Speciation Exam- Biology

Convergent Evolution

Where similar traits arise in two unrelated species

Divergent Evolution

Where an ancestral species splits into two or more increasingly distinct species

Allopolyploidy

Where two different species produce an infertile hybrid which then undergoes somatic doubling to form a fertile hybrid

Autopolyploidy

The multiplication of the genome of a single species which occurs when homologous chromosomes do not seperate during meiosis creating 2n gametes

Population Bottleneck

A sharp reduction in the size of a population due to environmental events

Founder Effect

A small number of individuals emigrate from a population or become geographically isolated from their original population

Selection Pressures

External factors in an environment that influence organisms ability to survive and reproduce

Analogous Structures

Structures or Traits in unrelated species that have a similar function, but do not have the same evolutionary origin

Homologous Structures

Structures that have similar evolutionary origin but have developed to suit different functions in species

Vestigial Structures

Remnants of features that served an important function in the organisms ancestors

Distruptive Selection

selection pressures favour both extremes over the average

Stabilising Selection

selection pressures favours the average over the extreme

Directional Selection

selection pressures favours one extreme over the average or the other extreme

Adaptive Radiation

Where a large number of new species evolve over a relatively short period of time from a common ancestor

Allopatric Speciation

When two populations become geographically isolated from each other

Sympatric Speciation

The formation of a new species without geographical isolation

Natural Selection

Where organisms better adapted to their environment tend to survive and produce more offspring

Gene Pool

The total number of different genes and alleles in a interbreeding population

Geographic Isolation

Species occur in different areas with no geographical overlap

Ecological Isolation

Species occupy or exploit different habitats within an area

Behavioural Isolation

Different courtship rituals, sounds calls or colouration

Temporal Isolation

Activity, mating or flowering occurs at different times of the day, month or year

Mechanical Isolation

Reproductive structures are incompatible and prevent the delivery or acceptance of gametes

Gametic Isolation

Gametes are incompatible and unable to fuse together and produce a viable zygote

Genetic Drift

Random fluctuations in allele frequencies due to chance events

Genetic Variation

the difference in alleles in the gene pool of a population

Allele Frequency

How often an allele appears in a population

Hybrid Inviability

two species breed and a zygote forms but the embryo does not develop properly

Hybrid Sterility

Two different species breed and the offspring is born but it is sterile

Hybrid Breakdown

Two different species produce a hybrid and is able to reproduce but following generations have reduced fertility

Niche

the role of the organism within the environment

Gene Flow

occurs when individuals move into (immigrate) or move out of a population (emigrate)

Sexual Selection

A type of natural selection where members of one sex choose mates of the other sex to mate with based on preferential phenotypic features

Punctuated Equillibrium

long periods of very little evolutionary change (stasis)interrupted by short bursts of rapid speciation which could be triggered by sudden changes in the environment

Gradualism

Evolutionary Processes proceed slowly but continuously and eventually the accumulation of changes result in speciation occurring

Coevolution

Occurs between two unrelated but closely interbreeding species and occurs when one species develops an evolutionary advantage

Cline

A pattern of gradual variation between individuals over a geographical area, typically as a result of environmental differences

Deme

A subset of a population that has limited gene flow with members of the larger population

Species

A group of organisms that can interbreed under natural conditions and are reproductively isolated from other species

Macroevolution

Evolution above the species level, especially with regard to the evolution of whole taxonomic groups over long periods of time

Microevolution

A change in allele frequency within a population, usually bought about by natural selection processes over shorter periods of time

Polyploidy

caused by errors during cell division that result in the cell having more than two copies of each chromosome

Molecular Clocks

Estimating the timing of evolutionary events based on the known (constant) rate of mutations in certain genes

Statigraphy

The order and relative position of strata and their relationship to the geological timescale. Used for dating fossils embedded in strata

Competitive Coevolution

When coevolution is found among species that have negative effects on each other