Evolution Website http evolution berkeley edu Evolution is

Evolution Website: http: //evolution. berkeley. edu/

Evolution is the explanation of many facts of life FACTS: Life has change through time • Extinction is common • Species exist today that did not exist before Today’s species share many features • Similar DNA and proteins • Same genetic code SCIENTIFIC EXPLANATION: Descent with modification (theory of evolution) Independent lines of evidence to support it:

Misconceptions about Evolution Biology professor interviewed in Colbert Report Evolution is NOT in conflict with any religion Evolution, as science, looks for natural explanations to natural phenomena

Microevolution: descent with modification within a population POPULATION is a group of organisms of the same species that live in the same area PARENTS OFFSPRING What has been modified? the individual? Frequency of the phenotypes in the population has changed over time Microevolution can also be defined as the change in the proportion (frequency) of alleles over time

A population of butterflies has two alleles for color: blue alleles and green alleles. The blue allele is dominant. Under what circumstances will the frequency of the blue allele increase? Select the three statements that apply.

The Hardy-Weinberg equations can be used to estimate frequencies of the alleles, phenotypes and genotypes of a population p = proportion (frequency) of the dominant allele in the population q = proportion (frequency) of the recessive allele in the population p 2 = proportion (frequency) of homozygous dominant individuals q 2 = proportion (frequency) of homozygous recessive individuals 2 pq = proportion (frequency) of heterozygous individuals

1. In a large population of monkeys, the frequency of the recessive allele is 0. 1. There is no migration and no selection. What is the frequency of the dominant allele? Assume that there are two alleles of this gene. A. 99% B. 90% C. 10% D. 50%

2. In a certain group of African people, 4% are born with sickle-cell disease (homozygous recessive). In this case, only homozygous recessive individuals have sickle-cell disease. Heterozygous individuals not only don't have sickle-cell disease, they are resistant to malaria. What percentage of the population is heterozygous and resistant to malaria? a. 4% b. 16% c. 32% d. 80%

Applications of Hardy-Weinberg principle: For Public health scientists The Hardy-Weinberg equation is used for estimating how many people carry alleles (are heterozygous) for certain inherited diseases. For biologists: The Hardy-Weinberg equation is often used to test whether evolution is occurring in a population.

3. Is this population of moths evolving? Brown color is determined by the dominant W allele and white color is determined by the recessive w allele.

What are the causes (mechanisms) for microevolution?

Two Types of Genetic Drift Bottle neck Effect: Genetic drift resulting from a drastic reduction in population size Founder effect Bottle neck effect Founder Effect: Genetic drift due to colonization by a limited number of individuals from a parent population.

Identify the type of mechanisms for each scenario

4. Which of the following is the most predictable outcome of increased gene flow between two populations? a. lower average fitness in both populations b. higher average fitness in both populations c. increased genetic difference between the two populations d. decreased genetic difference between the two populations

Fill the following chart

Fill the following chart

5. Which of the following are causes of evolutionary change? Natural selection Genetic drift Gene flow Mutation All of the above

A population is at Hardy-weinberg equilibrium when the allele frequencies don’t change over time

Conditions that need to be met for a population to be in H-W equilibrium (i. e. not evolving)

Natural Selection: a closer look 6. Identify the four postulates of natural selection. a. Individuals in a population vary in the traits they possess. b. All individuals in a population have equal reproductive success. c. Survival and reproductive success are variable among individuals in a population. d. Individuals in a population all possess the same traits. e. Individuals with certain traits are more likely to survive and reproduce. f. Some trait differences are heritable.

Types of Natural Selection depending on which phenotype is being favored 7. In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following? a. The value of a particular characteristic; characteristics of an organism can include such traits as size and color. b. Time c. The number of individuals

8. Identify each type of natural selection

9. Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today? Disruptive selection Stabilizing selection Directional selection 10. Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers? Disruptive selection Stabilizing selection Directional selection 11. Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards? Directional selection Disruptive selection Stabilizing selection

11. Which type of selection tends to increase genetic variation? Directional selection Disruptive selection Stabilizing selection 12. True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population. True False

Misconceptions about Natural Selection: “Natural Selection gives a species what it needs” When the environment changes, a population can survive or die out, depending on the variation present before the change. Natural selection is more of an editing process than a creating process

Misconception: “Natural selection is the survival of the strongest and fastest” More important than surviving is reproducing FITTNESS: The contribution an individual makes to the next generation, relative to the contributions of other individuals. Natural selection does not act only on the traits that allow for survival of the individual but also on the traits that increase ability to find a mate and reproduce

13. Which statement describes the finch with the greatest evolutionary fitness? A. A finch that lives to be 3 years old and has four offspring, two of which survive to reproduce themselves B. A finch that lives to be 5 years old and has five offspring, one of which survives to reproduce C. A finch that lives to be 2 years old and has four offspring, all of which survive to reproduce themselves D. A finch that lives to be 7 years old and has three offspring, all of which survive to reproduce E. All are equally fit

Some traits are selected for even if they are a burden to health or survival of the individual Because they increase the fitness of the individual Sexual selection (non random mating): a process in which individuals with certain inherited characteristics are more likely than other individuals of the same sex to obtain mates. due to mate choice (in which individuals of one sex, usually the females, are choosy in selecting their mates from the other sex) or male competition direct competition among individuals of one sex for mates of the opposite sex

14. Sexual selection is most similar to? A. Disruptive selection B. Directional selection C. Genetic drift D. stabilizing selection E. Gene flow

Misconception: “Natural selection will produced perfectly engineered organisms” Natural selection is THE SURVIVAL OF THE FIT ENOUGH Reasons why there are not faster cheetah: Variation not present not possible Trade-offs

Misconception: Natural Selection should eliminate bad genes • Bad genes might not really reduce fitness Example: Huntington’s disease • Bad genes might be maintained by heterozygote advantage Example: Sickle cell disease

Artificial Selection: Humans (instead of nature) select for which individuals in the population reproduce (those with the desired phenotype)

15. Since hands allow humans to carry out many tasks essential to survival, such as obtaining food, building shelter, and using tools, you could imagine that having three hands would provide a significant fitness advantage. Which is the best explanation for why natural selection has not resulted in humans with three hands? A. Natural selection has not had enough time to produce an optimal anatomical structure for humans. B. There must be disadvantages to having a third hand that outweigh the advantages. C. Natural selection is constrained by evolutionary history, and can only act on existing variation. D. The absence of a third hand is primarily the result of environmental influences.

16. An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population happens to have broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, what effect has the ground-squirrel population experienced during the earthquake? directional selection a genetic bottleneck a founder event disruptive selection

17. The fruit fly Drosophila melanogaster has an allele that confers resistance to DDT and similar insecticides. Laboratory strains of D. melanogaster have been established from flies collected in the wild in the 1930 s (before the widespread use of insecticides) and the 1960 s (after 20 years of DDT use). Lab strains established in the 1930 s have no alleles for DDT resistance. In lab strains established in the 1960 s, the frequency of the DDT-resistance allele is 37%. Explain why each of the statements below is TRUE or FALSE. a. Some fruit flies evolved resistance to DDT in order to survive. b. The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread. c. Fruit flies became more resistant to DDT over time. d. When DDT was widely used, fruit flies with DDT resistance had greater evolutionary fitness than fruit flies lacking DDT resistance. Alleles for DDT resistance may have been present but rare prior to DDT use. f. Alleles for DDT resistance arose by mutation during the period of DDT use because of selection for pesticide resistance.