Essay About Artificial Selection And Selective Breeding

Biocomplexity – Background to Evolution
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Lecture 4: Background to Evolution
Artificial Selection
Artificial selection (or selective breeding) describes intentional breeding for certain traits, or combination of trait.
Artificial selection IS evolution
Natural Selection
Variations of conspecific individuals are genetically based.
Some traits are better at surviving than others, increasing changes of surviving and reproducing.
Offspring than inherit the traits of their successful parents.
Variation is random, but selection is directional
E.g. resistance to insecticides or antibiotics.
Selection Pressure
Certain characteristics increase the fitness over other members of its species.
Sexual selection, mimicry, predation.
Process of Evolution
Two events are involved in evolutionary divergence among organisms.
Phylesis
The events that modify a species WITHOUT causing new species to originate.
Much like that of adaption.
Speciation
The events that lead to the origin of new taxa.
Think of it as: Speciation = branching, while phylesis = branch lengths
The biological changes during speciation are constrained by pre-existing features.
Mot traits have clearly risen from pre-exiting traits that have been modified to perform a new function.
The Process of Speciation
Remember that:
Species – a group of interbreeding populations that share a gene pool.
Gene flow – is the migration of individuals or genes among populations.
Over time, isolation may occur which leads to rising differences between populations and they begin to accumulate.
The separated populations experience different mutation and environments.
The separation leads to the differences not being shared or blended in the gene flow.
Speciation completes hen the growing differences become great enough to prevent interbreeding.
Reproductive Isolation Mechanisms prevent interbreeding and keep species apart even when they co-habit in the same place.
How does a species arise?
Sympatric Speciation
Occurs WITHOUT physical separation of the gene pools.
Allopatric Speciation
Requires a physical barrier within the gene pool
Parapatric Speciation
Occurs