Response to Changes in the Environment (Edexcel IGCSE Biology): Revision Note

Response to Change

• Organisms must be able to detect changes (stimuli) in their environment and respond in order to survive

• A stimulus is a change in the environment that can be detected by an organism (eg. light, temperature, sound, chemicals, touch)

• Receptors detect stimuli

  • In humans, receptors are found in sense organs

  • In plants, specialised cells detect stimuli such as light, gravity or water

• The organism then produces a response to the stimulus

• Examples of responses include:

  • Moving towards or away from something

  • Secreting chemicals

  • Adjusting body processes

• The response increases the organisms chance of survival (eg. escaping predators, finding food, maintaining internal conditions)