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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.