Mocks Flashcards
What is convergent evolution
Where species with similar niches develop similar adaptations over time, despite having different ancestors. This is due to exposure to similar selection pressures
Analogous organs
Organs have the same basic structure and function but have evolved independently from different ancestral organs in unrelated species
Ecological equivalents
When species with different origins, develop similar adaptation because they occupy similar niches and different geographic areas
Divergent evolution
Occurs when two or more related groups develop different adaptations over time because they occupy diff niches
Adaptive radiation
 When one common ancestor develops into different species
Homologous organs
Diff function same structure
Parrallel evolution
Similar features evolve in species with a common ancestor- due to similar selection pressures
Co- evolution
The reciprocal evolutionary affect to species can have on each other when they interact. Each species provides a natural selective influence and they evolve together.
What is speciation
The process in which new species are formed
Why does speciation occur
When gene flow is prevented and reproductive isolating mechanisms are built up in the diff populations
Punctuated equilibrium
short periods of rapid chance and long periods of slow change. Usually occurs when new niches become available as a result of migration.
Genetic drift
Random chance that changes gene frequency
Speciation
The formation of a new species from a common ancestor
Allopatric speciation
A result of geographical isolation
Pattern of evolution
Different species living in a similar environment start to look similar
Deme
A localised population
Ecological isolation
Organisms don’t interbreed because of niche differences
Polyploidy
When somatic cells have more than 2n sets of homologous chromosomes, results from mutation and cause instant speciation
Post zygotic isolation
Factors that prevent a hybrid persisting as a new species.
Pre zygotic isolation
Factors that prevent hybrid from being conceived
Sympatric speciation
Due to isolating mechanisms other than geography- happens in the same place
Cline
A gradual variation in the characteristics of a species or population over a geographical range
Reproductive isolating mechanism
A barrier that prevents two organisms from differing species from mating and producing fertile offspring
Species
A group of related individuals that is able to interbreed and produce fertile offspring
Evolution
The accumulation of changes over time that ensure organisms are well adapted to their environment
Gene flow
Refers to alleles passed between populations by migration
Gene pool
Total set of genes in population
Directional selection
Selects against one of the extremes
Disruptive selection
Selects against the middle and favours the two extremes- leading to speciation
Stabilising selection
Selects against the two extremes and favours the middle
Instantaneous speciation
Type of speciation that occurs by polyploidy- resulting in a new species being formed in one generation
Factors that cause pre zygotic isolation
Geographical isolation, temporal, ethnological (behaviour), ecological, structural differences and gamete incompatibility
Discuss a likely polyploid process
.
• Chromosome pairs are not pulled apart correctly giving diploid / multiploid gametes which may lead to a new polypl
Comparative anatomy
Evidence for evolution- homologous (related) analogous (unrelated)
Hybrid sterility
Produced a hybrid, set a sterile and unable to produce offspring
Hybrid inviability
Reduces a hybrid capacity to mature into a healthy fit, adult, don’t survive the embryonic stages
Hybrid breakdown
Reproductive failure that appears after the F2 generation, preventing the second gen from producing fertile offspring
