Overview
Behavior (ethology) is a smaller part of the exam, but questions are usually experiment-based and can be answered by careful reading. Most of them ask you to design or interpret an experiment that separates an innate response from a learned one.
Learn the classic categories. Then practice explaining behavior at two levels: how it works (the mechanism) and why it evolved (its function).
Core concepts
10.1Innate and learned behavior
Fixed action patterns are triggered by sign stimuli and run to completion. Learning includes habituation, imprinting (during a sensitive period), classical conditioning, operant conditioning, and observational learning.
Many behaviors combine both. Birdsong, for example, needs an innate template plus learning during a sensitive period.
Key terms: fixed action pattern · sign stimulus · habituation · imprinting · operant conditioning
10.2Proximate and ultimate explanations
Proximate explanations cover mechanism and development (hormones, neural circuits, triggers). Ultimate explanations cover evolutionary function and history.
A good answer names the level it is working at. "Birds migrate because day length changes" is proximate. "Because migrating improves survival and reproduction" is ultimate.
Key terms: proximate cause · ultimate cause · Tinbergen's questions · adaptive value
10.3Foraging and communication
Optimal foraging theory predicts that animals balance energy gained against time, energy spent, and risk. Communication signals can be visual, chemical (pheromones), acoustic, or tactile. The honeybee waggle dance encodes direction relative to the sun and distance to a food source.
Honest signals tend to be costly or hard to fake, which is why they stay reliable.
Key terms: optimal foraging · pheromone · waggle dance · honest signal · territoriality
Practice
Review the concepts above, then complete the practice set. Missed a question? Read the explanation and try a similar problem.
Common mistakes
| Mistake | Instead |
|---|---|
| Explaining a behavior by what the animal "wants." | Describe the mechanism (proximate) or the fitness consequence (ultimate). Do not assign intentions. |
| Calling any response to a stimulus "learned." | Learning means behavior changes with experience. Check whether naïve animals respond the same way. |
| Misusing relatedness values. | Full siblings: r = 0.5. Half siblings: r = 0.25. First cousins: r = 0.125. |
Recommended resources
- OpenStax Biology 2e, Chapter 45.7 (Behavioral Biology) Textbook (free)
- HHMI BioInteractive Videos & data activities
- Khan Academy: Behavioral ecology Videos
Further reading
- Campbell Biology, chapter on behavioral ecology.
- Alcock / Rubenstein, Animal Behavior.
10.4Social behavior and altruism
Kin selection: Hamilton's rule predicts that altruism is favored when rB > C (relatedness × benefit to the recipient > cost to the actor). Reciprocal altruism can work between unrelated individuals who interact repeatedly.
Mating systems (monogamy, polygyny, polyandry) tend to follow the certainty of paternity and the amount of parental care each sex provides.
Key terms: kin selection · Hamilton's rule · inclusive fitness · reciprocal altruism · sexual selection