- Describe a control system by which an animal maintains a stable internal environment. Annotated diagrams or models may be used to support the description.
For Merit include and explanation of:
- how or why an animal maintains a stable internal environment
- how a specific disruption results in responses within a control system to re-establish a stable internal environment.
For Excellence include at least one of:
- a discussion of the significance of the control system in terms of its adaptive advantage
- an explanation of the biochemical and/or biophysical processes underpinning the mechanism (such as equilibrium reactions, changes in membrane permeability, metabolic pathways)
- an analysis of a specific example of how external and/or internal environmental influences result in a breakdown of the control system.
A control system that maintains a stable internal environment (homeostatic system) refers to those that regulate:
- body temperature
- blood pressure
- osmotic balance
- level of blood glucose
- levels and balance of respiratory gases in tissues.
The biological ideas related to the control system includes the:
- purpose of the system
- components of the system
- mechanism of the system (how it responds to the normal range of environmental fluctuations, interaction and feedback mechanisms between parts of the system)
- potential effect of disruption to the system by internal or external influences.
Environmental influences that result in a breakdown of the control system may be external influences such as extreme environment conditions, disease or infection, drugs or toxins, or internal influences such as genetic conditions or metabolic disorders.