Selection and Speciation – Flashcards
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Explain how natural selection could produce a copper tolerant plant in the mine waste.
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-Variation in original population (1)
-Copper tolerant individuals are more likely to survive (1)
-These reproduce and pass on genes(1)
-Increase in frequency of copper tolerant alleles (1)
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Directional selection
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-When over time the environment changes in a particular way. There is selection pressure for species to change in response to the environment
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Explain how this can lead to a new species.
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1.Isolated because can't pollinate other flowers
2.Different selection pressures
3.Mutations
4.Different features are selected for
5.Become reproductively isolated
*Un-able to produce fertile offspring*
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Explain how natural selection may have led to different frequencies of varieties of peppered moths.
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-Variations due to mutations
-Camouflage means better adapted moths are able to survie
-Reproduce and pass on alleles to offspring
-Increase in allele frequency
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Suggest how the peppered moths can develop into a separate species.(3)
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1. Geographical Isolation so no gene flow
2.Different selection pressures
3.Mutations occur
(4.Alleles selected for, advantageous adaptation survive and reproduce
5.become reproductively isolated)
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Stabilising selection
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-Occurs in unchanging environment
-Initial range of values in which mean is best adapted
-mean is selected for
-mean is unaltered
-range is reduced
-repeated over many generations
-increasing portion of populations become well adapted to environment
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Use information in figure 1 and your own biological knowledge to explain how the production of cyanide depends on the genotypes of the clover plants.
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-Dominant alleles will be expressed in heterozygotes
-Any cyanogenic plant must possess both dominant alleles
-Any cyanogenic plant must produce both enzymes
-Any acynogenic plant can not complete the pathway
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Explain the poportions of cyanogenic and acyanogenic plants in clover populations growing in the area where the mean minimum temperature is below -4degrees and in the area where it is above 10 degrees.
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-All plant are acyanogenic below -4degrees and most are cyanogenic above 10degree
-Cyanogenic plant cells freeze below -4 degrees
-Releasing cyanide into own tissues
-Damaging plants
-Selective advantage not to produce cyanide at -4 degrees
-slugs are inactive anyway at lower temperatures
-Cyanide production kills slugs but that is only an advantage at higher temperatures
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Explain why crossing over can contribute to genetic variation(3)
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- Sections of chromatids exchanged
-Sections have different alleles
-New combination of alleles arise
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Each store of maize seeds shown above have different lenghts.Explain one cause of this variation
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-Length is controlled by many genes
-Each gene may have a different allele
