Animal Biology and Physiology
What this domain tests
Animal Biology and Physiology covers homeostasis, nervous and endocrine control, circulation, gas exchange, digestion, osmoregulation, and muscle function. Questions often require interpreting feedback loops and transport systems.
Core rules and concepts
- Homeostasis maintains internal stability through negative feedback: a deviation triggers a response that reduces the deviation. Positive feedback amplifies a change and is less common.
- Neurons transmit action potentials; myelinated axons conduct faster by saltatory conduction. At synapses, neurotransmitters cross the cleft and bind receptors on the postsynaptic cell.
- Mammalian circulation is double and closed. Arteries carry blood away from the heart; veins return it. Capillaries have thin walls for exchange.
- Gas exchange depends on partial-pressure gradients and surfaces with large area and thin diffusion distance. Osmoregulation balances water and solute gain and loss.
Worked example
Cardiac output = heart rate × stroke volume. If heart rate is 75 beats min−1 and stroke volume is 70 mL beat−1, cardiac output = 75 × 70 = 5,250 mL min−1 = 5.25 L min−1. Reasoning: each beat ejects 70 mL, and 75 beats occur each minute, so multiplying gives the volume pumped per minute. An increase in either variable raises output.
Traps
Do not claim arteries always carry oxygenated blood; pulmonary arteries carry deoxygenated blood. Do not confuse negative feedback with “no change.” In action-potential diagrams, depolarization is due to Na+ entry and repolarization to K+ exit. Distinguish stroke volume from cardiac output.