Question 2
LIST OF SPECIMENS
Specimen A - Fresh/wet preserved mosquito larva in a Petri dish containing water.
Specimen B - Fresh/wet preserved maggot in a Petri dish containing water.
Specimen C - Gill of fish (freshly procured) in a Petri dish containing water.
Specimen D - Lung of a small mammal (freshly preserved).
Specimen E - Dicotyledonous leaf (freshly plucked).
Specimen F - Membranous wing of a Cockroach.
Specimen K - Flower of Pride f Barbados or Caesalpinia.
Specimen L - Mature Elephant grass or Guinea grass.
Specimen M - Flower of Hibiscus plant.
Study specimens C, D and E and answer questions 2(a) to 2(c).
(a)(i) Name the organism from which each of specimens C, D and E are obtained. [3 marks]
(ii) State the function common to specimens C, D and E. [1 mark]
(iii) State three observable features which adapt specimen C to its function.[6 marks]
(b)(i) State two observable structural similarities in specimens C and D.[3 marks]
(ii) State three observable structural differences between specimens C and[3 marks]
(c) Make a drawing, 6 cm to 8 cm long of specimen C and label fully. [9 marks]
Observation
In 2 (a) (i), candidates did not pay attention to the word ‘Name’ which means the particular name of the organism should be given. They were giving group names like Mammal, plant instead.
In 2 (a) (ii), majority of candidates could state the function common to specimens C, D and E, although some lost marks because of wrong spelling of the terms.
In 2 (a) (iii), some candidates could hardly relate features with their functions. Some candidates just mentioned the features without relating them to their functions.
In 2 (b) (i) and (ii), many candidates lost marks here because they could not observe the specimens to write the similarities and differences between a gill and a lung.
In 2 (c), the marks on quality were lost by many candidates while they got the marks for details. Some candidates did not draw to the specification given and did not give the magnification and title to the diagram.
The expected answers include:
(a) (i) Name of organism where specimens C/Gill, D/Lung and E/Leaf are obtained
Specimen C/ Gill
Tilapia/Catfish/any correctly named bony fish.
Specimen D/Lung
Goat/cow/guinea pig/any correctly named mammal.
Specimen E/Leaf
Mango plant/cashew plant/orange plant/any correctly named dicotyledonous plant.
(ii) Function common to specimens C/Gill, D/Lung and E/Leaf
Gaseous exchange/respiration
(iii) Observable features that adapt specimen C to its function
- It is moist; for diffusion of dissolved gases/gaseous exchange;
- It is thin-walled/thin membrane; to make diffusion easy;
- It is richly supplied with blood vessels/blood capillaries/highly vascularised; as diffusion medium/for gaseous exchange;
- Has a large surface area; to increase the rate of diffusion of gases.
(b) (i) Observable similarities between specimens C and D
- Both have a network of capillaries/are highly vascularised;
- Both are pink/red in colour;
- Have moist surfaces;
- Are thin-walled/thin membrane.
Have large surface area.
(ii) Observable structural differences between specimens C and D
Specimen C/ Gill |
Specimen D/Lung |
|
gill rakers absent; |
|
gill arch/bar absent; |
|
gill lamella absent; |
|
gill filaments absent; |
|
pleural membrane present; |
|
pleural cavity present; |
|
fluffy/soft |
(c) Diagram/Drawing of specimen C/Gill
Title (TL)
Quality (Q)
Size (SZ) (6cm to 8cm long)
Clarity of lines (CL)
Neatness of labels (NL)
Magnification (MG) (x½ to x3)
Details (D)
At least three rakers shown (TR)
At least three filaments shown (TF)
Gill bar/arch drawn in double lines (GB)
Labels (L)
Gill raker, Gill bar/arch, Gill filament; Gill lamella.