Speciation The formation of New Species. Speciation Speciation: evolution of a new species Microevolution: changes in gene (allele) frequencies and phenotypic.

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Presentation transcript:

Speciation The formation of New Species

Speciation Speciation: evolution of a new species Microevolution: changes in gene (allele) frequencies and phenotypic traits in a population cause a creation of a new species Modes of speciation Allopatric - evolution of a species as a result of geographic isolation Sympatric - evolution of a species within the same geographic area

Patterns of Selection Stabilizing selection: selection against individuals exhibiting variations in a trait that deviate from the current population average (eg. Favour short and tall) Directional selection: selection that favours an increase or decrease in the value of a trait from the current population average Eg. Favour tall

Disruptive selection: selection that favours two or more variations or forms of a trait that differ from the current population average.

Bottlenecks A large percentage of a population is killed and therefore unable to reproduce

Sexual Selection Sexual selection favours the selection of any trait that influences the mating success of the individual Sexual dimorphism: differences in the physical appearance between male and females, not usually applied to behavioural differences between sexes

Reproductive Isolating Mechanisms These can be either behavioural, structural or biochemical traits that will prevent an individual from one species from mating with an individual of another species What is a species? Simply - if you can mate and have fertile offspring you are the same species

Pre/Post zygotic Mechanisms for the prevention of interspecies mating can be seen either prezygotic or post-zygotic PreZygotic - prevent mating and fertilization The following are examples to prevent mating Ecological - different areas Temporal - When Behavioural - signals for attracting mates

The following prezygotic mechanisms prevent fertilization Mechanical isolation - sperm/eggs are physically separated Gametic isolation - sperm/eggs signal to each other don't match, they don't join

Postzygotic Mechanisms These mechanisms come into play if by chance an organism does get fertilized They prevent the offspring (hybrids) from reproducing Zygotic mortality - anything fertilized will not reach maturity Hybrid inviability - won’t live long Hybrid infertility - offspring live and are strong but won’t be able to have offspring of their own