| what is evolution | changes in organisms over generations as a result of genomic variations |
| what is natural selection | the non random increase in frequency of DNA sequences that increase survival and the non random reduction in the frequency of deleterious sequences |
| why is natural selection non random | only individuals with advantageous DNA sequences will survive
(only a specific group survive, survivors are not picked randomly) |
| what are deleterious sequences | harmful DNA base sequences |
| describe the theory of natural selection | in each generation more offspring are produced than it is possible for the environment to support each individual in the offspring has to compete and struggle to survive in order to reproduce and pass on its genes every individual in a population displays slightly different phenotypes due to random mutations. The individuals that possess characteristics that are better adapted to their environment are most likely to survive these individuals have advantageous DNA sequences which are non randomly selected for The less beneficial DNA sequences are gradually removed from the population as individuals displaying these characteristics have a reduced survival rate and chance of reproducing. They have deleterious DNA sequences which are non randomly selected against. |
| what can be done to polygenic characteristics to display that they have continuous variation / normal distribution | they can be graphed and tend to show a bell shaped normal distribution
this distribution indicates that there are fewer individuals with the more extreme measurement of the characteristic and many more with the average measurement of the characteristic |
| what can happen to a characteristic's distribution when a selection pressure acts on it | the distribution can be altered |
| describe stabilising selection | an average phenotype is selected for and extremes of the phenotype range are selected against |
| describe directional selection | one extreme of the phenotype range is selected for |
| describe disruptive selection | two or more phenotypes are selected for |
| what are the two types of gene transfer | vertical and horizontal |
| describe vertical gene transfer | genes are transferred from parent to offspring as a result of sexual or asexual reproduction |
| describe horizontal gene transfer | where genes are transferred between individuals in the same generation |
| is natural selection slower or faster in prokaryotes | natural selection is more rapid in prokaryotes as they can exchange genetic material horizontally, resulting in faster evolutionary change than in organisms that only use vertical transfer |
| what is a species | a group of organisms capable of interbreeding and producing fertile offspring, and which does not normally breed with other groups |
| what is a gene pool | consists of all the genes and their different alleles, present in an interbreeding population |
| what is speciation | the generation of new biological species by evolution as a result of isolation, mutation and selection
the isolation barriers are important in preventing gene flow between sub populations during speciation |
| what does the type of isolation barrier during speciation determine | what type of speciation is taking place |
| what type of speciation to geographical barriers lead to | allopatric speciation |
| what type of speciation do behavioural and ecological barriers lead to | sympatric speciation |
