Exercises: Inherited and environmental variation

Define the term "variation" and give two examples among students in your class.

Classify each characteristic as inherited, environmental, or both:

1. a) Eye colour

1. b) A scar on the knee

1. c) Height

1. d) Blood group

Name two ways in which variation arises in sexually reproducing organisms.

The heights of $10$ students in a class in Limerick, in cm, are: $152, 160, 158, 165, 170, 158, 162, 175, 158, 168$.

1. a) Calculate the mean height.

1. b) State the mode and the range.

1. c) Explain why height is described as showing continuous variation.

Two identical twins are raised in different parts of Ireland. One becomes taller than the other, and one has a darker skin tone because of time spent outdoors.

1. a) Explain why identical twins have the same inherited characteristics.

1. b) Explain the differences in height and skin tone, using the term "environmental factors".

1. c) Give two environmental factors that might affect height.

Hydrangea plants of the same variety grown in different soils produce blue flowers in acidic soil and pink flowers in alkaline soil.

1. a) State which type of variation is shown.

1. b) Explain what this tells you about the role of genes and environment.

1. c) Suggest how you would design a fair test to show this result.

Compare two characteristics: tongue rolling, which is mainly controlled by one gene, and human height, which is influenced by many genes and by nutrition.

1. a) Explain why tongue rolling shows discontinuous variation and height shows continuous variation.

1. b) Explain how the average height of a population can increase over generations without any change in genes.

1. c) Explain why variation is important for the survival of a species.

A researcher compares the mass of identical twins reared together with identical twins reared apart, and finds that the masses of twins reared apart differ more.

1. a) Interpret this result.

1. b) Explain why twin studies are useful for separating genetic and environmental effects.

1. c) Suggest one limitation of this type of study.

A population of mice in a field in Co. Clare includes both brown and white mice. Hawks hunt the mice, and white mice are more easily seen against the dark soil.

1. a) Predict how the proportions of brown and white mice will change over many generations.

1. b) Explain your prediction using the terms "variation", "inherited" and "natural selection".

1. c) Explain whether the change in the population would be reversed if the soil were covered by snow for many years.