Gene pool- complete range of alleles in a population. New alleles generated through mutation
Allele frequency is how often an allele occurs in a population, and evolution is the change in allele frequency over time
Individuals vary because of differences in alleles, meaning some are better adapted. Individuals with a beneficial allele are more likely to survive, reproduce and pass on their alleles. A greater population of the next generation inherit the beneficial allele. They in turn are more likely to survive and pass on the alleles, so frequency of the beneficial allele increase. This is natural selection
Speciation is the development of a new species, and occurs when populations of the same species become reproductively isolated
Ways changes in phenotype prevent populations successfully breeding- seasonal changes (individuals develop different mating seasons ect), mechanical changes (changes in genitalia) and behavioural changes (individuals develop new courtship rituals)
A population becomes reproductively isolated due to geographical isolation or random mutations. Random mutations result in the above phenotype changes
Geographical isolation occurs when a physic barrier divides populations. Conditions on either side are different, and different characteristics become more common due to natural selection. The individuals become so different that the groups become two different species
1 of 2
Evidence for Evolution
DNA evidence- Theory suggests all organisms evolved from shared common ancestors, and closely related species diverged more recently. Evolution is caused by gradual changes in the base sequence of organisms' DNA.
Scientists found that organisms which diverged from each other recently have more similar DNA as less time has passed for changes in DNA sequence to occur
Proteomics (study of proteins)- Related organisms have similar DNA sequences and so similar amino acid sequences in their proteins
Scientists found that organisms which diverged from each other recently have more similar proteins as less time has passed for changes to occur
The scientific community validates evidence about evolution. Scientists share and discuss their work in three main ways
1. Scientific journals- publish articles describing their work, allowing other scientists to repeat their experiments and see if they get the same results using the same methods. If the results can be replicated, the community are confident that the evidence is reliable
2. Peer review- before publishing in a journal, other scientists who work in the area review the work to check that it is valid and that it supports the conclusions
3. Conferences- meetings scientists attend to discuss work. Scientists with important/interesting results present their work and are questioned by other scientists
Comments
No comments have yet been made