BSC2011 Unit 1 Vocab

Natural Selection

Survival and reproduction of the fittest.

Variation

Any difference between organisms which has a genetic basis.

Adaptation

Any heritable trait that helps an organism’s survival and reproduction in its present environment.

Convergent Evolution

Similar phenotypes occur in distantly related lineages due to similar selective pressures.

Divergent Evolution

Lineages become increasingly different from each other as a result of different selective pressures.

Species

A group of organisms that are able to breed and produce fertile, viable offspring.

Hybrids

The reproduction between organisms that would not normally breed with each other.

Reinforcement

Hybrids are not good, causing the parents to continue separately.

Fusion

Hybrids are very good, causing the parent species to eventually become one.

Stability

Hybrids and parent species can both coexist and continue to be produced.

Gene Flow

The movement of alleles within and between populations.

Allopatric Speciation

Physical separation of the two new populations from the parent population, then subsequent speciation.

Dispersal

When a few members of a population move to a new area.

Vicariance

When geographic barriers physically divide the population.

Adaptive Radiation

The relatively rapid evolution of many species from a single ancestor.

Sympatric Speciation

Occurs when both new populations inhabit the same geographical range as the parent species.

Gradual Speciation

Species diverge gradually over time with changes in small intermediate steps.

Punctuated Equilibrium

New species diverge quickly from the parent species and then remain unchanged for long periods.

Gene

Unit of DNA that transmits genetic information and codes for a specific protein.

Phenotype

Observable trait of an individual, determined by genotype.

Genotype

Specific alleles present in an individual.

Diploid

2n, 2 copies of each chromosome, somatic (body) cells.

Haploid

n, 1 copy of each chromosome, gametes (egg & sperm).

Microevolution

Small-scale changes in allele frequency of a population, changes within a gene pool over generations.

Macroevolution

Large-scale changes in allele frequency over a long period, giving rise to new species.

Allele Frequency

The rate at which a specific allele occurs in a population.

Genotype Frequency

The rate at which a specific genotype occurs in a population.

Population Genetics

Measures the effect of natural selection on allele and genotype frequencies in a population.

Gene Pool

The sum of all alleles present within a population.

Hardy-Weinberg Equilibrium

Condition of no gene flow, natural selection, mutation, or genetic drift with random mating.

Genetic Drift

When allele frequencies change rapidly with no apparent advantage.

Founder Effect

Occurs when individuals leave their parent population to inhabit new areas.

Bottleneck Effect

An event that drastically reduces population size and only certain individuals survive.

Adaptive Evolution

Natural selection selects for beneficial traits/phenotypes and against deleterious traits/phenotypes.

Stabilizing Selection

Selective pressure for the average phenotype.

Directional Selection

Selective pressure for one extreme phenotype.

Disruptive/Diversifying Selection

Selective pressure for both extreme phenotypes.

Frequency Dependent Selection

Selection that varies with the rarity or commonness of phenotypes.

Positive Frequency Dependent Selection

Selection for common phenotypes.

Negative Frequency Dependent Selection

Selection for rare phenotypes.

Sexual Selection

Occurs when males’ ability to mate is more variable than females.

Sexual Dimorphism

Differences in phenotype between males and females beyond reproductive organs.

Handicap Principle/Good Genes Hypothesis

Phenotype is a disadvantage that only the fittest males can survive; signals superior genetic quality.

Taxonomy

The international classification system used to name organisms hierarchically.

Phylogeny

The evolutionary history of organisms and their relationships.

Rooted

A phylogenetic tree with a single common ancestor.

Branch Point

Indicates a single lineage that evolved from a common ancestor.

Basal Taxon

An unbranched lineage that evolved from a common ancestor.

Sister Taxa

Two lineages stemming from the same branch point.

Polytomy

A branch with three or more lineages.

Homologous Structures

Traits that are similar due to common ancestry.

Analogous Structures

Traits that evolved separately in organisms that do not share a common ancestor.

Shared Derived Characters

Novel evolutionary traits not present in an ancestor, only in descendants.

Shared Ancestral Characters

Traits that originated in an ancestor of the taxon.

Apomorphy

A novel derived character.

Synapomorphy

A character shared by the last common ancestor.

Autapomorphy

A novel character present in only one group.

Plesiomorphy

A shared ancestral character present in ancestor and descendants.

Monophyletic

Consists of a common ancestor and all its descendants.

Paraphyletic

Consists of an ancestral species and some, but not all, descendants.

Polyphyletic

Includes distantly related species but does not include their most recent common ancestor.