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The process in which new species develop from earlier forms.

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Presentation on theme: "The process in which new species develop from earlier forms."— Presentation transcript:

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2 The process in which new species develop from earlier forms.

3 Normally occurs slowly, most often in response to a change in a species’ environment.

4 The process in which new species develop from earlier forms. Normally occurs slowly, most often in response to a change in a species’ environment. Life is thought to have evolved from just a few unicellular organisms three billion years ago.

5 The process in which new species develop from earlier forms. Normally occurs slowly, most often in response to a change in a species’ environment. Life is thought to have evolved from just a few unicellular organisms three billion years ago. Evolution happens through ‘changes in the frequency of alleles in a population’ – some alleles do better than others.

6 The process in which new species develop from earlier forms. Normally occurs slowly, most often in response to a change in a species’ environment. Life is thought to have evolved from just a few unicellular organisms three billion years ago. Evolution happens through ‘changes in the frequency of alleles in a population’ – some alleles do better than others. Freq. of an allele = occurrence of that allele total number of alleles

7 Suppose a gene pool were to contain 50 individuals.

8 30 – Aa, 10 – AA and 10 – aa

9 Suppose a gene pool were to contain 50 individuals. 30 – Aa, 10 – AA and 10 – aa For the A allele it occurs 30 times from Aa

10 Suppose a gene pool were to contain 50 individuals. 30 – Aa, 10 – AA and 10 – aa For the A allele it occurs 30 times from Aa The A allele also occurs 20 times from AA (2x10)

11 Suppose a gene pool were to contain 50 individuals. 30 – Aa, 10 – AA and 10 – aa For the A allele it occurs 30 times from Aa The A allele also occurs 20 times from AA (2x10) The occurrence of the A allele is now 50 (30 + 20)

12 Suppose a gene pool were to contain 50 individuals. 30 – Aa, 10 – AA and 10 – aa For the A allele it occurs 30 times from Aa The A allele also occurs 20 times from AA (2x10) The occurrence of the A allele is now 50 (30 + 20) There are 50 individuals with two alleles so that the total number of alleles is 100 (50x2)

13 Suppose a gene pool were to contain 50 individuals. 30 – Aa, 10 – AA and 10 – aa For the A allele it occurs 30 times from Aa The A allele also occurs 20 times from AA (2x10) The occurrence of the A allele is now 50 (30 + 20) There are 50 individuals with two alleles so that the total number of alleles is 100 (50x2) Frequency of the A allele = 50/100 = 0.5

14 1.Suppose a gene pool were to contain 60 individuals. 20 were BB, 30 were Bb and 10 were bb. Calculate the frequency of the B allele. 2.A gene pool has 120 individuals. 60 were Aa, 20 were AA and 40 were aa. Calculate the frequency of the A allele.

15 Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way.

16 Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa

17 Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa If all the 10 individuals that showed this allele died or were forced to leave the population then:

18 Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa If all the 10 individuals that showed this allele died or were forced to leave the population then: Numerator is found from the Aa indiv. (30x1) = 30 a alleles

19 Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa If all the 10 individuals that showed this allele died or were forced to leave the population then: Numerator is found from the Aa indiv. (30x1) = 30 a alleles Denominator is found from the 30 Aa individuals + the 10 AA individuals (30x2 + 10x2 = 80) – total alleles.

20 Sometimes the recessive allele is bad because it makes the individuals phenotypically inferior in some way. Remembering we have 50 indiv. = 30 Aa, 10AA, and 10 aa If all the 10 individuals that showed this allele died or were forced to leave the population then: Numerator is found from the Aa indiv. (30x1) = 30 a alleles Denominator is found from the 30 Aa individuals + the 10 AA individuals (30x2 + 10x2 = 80) – total alleles. The frequency is now 30/80 = 0.375 – evolution is operating because there has been a change in allele frequencies.

21 Sickle-cell anaemia – red blood cells form a sickle shape. These abnormally shaped cells cause severe muscle pain and in extreme cases, death.

22 Cystic fibrosis – carried by 1 in 20 pakeha. The affected individual secretes abnormally thick mucus. This affects both their digestive and respiratory systems. In the lungs it provides a thick breeding ground for bacteria.


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