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Instant Speciation

Instant Speciation

When a new species forms through autopolyploidy or allopolyploidy, it has a different number of chromosomes than the original species. Because of this difference, the new species cannot interbreed with the original species

Founder Effect

A random change in the frequency of genes happens when a small group separates from the main population

Punctuated Equilibrium

There are long periods of little evolutionary change (stasis) interrupted by short bursts of rapid speciation

Hybrid breakdown

The hybrid offspring are fertile but produce infertile or non-viable offspring

Geological Record

Fossils preserved in sedimentary rock layers that can be used to trace the evolutionary history of a species

Stabilising Selection

Natural selection acting against the extremes of a range of variation, resulting in resistance to change in allele frequencies

Macro-evolution

The formation of a completely new species, genera, etc

Natural Selection

The process that brings out new species by the elimination of the less adapted individuals and the survival of the organisms which are better adapted

Vestigial Organ

Any part of an organism that has diminished (shrunk) in size during its evolution because the function it serves has decreased in importance

Reproductive Isolation

A barrier to breeding that exists due to differences in mating seasons or mating organs

Polyploidy

Mutation producing more than twice the normal haploid (one pair) number of chromosomes

Micro-Evolution

The accumulation of (through mutation) new characteristics in a species

Disruptive Selection

Natural selection acting against the middle of a range of variation

Prezygotic

Isolating mechanism that acts to prevent the fusion of gametes from different populations

Gradualism

Evolution proceeds slowly but continuously. Eventually the accumulated changes result in speciation

Genetic Drift

The change in allele frequency due to the accumulated effects of chance

Directional Selection

Natural selection against one end of a range of variation, resulting in a progressive change in allele frequency

Endemic

Found only in that country; native

Species

A group of organisms that normally interbreed in nature to produce fertile offspring and belong to the same gene pool

Allopatric Speciation

Speciation occurring where organisms are initially capable of actually interbreeding but cannot because they are geographically separated

→ the result of geographical isolation

Two type of reproductive barriers

Prezygotic barriers: stops mating from happening
Postzygotic barriers: prevents the hybrid offspring that was produced from reproducing or surviving

Hybrid Inviability

A zygote is formed but does not develop properly

Ring Species

Two apparently distinct species that are connected by a series of intermediate geographical and structural subspecies between which interbreeding can occur

Convergent Evolution

The development of superficially similar structures in unrelated organisms, usually because the organisms live in the same kind of environment

Analogous Structures

Different structures that serve a similar purpose/function in other organisms despite the fact that they have evolved differently

→ These are body parts in different species that have similar functions but do not share a common origin. They evolved independently in different species to solve similar problems.

Divergent Evolution

The type of evolution where a common ancestor divides into two or more lines with dissimilar characteristics due to the environments they live in

Parallel Evolution

The development of related organisms along similar evolutionary paths due to strong selective pressure acting on all of them in the same way

Hybrid Sterility

A hybrid forms but is sterile (cannot reproduce)

Evolution

The gradual process by which the present diversity of plants and animals arose from the earliest and most primitive organisms

Cline

A gradual variation in the characteristic of a species or population over its geographical range

Homologous Structures

These are body parts in different species that have a similar origin but may serve different functions. They show that these species share a common ancestor

Postzygotic

Isolating mechanism that acts after fertilization to prevent the exchange of genes between populations, by impairing development or fertility of offspring

Adaptive Radiation

This is when a single ancestor species rapidly evolves into many different forms to fill various new roles or environments. This usually occurs when the species encounters new habitats or niches that were previously unoccupied

Sympatric Speciation

Speciation occurring where organisms living within the same area are theocratically capable of interbreeding, but cannot because of difference in behaviour, flowering times, etc

These differences prevent them from mating, leading to the formation of new species.