AQA A-Level - Biology 
Organisms respond to changes in their internal and external environments 
(A-level only)

AQA | A-Level | Biology | Organisms respond to changes in their 
internal and external environments (A-level only) | Lesson 28

Stimuli, both internal and external, are detected 
and lead to a response (A-level only)

AQA | A-Level | Biology | Organisms respond to changes in their 
internal and external environments (A-level only) | Lesson 29

Nervous coordination (A-level only)

AQA | A-Level | Biology | Organisms respond to changes in their 
internal and external environments (A-level only) | Lesson 30

Skeletal muscles are stimulated to contract 
by nerves and act as effectors (A-level only)

AQA | A-Level | Biology | Organisms respond to changes in their 
internal and external environments (A-level only) | Lesson 31

Homeostasis is the maintenance of a stable 
internal environment (A-level only)