BIOE 20C

Essentialism (eidos)

Idea that every animal has a perfect essence

Scala Naturae

Hierarchy of different species from inanimate objects to spiritual beings

Uniformitarianism

Idea that natural processes that shaped the Earth act in the same manner and same rate throughout Earth’s history

Struggle for existence

Competition between organisms for limited resources and survival against environmental pressures

Survival of the fittest

Organisms best adapted to their environment are more likely to survive and pass on their traits

Fitness

Ability of an individual to produce offspring relative to others in the population

Adaptation

Any trait that increases fitness of an individual

Genotype

Determined by genes (DNA)

Phenotype

Trait – determined by genotypes

Biogeography

Closely related species live in the same geographic area

Homologous trait

A shared trait inherited from a common ancestor

Analogous trait

Similar traits with independent origins resulting from convergent evolution

Neutral Evolution

Idea that majority of molecular genetic variation is caused by the random drift of mutations instead of natural selection

Gene

Region of DNA that codes for a specific polypeptide

Locus

Physical location of a specific gene on a chromosome

Allele

Version of a specific gene

Homozygous

Having two identical versions of a specific gene (AA, aa)

Heterozygous

Having two different versions of a specific gene (Aa)

Dominant

Allele that masks presence of recessive allele

Recessive

Allele that is masked by presence of dominant allele

Hardy-Weinberg Equilibrium

Hypothesis that there is no evolution occuring

Natural Selection

Organisms that are better adapted to their environment tend to survive and produce more offspring, indicating higher fitness

Directional Selection

Allele frequency change in one direction

Stabilizing Selection

Alleles associated with a mean trait value is favored

Disruptive Selection

Alleles associated with both extremes of a trait distribution

Mating Selection

Occurs when individuals in a population differ in their ability to attract mates

Intersexual Selection (“Female choice”)

Females select mates based on aspect of male phenotype that may suggest higher fitness

Intrasexual Selection (“Male competition”)

Males compete for mates, and the winner is implied to have higher fitness

Genetic Drift

Change in allele frequency in a population due to random change, rather than natural selection

Genetic Bottleneck

A drastic reduction in population size which alters allele frequencies

Founder Effect

A small number of individuals start a new population; may not reflect the allele frequencies of the original population

Gene Flow

Movement of alleles from one population to another

Mutation

Production of new alleles through damage or replication errors in DNA

Genetic Diversity

Number and relative frequency of alleles in a population

Inbreeding

Mating between relatives

Inbreeding Depression

Reduction in survival, fertility, and fitness of offspring resulting from mating between relatives

Speciation

Evolutionary process by which populations evolve to become distinct species defined by reproductive isolation and genetic divergence

Genetic Isolation

Lack of interbreeding or gene flow between species, causing them to evolve independently

Species

Evolutionary independent population(s) distinguished by common characteristics

Biological species

Reproductively isolated from others

Morphological species

Based on differences in morphology

Phylogenetic species

A group of organisms that are genetically distinct from other organisms

Genetic Divergence

Process where isolated populations accumulate distinct genetic differences over time, causing their genomes to differ

Reproductive Isolation

Biological, behavioral, or physical barriers that prevent different species from interbreeding and producing fertile offspring

Prezygotic isolation

Zygote is never formed (in most cases, mating never even occurs)

Postzygotic isolation

Zygote is formed, but is inviable or infertile

Sympatric Speciation

Process by which new species evolve from a single ancestral population while inhabiting the same geographic location without any physical barriers

Autoploidy

Possession of multiple sets of chromosomes from the same species due to a mutation or meiotic error during gamete production

Alloploidy

Possession of multiple sets of chromosomes due to interspecies mating

Allopatric Speciation

Formation of new species due to the geographic isolation of populations, preventing gene flow

Dispersal/Colonization

A small number of individuals disperse to a new habitat and establish a new population

Vicariance

A population is split into two or more subpopulations by a geographic barrier

Orthologs

Homologous genes produced by a speciation event

Paralogs

Homologous genes produced by a duplication event

Regulatory gene

Specialized genes that control the transcription factor (gene expression) of other genes, determining the timing, location, and amount of protein produced

Homeotic genes

Regulatory genes that determine where certain anatomical structures, such as appendages, will develop in an organism

Homeobox gene

Specific DNA sequences found within homeotic genes that are involved in the regulation of patterns of an anatomical development

Hox genes

Type of homeobox genes that are only found in bilateral organisms

Phylogeny

Study of the evolutionary history, development, and relationships among groups of organisms

Taxon

Any group of organism that’s given a formal taxonomic name

Monophyletic group

Includes most recent common ancestor and all its descendants

Paraphyletic group

Includes most recent common ancestor but not all its descendants

Polyphyletic group

Groups without a common ancestor that are lumped together based on shared traits

Molecular Clock

Uses the average rate at which a gene or protein accumulates changes to estimate the time of divergence for a particular split in a phylogeny

Character

A phenotypic trait

Ancestral trait

A trait that is present in an organism and is shared with the most recent common ancestor

Derived trait

A trait that is present in an organism but was absent in the most recent common ancestor

Fossil

Physical trace of organism that lived in the past

Cladogram

Diagrams which determine the relationships between different clades or taxa by grouping organisms together based on their shared characteristics

Homoplasy

The independent evolution of similar traits in different species that do not share a recent common ancestor, often resulting from convergent evolution

Symplesiomorphy

A trait that is shared by members of a given clade and their most recent common ancestor

Synapomorphy

A trait that is shared by members of a given clade but not their most recent common ancestor