Levels of organisation Flashcards – AQA GCSE Combined Science: Trilogy (8464) — Biology — Foundation

What is a quadrat?

A frame used to sample organisms within a known area.

How can abundance be measured within a quadrat?

Count individuals, or estimate the percentage area covered by a species when individuals are difficult to distinguish.

How is a species’ frequency measured using quadrats?

As the proportion of sampled quadrats in which the species occurs.

Why are quadrats placed randomly in a habitat?

To avoid selecting only particular parts of the habitat.

What are the two benefits of taking multiple quadrat samples?

They allow a mean abundance to be calculated and make the estimate more representative.

How can mean individual count per quadrat be used to estimate population size?

$\text{Estimated population size} = \text{mean count per quadrat} \times \frac{\text{total habitat area}}{\text{quadrat area}}$

What is the purpose of representing data in a graph?

To make values and patterns easier to inspect.

When should a bar chart or a line graph be used?

Use a bar chart to compare separate categories and a line graph to show change across a continuous scale.

How should a graph’s axes be set up and labelled?

Place variables on appropriate axes, and label each axis with its quantity and unit where applicable.

What three features should a graph’s scales have?

They should cover the data range, use consistent intervals and make effective use of the plotting area.

How should values be plotted and represented on a graph?

Plot values accurately against the scales, then draw bars, points or lines as appropriate to the graph and data.

What are a predator and its prey?

A predator is a consumer that kills and eats another animal; the animal eaten is its prey.

Why can a predator population increase when prey become more abundant?

More prey provides more food for predators.

How can an increase in predation affect prey numbers?

It can contribute to a decline in the prey population.

Why may predator numbers fall when prey become less abundant?

Less prey is available as food.

How can a fall in predator numbers allow prey to recover?

Reduced predation allows the prey population to recover.

What features of a population graph can be used to compare predator and prey populations over time?

Their values, rises, falls, peaks and troughs.

Why do predator population peaks typically follow prey population peaks?

The predator population takes time to respond to changes in prey availability.