Adaptive Radiation
When a large number of species form to occupy different ecological niches.
Allopatry
Speciation as a result of geographical isolation.
Allopatric Speciation
Speciation occurring where organisms are initially capable of actually interbreeding but cannot because they are geographically separated.
Analogous Structures
Structures which have the same job but have different one make up e.g wings of a bird, bats and insects. These DO not share a common ancestor.
Biogeography
The study of the geographic distribution of organism.
Cline
A gradual variation in the characteristics of a species or population over a geographical range.
Co-Evolution
When one species or group changes its genetic composition in response to a genetic change in another.
Convergent Evolution
When different species living in the same environment come to look similar.
Divergent Evolution
When one species branches to form two or threes species.
Embryology
The study of how embryos develop, looking at what gens are turned off and on and when.
Endemic
Only found naturally in a certain country or area.
Evolution
The gradual process by which the present diversity of plants and animals arose from earliest and most primitive organisms.
Genetic Drift
The important random fluctuation in the frequencies of alleles due to chance events.
Geographic or topographic barrier
A physical barrier (for the species) that prevents gene flow e.g a mountain range may be a barrier for an insect.
Gradualism
Slow changes between populations that occur as a result of different selection pressures.
Homologous Structures
Structures which have similar evolutionary history but have developed to suit different functions e.g wing of bat, flipper of a dolphin and arm of human.
Hybrid
An individual formed by mating between genetically different populations or species.
Instant Speciation
The formation of a new species through autopolyploid or allopolyploid. Because the chromosome numbers of the new instant species do no match that of the original species they cannot interbreed.
Isolating Mechanism
Any mechanism that prevents interbreeding of hybrids.
Parallel Evolution
The development of related organisms along similar evolutionary paths due to strong selective pressures acting on all of them in the same way.
Polyploidy
When cells have more than 2n chromosomes, common in plants.
Punctuated Equilibrium
Where evolution consists of long periods of stability, followed by short rapid changes as result of critical selection pressures.
Reproductive Isolation
A barrier to breeding that exists due to differences in mating seasons or mating organs e.g flowers flowering at different times of the year.
Ring species
Two apparently distinct species that are connected by a series of intermediate geographical and structural subspecies between which interbreeding can occur.
Selection Pressure
The environmental factors that favour certain phenotypes.
Speciation
A mechanism by which new species are formed.
Species
A group of individuals with common features and ancestry, which will interbreed.
Sympatry
Speciation within the same area by natural selection; there are a number of niches and groups move into the niches best suited to them.
Temporal Behaviour
When gene flow is prevented due to the populations or species having different mating times of day or month or year.
Vestigal Organs
Any part of an organism that had diminished in size during its evolution because the function it serves has decreased in importance e.g appendix in humans.