Evolution, Natural Selection, and Evidence for Evolutionary Change

Comprehensive vocabulary flashcards covering the core principles, lines of evidence, mechanisms, and historical theories of evolution, natural selection, and adaptation.

Biological Evolution

The genetic change in a population of an organism over time.

Population (Evolutionary Unit)

The group level on which the process of evolution occurs; evolution takes place within a population and never in an individual.

Adaptation

Any structural, physiological, or behavioral trait that improves an organism's fitness and increases its chance of survival and reproduction in a specific environment.

Genetic Fitness

The state of possessing adaptations or traits that increase an organism's probability of surviving and successfully reproducing in its immediate environment.

Natural Selection

The evolutionary mechanism in which the environment favours the reproductive success of some individuals within a population over others, often termed 'survival of the fittest.'

Competition

An interaction where organisms within the same species or between different species compete for limited environmental resources, such as food, water, shelter, and mates.

Evolutionary Arms Race

A competitive dynamic between interacting predator and prey species where adaptations in one drive counter-adaptations in the other (e.g., agile gazelles escaping predators while fast cheetahs catch them).

Geological Strata

Rock layers containing fossils that document how organisms change over time; older, simpler organisms lie in deeper strata, while more complex organisms appear in higher strata.

Transitional Fossils

Fossilised remains that exhibit structural similarities to two distinct taxonomic groups, providing evidence that the two groups share an evolutionary relationship.

Archaeopteryx

A transitional fossil possessing bird-like characteristics (feathers) alongside reptilian traits (teeth, scales, wing claws, and a bony tail).

Biochemical Evidence for Evolution

Evidence of relatedness derived from comparing the degree of similarity in DNA base sequences ($A$, $T$, $C$, and $G$) and amino acid sequences across living things composed of universal molecules like DNA and ATP.

Biogeography

The scientific study of the geographic distribution of organisms across both living species and fossils, demonstrating how ancestral species disperse and adapt into ecological niches.

Homologous Features

Anatomical structures in different species that share a similar underlying bone or tissue architecture derived from a common ancestor, but differ in function (e.g., forelimbs of humans, cats, whales, and bats).

Comparative Embryology

The comparison of vertebrate embryos during development, which reveals shared homologous features, including tails and gill slits, supporting common descent.

Analogous Features

Structures that carry out the same function in different species but do not share a common evolutionary origin or structural composition (e.g., chitin-based insect wings versus bone-supported bat wings).

Vestigial Features

Anatomical structures that serve no useful current function in an organism but are homologous to functional, larger structures found in ancestral forms or other living organisms (e.g., human appendix, goose bumps).

Microevolution

Small-scale evolutionary change and shifts in allele frequencies that occur within a population over a small number of generations (e.g., the increase in the black allele of peppered moths during England's Industrial Revolution).

Macroevolution

Large-scale genetic change spanning centuries or millennia that operates between species, documented in the fossil record, leading to speciation, new body designs, or extinctions.

Antibiotic Resistance

The evolution of bacteria via natural selection that enables them to withstand antibacterial medications, often triggered when patients do not complete a full drug course, allowing surviving bacteria to reproduce.

Lamarck's Theory of Use and Disuse

An early evolutionary hypothesis proposing that traits developed or altered by an individual through use or disuse during its lifetime (such as a giraffe stretching its neck) are passed on directly to offspring.

Overproduction

A principle of natural selection stating that organisms produce more offspring than the environment can support, resulting in competition where weaker offspring die and better-adapted individuals survive.

Sexual Selection

A form of selection that acts on an organism's ability to successfully secure a mate and reproduce, even if the favored physical traits, songs, or courtship displays confer a survival disadvantage.

Sexual Dimorphism

A condition where males and females of the same species display differing traits, typically resulting in flashier males to attract mates and more subdued females to avoid predators and care for offspring.