Recent Species Discoveries and Microevolution in Humans

1. What do these images have in common?

2. What do these images have in common? Microbacterium hatanonis is a new species of extremophile bacteria so hardy that it lives and reproduces in cans of hairspray. A thread snake, Leptotyphlops carlae, is the smallest known snake. Here, it is coiled on an American quarter Tahina spectabilis, a rare species of palm, was discovered in Madagascar. It grows very tall, blooms spectacularly once, produces fruit, then dies. These photographs represent new species discovered and named since the year 2005.

3. App - Recent Adaptations in Humans HHMI's all slides Microevolution is when allele frequencies change from generation to generation - is evolution on the smallest scale

4. App - Sickle Cell Anemia microevolution An example of in humans is the prevalence of sickle-cell disease in Africa. Sickle-cell disease causes weakness, pain, and even death. The disease is caused by a allele; if a person has two of these recessive alleles, they sickle-cell disease. Carriers (Heterozygotes) of the sickle-cell allele have the disease, but are resistant to malaria. recessive have do not

5. changes to the gene pool Evolution = Without mutations and/or sexual reproduction, evolution does not occur. No changes to the gene pool is called the . The Hardy-Weinberg Equilibrium occurs when the frequency of alleles in a gene pool is constant over time. This equilibrium requires random mating, a large population, no movement in or out of the population, no mutations, and no natural selection. In real life, . Hardy-Weinberg Equilibrium there are always some changes to disrupt this

6. disruption Microevolution is the of the Hardy-Weinberg Equilibrium. By applying genetics and mathematics to the theory of natural selection we can determine whether a population is evolving!!!!!! Hardy-Weinberg Equilibrium Frequencies of alleles are constant Let p represent dominant allele Let q represent recessive allele Therefore p + q = 1 formula to calculate frequency of alleles In order to determine if a population is evolving or not we need a baseline, the formula to calculate frequency of genotypes (2 alleles) in a population p2 + 2pq + q2 = 1 p2 - homozygous dominant 2pq - heterozygous q2 - homozygous recessive p2 + 2pq + q2 = 1

7. HWE Example Approximately 16% of the population of mice have brown fur. The rest of the population has black fur. If we assume that the brown fur are homozygous recessive for the gene b, what is the frequency of homozygous dominants (BB) in the population? Of heterozygotes (Bb)? Let B - black fur dominant Let b - brown fur recessive We need to determine whether the question is talking about one allele or about a genotype which consists of 2 alleles. Brown fur - in order to show brown your genotype has to be bb, therefore the question is genotype bb = 0.16 = q2 frequency of the homozygous recessive square root of q = 0.4 p + q = 1 p = 1 - q = 0.6 BB = p2 = 0.36 = 36% frequency of the homozygous dominant 2 pq = 2 (0.6) (0.4) = 0.48 = 48% frequency of the heterozygotes We now have a baseline to determine if evolution occurs over a period of time! BB - 36% Bb - 48% bb - 16%

8. Microevolution is driven by natural selection, sexual selection, artificial selection, genetic drift, and gene flow. Natural selection is not random. The individuals have a reproductive advantage, so the frequency of their alleles in the gene pool is higher. S in the environment change the relative frequencies of phenotypes in a population. 1) NATURAL SELECTION fittest elective pressures App - Natural and Artificial Selection Slide 5 with videos

9. Stabilizing selection: the phenotypes are favoured Directional selection: of the phenotypes is favoured Disruptive selection: of phenotypes are favoured most frequent one extreme two or more extremes

10. Changes in the fitness of individuals changes the normal distribution of phenotypes in the population.  - Masses of human babies at birth is an example of stabilizing sel.  - Pesticide and antibiotic resistance are examples of directional selection.  - Darwin's finches is an example of disruptive selection

11. 2) Sexual Selection  - Sexual selection is not random; mates are often chosen based on their phenotype.  - Other individuals in the species screen, or select, the traits. The most common forms are and competition  - In natural selection, the environment screens the traits. female mate choice male vs. male

12. 3) Artificial Selection Examples - Artificial selection is not random.   - Breeding programs are used to produce desirable traits. (cats)  - Artificial selection can have usually in the form of genetic diseases. Eg. Horses HYPP (Hyperkalemic periodic paralysis is an inherited disease of the muscle which is caused by a genetic defect) Reducing genetic diversity making species vulnerable to evolutionary forces This registered American 
shorthair cat is the result of 
artificial selection. unintended consequences Activity C6 - Natural vs. Artificial

13. 4) Genetic Drift  Is , changing the gene pool due to chance Each new generation has a shift in the frequency of alleles based on which alleles get passed along to offspring (for example, the recessive gene may be lost in a few generations) Has a much greater effect on small populations Can have a major effect on a population   - the occurs when a population suddenly decreases, often due to a natural disaster  - this decrease variation in alleles in the population, decreasing genetic diversity  - the occurs in a new, isolated population  - this is likely what occurred with Galapagos finches random bottleneck effect reduces founder effect

14. 5) Gene Flow  Gene flow is a process.  Populations of a species are often by physical barriers, like mountains or oceans.  - In gene flow, genes are exchanged between two different populations if these barriers are overcome.  Interbreeding between populations or changes the frequency of alleles already present.  Gene flow tends to genetic differences between populations.  If extensive enough, a single population might replace the smaller ones that originally interbred. random isolated adds new alleles reduce

15. Homework 3C pg. 209 # 3~7, 12, 14, 15 pg. 223 # 7, 8, 9, 10, 12, 13 3U pg. 209 # 3~7, 12, 14, 15 pg. 223 # 6~13