NBB 201 / ANT 200: Section II - Mechanisms of Behavior

Comprehensive vocabulary flashcards covering Section II (Mechanisms of Behavior), including endocrinology, sexual differentiation, the white-throated sparrow case study, sexual selection, parental care, and affiliative behavior.

Eugenics

A term coined by Sir Francis Galton meaning "noble in birth," defined as the effort to improve the human race through the scientific management and control of human mating.

Positive Eugenics

A branch of eugenics that encouraged the reproduction of individuals deemed "fit" or of the "good kind" (e.g., through contests such as the U.S. "Fitter Family Fairs").

Negative Eugenics

A branch of eugenics aimed at lowering the birth rate or preventing reproduction of people deemed "unfit" or the "bad kind," executed through forced sterilization and institutionalization.

Ontogenetic Niche

A concept introduced by Meredith West and Andrew King (1987) proposing that organisms must be understood holistically as inseparable from their developmental environment rather than isolating nature from nurture.

Developmental Systems Theory (DST)

Susan Oyama's framework asserting that organisms inherit developmental systems rather than just genes, wherein nature is the product of nurture at one moment and becomes the resource for subsequent development.

Ontogeny

The course of development of a single organism across its lifespan (e.g., a frog's life cycle, gastrulation, learning to read, and puberty).

Suprachiasmatic Nucleus (SCN)

A cluster of neurons located just above the optic chiasm that maintains a circadian clock of approximately $24\text{ hours}$ in vertebrates through a negative feedback loop involving the $per$ gene and PER protein.

Intracrine

A chemical communication mode in which an intracellular signal acts directly inside the same cell that synthesized it.

Autocrine

A chemical communication mode where a chemical substance is released from a cell and acts back on surface receptors of that exact same cell.

Paracrine

A chemical communication mode where a signal acts on nearby adjacent cells (e.g., neurotransmitters diffusing across a synaptic cleft).

Endocrine

A chemical communication mode in which chemical messengers (hormones or neurohormones) are released into the bloodstream to reach distant physiological targets.

Ectocrine

A chemical communication mode where substances, such as pheromones, are released outside the organism's body to affect other individuals.

Neurohormone

A chemical messenger produced by neurons but secreted directly into the bloodstream to exert distant endocrine effects (e.g., oxytocin, vasopressin, and hypothalamic releasing hormones).

Hypothalamic-Pituitary Portal System

A closed, exclusive, one-way circulatory pathway (primary plexus to secondary plexus) carrying hypothalamic releasing and inhibiting hormones directly to the anterior pituitary.

Posterior Pituitary

A lobe of the pituitary gland that synthesizes no hormones of its own; it receives axon terminals from hypothalamic neurons (PVN and SON) and releases oxytocin and vasopressin into the blood.

Anterior Pituitary

An endocrine gland that receives regulatory neurohormones via the portal system and manufactures its own true hormones (e.g., ACTH, LH, FSH, TSH, GH, and prolactin) for release into general circulation.

Up-Regulation

An increase in the total number or density of cellular receptors for a specific hormone, resulting in a stronger biological response even if circulating hormone levels remain unchanged.

Down-Regulation

A decrease in the number or density of cellular receptors for a hormone, leading to a dampened target-tissue response.

Finasteride

A pharmacological agent that blocks $5\alpha\text{-reductase}$, the enzyme that converts testosterone to DHT, reducing circulating DHT levels by approximately $60\text{--}70\%$ to treat hair loss.

Steroid Hormones

Lipid-soluble hormones derived from a four-ring cholesterol backbone that require carrier proteins in the blood, cross plasma membranes freely, bind intracellular receptors acting as transcription factors, and exert slow, long-lasting effects.

Peptide Hormones

Water-soluble chains of amino acids that dissolve freely in blood, are stored in vesicles, bind extracellular membrane receptors to trigger second-messenger cascades, and act rapidly with short half-lives.

Challenge Hypothesis

The model proposed by Wingfield et al. (1990) stating that male testosterone surges during social challenges from other males over mate access or territory, but does not rise during non-reproductive challenges like predator defense.

Anisogamy

A reproductive system characterized by the union of two morphologically distinct gamete sizes (small, mobile sperm versus large, nutrient-rich ova), ancestral to all animals.

Isogamy

A reproductive system featuring gametes of equal size and morphology, often characterized as "sex without sexes."

Complete Androgen Insensitivity Syndrome (CAIS)

A condition caused by non-functional androgen receptors, preventing tissues from responding to androgens and leading to female external phenotypes despite an XY chromosomal constitution.

Organizational Effects

Permanent, largely irreversible structural alterations in neural and bodily tissues induced by hormones during critical sensitive periods of development (prenatal gestation and puberty).

Activational Effects

Reversible, temporary physiological or behavioral changes triggered in adulthood by circulating hormones acting upon previously organized neural circuits.

Pulsatile GnRH Release

The periodic, rhythmic firing of hypothalamic GnRH neurons that, combined with surges, is necessary to trigger the anterior pituitary to secrete LH and FSH during puberty onset.

ZAL2m Supergene

A large chromosomal inversion on chromosome 2 in white-throated sparrows that differentiates the aggressive, singing white-striped (WS) morph from the parental tan-striped (TS) morph.

ESR1 Gene

The gene encoding estrogen receptor 1; its elevated expression in the medial amygdala of white-striped sparrows causally drives their higher song rate and territorial aggression.

Vasoactive Intestinal Peptide (VIP)

A neurochemical whose elevated expression in the hypothalamic infundibular nucleus of tan-striped sparrows drives anterior pituitary prolactin release and parental provisioning.

Disassortative Mating

A mating pattern where individuals preferentially mate with phenotypically opposite partners, exemplified by white-throated sparrows almost exclusively pairing WS individuals with TS individuals.

Intrasexual Selection

A component of sexual selection involving competition between members of the same sex for mating access to the other sex (e.g., male-male combats or female-female competition).

Intersexual Selection

A component of sexual selection involving mate choice, wherein individuals display traits or ornaments to entice selection by the opposite sex (e.g., courtship dances).

Wanting (Sexual Behavior Stage)

The appetitive/motivational stage of sexual behavior driven biochemically by dopamine alongside gonadal sex steroids (testosterone and estradiol).

Liking (Sexual Behavior Stage)

The consummatory stage of sexual behavior (plateau to orgasm) characterized neurochemically by dopamine combined with endogenous opioids.

Sensitization (Rodent Parenting)

The process by which virgin or male rodents, which normally avoid or attack pups, exhibit maternal care after approximately $7\text{ days}$ of cohabitation due to olfactory habituation.

Medial Preoptic Area (MPOA)

The central hypothalamic integration hub of maternal care that activates the mesolimbic approach system (VTA to nucleus accumbens) while actively inhibiting the amygdala-driven avoidance circuit.

Baby Schema (Kindchenschema)

A suite of infantile physical features (large head, high forehead, large eyes, small lower face) identified by Konrad Lorenz that automatically elicits caretaking motivation via the nucleus accumbens.

Prairie Vole Pair Bonding Mechanism

A lifelong monogamous bond mediated by high densities of oxytocin receptors in the nucleus accumbens and vasopressin (V1a) receptors in the ventral pallidum, contrasting sharply with promiscuous montane voles.

Play (Burghardt, 2005)

Repeated, seemingly non-functional behavior differing structurally, contextually, or developmentally from adaptive versions, initiated when the animal is in a relaxed, low-stress setting.

Kangaroo Care

Direct skin-to-skin contact between premature infants and caregivers that stimulates endogenous oxytocin release, reduces stress hormones, and enhances developmental outcomes.

Indirect Genetic Effects (IGEs)

An evolutionary genetic phenomenon wherein the genes expressed in one individual alter the observable phenotype and social environment of another conspecific.