Why do you think female hyenas evolved to have a pseudopenis?
Female spotted hyenas evolved a pseudopenis likely due to high prenatal androgen (testosterone) exposure, which masculinizes their genitalia. It may serve as a byproduct of aggression-related hormones that increase dominance and social status. The pseudopenis is also used in social signaling and greeting rituals, reinforcing hierarchy and social bonds.
Give an example of sensory exploitation of signal receivers.
Male túngara frogs add “chucks” to their mating calls because females are neurologically biased to respond to low-frequency sounds. Males exploit this preexisting sensory bias, even though the call also attracts predators.
Why do female guppies prefer males with bright orange spots on their skin?
Female guppies evolved a preexisting sensory bias for orange color because they naturally eat orange fruits. Males exploit this bias—bright orange spots make them more attractive to females.
What is sensory bias? Give an example.
Sensory bias is when a preference for a particular signal evolves before the signal itself, due to preexisting sensory sensitivities.
Example: Female swordtails prefer males with long tails even before males in their species evolved swords.
What is the Panda Principle? How does this help explain how certain traits evolve?
The Panda Principle (or principle of imperfection) states that evolution works by modifying existing structures, not creating perfect ones from scratch.
Example: Panda’s “thumb” is a modified wrist bone.
It explains how traits evolve through adaptation of preexisting features, not perfect design.
Why do ravens advertise when they have found a food source? Do they always call? Why or why not?
Ravens call to attract other ravens when they find a large food source that a single bird cannot defend (like a carcass). By forming groups, they can overwhelm dominant territory holders.
They don’t call when they can monopolize small food sources—calling would just bring competition.
What is an illegitimate receiver? How can they have an impact on the evolution of communication systems?
An illegitimate receiver is an organism that intercepts a signal meant for others—like a predator hearing a mating call.
Impact: They can cause evolution toward quieter or less obvious signals to reduce detection risk.
Example: Predatory bats eavesdrop on frog mating calls.
One hypothesis of begging is sibling competition. Explain why this likely is not the case.
Begging intensity doesn’t always match food need or competition. Instead, begging is often a signal of need to parents, not just competition with siblings. Parents respond to honest signals of hunger, not purely to who begs loudest.
Why do so many animals settle disputes with harmless threats? Give an example. Why do even losers gain fitness by contests that are settled quickly?
Threat displays (like roaring, puffing up, or color displays) avoid injury and energy loss.
Example: Red deer roar contests often settle dominance without fighting.
Losers still gain fitness by avoiding serious harm and living to reproduce another day.
What support do we have that honest signaling is translated into settling disputes?
Honest signals are often physiologically linked to actual strength or condition, making them reliable.
Example: Roar pitch in red deer correlates with body size; opponents use it to decide whether to escalate, often ending fights early.
Explain the differences between habitat restoration and habitat management. Give an example of a successful habitat restoration.
Habitat restoration: Returning a degraded habitat to its original state.
Example: Restoring wetlands in the Everglades.
Habitat management: Maintaining or manipulating a habitat for a target species or condition.
Example: Controlled burns in grasslands to maintain open habitat for certain birds
Discuss an example of how organisms evaluate habitat quality.
Animals assess cues like food availability, shelter, or presence of conspecifics.
Example: Female songbirds choose territories where other females successfully raised chicks—indicating good habitat.
In American robins, habitat selection is affected by experience. In particular, birds whose nesting attempts have failed in one year often do not return to the same spot to try again the next year. Explain using conditional strategies.
This is a conditional strategy: behavior changes based on past success.
If nesting failed, robins disperse to improve reproductive success; if successful, they return (site fidelity). The choice depends on prior experience.
Explain why many organisms disperse from where they were born. How does this sometimes differ between males and females?
Dispersal reduces inbreeding and competition with relatives.
Often, males disperse more (in mammals) to avoid mating with relatives, while females disperse more in some birds to avoid competition for nesting sites.
Why do many birds choose to migrate? Explain the possible benefits.
Migration allows birds to exploit seasonal food abundance, avoid harsh climates, and increase breeding success by moving to areas with more resources or fewer predators.
How do birds minimize the costs of migration?
Flying in V-formations to reduce wind resistance
Using favorable wind currents
Storing fat reserves before migration
Stopping at refueling sites along the way
Why do monarch butterflies migrate specifically to the Oyamel Fir Forests in Mexico?
The Oyamel forests provide cool, moist, and stable conditions that reduce energy use and prevent desiccation—ideal for overwintering survival.
Some birds use migration as a conditional tactic. What are some examples of conditions where they might choose to leave or stay?
Migration depends on environmental conditions and body condition.
Example: In partial migrants like robins, healthy or dominant individuals stay if food is available, while weaker or subordinate ones migrate.
What are some ways animals can minimize the cost of territoriality?
Using visual or vocal boundaries instead of fighting
Sharing territories seasonally
Defending only when necessary (e.g., during breeding)
Why are many animals territorial?
Territoriality ensures access to critical resources—food, mates, or nesting sites—by excluding competitors, thus improving reproductive success.
Explain the Dear Neighbor Effect.
The Dear Neighbor Effect occurs when established neighboring territory holders show reduced aggression toward each other compared to strangers.
Since they know each other’s boundaries, this reduces conflict and energy costs.
What does a male bowerbird gain by spending the better part of 8 months each year
constructing his bower?
A male bowerbird shows off his intelligence, skill and genetic fitness by building a bower. A female will choose a mate based on bower quality, decoration and the male’s courtship.
Why have most species evolved to have female choosiness, and males having to
advertise their “goods”? How can observing species that have this flipped help explain
why?
Females invest more in reproduction (larger gametes, parental care and pregnancy). Males maximize their fitness by mating often, and females maximize this by choosing the “best quality” mate.
For example in seahorses, males get pregnant and females compete while males choose mates because in this case, males invest more.
Why do sexes differ in the resources they donate to a fertilized egg? Explain the
evolutionary theory of sex differences.
Females produce few, energy rich, large eggs while males produce many small sperm. This difference (anisogamy) drives the evolution of sex difference. Females choose and males compete. Evolution is going to favor behaviors that maximize reproductive success for both sides given of their investment.
