Unit 2: Organisms and Evolution - Key Vocabulary

Comprehensive vocabulary flashcards covering field sampling techniques, evolution, natural selection, genetics, reproductive strategies, and parasitology from Unit 2: Organisms and Evolution.

Hazard

Something that has the potential to cause harm or damage to a biologist or organism.

Risk

The likelihood that a hazard will cause harm under the specific circumstances or exposure of an activity.

Point count

A sampling technique in which an observer records all individuals seen from a fixed location over a specified period to compare across sites or dates.

Stratified sampling

A sampling method in which a study area or population is divided into distinct categories (strata), with each category sampled appropriately, often in proportion to its size.

Taxonomy

The identification, naming, and classification of organisms into hierarchical groups based on shared characteristics and morphology.

Phylogenetics

The study of the evolutionary history and relationships among individuals or groups of organisms, often represented as a phylogenetic tree.

Model organism

A species that is easily studied or has been well studied, providing biological information and principles that can be applied to other less accessible species.

Indicator species

Organisms whose presence, absence, or abundance provides critical information regarding environmental qualities, such as the presence of a pollutant.

Mark-recapture

A method used to estimate mobile population sizes using the Lincoln index formula $N = \frac{M \times C}{R}$, assuming random mixing, equal capture probability, and a closed population.

Ethogram

A comprehensive list of clearly defined, species-specific behaviours to be observed and recorded in an observational animal study.

Time budget

The proportion of total observation time that an animal spends carrying out each of the different behaviours defined within an ethogram.

Latency

The length of time between the presentation of a stimulus and the onset of the resulting behavioural response.

Anthropomorphism

The attribution of human characteristics, emotions, or intentions to non-human animals, which can lead to scientifically invalid conclusions.

Evolution

The change over generations in the proportion of individuals within a population differing in one or more inherited traits, reflected in changes in allele frequencies.

Natural selection

The non-random change in allele frequencies caused by differential survival and reproductive success between individuals carrying distinct inherited phenotypes.

Sexual selection

The non-random process favouring the transmission of alleles that increase an individual's success in obtaining mates and producing offspring.

Sexual dimorphism

A difference in appearance, size, or ornamentation between males and females of the same species in characteristics other than reproductive organs.

Genetic drift

A random change in allele frequencies between generations resulting from chance events rather than fitness, having the strongest effect in small populations.

Population bottleneck

A drastic reduction in population size that persists for at least one generation, causing random under- or over-representation of alleles and reduced genetic diversity.

Founder effect

The establishment of a new population by a small group of isolated individuals carrying an allele sample that is not representative of the original gene pool.

Hardy-Weinberg principle

A mathematical model stating that allele and genotype frequencies ($p^2 + 2pq + q^2 = 1$) remain constant across generations in the absence of evolutionary influences.

Absolute fitness

The ratio between the abundance or frequency of a particular genotype after selection to its abundance or frequency before selection ($\text{Absolute fitness} = \frac{\text{frequency after selection}}{\text{frequency before selection}}$).

Relative fitness

The ratio of surviving offspring per individual of a particular genotype compared to the surviving offspring per individual of the most successful genotype.

Co-evolution

The process whereby two or more interacting species undergo evolutionary reciprocal changes in response to selection pressures exerted by one another.

Red Queen hypothesis

A co-evolutionary concept stating that interacting species must continuously adapt and evolve merely to maintain their relative fitness against their co-evolving counterparts.

Parthenogenesis

A form of asexual reproduction involving the development of offspring from a female gamete without the requirement of fertilisation.

Homologous chromosomes

Chromosomes of identical size and centromere position that carry the same sequence of genes at the same loci, although the alleles may differ.

Chiasmata

The physical points of contact between non-sister chromatids of a homologous pair where genetic material is exchanged during crossing over.

Crossing over

The random exchange of corresponding sections of DNA between non-sister chromatids during meiosis I, yielding genetically distinct recombinant chromosomes.

Independent assortment

The random orientation and segregation of maternal and paternal homologous chromosome pairs along the equatorial spindle during meiosis I.

Linked genes

Genes residing on the same chromosome that tend to be co-inherited unless separated by crossing over during meiosis.

Recombination frequency

The calculated percentage of recombinant offspring in a cross ($\frac{\text{recombinant offspring}}{\text{total offspring}} \times 100$), used to determine gene map distances on chromosomes.

SRY gene

A master sex-determining gene located on the mammalian Y chromosome encoding a transcription factor that triggers testis differentiation and male characteristics.

X chromosome inactivation

The random transcriptional silencing of most genes on one X chromosome in mammalian $XX$ embryonic cells, achieving dosage compensation between sexes.

Hermaphrodite

An individual organism possessing fully functioning male and female reproductive structures that can produce both types of gametes.

Parental investment

Any resource, energetic, or protective contribution by a parent to an offspring that improves its survival while limiting future reproductive opportunities.

Anisogamy

The condition of producing gametes of dissimilar size, specifically small, mobile sperm versus large, nutrient-rich eggs requiring greater female investment.

r-selected species

Organisms that mature rapidly, reproduce early, and produce large quantities of small offspring with low individual parental care in unstable environments.

K-selected species

Organisms that mature slowly, live longer, and produce fewer, larger offspring with substantial parental care and high investment in stable habitats.

Monogamy

A mating system where an individual pairs exclusively with one partner during a breeding season, often cooperating extensively in parental care.

Polygyny

A polygamous mating pattern where a single male mates exclusively with multiple females within a single breeding season.

Polyandry

A polygamous mating system where a single female mates with multiple males within a single breeding season.

Reversed sexual dimorphism

A condition in which females are larger, more colourful, or more conspicuous than males, as observed in species like the red-necked phalarope.

Honest signal

A costly display, ornament, or trait that genuinely indicates an individual's genetic quality, vigour, or low parasite burden.

Lekking

A mating system in which males congregate in a communal arena (lek) to perform competitive courtship displays to prospective visiting females.

Sign stimulus

A specific environmental cue that acts as a trigger to elicit an innate, stereotypical sequence of behaviour known as a fixed action pattern.

Fixed action pattern (FAP)

An innate, stereotyped behavioural sequence that, once triggered by a specific sign stimulus, proceeds automatically to completion.

Imprinting

A rapid, irreversible form of learning that occurs during a critical, sensitive developmental window in early life, producing persistent behavioural patterns.

Ecological niche

A multi-dimensional summary of all tolerances, requirements, resources, and environmental conditions needed for a species to sustain its population.

Fundamental niche

The entire hypothetical range of physical conditions and resources that a species could occupy and exploit in the complete absence of interspecific competition.

Realised niche

The actual set of conditions and resources a species occupies in nature after being constrained by interspecific competition and other biotic interactions.

Competitive exclusion

The principle stating that two species competing for the exact same limiting resources cannot coexist, resulting in the decline and local extinction of the weaker competitor.

Resource partitioning

The differential exploitation of shared resources by competing species at different times, zones, or manners, facilitating coexistence through realized niche divergence.

Degeneration (parasitic)

The evolutionary loss or drastic reduction of redundant structures and organs in a parasite because the host provides for its basic physiological needs.

Definitive host

The specific organism in which a parasite attains sexual maturity or carries out the sexual reproduction stage of its life cycle.

Intermediate host

An organism required within a parasite's life cycle in which it undergoes development, larval transitions, or asexual multiplication before reaching the definitive host.

Vector

An organism that actively carries and transmits an infectious parasite from one host to another, and may additionally act as a biological host.

Retrovirus

An RNA virus that produces DNA from its RNA genome using the enzyme reverse transcriptase, which subsequently integrates into the host genome.

Extended phenotype

The manifestation of a parasite's genes outside its physical body, specifically demonstrated through parasite-induced alterations in host behaviour that promote transmission.

Clonal selection

The process whereby the binding of a foreign antigen selectively stimulates a complementary lymphocyte to divide rapidly, establishing a population of identical clones.

Variable region (antibody)

The distinct antigen-binding region of an antibody where the hypervariable amino acid sequence confers specific binding to a singular complementary antigen.

Apoptosis

Regulated, programmed cellular self-destruction induced by natural killer cells or cytotoxic lymphocytes to eliminate virus-infected or abnormal host cells.

Antigenic variation

The evolutionary mechanism whereby a pathogen alters its surface antigens over time or throughout an infection, evading existing host immunological memory.

Viral latency

A dormant state in which a virus's genetic material persists inside a host cell without actively manufacturing new viral progeny, evading immune surveillance.

Herd immunity threshold

The critical density or proportion of immune individuals within a population necessary to prevent the sustained epidemic transmission of an infectious pathogen.