Edexcel IGCSE Biology: Double Science 复习笔记 1.1.4 Living Organisms: Response to Surroundings

• The sensitivity of an organism refers to its ability to detect and respond to stimuli in its surroundings
• Responding to the environment around them gives an organism the best chances of survival

Sensitivity responses in animals

• In humans, the nervous system provides a complex system of receptors, neurones and effectors which detect and respond to different stimuli using electrical impulses
• The endocrine system also allows a response to stimuli using chemical messengers, which travel in the blood, called hormones

The nervous system and endocrine system allow humans to respond to their environment

Sensitivity responses in plants

• In plants, responses are controlled by chemicals and are usually much slower
  • Geotropism describes a plants response to gravity which causes the roots to grow down into the soil
  • Phototropism describes a plant's response to light which causes shoots to grow towards sunlight

   

Phototropism and geotropism allow plants to respond to their environment

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