General bio

bottle neck effect

the original population is reduced to a small size suddenly due to a catastrophic event (eg flood or landslide) or human action (eg introduction of predator) the surviving population is small and so allele frequency is not representative of the original population. population will usually have reduced genetic diversity and genetic drift will have a big impact as few individuals to buffer the effects.

founders effect

when a small number of individuals emigrate (leave) a population and become geographically isolated (no gene flow) from the original population. this new population is call the founders population. the founders population with usually have a gene pool that is not representative of the allele frequencies present in the original gene pool. founder population will see the affects of genetic drift as there are fewer individuals to buffer the effects of change in the gene pool. founder population also has lower genetic diversity.

function of meiosis

the function of meiosis is to produce gametes (sperm and egg) that have half the genetic material through processes like crossing over, independent assortment, and segregation that increase the genetic variation of gametes an therefore offspring.

genetic drift

the change in allele frequency within a population due to change. it is random and not driven by fitness or natural selection

independent assortment

independent assortment is when homologous pairs of chromosomes arrange themselves either side of the cell equator independently of all other homologous chromosome pairs. this causes genetic variation as the random alignment can produce different combinations of maternal and paternal genetic information so offspring can be different. independent assortment only causes variation in unlinked genes. it occurs during metaphase one of meiosis shortly after crossing over.

crossing over

crossing over is when maternal and paternal non sister chromatids tangle at the chiasma break and rejoin to form recombinants. the recombinants have different genetic paternal to the parents causing genetic variation in the offspring.crossing over occurs during prophase 1 of the meiosis cycle

natural selection

natural selection occurs when there is an environmental change (eg change in climate) or selection pressure (eg predators) that causes some individual to have a survival advantages as they are better suited/ adapted to the change, others who are not adapted will not survive as well and therefore not reproduce and decrease the allele in the gene pool