Organism Responses, Ecological Relationships, and Hominin Evolution

Comprehensive vocabulary flashcards covering organismal responses to environmental stimuli (taxes, kineses, homing, navigation, and biological rhythms), plant tropisms and photoperiodism, intraspecific and interspecific ecological interactions, and hominin biological and cultural evolution.

Innate behaviour

A behaviour that is genetically determined and performed even if an organism is raised in isolation.

Learned behaviour

A behaviour acquired through individual experience, such as trial and error, observation, or memory of past events.

Taxis

The movement of a whole organism or cell in response to an external directional stimulus, either towards (positive) or away from (negative) it.

Negative phototaxis

A directional locomotion response where an entire organism moves directly away from a light stimulus.

Kinesis

A non-directional, random movement of an organism where the rate of activity changes in response to the intensity of an external stimulus rather than its direction.

Orthokinesis

A form of kinesis in which the speed of movement of an organism varies with the intensity of the stimulus.

Klinokinesis

A form of kinesis in which the rate of turning of an organism varies with the intensity of the stimulus.

Navigation

The mechanism used by animals to reach a specific destination during homing or migration by orientating using cues like the sun, stars, Earth's magnetic field, or landmarks.

Waggle dance

A ritualized dance performed by honey bees to communicate the direction and distance of food sources relative to the sun.

Homing

The innate ability of an animal to return to its home site or nest after travelling away in search of food, water, or mates.

Migration

The regular mass movement of organisms of the same species from one region to another, which can be cyclical (returning to origin) or one-way.

Circatidal rhythm

An endogenous biological rhythm with a period of approximately $12.4\,\text{hours}$, driven by tidal cycles caused by the moon's gravitational pull.

Circadian rhythm

An endogenous biological rhythm with a period of approximately $24\,\text{hours}$, synchronized with the daily solar cycle caused by Earth's rotation on its axis.

Circalunar rhythm

An endogenous biological rhythm with a period of approximately $29.5\,\text{days}$, aligned with the changing phases of the moon as it orbits Earth.

Circannual rhythm

An endogenous biological rhythm with a period of approximately $365.25\,\text{days}$, tied to annual seasons resulting from the tilt and orbit of the Earth.

Endogenous clock

An internal timing mechanism within an organism that regulates biological rhythms independently of external environmental stimuli.

Zeitgeber

An external environmental time cue (or 'time giver') that entrains and synchronizes an organism's endogenous biological clock with external cycles.

Free-running period

The duration of one cycle of an endogenous biological rhythm when an organism is kept in constant environmental conditions deprived of zeitgebers.

Melatonin

A hormone involved in mammalian biological clocks that induces rest in diurnal animals and increases activity in nocturnal animals.

Vernalisation

A physiological requirement for a period of cold temperature before certain seeds can germinate or plants can flower.

Abscission

The natural shedding or detachment of parts of a plant, such as leaves or ripe fruit, commonly to prevent excessive water loss in winter.

Meristem

The plant tissue located at the growing tips of roots and shoots where cells continuously divide by mitosis.

Auxin

A phytohormone that promotes permanent cell elongation in growing stems and shoots by decreasing cell wall pH, and inhibits elongation in roots.

Cytokinins

Phytohormones that promote cell division within plant tissues.

Gibberellins

Phytohormones that stimulate stem elongation and break dormancy to trigger seed germination.

Ethylene

A gaseous phytohormone responsible for triggering and regulating the ripening of fruit in plants.

Abscisic acid

A phytohormone that promotes seed dormancy and induces stomatal closure during stressful or adverse environmental conditions.

Tropism

The directional growth response of a plant towards or away from an external stimulus, resulting from irreversible, permanent changes in cell size.

Statoliths

Dense, starch-filled amyloplast organelles located in the cells of the root cap that settle downwards to help plants perceive gravity.

Nastic response

A rapid, reversible movement of a plant part in response to the intensity of a stimulus, mediated by changes in turgor pressure rather than direction.

Thigmonasty

A reversible, non-directional plant movement occurring in response to touch or mechanical stimulation, such as the sudden closure of Mimosa pudica leaves.

Nyctinasty

A reversible, non-directional sleep movement of plant leaves or petals that open during the day and close at night in response to darkness.

Pulvini

Specialized joint-like motor organs situated at the bases of leaves or leaflets that undergo rapid osmotic shifts in turgor pressure to drive nastic movements.

Photoperiod

The relative duration of light and darkness an organism is exposed to within a continuous $24\,\text{hour}$ period.

Phytochrome

A light-sensitive plant photoreceptor pigment that converts between two interconvertible forms, inactive $\text{Pr}$ and biologically active $\text{Pfr}$.

Short-day plants

Plants that flower only when night length exceeds a critical threshold, because flowering is inhibited by active $\text{Pfr}$ and requires low levels of $\text{Pfr}$.

Long-day plants

Plants that flower only when night length is shorter than a critical threshold, because flowering is directly promoted by high levels of active $\text{Pfr}$.

Cooperative group

A social association of individuals of the same species living together to mutually enhance survival through role specialization and group defense.

Agonistic behaviour

Ritualized intra-specific interactions involving combat, displays, postures, or vocalizations that establish dominance without causing fatal physical harm.

Dominance hierarchy

A linear or complex ranking system of individuals within a social group from most dominant (alpha) to most subordinate (omega).

Home range

The geographic area over which an individual or group regularly wanders and collects resources, which is not actively defended and may overlap with others.

Territory

A specific geographic area containing valuable resources that is exclusively occupied and actively defended against conspecific intruders.

Courtship

A suite of species-specific ritualized behaviours designed to attract a mate, evaluate fitness, and establish or maintain a pair bond.

Sexual dimorphism

Distinct physical differences in size, coloration, or morphology between males and females of the same species.

Pair bond

A prolonged, stable social and reproductive association between two individuals that typically involves shared parental investment in offspring.

Monogamy

A mating system where one male pairs exclusively with one female during a reproductive cycle, usually with shared parental care.

Polygyny

A mating system where one male mates with multiple females, with significant parental investment occurring.

Polyandry

A mating system where one female mates with multiple males, with significant parental investment occurring.

Polygynandry

A mating system in which multiple males mate with multiple females, accompanied by mutual parental investment.

Promiscuity

A mating system where multiple males mate with multiple females without any subsequent parental investment.

r-strategy

A reproductive strategy adapted to unstable environments characterized by high birth rates, large numbers of offspring, and negligible parental investment.

K-strategy

A reproductive strategy adapted to stable environments characterized by low birth rates, few offspring, and high, sustained parental investment.

Altruism

A behaviour that benefits the fitness of another conspecific individual at an energetic or survival cost to the actor.

Kin selection

An evolutionary strategy that favors behaviours benefiting genetic relatives, thereby increasing the transmission and survival of shared alleles.

Symbiosis

A close, prolonged physical association between two distinct species where at least one species derives a fitness benefit.

Antibiosis

An interspecific association or chemical interaction that is detrimental or inhibiting to at least one of the participating organisms.

Mutualism

An ecological symbiotic interaction between individuals of two different species in which both parties derive a fitness advantage ($+/+$).

Commensalism

A symbiotic relationship in which one species benefits while the other species is neither helped nor harmed ($+/0$).

Exploitation

An ecological interaction where one species benefits at the direct expense and harm of another species ($+/-$), including predation, herbivory, and parasitism.

Endoparasite

A parasite that lives inside the body, organs, or cells of its host, such as a tapeworm.

Ectoparasite

A parasite that lives externally on the skin, feathers, or outer surface of its host, such as a flea.

Haustorium

A specialized root-like penetration organ of a parasitic plant that taps into the host vascular bundle (xylem and/or phloem) to extract nutrients.

Parasitoid

An organism whose larvae live as parasites inside a host, gradually consuming its living tissues and ultimately killing it.

Brood parasite

A bird species, such as a cuckoo or cowbird, that lays its eggs in the nests of other species, leaving the host parents to rear its young.

Aposematism

The use of conspicuous warning visual coloration, sounds, or scents by unpalatable or noxious prey to deter potential predators.

Batesian mimicry

A defensive phenomenon where a harmless or palatable species evolves to resemble the warning signals of an unpalatable or dangerous species.

Müllerian mimicry

A defensive phenomenon where two or more distinct unpalatable or harmful species evolve mutual resemblance to reinforce predator avoidance.

Aggressive mimicry

An adaptation where a predator or parasite mimics a harmless, benign, or rewarding model to lure prey or infiltrate nests undetected.

Fundamental niche

The total theoretical range of environmental conditions and resources a species can tolerate and occupy in the complete absence of competition.

Realised niche

The actual narrow portion of the fundamental niche that a species occupies and exploits due to limitations imposed by competition.

Gause's competitive exclusion principle

The ecological principle stating that two species competing for the exact same limiting resource cannot stably coexist; one will eventually outcompete or eliminate the other.

Allelopathy

A form of antibiosis in which a plant releases biochemical compounds that inhibit the germination, growth, or reproduction of neighbouring competing plants.

Hominid

Any member of the family Hominidae, comprising all extant and extinct great apes (humans, chimpanzees, gorillas, orangutans) and their immediate ancestors.

Hominin

Any member of the human lineage consisting of modern humans and all extinct ancestral species along the branch after splitting from chimpanzees.

Brachiation

A specialized mode of arboreal locomotion where an animal propels itself forward by swinging hand-over-hand along branches.

Valgus angle

The inward bicondylar tilt of the femur that positions the knee joints closer to the midline directly below the centre of gravity during bipedal standing and walking.

Foramen magnum

The large opening at the base of the skull through which the spinal cord passes, situated centrally beneath the cranium in bipedal hominins.

Hallux

The big toe of the foot, which is robust, non-opposable, and adducted in alignment with other toes in bipedal hominins to provide forward propulsion.

Broca's area

A specialized cortical region of the frontal lobe associated with the motor organization and production of speech.

Wernicke's area

A cerebral region within the temporal lobe associated with the comprehension and recognition of spoken language.

Cranium

The portion of the skull that encloses, encases, and protects the brain.

Oldowan tool culture

The earliest stone tool technology, characterized by simple river cobble choppers and flakes produced with few strikes, associated with Homo habilis.

Acheulean tool culture

A Lower Palaeolithic stone tool industry characterized by tear-drop bifacial hand axes shaped by many deliberate blows, associated with Homo erectus and Homo ergaster.

Mousterian tool culture

A Middle Palaeolithic tool technology using the Levallois technique to produce precise, specialized stone flakes, associated with Homo neanderthalensis.

Levallois technique

A refined method of tool manufacture in which a stone core is systematically prepared with many strikes before striking off a single, pre-determined flake.

Upper Palaeolithic tool culture

A sophisticated stone tool industry associated with Homo sapiens, utilizing varied materials (bone, antler, flint) to produce highly specialized blades and composite tools.

Out-of-Africa theory

The evolutionary model proposing that anatomically modern Homo sapiens evolved exclusively in Africa approximately $300,000\text{ to }200,000\,\text{years ago}$, then migrated out and replaced archaic hominins with no interbreeding.

Multiregional theory

The evolutionary model proposing that modern Homo sapiens evolved simultaneously in Africa, Europe, and Asia from ancestral Homo erectus populations maintained by continuous gene flow.

Assimilation model

The hybrid evolutionary model stating that Homo sapiens originated in Africa, dispersed across Eurasia, and interbred with indigenous archaic hominin populations like Neanderthals and Denisovans.

Admixture

The introduction of novel genetic material into a lineage resulting from the interbreeding of two previously isolated hominin populations.

Mitochondrial DNA (mtDNA)

Extranuclear DNA inherited maternally without crossing over or recombination, functioning as a reliable molecular clock to trace ancestral maternal lineages.

Humerofemoral index

The morphological ratio defined as $\left(\frac{\text{humerus length}}{\text{femur length}}\right) \times 100$, where higher indices denote longer relative forelimbs indicative of arboreal locomotion.

Laetoli tracks

A $27\,\text{m}$ trackway of fossilized footprints in volcanic ash in Tanzania dating to $3.7\,\text{Ma}$, demonstrating upright habitual bipedal locomotion in Australopithecus afarensis.