Causes of Animal Movement (AQA A Level Biology)

Investigating Environmental Factors That Cause Animal Movement

• Environmental factors can be abiotic or biotic

• Abiotic factors are the non-living parts of an environment

  • For example: temperature, wind, humidity and soil pH

• Biotic factors are the living parts of an environment

  • For example: competition, predation and disease

• Experiments can be carried out to investigate the effect of abiotic factors on the movement of animals

  • Choice chambers and mazes are often used in these experiments and woodlice and maggots are commonly the model animals

• A scientist called J. Cloudsley-Thompson carried out the first experiments on woodlouse behaviour

• One of his experiments focused on the response of woodlouse to humidity

• He used large choice chambers that were divided into two sections

Apparatus

• Choice chambers

• Lids

• Distilled water (fixed volume in each choice chamber)

• Drying agent (fixed volume in each choice chamber)

• Gauze platforms

• Woodlice

• A dark cupboard

• A bright well-lit room

Method

• Divide each choice chamber into two sections

  • Add a fixed volume of distilled water to one side and a fixed volume of drying agent to the other

  • This allows for the humidity to be controlled in each section

• Insert gauze platforms into the choice chambers

  • This keeps the woodlice at a safe distance from the water and drying agent

  • Note that woodlice are able to move between sections

• Divide the woodlice into two even-sized groups

  • Drop the woodlice from group A into choice chambers kept in the dark

  • Drop the woodlice from group B into choice chambers kept in the light

• The woodlice can be dropped into the chamber using the hole in the lid so that they fall into the centre of the choice chamber

• Record the position of the woodlice in each choice chamber after 15 minutes

  • They should fall into the following categories: moving around, stationary on the dry side, stationary in the centre or stationary on the humid side

• Repeat the experiment several times for all conditions

Results and analysis

• A significant percentage of the woodlice (in all groups) moved to the humid side

  • This is a beneficial response as it helps to prevent water loss from the respiratory surfaces of the woodlice

• The woodlice responded to humidity more actively when in the light

  • This is advantageous - if the woodlice are subject to dry conditions during the day when they are more likely to dehydrate then they are even more likely to move towards humid conditions (under a stone, log etc)

• The woodlice tended to stop moving when in humid conditions

  • This means they are able to remain within favourable conditions that reduce water loss

Limitations

• In this experiment, the conditions that the woodlice were kept in prior to the experiment have not been stated

  • If the woodlice were kept in dark or light conditions it could affect their response during the experiment

• The behaviour of the woodlice was not observed during the experiment

  • It can not be said if their behaviour was taxis (directional response) or kinesis (non-directional response) that randomly caused them to end up in the humid section

The choice chamber has two sections, one with low humidity and one with higher humidity