Edexcel iGCSE Biology-3.30 Response to Changes in the Environment- Study Notes- New Syllabus
Edexcel iGCSE Biology-3.30 Response to Changes in the Environment- Study Notes- New syllabus
Edexcel iGCSE Biology-3.30 Response to Changes in the Environment- Study Notes -Edexcel iGCSE Biology – per latest Syllabus.
Key Concepts:
3.30 understand how organisms are able to respond to changes in their environment
Response to Environment
🌱 Introduction
All living organisms need to sense and respond to changes in their environment (stimuli) to survive and reproduce.
This ability is called sensitivity or responsiveness.
🔹 Key Terms
- Stimulus → Any detectable change in the environment (e.g. light, temperature, sound, chemicals).
- Receptor → Specialized cell/organ that detects the stimulus.
- Effector → Muscle or gland that carries out the response.
- Response → The action taken (movement, secretion, etc.).
🔹 Why Response is Important
- Helps organisms find food.
- Avoids danger/predators.
- Maintains homeostasis (stable internal environment).
- Aids survival and reproduction.
📖 Examples
- Plants:
• Phototropism → shoot grows towards light.
• Gravitropism → roots grow downwards into soil. - Animals:
• Eyes detect light → brain processes → muscles move.
• Withdrawal reflex when touching something hot.
📊 Stimulus – Response Pathway
| Step | Description | Example |
|---|---|---|
| Stimulus | Environmental change | Hot object |
| Receptor | Detects change | Skin receptors |
| Coordination | Brain/spinal cord | Sends message |
| Effector | Muscle/gland | Arm muscle contracts |
| Response | Final action | Hand pulled back |
⚡ Quick Recap
Organisms detect stimuli using receptors.
Effectors (muscles/glands) carry out the response.
Responses improve survival (food, safety, reproduction).
Pathway: Stimulus → Receptor → Coordinator → Effector → Response.
👉 Mnemonic: SR-CER = Stimulus → Receptor → Coordinator → Effector → Response.