Biology Unit 4 Topic 2 Evolution (QCAA - from quizlet)

Evolution

Gradual change in the genetic composition of a population during successive generations, which may result in the development of a new species.

Microevolution

Small-scale variation of allele frequencies within a species or population, in which the descendant is of the same taxonomic group as the ancestor

Macroevolution

The variation of allele frequencies at or above the level of species over geological time, resulting in the divergence of taxonomic groups, in which the descendant is in a different taxonomic group to the ancestor

Natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

Selection pressures

The environmental factors that 'select' for certain phenotypes

phylogenetic tree

A branching diagram that represents evolutionary relationships between organisms, based on genetic similarity. Branch length indicates genetic differences (mutations).

Speciation

The formation of new and distinct species in the course of evolution.

Evolutionary radiation

The proliferation of a large number of species from a single ancestor.

Gene pool

Allele frequency

Number of times an allele occurs in a gene pool as a proportion of all the alleles in that pool for the same gene.

Genetic drift

A change in the gene pool of a population due to chance

Extinction

A term that typically describes a species that no longer has any known living individuals

Mass extinction

Event during which many species become extinct during a relatively short period of time; possibly due to a catastrophic global event.

Adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species

Bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population

Founder effect

Genetic drift that occurs after a small number of individuals colonise a new area

Directional selection

Form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve

Disruptive selection

Form of natural selection in which a single curve splits into two; occurs when individuals at the upper and lower extremes of a distribution curve have higher fitness than individuals near the middle

Stabilising selection

Type of selection that favours the mean of the distribution because the extremes are at a selective disadvantage - frequency of mean phenotype increases

Positive selection

Natural selection that increases the frequency of a favourable allele

Negative selection

Natural selection that decreases the frequency of a harmful allele

antibiotic resistance

Resistance evolving rapidly in many species of prokaryotes due to overuse of antibiotics, especially in agriculture.

Species

A group of organisms that are closely related and can interbreed to produce fertile offspring

Gene pool

The range of genes and all their alleles present in a population.

Gene flow

Movement of alleles from one population to another

Immigration

Movement of individuals into a population

Emigration

Movement of individuals out of a population

Reproductive isolation

Separation of species or populations so that they can no longer interbreed and produce fertile offspring

Pre-zygotic isolation

Isolating mechanisms that prevent mating and/or fertilisation

Post-zygotic isolation

Isolating mechanisms that occur after fertilisation, eg. zygote not viable, offspring are sterile, etc.

Allopatric speciation

The process of speciation that occurs with geographic isolation

habitat fragmentation

Breakup of a habitat into smaller pieces, usually as a result of human activities.

Sympatric speciation

The formation of new species in populations that live in the same geographic area

Parapatric speciation

Speciation pattern in which populations speciate while in contact along a common border

Divergent evolution

The evolutionary pattern in which species sharing common ancestry become more distinct due to different selection pressures

Convergent evolution

When two organisms that lack a recent common ancestor become alike as they adapt to a similar niche

Parallel evolution

Two related species that have made similar evolutionary adaptations after their divergence from a common ancestor

Coevolution

Process by which two species evolve in response to changes in each other

Analogous structures

Body parts that share a common function, but not structure

Homologous structures

Structures in different species that are similar because of common ancestry.