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
