Question 1
The diagram below represents a transverse section through a human skin. Use it to answer the questions that follow
- Name the parts labeled B and R
- Give the functions of each of the parts C and P
- Mention two ways in which the skin helps to keep the body warm
- Skin lightening cosmetics are used by some people. State two adverse effects such cosmetics may have on the skin.
Answer
-
B – Nerve endings;
R – Cornified layer -
C – Secretes sebum which makes the skin supple/flexible/waterproof/ is antiseptic
P – Gives rise to new epidermis/malpighian layer/has melanin which protects the skin from ultraviolet rays -
Presence of adipose tissue which acts as an insulating layer;
Presence of blood vessels which constrict so as to enhance blood flow to deeper layers -
- Can cause skin cancer because the skinis affected by ultraviolet radiation
- Reduce melanin hence reducing pigmentation
Question 2.
An experiment was carried out to determine the rate of transpiration in three plants A, B and C. Plants A and B belonged to different species while plants B and C belonged to the same species. Plant C had all its leaves removed. The three plants were of similar size and were exposed to the same environmental conditions. The results are as shown in the graphs below
- Suggest possible environmental conditions under which the experiment was carried out between 30 and 60 minutes
- Account for the results obtained for plant C
-
Suggest the habitat for plant A and B. Give reasons for your answer.
Answer
-
- Strong air currents / winds;
- High temperatures; -
- Absence of leaves/stomata absent;
- Transpiration is reduced/ little transpiration -
Habitat for A: Arid/dry/desert/semi-desert;
Reason: Low rate of water loss/ little water lost
Habitat for B: Areas of adequate water / high rainfall/ plenty of water;
Reason: High rate of water loss / more water lost / A lot of water loss
Question 3
The diagram below represents a food web in a terrestrial ecosystem.
- Which organism has the highest number of preys
- Construct a food chains with snakes as tertiary consumers
- State the trophic level occupied by hawks in the food chains constructed in b) above
- Describe how capture – recapture method can be used in estimating the population of fishes in a lake.
Answer
- Hawks
- Construct a food chains with snakes as tertiary consumers
- Quaternary consumers
- Green plants → Grasshoppers → Lizards → Snakes → Hawks
- Capture some fish, mark and release; them (without harming them). Record as first marked (FM);
After 24 hours, collect as many organisms ar possible in the same area. Record the number collected as second capture (SC);Record the number of those previously marked as marked recapture (MR);
Question 4
Study the diagram below and answer the questions that follow
- Identify the diagram
- Name the parts labeled A, B and D
- State the role of B and C
-
i) Protandry
ii) Protogyny
Answer
- A (mature) embryo sac
-
A - Antipodal cells;
B - Polar nuclei;
C - Synergids; -
B – Polar nuclei fuses with one male nucleus to form a primary triploid;
C – Egg cell fuses with another male nucleus to form a primary diploid; -
Protandry – Is where the stamens ripen earlier than the stigma;
Protogyny – Is where the stigma matures earlier than the stamens;
Question 5
In a family with four children, three were found to have normal skin pigmentation while one was an albino. Using letter A to represent gene for normal skin pigmentation and a to represent the gene for albinism.
- What are the genotypes of the parents?
- Work out the genotypes of the normal pigmented children and the albino child
- What is the probability that the fifth child will be an albino?
Answer
- Aa; Aa
-
Normal children AA, Aa;
Albino child aa; - 25%