For each of the examples given below, suggest whether the variation is caused by genes alone, or by both genes and environment. Blood group in humans Foot size in humans Leaf length in a species of tree Presence of horns in cattle

Genetic variation is the difference in DNA among individuals or the differences between populations. There are multiple sources of genetic variation, including mutation and genetic recombination. Mutations are the ultimate sources of genetic variation, but other mechanisms such as sexual reproduction and genetic drift contribute to it as well. A plant in the shade of a big tree will grow taller as it tries to reach more light. Variation caused by the surroundings is called environmental variation. Here are some other examples of features that show environmental variation: your language, your religion. Hence, it shows that the given example, blood group in humans and presence of horns in cattle genes both are genetic variation. Whereas, the foot size in humans and leaf length in a species of tree genes are environmental variation.

E M B I B E

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.1

EASY

Upper Secondary: IGCSE

IMPORTANT

Earn 100

Decide whether each of these features shows continuous variation or discontinuous variation.

Leaf length in a species of tree.

Important Questions on Variation and Natural Selection

EASY

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.1

Decide whether each of these features shows continuous variation or discontinuous variation.

Presence of horns in cattle.

EASY

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.2

For each of the examples given below, suggest whether the variation is caused by genes alone, or by both genes and environment.

Blood group in humans
Foot size in humans
Leaf length in a species of tree
Presence of horns in cattle

MEDIUM

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.3

The photograph shows a small mammal called a tarsier. Tarsiers feed on insects, which they hunt at night. How is the tarsier adapted for survival in its environment?

Question Image

MEDIUM

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.4

Explain why the proportion of dark peppered moths near Manchester in Britain increased at the end of the

19

th century.

EASY

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.5

Why is it unwise to use antibiotics unnecessarily?

EASY

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.6

What is meant by stabilizing selection? Give one example.

MEDIUM

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.7

Draw a genetic diagram to show how two heterozygous parents can have a child with sickle cell anaemia?

MEDIUM

Upper Secondary: IGCSE

IMPORTANT

Cambridge IGCSE® Biology Coursebook Third Edition>Chapter 19 - Variation and Natural Selection>Questions>Q 19.8

Imagine you are a farmer with a herd of dairy cattle. You want to build up a herd with a very high production of milk. You have access to sperm samples from bulls, for each of which there are records of the milk production of his offspring. What will you do?