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Agents that change gene frequencies

Agents that change gene frequencies

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Agents that change gene frequencies

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  1. Agents that change gene frequencies

  2. Natural Selection • Involves the environment selecting for/against certain phenotypes

  3. Natural Selection • Involves the environment selecting for/against certain phenotypes • These ‘better adapted’ phenotypes survive and leave more offspring carrying the ‘better’ allele.

  4. Natural Selection • Involves the environment selecting for/against certain phenotypes • These ‘better adapted’ phenotypes survive and leave more offspring carrying the ‘better’ allele. • Eg – Kea (mountain species of Sth Is) and Kaka (bush species of Nth Is).

  5. Natural Selection • Involves the environment selecting for/against certain phenotypes • These ‘better adapted’ phenotypes survive and leave more offspring carrying the ‘better’ allele. • Eg – Kea (mountain species of Sth Is) and Kaka (bush species of Nth Is). Thought to share common ancestor – Kea’s ancestor would tolerate harsh winters. Those that couldn’t, would emigrate or die.

  6. Natural Selection • Involves the environment selecting for/against certain phenotypes • These ‘better adapted’ phenotypes survive and leave more offspring carrying the ‘better’ allele. • Eg – Kea (mountain species of Sth Is) and Kaka (bush species of Nth Is). Thought to share common ancestor – Kea’s ancestor would tolerate harsh winters. Those that couldn’t, would emigrate or die. The frequency of the ‘cold tolerant’ allele would increase.

  7. Natural Selection • Involves the environment selecting for/against certain phenotypes • These ‘better adapted’ phenotypes survive and leave more offspring carrying the ‘better’ allele. • Eg – Kea (mountain species of Sth Is) and Kaka (bush species of Nth Is). Thought to share common ancestor – Kea’s ancestor would tolerate harsh winters. Those that couldn’t, would emigrate or die. The frequency of the ‘cold tolerant’ allele would increase. With time, temp barriers, and change in behaviour would have separated the ancestral birds so much that they became two different species.

  8. Genetic drift • Involves the loss, decrease, or increase of an allele in a small population by chance alone.

  9. Genetic drift • Involves the loss, decrease, or increase of an allele in a small population by chance alone. • Eg – ‘population’ of just one couple. Both are heterozygous for brown eyes.

  10. Genetic drift • Involves the loss, decrease, or increase of an allele in a small population by chance alone. • Eg – ‘population’ of just one couple. Both are heterozygous for brown eyes. • Bb x Bb (phenotype) B or b (genotype)

  11. Genetic drift • Involves the loss, decrease, or increase of an allele in a small population by chance alone. • Eg – ‘population’ of just one couple. Both are heterozygous for brown eyes. • Bb x Bb (phenotype) B or b (genotype) • The couple have 2 kids. The chances of 1 kid being BB is ¼

  12. Genetic drift • Involves the loss, decrease, or increase of an allele in a small population by chance alone. • Eg – ‘population’ of just one couple. Both are heterozygous for brown eyes. • Bb x Bb (phenotype) B or b (genotype) • The couple have 2 kids. The chances of 1 kid being BB is ¼ • Chances of both kids being BB is 1/16 ( ¼ x ¼ )

  13. Genetic drift • Involves the loss, decrease, or increase of an allele in a small population by chance alone. • Eg – ‘population’ of just one couple. Both are heterozygous for brown eyes. • Bb x Bb (phenotype) B or b (genotype) • The couple have 2 kids. The chances of 1 kid being BB is ¼ • Chances of both kids being BB is 1/16 ( ¼ x ¼ ) • Therefore there is a 1/16 change of losing the ‘b’ allele altogether by chance alone.

  14. Genetic drift • Involves the loss, decrease, or increase of an allele in a small population by chance alone. • Eg – ‘population’ of just one couple. Both are heterozygous for brown eyes. • Bb x Bb (phenotype) B or b (genotype) • The couple have 2 kids. The chances of 1 kid being BB is ¼ • Chances of both kids being BB is 1/16 ( ¼ x ¼ ) • Therefore there is a 1/16 change of losing the ‘b’ allele altogether by chance alone.

  15. The Founder effect • If only a few individuals move into a new area, they may only have a few of the available genes from the gene pool of that species.

  16. The Founder effect • If only a few individuals move into a new area, they may only have a few of the available genes from the gene pool of that species. • Isolated islands have shown rapid evolution because of this.

  17. The Founder effect • If only a few individuals move into a new area, they may only have a few of the available genes from the gene pool of that species. • Isolated islands have shown rapid evolution because of this. • It is unlikely that the few individuals that colonise a new area will have the allele frequencies of the original population.

  18. The Founder effect • If only a few individuals move into a new area, they may only have a few of the available genes from the gene pool of that species. • Isolated islands have shown rapid evolution because of this. • It is unlikely that the few individuals that colonise a new area will have the allele frequencies of the original population. • This new ‘founder’ population will have the potential to be different so evolution will occur faster due to different gene pools.

  19. Bottleneck effect • Disasters can reduce a population to a few survivors.

  20. Bottleneck effect • Disasters can reduce a population to a few survivors. • Deaths are often random so the survivors are not representative of the original gene pool.

  21. Bottleneck effect • Disasters can reduce a population to a few survivors. • Deaths are often random so the survivors are not representative of the original gene pool. • Some alleles will be above normal number, and some will be lost altogether.

  22. Bottleneck effect • Disasters can reduce a population to a few survivors. • Deaths are often random so the survivors are not representative of the original gene pool. • Some alleles will be above normal number, and some will be lost altogether. • Bottleneck effect reduces genetic variability in the population

  23. Bottleneck effect • Disasters can reduce a population to a few survivors. • Deaths are often random so the survivors are not representative of the original gene pool. • Some alleles will be above normal number, and some will be lost altogether. • Bottleneck effect reduces genetic variability in the population • EG – Chatham Island robin. <5 population. ‘Blue’ a female who had 200 chicks (there is very little genetic variation between them)

  24. Bottleneck effect • Disasters can reduce a population to a few survivors. • Deaths are often random so the survivors are not representative of the original gene pool. • Some alleles will be above normal number, and some will be lost altogether. • Bottleneck effect reduces genetic variability in the population • EG – Chatham Island robin. <5 population. ‘Blue’ a female who had 200 chicks (there is very little genetic variation between them) so survival was touch and go for years.