U4 T2 Flashcards
what is evolution?
the process of genetic change in living organisms that results in new forms and species over time
what is microevolution?
small changes in allele frequency in a population that does not result in the creation of a new species
what is macroevolution?
large changes in allele frequency over multiple generations that results in the creation of a new species
what is allele frequency?
the rate at which an allele occurs in a population
what is a species?
two or more organisms that can reproduce together to create offspring that is both viable and fertile
why are multiple definitions of species needed?
some organisms such as bacteria reproduce asexually
what is evolutionary radiation?
the appearance of new forms or taxa of a speices over time. Look at the U4T2 lesson 2 PPT for graphs for exam
what is a mass extinction?
the dissappearance of a large number of species in a relatively short time frame. Graphs in U4T2 PPT
what is speciation?
the evolution of a new species
what is the difference between rooted and unrooted phylogenetic trees?
rooted show genetic distance including common ancestors, unrooted only show genetic distances. Graphs in U4T2 lesson 3 PPT
what is natural selection?
The process by which individuals with the most favorable characteristics have an increased chance of surviving and reproducing (fecundity) compared to those that don’t. must understand alleles, genotypes and phenotypes from U4T1
when does natural selection occur?
when environmental pressures confer a selective advantage to a specific phenotype to increase it’s survival (viability) and reproduction (fecundity)
what is the equation for allele frequency?
allele frequency = 100(2no. of homozygotes with the allele + no. of heterozygotes)/(2*no. of individuals in the population). Answer ranges from 0 to 1. 0 means none have the allele, 1 means all have the allele (homozygous)
what is positive selection of alleles?
promotes the spread of beneficial alleles. Allele frequency increases
what is negative selection of alleles?
hinders the spread of detrimental alleles. Allele frequency decreases
what are the types of selection?
stabilising, directional and disruptive
what is stabilising selection?
intermediate phenotypes are favoured over extremes (e.g. instead of black or white fur, grey is preferred)
what is directional selection?
one side of the bell curve is favoured over the rest (e.g. white fur is preferred over black or grey)
what is disruptive selection?
both ends of the bell curve are favoured over the middle ground; favours extremes (e.g. white and black fur favoured over grey fur)
look at U4T2 lesson 4 for graphs
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what are the main processes of microevolutionary change
mutation, gene flow, genetic drift
what is mutation
random variations in genetic sequences, can create new alleles. Can be beneficial or detrimental. Only passed on if gametes mutate
how is mutation the ultimate sourvce of genetic varitation?
it introduces new alleles into a population
what is gene flow
movement of genetic material between populations of a species. Caused when individuals join or leave a population
what is genetic drift
random fluctuations in allele frequency in a population over time can occur due to bottle neck effect or founder effect
what is the bottleneck effect
catastrophic events or periods of adverse conditions decrease the size of a population, potentially resulting in the loss of a number of alleles in the population
what is the founder effect
a few individuals carry alleles to a new isolated area and a new population is established with different allele frequencies than the original population. Depends on the allele frequencies of the founders
look at U4T2 lesson 5 for examples of gene flow and genetic drift
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