Biotic factors: Students should be able to extract and interpret information from charts, graphs and tables relating to the effect of biotic factors on organisms within a community.

The idea

Biotic factors are living influences on organisms in a community, such as food availability, predators, pathogens and competition. To extract information, read the title, axis labels, units and key first, then locate the relevant data point or trend. To interpret, link the pattern to a biological effect: for example, a graph showing increasing predator numbers followed by falling prey numbers suggests predation reduces prey population. In a table, compare values across rows or columns to identify which factor changes most. Always quote figures with units and state the direction of change. Explain the effect using cause and effect, not just description, and consider that other biotic or abiotic factors may also act.

What earns the marks

• Identify the independent variable, dependent variable and any control or comparison group from the chart, graph or table.
• Read values accurately from axes or table cells, including units and any stated uncertainty or sample size.
• Describe the trend or pattern, such as increase, decrease, plateau or cyclical change, using comparative language.
• Interpret the pattern biologically, linking a named biotic factor to a named effect on organisms in the community.
• Use data as evidence, quoting specific figures with units to support the interpretation.
• Recognise limitations, such as correlation not proving causation or other factors affecting the community.

Common mistakes and how to put them right

• Describing the graph shape without interpreting it biologically.

  Put it right by linking each trend to a named biotic factor and its effect on organisms.

• Reading the wrong axis or ignoring units.

  Put it right by checking axis labels, scales and units before quoting any value.

• Treating a correlation as proof of cause.

  Put it right by stating that the data suggest a relationship and that other factors may also be involved.

Exam tips

• Underline the command word, such as describe or explain, and match your answer to it.
• Quote at least one pair of figures with units from the chart, graph or table as evidence.
• Use comparative connectives such as whereas, therefore and as a result to make the link between data and biology clear.