Functions of malphigian layer
- gives colour to the skin
- provides cells to replace worn out cells
-protects the skin against ultra violent rays.
- Functions of Sebaceous gland
-secretes oil/sebum, to lubricate the hair follicle/skin
reduces dryness of skin
(d)Function of human skeleton
- Skeleton protect delicate organs in human body e.g. skull protects
;the brain eyes, ears and nose;
- Skeleton provides a rigid frame work for the human body;
- Acts as points of attachment to muscles;
- Manufacture red blood cells in bone, bone marrow;
- It stores minerals in bone matrix e.g. calcium and phosphorus salt;
- It gives shape to the body
- Acts as lever system;
- It aids breathing movements i.e. ribs;
- Aids in movement/locomotion of the body.