Evolution By: Dayne Michael, Ari Argoud, Torrey Donovan, Sara Atun, and Miranda Katz

Vocab Review Scientific Theory: an explanation of natural phenomenon supported by a large body of scientific evidence obtained from many different investigations and observations Evolution: a gradual change in species (populations) through adaptations over time Natural Selection: process by which individuals that are better suited for their environment survive and reproduce most successfully (also called survival of the fittest) Speciation: a process of producing two individual species from one -member of the population no longer interbred within their natural environment

3 Types of Natural Selection Natural Selection is a mechanism for change in a population and is responsible for most evolutionary change by selectively changing genetic variation through differentiated survival and reproduction; goal is to be “fit enough” 1. Stabilizing Selection: 2. Directional Selection:

3 Types of Natural Selection Continued 3. Disruptive Selection:

Evidence for Evolution Structural Adaptations Physiological Adaptations Fossils Anatomy -a vestigial structure does not have current function but may have been useful to an ancestor Embryology Biochemistry - comparing DNA and RNA

How Do We Know What Happened When? 1. Radiometric Dating relies on half-life decay of radioactive elements to allow scientists to date rocks and materials directly 2. Statigraphy provides a sequence of events from which relative dates can be extrapolated. 3. Molecular clocks allow scientists to use the amount of genetic divergence between organisms to extrapolate backwards to estimate dates. Easy way to memorize: V= variation I=inheritance S=selection T=time

Review of Evolution of Populations Sources of genetic variation: mutations and genetic shuffling. Genetic drift: random change in allele frequency Founder effect: changes in allele frequency as a result of the migration of a small group of a population

Population Genetics 5 factors affecting gene pools 1. Non-random mating 2. Gene flow: immigration and emigration (the flow of genes entering or leaving a population) 3. Mutations 4. Genetic Drift: changes in allele frequency by chance events 5. Natural selection acting on a phenotype variation

Population Genetics Continued Changes in Genetic Equilibrium A population in genetic equilibrium is not evolving. Both alleles and phenotypes remain the same. Any factor that affects the genes in a gene pool can change allele frequencies and shift the genetic equilibrium

Patterns of Evolution A. Divergent evolution: when species that were once similar diverge (become more and more different) B. Adaptive evolution: when one species evolves into an array of different species to fit different environmental habitats C. Convergent evolution: when species that were unrelated evolve similar characteristics

Why Natural Selection Acts on the Phenotype Rather Than the Genotype of an Organism Natural selection acts on the phenotype of an organism because the organisms with the best phenotypes are the ones that survive to pass their genes on to their offspring. Then, that trait can eventually take over the entire population.

Review Questions What is Evolution? a) A change over time of a certain species b) Collected observations and evidence of a species c) Characteristics of a certain species Darwin’s theory of evolution included all of the following concepts except a)Individual organisms differ b)Some variation in organisms is heritable c)All organisms of the same species inherit the same traits Structures that have different mature forms that develop from the same embryonic tissue are called: a)Vestigial organs b)Homologous structures c)Embryonic appendages Individuals that are better suited to their environment, that is- with adaptations that enable fitness, survive and reproduce most successfully is an example of: a)Struggle for existence b)Fitness adaptation c)Survival of the fittest What is “On the Origin of Species” a)A publication by Charles Darwin b)Descent of Modification c)Tendency towards perfection

Review Questions Continued Which of the following is not evidence of evolution a)Fossil records b)Geographic distribution of living species c)The struggle for existence Which of the following is a source of genetic variation a)Mutations b)Fitness c)Talents Random change in allele frequency of a population is called a)The founder effect b)Genetic drift c)Mutations What is not a factor affecting the gene pool a)Non random mating b)Gene flow c)Relative frequency The kaibab squirrel evolved from the abert squirrel. The kaibab squirrels were isolated from the main population by the Colorado river. This is an example of: a)Behavorial isolation b)Geographic isolation c) Temporal isolation

Answers 1 - a 2 - c 3 - b 4 - c 5 - a 6 - c 7 - a 8 - b 9 - c 10 - b