Speciation and artificial selection Flashcards
Define speciation:
Formation of new species through process of evolution.
No longer able to interbreed
–>produce fertile offspring with OG species.
What events can lead to speciation?
~Population members become isolated.
–> No gene flow between 2 groups
~Alleles within group undergo random mutations
–> different selection pressures so alleles will be selected for/against
Accumulation of mutations + changes in allele frequencies over many generations = large change in phenotype
–> reproductively isolated = different species
Define allopatric speciation:
Geographically isolated
When some members of population are separated from rest of group by physical barrier (river/sea).
different environments = different selection pressures = different physical adaptations
Small population –> founder effect
Give example of allopatric speciation:
Finches inhabiting Galapagos Islands
Adaptive radiation –> rapid organism diversification takes place
New species evolved with new beaks adapted to food availability
Define sympatric speciation:
occurs within population that share same habitat.
2 different species interbreed + form fertile offspring
–> hybrid (new species) = different number of chromosomes to either parent
–> no longer interbreed with members of either parent population.
e.g: blind mole rats
Why are plants more likely to go through sympatric speciation?
Indiscriminate release of large number of pollen grains.
What are 2 types of reproductive barriers?
Prezygotic reproductive barriers: prevent fertilisation + formation of zygote
Postzygotic reproductive barriers: Result of hybridisation –> reduce viability/reproductive potential of offspring.
What does polymorphic mean?
Display more than 1 distinct phenotype.
Define term ‘wild type’
Most common/normal characteristic
What is artificial selection?
Selection for breeding of plants/animals with desirable characteristics by farmers/breeders.
Involved inbreeding
Process repeated many generations resulting in change to frequency allele within population
Eventually speciation
What are the problems caused by inbreeding?
Decreases gene pool –> decrease genetic diversity –> reduces inbred organisms to adapt to environment.
Genetically similar organisms likely to have same recessive alleles
–> greater chance of offspring being homozygous for the trait.
Reduces organisms ability to survive + reproduce
What are gene banks?
Store biological samples
e.g: sperm
Alleles from gene banks used to increase genetic diversity (outbreeding)
–> reduces occurrence of homozygous recessive + increases potential to adapt to environmental changes
