SUBJECT: BIOLOGY Worksheet no.4: Variation and selection Teacher: Ali Ashraf M.Sc (Biochemistry) 1 Fig. 1.1 shows three different insects.
Vespula flavopilosa Vespula rufa Callicera rufa
insect 1 insect 2 insect 3
Fig. 1.1
(a) Insects 1 and 2 are more closely related to each other than to insect 3.
(i) Explain how the binomial names indicate that insects 1 and 2 are more closely related.
[2]
(ii) Explain how the appearance of the three insects suggests that insects 1 and 2 are more closely related.
[2]
1 Vespula flavopilosa gives a painful sting. The insect shown in Fig. 1.2 is very similar in appearance to Vespula flavopilosa but does not give a sting.
Chrysotoxum cautum
Fig. 1.2
(b) Chrysotoxum cautum is very similar in appearance to Vespula flavopilosa. Explain how this is an advantage.
[2]
(c) It is thought that Chrysotoxum cautum evolved from an insect that did not have any stripes.
Suggest how these insects became striped.
[5]
2 [Total: 11] 2 One variety of the moth, Biston betularia, has pale, speckled wings. A second variety of the same species has black wings. There are no intermediate forms.
Equal numbers of both varieties were released into a wood made up of trees with pale bark. Examples of these are shown in Fig. 2.1.
Fig. 2.1
After two weeks as many of the moths were caught as possible.
The results are shown in Table 2.1.
Table 2.1
wing colour of moth number released number caught
pale, speckled 100 82 black 100 36
(a) (i) Suggest and explain one reason, related to the colour of the bark, for the difference in numbers of the varieties of moth caught.
[1]
(ii) Suggest and explain how the results may have been different if the moths had been released in a wood where the trees were blackened with carbon dust from air pollution.
[2] 3 Table 2.2 shows the appearance and genetic make-up of the different varieties of this species.
Table 2.2
wing colour genetic make-up
pale, speckled GG; Gg black gg
(b) (i) State the appropriate genetic terms for the table headings.
wing colour
genetic make-up [2]
(ii) State and explain which wing colour is dominant.
dominant wing colour
explanation
[2]
(c) State the type of genetic variation shown by these moths. Explain how this variation is inherited.
[3]
4 3 Fig. 3.1 shows three species of zebra.
Equus burchelli
Equus grevyi
vertical stripe
horizontal stripe
Equus zebra
Fig. 3.1
5 (a) Describe one method a scientist could use to show that the zebras shown in Fig. 3.1 are different species.
[1]
(b) Studies have shown that the hotter the environment, the more stripes zebras have.
(i) State the type of variation which would result in different numbers of stripes.
[1]
(ii) Study Fig. 3.1. Suggest which species of zebra lives in the hottest environment.
[1]
(c) Occasionally, zebras are born that are almost completely black. The change in appearance is the result of mutation.
(i) State the term that is used to describe the appearance of an organism.
[1]
(ii) Define the term mutation.
[2]
(d) Tsetse flies attack animals with short fur, sucking their blood and spreading diseases.
Fig. 3.2 shows a tsetse fly. This fly is an insect, belonging to the arthropod group.
Fig. 3.2
6 (i) State one feature, visible in Fig. 3.2, which is common to all arthropods.
[1]
(ii) State two features, visible in Fig. 3.2 , which distinguish insects from other arthropod groups.
1.
2. [2]
(e) Scientists have discovered that zebras with more horizontal stripes attract fewer tsetse flies.
(i) Suggest why the stripes on the head and neck of the zebra would be an advantage when it feeds on grass on the ground.
[2]
(ii) Describe how a species of zebra could gradually develop more horizontal stripes.
[3]
[Total: 14]
4 Cheetahs, Acinonyx jubatus, are carnivores found in the dry grasslands and woodlands of southern Africa. Cheetahs hunt for food during the day. They eat deer and antelope.
The cheetah is the fastest mammal on land but can only run at high speed (sprint) over a short distance. Its hunting strategy is to creep up on prey and then sprint to catch them.
Fig. 4.1 is a photograph of a cheetah in its natura l habitat.
Fig. 4.1
7 (a) Suggest how these adaptive features enable cheetah s to survive in their natural environment.
