Speciation Flashcards
(18 cards)
What is reproductive isolation?
When populations can’t interbreed successfully to produce viable fertile offspring
How does reproductive isolation result in genetic isolation?
Lack of gene flow between populations due to reproductive barriers means they cannot interbreed successfully preventing gene exchange between populations facilitating speciation
What are prezygotic reproductive barriers and give an example?
Prevent fertilisation and zygote formation acting before egg fertilisation
e.g habitat isolation or variations in mating rituals
What are postzygotic reproductive barriers?
Often result of hybridisation between different species
produce infertile or non-viable hybrid offspring reducing their reproductive potential
Outline the process of allopatric speciation?
1) some members of population are geographically separated from rest by physical barrier e.g mountains
2) geographical separation exposes parts of population to different environmental pressures
3) prezygotic reproductive barriers lead to reproductive isolation
4) reproductive isolation prevents gene flow and physical separation leads to genetic divergence
5) causes populations to evolve separately forming separate species
Outline the process of sympatric speciation?
1) speciation occurs within same geographical location
2) ecological or behavioural separation mechanisms e.g different habitat preference, mate selection, or chromosomal changes lead reproductively isolated
3) reproductive isolation prevents gene flow leading to genetic divergence
4) causes populations to evolve separately forming separate species
What is speciation?
Process by which new species are formed
Why does speciation typically occur?
- reproductive isolation of populations, which is inability of 2 groups of organisms to breed with 1 another
- genetic divergence driven by natural selection and genetic drift
What is adaptive radiation?
Phenomenon where organisms diversify rapidly from an ancestral species into wide array of new forms each adapted to specific ecological niche
When is adaptive radiation more likely to occur?
When change in environment makes new resources available
What is artificial selection?
Humans breed organisms selectively for specific genetic traits determining which individuals reproduce
changes allele frequencies by favouring certain traits that become more common over time
Outline the process of artificial selection?
1) select population displaying variation
2) select individuals with desired traits e.g like high milk production in female cattle and male cattle with female relatives
3) selectively breed individuals together displaying desired traits
4) grow and test offspring for desired traits
5) repeat selection process across many generations
What does artificial selection create?
Population of individuals all showing certain desired characteristics that can be further inbred to produce offspring with characteristics
Describe what inbreeding leads to?
- decreased genetic diversity
- reduce heterozygosity
- increased homozygosity
- inbreeding depression
- reduced fitness and adaptability
Describe what outbreeding leads to?
- increased genetic diversity
- increased heterozygosity
- decreased homozygosity
- hybrid vigour
- increased fitness and adaptability
How can genetic biodiversity be maintained and give an example?
Storage of biological samples encompassing broad gene pool
e.g in gene and seed banks
What might samples in a gene or seed bank be?
Seeds = from wild-type and domestic varieties
Reproductive cells = like egg cells and sperm cells
How can wild type alleles from gene and seed banks be used?
Outbreeding to increase genetic diversity after inbreeding. This reducing frequency of harmful recessive alleles and increasing ability of populations to adapt to environmental change
