Lesson 4 - Mechanisms of Evolution PDF

M ECH A N ISM O F EVO LUT IO N The learners shall be able to explain the mechanisms that produce change in populations from generation to generation (STEM_BIO11/12-IIIc-g-9)  Observe the two pictures and recognize the similarities and the differences between ind...

M ECH A N ISM O F EVO LUT IO N The learners shall be able to explain the mechanisms that produce change in populations from generation to generation (STEM_BIO11/12-IIIc-g-9)  Observe the two pictures and recognize the similarities and the differences between individuals or animals belonging to the same species. ✓ Process ✓ Biological population ✓ Inheritable characteristics ✓ Successive generations of the population ✓ develops in a long period of time ✓ adapt changes in the environment Aristotle Charles Darwin George-Lewis Leclerc Comte de Buffon  1809 1859 Species evolved from Species evolved an existing species from the process of through environmental natural selection forces. Traits can be which cause passed from next Charles Lyell variations within generation. the population. 1830 All changes in the environment are uniform and gradual. Jean Baptiste Alfred Russel Lamarck Wallace Jean Baptiste Charles Darwin Lamarck Theory of Acquired Characteristics Holds that organisms experiencing such a modification can transmit such a character to its offspring Jean Baptiste Lamarck  Theory of Use and Disuse Parts of the organism that is regularly use will undergo hypertrophy and will be developed. Jean Baptiste Lamarck  Theory of Need Changes in the environment can arise to NEW NEEDS, required for species’ survival Jean Baptiste Lamarck Survival of the Fittest Organisms adapt to their environment and survive Charles Darwin Descent with Modification Species has descended and change over time Charles Darwin Theory of Evolution by Natural Selection VS Inherited Changes characteristics Mechanism of Evolution Natural Selection: process through which populations of living organisms adapt and change Theory of Evolution by Artificial Selection Wild Mustard Plant Mechanism of Evolution Artificial Selection: identification of desirable traits by humans to perpetuate it to future generation Gene Flow - introduction of genetic material, by interbreeding from one population of another species to another Genetic Drift -change in allele frequency due to a chance event - the frequency of a trait changes by chance randomly Mutation -genes are damaged or changed that alter DNA sequence Ha rdyWei nber gPr inc ipl e Ha rdyWei nber gPr inc ipl e states that in an infinitely large, interbreeding population in which mating is random and in which there is no selection, migration, or mutation, gene and genotype frequencies will remain constant from generation to generation  a population’s allele and genotype frequencies are constant unless there is some evolutionary force acting upon them Wilhelm Weinberg Godfrey Hardy Ha rdyWei nber gPr inc ipl e The Hardy-Weinberg principle states that a population’s allele and genotype frequencies will remain constant in the absence of evolutionary mechanisms. 1.no mutations 2.no immigration/emigration 3.no natural selection 4.no sexual selection 5.a large population p 2 + 2pq + q 2 =1 p+q=1 p = frequency of the dominant allele in the population q = frequency of the recessive allele in the population 2 p = percentage of homozygous dominant individuals 2 q = percentage of homozygous recessive individuals 2pq = percentage of heterozygous individuals Sample Problem Set Example 1. View the Dragons below. The winged trait is dominant. 7 of 21 are aa =q2 =.33 q =.58 p =.42 2 p =.18 2pq =.49--> number of heterozygotes The frequency of two alleles in a gene pool is 0.19 (A) and 0.81(a). Assume that the population is in Hardy Weinberg equilibrium. a. Calculate the percentage of heterozygous individuals in the population b. Calculate the percentage of homozygous recessives in the population. Answer: (a) Calculate the percentage of heterozygous individuals in the population. 2pq = (2)(0.19)(0.81) = 0.3078 30.8% (b) Calculate the percentage of homozygous recessives in the population. q2 = (0.81)2 = 0.6561 65.6% Sixteen percent of a population is unable to taste the chemical PTC. These non-tasters are recessive for the tasting gene. 1. What percentage of the individuals in the population are tasters? 2. What is the frequency of the dominant and recessive allele? 3. What percentage of the population are heterozygous for the trait? Answer: q2 = 0.16 q = 0.4, therefore p = to 0.6 1. 84% 2. 0.6 frequency of the dominant and 0.4 frequency of recessive allele 3. 2pq 4. 2 (0.6)(0.4) = 0.48 frequency of heterozygous allele or 48% 2. You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following: A. The frequency of the "aa" genotype. B. The frequency of the "a" allele. C. The frequency of the "A" allele. D. The frequencies of the genotypes "AA" and "Aa." E. The frequencies of the two possible phenotypes if "A" is completely dominant over "a." Answer: A. The frequency of the "aa" genotype. (0.36) B. The frequency of the "a" allele. (0.6) C. The frequency of the "A" allele. (0.4) D. The frequencies of the genotypes "AA" and "Aa." (0.16 and 0.48) E. The frequencies of the two possible phenotypes if "A" is completely dominant over "a." (0.36 will show recessive trait, 0.64 will show the dominant trait)