Question 3
The diagrams below are illustrations of organisms. Study them and answer questions 3(a) to 3(d).
(a) (i) Name organism G and H.[2 marks]
(ii) Name the parts labelled I to VIII.[4 marks]
(iii) State one function each of the parts labelled I, V and VIII. [3 marks]
(b)(i) State four observable structural similarities between G and H.[4 marks]
(ii) State five observable structural differences between G and H.[5 marks]
(c) (i) Name the Class of eachof organism G and H. [2 marks]
(ii) Name one habitat each of organism G and H. [2 marks]
(d) State two observable features each that adapt:
(i) organism G to its mode of feeding; [4 marks]
(ii) organism H to escaping from predators.[4 marks]
Observation
Most candidates were unable to correctly label the parts of the skin, state their functions and state ways by which the organ controls body temperature during hot and cold days. This made candidates score poorly in this question. Some of the candidates that scored some marks were able to state ways of caring for the skin.
The expected answers are:
(a) (a) (i) Identification of organ
Skin/mammalian skin
1 x 1 [1 mark] (ii) Name of labelled parts
I - Hair/Hair shaft VI - Blood vessel/blood capillary;
II - Sebaceous gland; VII - Subcutaneous Fat/adipose tissue;
III - Erector muscle; VIII - Receptor cells/sensory cell/touch receptor/touch corpuscle..
IV - Sweat pore; IX - Dermis;
V - Sweat gland X - Epidermis. 10 x ½ [5 marks]
(b) Functions of the organ
- Removal of waste products through sweat/production of sweat/excretion.
- Response to stimuli/sensitivity (to heat, cold, touch, and pressure).
- Manufacture of vitamin D;
- Insulator for the body/maintenance of body temperature;
- Protection of the body from damage;
- Secretion of sebum (which keeps the skin soft and supple).
(c) Reaction of the part labelled I/Hair when the temperature is:
(i) Low
It stands erect/perpendicular/vertical
(ii) High
It bends/lies flat
(d) Function of the parts labelled II, III, V, VI, VIII and X
II/Sebaceous gland: secretes sebum/oily substance;
III/Erector muscle: controls position of the hair;
V/Sweat gland: produces sweat;
VI/Blood vessel/blood capillary: supplies blood/food and oxygen
to the skin.
VIII/Receptor cell: for sensation/picking up stimuli;
X/Epidermis: protection/protection of inner layers/entry for disease causing
organisms/pathogens.
(e) ways by which the organ/skin controls body temperature during a:
(i) hot day
- Sweating increases;
- Lowering of hairs to force out air trapped;
- Vasodilation;
- Decreasing metabolic activities.
(ii) cold day
- Reduced sweating;
- Raising of hairs so as to trap more air;
- Increase in metabolic activities;
- Vasoconstriction;
- Adipose tissue prevents loss of heat.
(f) Vitamin produced by the organ
Vitamin D
(g) Care of the organ/skin
- Wearing clean clothes;
- Eating balanced diet;
- Treating skin diseases immediately;
- Avoiding use of injurious chemicals/bleaching creams/allergic substances/sharp object;
- Treating wounds/cuts immediately;
- Having regular exercise;
- Taking bath with clean water regularly/use of medicated soap;
- Drinking lots of water.
- Avoiding over exposure to sunlight.
- Use of body cream to avoid dryness of the skin.