Communities: Students should be able to extract and interpret information from charts, graphs and tables relating to the interaction of organisms within a community.

The idea

This skill means reading data about organisms in a community and working out what the numbers show about their interactions. Charts, graphs and tables might show population sizes over time, predator and prey numbers, or the effect of removing a species. To extract information, read the axes, units, labels and key carefully, then quote specific values. To interpret, describe the trend and link it to an interaction: for example, if prey numbers rise, predator numbers may rise soon after because more food is available, and then prey numbers fall as more are eaten. Predator-prey graphs often show peaks and troughs with the predator peak lagging behind the prey peak. Always compare like with like, use the data rather than general knowledge alone, and suggest a reason for each pattern you describe.

What earns the marks

• Read axes, units, labels and keys correctly, and quote specific values from the chart, graph or table.
• Describe trends over time, such as increases, decreases, peaks, troughs or cyclical patterns in population sizes.
• Interpret a predator-prey relationship by linking a rise in prey numbers to a later rise in predator numbers, and a fall in prey numbers to increased predation.
• Explain how data show interdependence, for example a fall in one species leading to a fall in a species that depends on it for food or pollination.
• Compare data for two or more species and use the comparison to support a conclusion about their interaction.

Common mistakes and how to put them right

• Reading values from the wrong axis or ignoring the units.

  Put it right: Check the axis label and unit before quoting a number, and state the unit with the value.

• Describing a trend without using data.

  Put it right: Support every statement with a figure, such as 'the prey population rose from 200 to 600 between year 1 and year 3'.

• Confusing correlation with cause.

  Put it right: Use the data to suggest a possible interaction, then explain the biological reason, such as more prey providing more food for predators.

Exam tips

• Quote numbers with units and refer to the correct species and time period in every data answer.
• Use comparative language such as 'higher than', 'lower than' or 'increased by' rather than vague words like 'more' or 'less'.
• When explaining a lag between predator and prey peaks, state that the predator response happens after the prey change because predators need time to reproduce.