Page 46 - Science Coursebook

3.2 Variation

In Stage 7, you learnt that living organisms are classified into
species. A species is a group of organisms that share the same
features, and that can breed together to produce fertile offspring.

Although all the members of a species share the same features,

no two individuals are ever exactly alike. The differences
between the individuals within a species are called variation.
All of these snails are the same species.
Question

1 The Latin name of the species of snail shown in the photograph is
Cepaea nemoralis.
a Why do scientists give species Latin names?
A+I b Snails are eaten by birds. Snails with plain yellow or cream shells are
generally found in dry grass, while snails with stripes are often found
in woodland. Suggest why.

Activity 3.2
Measuring variation in humans

SE In this activity, you are going to measure and record the variation in wrist
circumference in your class. If you have forgotten about tally charts and
frequency diagrams, you may need to look back at the work you did in Stage 7.
1 Measure the circumference of the right wrist of every person in your class.
Write down your measurements in a list. Remember to write down the
units you have used for your measurements.
2 Use your measurements to calculate the mean (average) wrist circumference
of the people in your class.
3 Draw a results table like this. You may need to change the numbers in the

first column a little, to fit the range of measurements you have found. (Have
a look at the smallest and largest measurements you have made.)

Wrist circumference / cm Tally Number of people
8.0–8.9
9.0–9.9
10.0–10.9
11.0–11.9
12.0–12.9
13.0–13.9
14.0–14.9
15.0–15.9
16.0–16.9

continued ...

44 3 Variation and inheritance

A+E