Evolution Concept 1 - Natural Selection

Evolution

Biological change in populations over time that makes descendants genetically different from ancestors.

Microevolution

Evolution on a small scale affecting a single population.

Macroevolution

Evolution on a large scale involving changes in species across populations.

Creationism

Belief that life was created rather than evolved through natural processes.

Catastrophism

Idea that sudden catastrophic events shape Earth's history.

Gradualism

Idea that change happens slowly and continuously over long periods.

Struggle for existence

Competition for limited resources, connected with Malthus's ideas.

Uniformitarianism

Idea that the same natural processes operating today also operated in the past.

Inheritance of acquired traits

Lamarck's idea that traits gained during life could be passed to offspring.

Natural selection

Process where organisms with beneficial heritable traits survive and reproduce more, changing populations over time.

Adaptation

A feature that helps an organism survive better in its environment.

Survival of the fittest

Idea that organisms better suited to the environment are more likely to survive and reproduce.

Fitness

A measure of how well an organism can survive in its environment.

Overproduction of offspring

Producing many offspring, causing competition for limited resources.

Variation

Differences in physical traits among organisms.

Random mutation

A random DNA change; the ultimate source of genetic variation.

Genetic recombination

New allele combinations formed during meiosis, such as crossing over.

Gene flow

Movement of genes into or out of a population through migration.

Gene pool

The combined alleles of all individuals in a population.

Descent with modification

A change in gene frequency over time; populations, not individuals, evolve.

Phenotype

An organism's observable traits.

Directional selection

Selection that increases an extreme version of a trait in a population.

Disruptive selection

Selection that favors both extremes and removes average traits.

Stabilizing selection

Selection that favors the average trait and eliminates extremes.

Allele frequency

How often an allele appears in a population's gene pool.

Dominant allele frequency

The frequency of the dominant allele, represented by p.

Recessive allele frequency

The frequency of the recessive allele, represented by q.

Genotype frequency

How often a genotype appears in a population.

Mechanisms of microevolution

Mutations, natural selection, genetic drift, gene flow, and non-random mating.

Genetic drift

Random change in allele frequencies in a population over time.

Non-random mating

Mating that does not occur by chance, including sexual selection.

Sexual selection

Selection where certain traits increase mating success.

Genetic equilibrium

A condition where allele frequencies in a population stay the same over time.

Hardy-Weinberg equilibrium

A model that predicts genotype frequencies when a population is not evolving. p^2 + 2pq + q^2 = 1 with p + q = 1.