• 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

轉載自savemyexam