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The only source of new alleles is by mutations - They are rare and random.

Only the mutations that occur in the information of gametes are passed on to the next generation.

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In meiosis cell division, the homologous chromosomes line up in pairs on the equator of the spindle and then move to opposite poles.

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The relatedness of species can be deducted from the differences in their DNA

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Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. Allopatric is more common than sympatric. Speciation through niche isolation and also reproductive isolation

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Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap or are even identical, so that they occur together at least in some places.

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Allopatric specition is the divergence of a species after it is subdivided into geographically isolated populations

stage1- moving to new enviroments

stage 2- geographical isolation

stage 3- diffrent selection pressures

stage 4- reproductive isolation

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Large scale mutation can during meiosis, which can fundamentally change chromosome structure.

Deletion: Break may occur at two points on the chromosome and the middle piece of the chromosome falls out. They then rejoin, to form deficient genes.

Inversion: The middle piece of the chromosome falls out and rotates through 180degrees and then rejoins.

Translocation: A piece of one chromosome breaks off and joins onto another chromosome. Then passed to gametes and receives extra genes

Duplication: A segment is lost and added to its homologue.

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results from mating between 2 species. the resulting hybrid may be sterile. This can cause the organism to have all chromosomes having a homologue with which to pair during meiosis. self fertilisation may then produce a viable, fertile hybrid

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1- stabilizing selection- this type of selection maintains the population in a stable form because it favors the average phenotype at the expense of the extreme direction

2- Directional selection- this type favours the phenotype of one extreme over the average or the other extreame, so there is a shift of the average in one direction

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A new species may form gradually over a long period of time.

Two main models have been proposed for the rate at which evolution occurs: punctuated equilibrium and phyletic gradualism

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daughter species exert powerful selection pressure on each other after speciation

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this is responsible for most evolutionary change, by reducing and changing genetic variation; some combinations of alleles are more likely to help survival and reproduction than others.

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Assumes that populations slowly  diverge by accumulatingadaptive

characteristics in response to different selective pressure. Gradually changes to different selective pressures.

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It describes the process by which species by which species from different evolutionary lineages come to resemble each other because they have similar ecological niches. Analogous structures: having the same structure but still unrelated.

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The term for the random changes is allele frequencies that occur in all populations.

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Population bottlenecks occur when population numbers and diversity fall dramatically although a populations' numbers may recover often its genetic diversity does not.

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One species effects the evolution of another. Results from close interspecies relationships and can produce organisms which are evolved to explicit each other, or to attack or avoid each other. One species evolves in favour of the other mutualistic relationship

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A small group of individuals isolated from the original population may carry a non-representive sample of alleles and evolve differently to the original population. Consequences of founder effect- the separated population may evolve differently from that of the parent population because of different environmental conditions.

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Diversification among the descendants of a single ancestral group to occupy different niches. The result of a sudden availability of a diversity of niches

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Polyploidy is a condition in which a cell or organism contains three or more times the haploid number of chromosomes. It is rare in animals but more common in all major groups of plants. Natural Polyploidy species occurs in animals among hermaphrodites.