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9 Cards in this Set
- Front
- Back
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Define speciation |
Evolution of a new species from am existing species |
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When do organisms share the same gene pool? |
When they are within in a population and interbreed with one another |
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What happens if the population is split? |
Flow of alleles will not be the same |
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What happens if a population face different environmental conditions? |
Different alleles will be favoured Frequency of the allele in each species may be so different they can no longer interbreed and become 2 different species |
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When does geographical isolation occur? |
When physical barriers prevent 2 populations from breeding with one another |
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Describe the progression of a species to lead to two species |
Species X lives in a rainforest Individuals of species x form a single gene pool and freely interbreed Climate changes over many years lead to drier conditions that separate the species into two different populations Further climate changes could cause one area to be drier and warmer and the other to be wetter and colder In 1st region individuals that have phenotypes that allow individuals to be better suited for warmer and drier conditions are favoured In 2nd region individuals that have phenotypes that allow individuals to be better suited for colder and wetter conditions are favoured Type and frequency of alleles in the gene pool may differ over time until they become so different that they are now different species If species are reunited they would no longer be able to interbreed |
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Lake Malawi in East Africa contains around 400 different species of cichlids which are small, brightly coloured fish. All these species have evolved from a common ancestor. During the last 700,000 years there have been long periods when the water level was much lower and Lake Malawi split up into many smaller lakes. Explain how speciation of cichlids may have occurred following the formation of separate, smaller lakes . |
Isolation of 2 populations Variations already present due to mutations Different environmental conditions / selection pressures Selection of different features and so different alleles Different frequency of alleles Separate gene pools / no interbreeding |
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Many species of cichlids are similar in size and, apart from their colour, in appearance. Suggest how the variety of colours pattern displayed by these cichlids may help to maintain the fish as separate species |
Selection of mate dependent on colour pattern Prevents interbreeding / keeping gene pools separate |
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In a investigation, the tolerance to copper ions of the grass Agrostia tenuis was determined. Samples were taken of plants growing in waste from a copper mine and from nearby areas just outside the mine. The mean copper tolerance of plants from the mine waste was found to be four times higher than that of plants in the surrounding area. Copper-tolerant Agrostis Tenuis plants flower at a different time from those which are not Copper-tolerant. Explain how this might eventually lead to the production of a new species of Agrostis |
Reproductivity isolated so no interbreeding due to different flowering times Conditions different for two populations / different selection pressures Different features of plants are selected Populations become genetically different Unable to produce fertile offspring |
