Unit 3

What is the primary function of an endogenous biological clock?

To adaptively coordinate physiology and behavior with environmental cycles, even without external cues.

What’s the difference between the endogenous and environmental stimulus hypotheses?

Endogenous: behavior is controlled internally; Environmental: behavior is prioritized based on external feedback.

What evidence supports the existence of internal biological clocks in animals?

Crickets kept under constant light still follow a calling rhythm, which adjusts after exposure to dark—a sign of internal rhythm entrainment.

Where is the master circadian clock in mammals?

The suprachiasmatic nucleus (SCN) in the hypothalamus.

Which genes regulate circadian rhythms at the molecular level?

per, tau, and tim genes, which produce proteins in ~24-hour cycles.

What are predictable environmental cues used to entrain behavior?

Light-dark cycles, tidal patterns, lunar phases, and seasons.

What are examples of unpredictable cues that influence behavior?

Rainfall and sudden changes in food availability.

Why do rufous-winged sparrows use rainfall as a reproductive cue?

Because in desert environments, food availability improves only after rain—making rainfall more informative than day length.

How do marine iguanas adjust behavior to their environment?

Larger iguanas forage subtidally despite heat loss, while smaller ones stay intertidal—based on size and energetic cost.

Where do hormones come from, where do they go, and what do they do?

Made by endocrine glands → travel via blood → affect growth, metabolism, behavior, reproduction

What’s the difference between negative and positive hormonal feedback?

Negative feedback reduces hormone production (homeostasis); positive feedback amplifies it (e.g., oxytocin in childbirth).

How do steroid hormones differ from peptide hormones in action?

Steroids: enter cells and alter gene expression (slow, long-lasting). Peptides: act on cell surfaces (fast, short-lived).

Classify the hormone signaling:Testosterone in roosters, ADH in kidneys, Local signal to a nearby cell

Endocrine, Neuroendocrine, Paracrine (respectively)

Why do steroid hormones cause longer-lasting effects than polypeptides?

They alter gene transcription, affecting long-term protein production

What's the difference between organizational and activational effects of hormones?

Organizational: permanent developmental changes; Activational: short-term behavioral effects.

What is cryptic coloration?

A camouflage strategy where animals blend into their surroundings to avoid detection.

Why might an animal choose to be conspicuous to predators?

To advertise unpalatability (aposematism) or fitness (stotting in gazelles).

What’s the difference between Batesian and Müllerian mimicry?

Batesian: harmless species mimics harmful one; Müllerian: multiple harmful species share similar warning coloration.

What are costs and benefits of social defense?

Benefit: safety in numbers; Cost: increased competition and visibility.

How does optimality theory apply to anti-predator behavior?

Predicts behaviors will evolve to maximize benefits (like survival) and minimize costs (like energy or exposure).

What do the HPG and HPA axes have in common?

Both begin in the hypothalamus, involve the pituitary gland, use hormonal cascades, and rely on negative feedback loops.

What is the main function of the HPG axis?

Regulates reproduction and sex hormone production (testosterone, estrogen, progesterone).

What is the main function of the HPA axis?

Regulates the body’s stress response via cortisol release.

What hormone does the hypothalamus release in th eHPG axis?

Gonadotropin-reeasing hormone (GnRH

What hormone does the hypothalamus release in the HPA axis?

Corticotropin-releasing hormone (CRH)

What are the pituitary hormones in the HPG and HPA axes?

HPG: LH and FSH; HPA: ACTH

What are the target organs of the HPG and HPA axes?

HPG: gonads; HPA: adrenal cortex

what does the dilution effect hypothesis suggest?

being in a group reduces the chance that any one individua is attacked

what would disprove the dilution effect hypothesis?

if predation risk per bee is unchanged or higher in larger groups

What does the predator confusion hypothesis purpose?

that predators struggle to target individuals in a large active group

What evidence would reject the predator confusion hypothesis propose?

if the assassin bug is equally or more successful at capturing prey in larger groups

what does the increased vigilance hypothesis suggest?

more bees = more eyes= faster predator detection and escape

what would disprove the increased vigilance hypothesis?

if a group of bees respond to predators no faster than solitary bees

what is a zeitgeber?

a cue from the environment that helps reset internal biological clocks

what causes a freemartin to become infertile?

exposure to male hormones while sharing the womb with a male twin

what gland secretes melatonin, and when is it produced most?

pineal gland, at night

what is the role of the corpus luteum in the ovarian cycle?

produces progesterone to support the uterine lining