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Meiosis and Genetic variation (Genetic diversity (Population is a group of…
Meiosis and Genetic variation
Directional selection
Environmental conditions are usually unstable
Antibiotic resistance
Favours individuals outside the mean and at the extreme ends of the spectrum
Adverse traits favour the individuals
Stabilising selection
Environmental conditions stable
mean population favoured
Extreme population have no advantage in this environment
Genetic diversity
Population is a group of individuals of the same species that live in the same place and can interbreed
Greater genetic diversity of an area the more likely individuals are to survive if there is an environmental change
Described as the total number of different alleles in a population
Natural selection occurs where species with desirable characteristics are passed on to the next generation
Reproductive success is affected by: Allele frequency and Gene pool
Random mutations will occur within the gene pool, most of these mutations will be harmful and at a disadvantage to the individual
Sometimes mutations can be of an advantage to the individual in the right environment, then when the change occurs the population of these advantageous allele's will increase with the less advantageous allele's being reduced
Meiosis
Replication of sex cells in gametes
Same stages as in Mitosis but happens twice as four cells are produced
23 chromosomes found in each haploid
Two divisions occur in meiosis, within this there are several stages where variation can occur
Process
Genetic recombination occurs where parts of the chromosomes swap over
Chromosomes are then separated into two cells
First division occurs, homologous chromosomes line up on the equator of the cell
Second division begins to occur as chromosomes split into chromatids