Genetic Diversity & Natural Selection Flashcards
Definition of Genetic Diversity
Number of different alleles in a species or population
How can Genetic Diversity be increased?
DNA Mutations
Gene Flow
How can Mutations cause Genetic Diversity?
- Deletion, Addition or Substitution of a nucleotide
- Deletion or Translocation of part or of a Chromosome
- Aneuploidy - Loss or gain of a single chromosome
- Polyploidy - Addition of whole Chromosome sets
How can Sexual Recombination cause Genetic Diversity?
- Independent assortment of chromosomes in meiosis
- Crossing-over during meiosis
- Random fertilisation
Define Gene Flow
Introduction of different alleles into a population that occurs when individuals from another population migrate into them and reproduce.
Define Genetic Bottleneck
A genetic bottleneck is an event that causes a large reduction in a population.
Reduces Genetic Diversity because it decreases the number of alleles.
Define Founder Effect
The frequency of each allele in new colony may be very different to original, so an allele that was very rare in the original population may be more common in the new colony.
How could the Founder Effect occur?
The founder effect can occur as a result of migration leading to geographical separation or if a new colony is separated from the original population
Define Natural Selection
Fittest of the survival
Randomly-occurring mutations sometimes result in a new allele being formed
Benefit of Natural Selection
Increases the number of advantageous alleles in a population.
Define Evolution
Gradual change in species over time
Both adaptation and selection are key factors in evolution
Define Speciation
The formation of a new species . It covers when gene flow has effectively stopped between populations where it previously existed.
Define Allopatric Speciation
Geographical Isolation
Define Sympatric Speciation
Changes in reproductive mechanism due to mutations in alleles
Define Biodiversity
Variety of living organisms in a particular area.
