Question 8
- (a)
- (i) What is meant by the term homeostasis? [ 2 marks ]
- (ii) Explain how the human body maintains a constant body temperature in a cold environment. [ 5 marks ]
- (b) State:
- (i) three food sources of iodine; [ 3 marks ]
- (ii) two deficiencies of iodine; [ 2 marks ] (iii) one function of fluorine in the human body. [ 1 mark ]
- (c) Draw and label an elbow point. . [ 7 marks ]
Observation
This question was attempted by many candidates and their performance was poor. In part (a)(i) candidates took osmosis definition for homeostasis and in (ii) candidates could not correctly explain how the human body maintains a constant body temperature in a cold environment. In part (b) candidates could not correctly state deficiencies of iodine and also state function of fluorine in the human body. In part (c) candidates could not correctly draw and label an elbow joint.
However, the expected answers are as follows:
8 (a)(i) HOMEOSTASIS
This is the maintenance, of a constant pH, of internal environment/fluid tissues of the human body
(ii) EXPLANATION OF HOW HUMAN BODY MAINTAINS CONSTANT BODY TEMPERATURE IN A COLD ENVIRONMENT
- body metabolism increases
- produces more heat
- and the blood vessels of the skin constrict
- erector muscles contract
- hair on the body is raised
- trapping more air on the surface of the skin
- reducing heat loss by radiation / convection / conduction
- shivering may occur
(b)(i) FOOD SOURCES OF IODINE
- sea food/named/eg. crayfish
- green vegetables/named eg onion
- iodized common salt
- fresh fish / dried fish
(ii) DEFICIENCIES OF IODINE
- goitre
- dwarfism
- poor metabolic activity/growth
- cretinism
N.B:- Only correct spellings of scientific words/names will score
(iii) FUNCTION OF FLUORINE
- for healthy teeth development
- prevention of cavity formation in the teeth/prevents tooth decay.
(c) DRAWING AND LABELLING OF AN ELBOW JOINT
Labelling:
I - humerus
II - biceps muscle
III - synovial fluid
IV - radius
V - ulna
VI - cartilage
VII - tendon