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General Biology 2 Notes Week 2

by: Christina Hancock

General Biology 2 Notes Week 2 EBIO 1220

Marketplace > University of Colorado at Boulder > Science > EBIO 1220 > General Biology 2 Notes Week 2
Christina Hancock

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These notes cover General Biology 2 Chapters 21, 22, and 23.
General Biology 2
Dr. Carol Kearns
Class Notes
General Biology 2
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This 8 page Class Notes was uploaded by Christina Hancock on Friday January 22, 2016. The Class Notes belongs to EBIO 1220 at University of Colorado at Boulder taught by Dr. Carol Kearns in Winter 2016. Since its upload, it has received 20 views. For similar materials see General Biology 2 in Science at University of Colorado at Boulder.


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Date Created: 01/22/16
Thursday, January 21, 2016 Gen. Biology Notes Week 2 Evolutionary Forces Chapter 21 Microevolution- is a change in allele frequencies in a population over generations Macroevolution- refers to the origin of new groups of organisms, the appearance of major new features in organisms, and the changes in diversity associated with mass extinctions. Microevolution Population- Group of individual species living in the same place at the same time. In population genetics, we consider… Evolution = a change in allele frequencies in a population over time Changes in allel frequencies in a population indicates evolution. Natural Selection is a main force in evolution. Yet other forces can also result in evolution Forces that can change alley frequencies in population: • Mutations • Genetic Drift • Migration or Gene Flow • Non-random mating • Natural Selection ——————————————————————————————————————— 5 Conditions for Non-evolving Populations are Rarely met in Nature: No Mutations Extremely large population size 1 Thursday, January 21, 2016 Random Mating No Natural Selection No gene flow Natural populations can evolve at some loci, while being stable at other gene loci. Forces that can change allele frequencies in populations: • Mutations • Genetic Drift • Migrations or Gene Flow • Non-random mating • Natural Selection Mutation Mutations are changes in nucleotide sequence of DNA • Mutations cause new genes and elves to arise • Only mutations in cells the produce gametes can be passed to offspring MUTATION = the raw material for evolutions - Neutral Mutations, Beneficial, and Detrimental Mutations Rate: • Low on a per-gene basis, but organisms have many genes Mutation rates are variable: • Among individuals • Among species Variation among genes • Genetic Drift Genetic Drift is unpredictable fluctuations in allele frequencies in small populations, due to chance. - Does not lead to adaptions 2 Thursday, January 21, 2016 - Leads to fixation of allele - Important in small populations - Related to the found effect Fixation: only ONE allele remains in the populations. All other are gone. SO the trait is FIXED in that there is only one option. Founder Effect: Occurs when a small group of individuals establishes a new population. Some characteristics may be present at a higher frequency. Ex. Abnormally high incidence of asthma in Hutterite population. The Hutterites are a religious community in the located in the Dakotas and Canada. Originally, a small group of Hutterites migrated from Europe. Only marriage within the religion was acceptable. Bottlenecking: As a result of genetic drift: • Populations lose alleles • Populations lose genetic diversity • Separate populations divert from each other • Genes can become “fixed” 3 Thursday, January 21, 2016 Migration or Gene Flow Migration is movement of alleles between populations. What are the mechanisms for gene flow? - Movement of pollen, movement of individuals, movement go gametes. - Migrations introduces new alleles and changes the frequencies of alleles present - If two populations have different selective forces an they gene pool mix through migration, we can expect a change in allele frequencies. - Gene Flow makes populations more similar - Gene Flow affect local adaptions by messing up adaptations Non-Random Mating • Inbreeding - close relative mate with each other Disadvantages: Reduced genetic variation, Higher chance for mutation Consequences: Expression of deleterious recessive alleles, Loss of Heterozygous advantage Endangered species usually exist in small populations. Genetic drift can fix bad genes. Inbreeding can reduce survival and fitness resulting in smaller populations. Result: an extinction vortex Advantages: Preserve fit genotype, Reproductive Assurance • Outbreeding - Outbreeding Depression: When plants or animals try and mate with another plant or animal so far way that the environment is so different the mating an survival does not work. • Sexual Selection for a Particular Type - Sexual Selection is natural selection for mating success It can result in sexual dimorphism, marked differences between the sexes ins secondary sexual characteristics Sometimes sexual selection seems to contradict survival of the fittest. (ex.Peacock) Male to Male competition- Males compete for the opportunity to mate with females. 4 Thursday, January 21, 2016 Female Choice- Female lions prefer to mate with male lions with dark manes • Positive Assortative Mating - Like individuals mate with like individuals Ex. Little people mate with little people. • Negative Assortative Mating - Opposite attracts. Individuals mate with unlike individuals. Ex. Some species of flowers, and Mice. • Natural Selection - Naturals selection is the only one of these forces that can produce adaptation. What is adaptation? The way the organisms change to fit their current environment. Three modes of selection : Directional Selection: Favors individuals at one end of the phenotype range Disruptive Selection: Favors individuals at both extremes of the phenotypic range Stabilizing Selection: Favors intermediate variants and acts against extreme phenotypes. Naturals Selection is the explanation of ALL adaptions The rate of Naturals Selection can vary: Rate Depends on: - The generation time of the organism - The frequency of the allele in the population - The selection coefficient associated with the allele ——————————————————————————————————————— Species and Speciation Chapter 22 What is a Species? There are many different types of species and different ways to define them. Modern definitions of species attempt to incorporate evolutionary history. 5 Thursday, January 21, 2016 • Biological Species Concept: Emphasizes reproductive isolation. Reproductive Isolation: - Biologists categorize the mechanisms that stop gene flow between populations as being either pre zygotic or post-zygotic - Pre zygotic Isolation: Occurs when individuals of different species are prevented from mating. - Post Zygotic Isolation: Occurs when individuals from different populations do mate, but they hybrid offspring produced have low fitness and do not survive or produce offspring. Ex. Mule. • Morphospecies Concept: Emphasizes morphological differences. (ex. fossils) - Biologists identify evolutionary independent lineages by differences in size, shape, or other morphological features. - This concept is based on the idea that distinguishing features are most likely to arise if populations are independent and isolated from gene flow. • Ecological Species Concept: Looks at how species differing their interactions with the environment. • Phylogenetic Species Concept: is based on reconstructing the evolutionary history of populations. This concept can be applies to any population. What helps to maintain species? - Song/vocalizations - Behaviors - Color Patterns - Breeding Season Timing - Mechanical or chemical differences - Hybrids are not fit ——————————————————————————————————————— Macroevolution Chapter 23 — Long Term impacts of mass extinctions — Origin of entire new groups of organisms — Major new features or processes 6 Thursday, January 21, 2016 — Changes in diversity due to mass extinctions — Patterns of evolution on a large time scale Fossils : Fossil Record documents the history of life. Limitations of Fossil Record: - Habitat bias: (Certain places fossilize better) - Taxonomic bias: (Certain types of organisms are more likely to be fossilized) - Temporal bias: - Abundance bias: (Rare species, chances of them becoming fossilized is low) Fossil record is divided into four eras: Precambrian: From the formation of earth through the appearance of multicellular soft- bodied organisms. Paleozoic: The diversification of animals, plants, and fungi. Mesozoic: “Age of reptiles” (Dinosaurs) Cenozoic: “Age of Mammals” (Current Era) ** Each era ended with a major extinction** Macroevolution: - Large scale changes in the composition of organisms on earth Mechanisms for Macroevolution: Continental Drift: Earths continents move slowly over the underlying hot mantle through this process. Oceanic and continental plates can collide and serape, or slide past each other. Interactions between plates cause the formation of mountains and island, and earthquakes. • A reduction in shallow water habitats • A colder and drier climate inland • Changes in climate as continents moved towards and away from the poles • Changes in ocean circulation patterns leading to global cooling 7 Thursday, January 21, 2016 Homeotic Gene duplication/ Mutation: HOX genes determine such basic features as where wings and legs will develop on a bird or insect. Duplication of these regulatory genes allows more complexity in animal form. Mutation obviously mutates this process. Heterochrony: Is an evolutionary change in the rate or timing of developmental events. It can have significant impact on body shape. The contrasting shapes of human and chimp skulls are the results of small changes in relative growth rates. Mass Extinctions: In each of the five mass extinction events, more than 50% of Earths species became extinct. “The Big Five” Mass Extinctions are obviously examples. (ex. dinosaurs) Adaptive Radiation: The rapid formation of many species from a single ancestral species. An example of this would be when plants developed a waxy cuticle, they could live on land or the formation of the exoskeleton. Both of these processes opened many new opportunities for rapid speciation. New Designs for living: (Such as endosymbiosis- the evolutionary theory that explains the origin of eukaryotic cells form prokaryotes.) Exaptation: a structure that evolved in one context takes on new role. In other words; structures the have formed to fit one purpose, or context can evolve to take on different functions. 8


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