Speciation and Evolution

adaptive radiation

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

allele frequency

a measure of how common a certain allele is in the population/simply proportions of each allele (different versions of a gene) within a population

allopartic speciation

occurs when a species gets split into two geographically isolated populations (initially are capable of breeding but aren't able to)

allopolyploidy

A type of polyploidy in which the chromosome complement consists of more than two copies of chromosomes derived from different species (but closely related). It occurs when two species mate to produce a hybrid species.

analogous structures

structures that do not have a common evolutionary origin but are similar in function / anatomical similarities among unrelated species that result from convergent evolution

Autopolyploidy

A type of polyploidy where the multiple sets of chromosomes are all derived from the same species/
The state of having more than two full sets of chromosomes due to a mutation that doubled the chromosome number

artificial selection

Breeding organisms with specific traits in order to produce offspring with desired identical traits.

convergent evolution

Process by which unrelated organisms independently evolve similar anatomical structures when adapting to a similar niche

Co-evolution

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

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 ends of a distribution curve have higher fitness than individuals near the middle

divergent evolution

an accumulation of changes in the gene pool's of two (or more) populations, leading to the formation of races, sub-species, species etc.

Emigration

movement of individuals out of a population

Evolution

The gradual change and process of change in traits in species over time. This is the formation of diversity across biological populations.

founder effect

Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population

gene flow

the movement of genes into or out of a population

gene pool

All the genes, including all the different alleles for each gene, that are present in a population at any one time

genetic drift

any random change to the allele frequency of a population

genetic equilibrium

situation in which allele frequencies in a population remain the same

geographical isolation

form of reproductive isolation in which two populations are separated physically by geographic barriers, and cannot exchange genetic material with each other

homologous structures

similar structures that related species have inherited from a common ancestor, but have been developed by each species to suit different functions

Hybrid

The offspring of a mating where the parents differ in at least one characteristic. The term is usually applied to offspring of widely different parents, e.g. different varieties/species.

Hybridization

Is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction.

Immigration

Movement of individuals into a population

Instant speciation

The formation of a new species through autopolyploidy or allopolyploidy. Because the chromosome numbers of the new 'instant' species do not match that of the original species they cannot interbreed.

Inbreeding

A selective breeding method in which two individuals with identical or similar sets of alleles are crossed. Occurs when closely related individuals produce offspring together

Macro evolution

Major evolutionary change. The formation of a completely new species, genera, etc.

Micro evolution

Small adaptive changes within a species' gene pool/The accumulation of (through mutation) of new characteristics in a species.

Mutations

Random errors in gene replication that lead to a change in the sequence of nucleotides. The source of all genetic diversity to the sequence of bases in an individual's genome.
It is the only way of creating new alleles.

natural selection

the gradual process by which heritable traits become either more or less common in a population as a result of their impact on reproductive success/A natural process resulting in the evolution of organisms best adapted to the environment.

Non-disjunction

the failure of homologous chromosomes or sister chromatids to separate properly during cell division, which results in cells with more than 2 chromosome sets

Polyploidy

A condition/chromosomal alteration in which the organism possesses more than two complete chromosome sets.

population bottleneck

form of genetic drift in which a population becomes extremely small; may lead to differences in allele frequencies and a loss in genetic variability (population size is sharply reduced due to some catastrophic event)

post-zygotic isolation

mating occurs, but some mechanism prevents fertilisation (the egg and sperm from fusing)

pre-zygotic isolation

occurs when some mechanism prevents fertilisation (the egg and sperm from fusing)

Punctuation equilibrium

a theory that states evolution occurs primarily through short bursts of intense speciation followed by lengthy periods of being in stasis or little change/equilibrium

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

sexual selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.

selection pressure

see my own definition in pukapuka

stabilizing selection

form of natural selection by which the centre of the curve remains in its current position; occurs when individuals near the centre of a distribution curve have higher fitness than individuals at either end

Speciation

the formation of new and distinct species in the course of evolution. It occurs when sympatric or allopatric populations diverge so much from the parent population that interbreeding cannot occur

Species

A category used in the classification of organisms that consists of a group of organisms that can usually breed together and produce fertile offspring.

sympatric speciation

occurs when a single species develop into two distinct species as a result of reproductive isolation, despite living in the same geographical area

vestigial organism

any part of an organism that has diminished in size during its evolution because the function it serves has decreased in importance/organ that serves no useful function in an organism