Evolutionary Biology, Primate Taxonomy, and Human Life History

Comprehensive vocabulary flashcards covering evolutionary theory, speciation mechanisms, primate classification, behavioral ecology, social organization, and human biological life history.

Biological Species Concept

Defines a species as a group of natural populations whose members can interbreed in nature and produce viable, fertile offspring, while being reproductively isolated from other such groups.

Reproductive Isolating Barrier (RIB)

A mechanism that prevents sperm and egg from coming together, preventing different species from interbreeding and producing viable, fertile offspring.

F1 Inviability

A post-zygotic barrier incompatible with life, where a zygote can form but fails to survive development and dies.

F1 Sterility

A post-zygotic barrier where hybrid offspring survive but are sterile and cannot reproduce (e.g., a mule), keeping the two gene pools separate.

Hybrid Breakdown

A post-zygotic barrier where viable offspring are produced, but they suffer reproductive problems such as reduced fertility or complete sterility (e.g., ligers, red wolves).

Phylogenetic Species Concept

Also known as the morphological species concept; defines species based on physical body shape and structural similarity.

Anagenesis

Straight-line evolution over time, where an ancestral form transforms sequentially into subsequent forms (form a changes to form b to form c).

Cladogenesis

Branching evolution where a parent species splits into two or more distinct, independent descendant lineages.

Clade

A group of organisms that share common traits and are derived from a common ancestor.

Adaptive Radiation

The rapid diversification of a single ancestral species into a wide variety of new forms as they adapt to different environmental niches and resource types.

Gradualism

An evolutionary model characterized by the slow and steady accumulation of variation, predicting a smooth transition between forms.

Punctuated Evolution

An evolutionary pattern characterized mostly by long periods of stasis interspersed with short, rapid periods of change.

Orthogenesis

The debunked evolutionary misconception that evolution is directed toward a specific, predetermined goal or endpoint.

Chronometric Dating

Also known as exact dating; a method that measures the radiometric decay of particles in substances to calculate an exact age.

Relative Dating

A method used to determine whether a specimen is older or younger relative to others based on positional sequence (analogous to a stack of laundry, where the newest is on top).

Phylogeny

A branching diagram depicting the evolutionary history and genealogical relationships among species or groups of organisms.

Homology

Traits in two or more species that share similar underlying anatomical structures because they were inherited from a common ancestor, regardless of whether they have a similar function.

Homoplasy

Also known as an analogous trait; physical traits in different species that share similar functions but have different structural origins and evolved independently, rather than being present in a common ancestor.

Parallel Evolution

The independent evolution of similar traits or adaptations in closely related lineages that split from a common ancestor that lacked the trait (e.g., dentition size increase in hominids approximately 3 million years ago).

Convergent Evolution

The independent evolution of similar adaptations in distantly related evolutionary lines that do not share the trait from a common ancestor (e.g., Tasmanian wolf and gray wolf skull/teeth similarities).

Primitive Trait

An ancestral trait that has remained unchanged from its ancient evolutionary state.

Derived Trait

A novel trait that has changed or modified from the ancestral state.

Cladistics

A taxonomic method that builds biological classifications by counting only shared derived traits, while ignoring shared primitive traits.

Phenetics

A taxonomic method that groups organisms based on overall physical similarities, counting both primitive and derived shared traits without distinguishing homology from homoplasy.

Class Mammalia

A vertebrate class defined as warm-blooded, hairy animals whose young are nourished by milk produced from the mother's mammary glands.

Eutherians

Placental mammals that develop inside the mother nourished by a placenta and give birth to a mature fetus.

Prototherians

Primitive mammals that reproduce by laying eggs.

Metatherians

Marsupial mammals that give birth to an extremely immature fetus and nurse it inside an external pouch.

Homeotherm

An organism capable of maintaining a constant internal body temperature, allowing survival across diverse environments at a high energetic cost.

Heterodont

An animal possessing specialized, differentiated teeth to process diverse food types, but limited to two sets over a lifetime.

K-selected

A reproductive strategy prioritizing offspring quality over quantity through high parental investment and care (e.g., gorillas).

r-selected

A reproductive strategy prioritizing offspring quantity over quality, characterized by little to no parental care (e.g., frogs, fish).

Binocular Stereoscopic Vision

Vision involving overlapping visual fields (binocular) where both sides of the brain process signals from both eyes (stereoscopic), enabling precise 3D depth perception.

Prosimian

A suborder of primates characterized by a heavy reliance on olfaction, small brains relative to body size, small body size, nocturnal habits, vertical clinging and leaping, and a closed bony eye ring.

Anthropoid

A primate group including monkeys and hominoids, characterized by larger bodies, larger and more complex brains, reliance on visual processing, fully enclosed eye sockets, and mostly diurnal activity.

Platyrrhines

New World monkeys (superfamily Ceboidea) that possess four extra premolars, prehensile tails, flat noses with side-facing nostrils, and exclusively arboreal lifestyles.

Catarrhines

Old World monkeys and apes that share the human dental formula, inhabit a wide variety of environments, and include cercopithecoids and hominoids.

Hominoids

A group consisting of humans and non-human apes, characterized by the absence of tails, larger body size, superior climbing ability, greater intelligence, distinct lower molar structure, and K-selection.

Socioecology

The study of animal social structure and organization in relation to environmental variables and ecological conditions.

Sociobiology

The study of behavior from an evolutionary perspective, focusing specifically on natural selection and the genetic basis underlying social behaviors.

Dilution Effect

An anti-predator advantage of living in large groups where an individual's probability of being captured is reduced because a predator is likely to catch another, slower group member.

Resource Defense Model

Richard Wrangham's hypothesis stating that primates form cooperative social groups to defend food patches that are valuable, clumped in space and time, and large enough to support multiple individuals.

Differential Reproductive Investment

The asymmetry in energy and time invested into offspring, causing females to be choosy about mates due to high caloric and time costs, while males compete to mate with multiple females.

Intrasexual Selection

A form of sexual selection resulting from direct competition among members of the same sex (typically males fighting or killing) for access to mates.

Intersexual Selection

A form of sexual selection resulting from the preference of one sex for specific traits in the opposite sex (typically female choice based on male courtship displays or physical traits).

Dominance Hierarchy

A ranked social order that dictates priority of access to contested resources, conferring substantial reproductive advantages particularly to high-ranking males.

Cole's Paradox

The evolutionary dilemma questioning why organisms do not commit maximum effort to immediate reproduction; resolved by recognizing that fitness reflects total lifetime reproductive success through energy allocation and life event scheduling.

Altruism

A behavior in which an individual deliberately lowers its own biological fitness to enhance the reproductive fitness of another individual.

Group Selection

The concept that altruistic traits evolve to enhance the survival or greater good of the group rather than the individual; considered inadequate for explaining individual altruism.

Kin Selection (Inclusive Fitness)

An evolutionary strategy where individuals perform altruistic acts for genetic relatives, thereby promoting the survival and propagation of shared genes into the next generation.

Reciprocal Altruism

Altruistic behavior between individuals (including non-kin) based on mutual exchange, which requires frequent interactions, memory of past interactions, and the ability to detect cheaters.

Allometry

The study of differential rates of growth among distinct anatomical structures or parts of the body during ontogeny.

Valgus Angle

The inward angle of the human femur directing the knee toward the body's midline, which stabilizes center of gravity during bipedal walking.

Estrus

A physiological period of sexual receptivity accompanied by visible physical signs indicating that an animal is ovulating; absent in humans, who mate throughout the cycle.

Infancy (Human Growth Stage)

The first post-natal stage of human development, spanning from birth to weaning.

Childhood (Human Growth Stage)

The second post-natal stage of human development, spanning from weaning until the termination of brain growth.

Juvenile Stage (Human Growth Stage)

The third post-natal stage of human development, spanning from the completion of brain growth to the onset of sexual maturation.

Adolescence (Human Growth Stage)

The fourth post-natal stage of human development, spanning from the initiation of sexual maturation to the cessation of skeletal growth.

Adulthood (Human Growth Stage)

The fifth post-natal stage of human development, beginning at the end of physical growth.

Secular Trend in Menarche

The documented historical trend where females experience their first menstrual cycle at progressively earlier ages in recent generations.

Grandmother Hypothesis

An evolutionary explanation for menopause proposing that women cease reproduction to avoid high-risk late childbirth and instead enhance inclusive fitness by investing in grandchildren.

Ova Depletion Hypothesis

A physiological explanation for menopause stating that older females stop reproducing simply because they exhaust their supply of viable ova due to genetic constraints.