AQA A Level Biology复习笔记6.1.6 Causes of 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