Survival & Response (AQA A Level Biology): Revision Note

Responding to change aids survival

• The ability to respond to changes in the environment aids survival in living organisms, e.g. it allows organisms to:

  • find food

  • avoid predators

  • stay in suitable conditions

• The process of detecting and responding to change is as follows:

  1. a stimulus is detected by receptor cells, e.g.:

     • light is detected by photoreceptor cells in the eye

     • changes in blood glucose are detected by beta cells in the pancreas

  2. information from receptors is processed by a coordinator, which could be part of:

     • the nervous system, e.g. the brain or spinal cord

     • the hormonal system, e.g. the pancreas or pituitary gland

  3. an effector responds appropriately to the environmental change; effectors can be either:

     • muscles, which allow the organism to move

     • glands, which secrete chemicals inside the body

• Signals between receptors, coordinators and effectors may involve:

  • nervous communication: electrical impulses in neurones

  • hormonal communication: chemicals in the blood