AP® Biology · Unit 8 · Topic 8.1
Communication and Information Exchange
Animals pass information to each other through signals like movements, chemicals, and sounds, and natural selection shapes these signals because they help genes survive, sometimes even through relatives rather than the signaler itself.
Communication in ecology means one organism's signal changes another organism's behavior in a way that affects both their fitness. A forager honeybee returning to the hive with news of food does a waggle dance: a figure-eight pattern with a straight run through the middle. The angle of that straight run, measured against vertical on the honeycomb, matches the angle between the food and the sun outside. The length of time spent waggling during the straight run scales with how far away the food is. Other bees in the dark hive read the dance with touch and sound, then fly off using the sun as their own compass.
Ants solve the same problem differently. A scout finds food and walks back to the nest laying a pheromone trail. Nestmates follow the scent outward, and successful foragers reinforce the trail on their way back, making it stronger. Unvisited or depleted paths get no reinforcement, and the pheromone simply evaporates, so the trail fades. This feedback loop means the colony's foraging pattern constantly updates: wipe out the trail and foragers scatter randomly again, rediscovering food sources through individual search until new trails form and sharpen through repeated reinforcement.
Not every signal benefits the signaler directly. An alarm call warns nearby animals of a predator but can draw attention to the caller. This looks like it should be selected against, yet it persists because of kin selection: if the call protects enough close relatives, who share many of the caller's genes, the genes for alarm-calling still spread even if the individual caller is sometimes lost. This ties communication back to the unit's larger theme that individual behaviors are explained by their effects on gene survival, not just personal survival.
Key terms
- Waggle dance
- A figure-eight movement honeybees perform to communicate the direction and distance of a food source.
- Pheromone
- A chemical signal released by an organism that changes the behavior of others of its species.
- Kin selection
- Natural selection favoring traits that help relatives survive and reproduce, even at a cost to the individual.
- Fitness
- A measure of an organism's reproductive success, often including effects on the reproduction of close relatives.
Watch it explained
- How it worksHow does the angle and duration of the waggle dance encode a direction and a distance?
- How it worksWalk me through a pheromone trail forming and then fading between an ant nest and food.
- Going furtherWhat happens to a colony's foraging pattern when the pheromone trail is wiped out?
- Common mistakeWhy isn't an alarm call that endangers the caller an evolutionary contradiction?
Check yourself
End of topic.