BIOL 120 Week 7 Notes
BIOL 120 Week 7 Notes BIOL120
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This 5 page Class Notes was uploaded by Julia Delaluz on Sunday April 3, 2016. The Class Notes belongs to BIOL120 at Towson University taught by Dr.Partain in Winter 2016. Since its upload, it has received 6 views. For similar materials see Principals of biology in Biology at Towson University.
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Date Created: 04/03/16
Julia Delaluz BIOL 120 Week 7 Notes 3/28-4/1 Developing the Hypothesis of Common Descent Darwin/s records and drawings, along with samples he collected supported the hypothesis of common descent- that all modern organisms are descent from a single common ancestor Darwin took 20 years to gather strong documentary support, finally publishing On the Origin of Species in 1859 o Main point is hypothesis proposing how species come about- the process of evolution through natural selection (also proposed by Alfred Russell Wallace in 1858will not be tested on) o Also presents evidence in support of the common descent theory Evolution Based on observations Variation within a species Characteristics are inherited Many offspring born, not all live to reproduce Some offspring have characteristics that give them good survival chance TIME Observation #1: o Individuals within populations vary: o Differences in appearance- colors of wolves o Differences in production of chemicals Amount of caffeine in coffee seeds Observation #2: o Some variation among individuals can be passed on to their offspring (heritability): o Offspring tend to have the same or similar characters as their parents o Pigeons with fan-shaped tails have offspring with fan-shaped tails Observation #3: o Populations of organisms produce more offspring than will survive: o The capacity to reproduce far outstrips the resources of the environment If all of the offspring of one breeding pair of elephants live, there will be over 15 million elephants in the group after 500 years Observation #4: o Survival and Reproduction are not Random: subset of individuals that survive long enough to reproduce is not an arbitrary group Julia Delaluz BIOL 120 Week 7 Notes 3/28-4/1 some variants in a population have a higher likelihood of survival and reproduction than other variants do the relative survival and reproduction of one variant compared to others in the same population is its fitness traits that increase an individuals fitness in a particular environment are called adaptations individuals with high fitness have more characteristics that are appropriate for that particular environment o ‘Survival of the Fittest’ Natural selection results in the survival of individuals who are best for the current environment given the current variants in the population This is all relative (to the climate, the environment) Darwin’s Inference Natural Selection Causes evolution o Natural selection ‘selects for’ adaptive characteristics o Individuals with high fitness reproduce more often o Those adaptive alleles are passed on more often MicroEvolution Small changes, still same species, occurs over a long time Change in allele frequencies of a population over time Individuals don’t change- populations do Gene Pool: all of the alleles in a population Populations evolve due to… o Diversity, environment o Diversity arises from… Meiosis: crossing over, independent assortment Sexual reproduction, mutations Mate selection (nonrandom mating) Migration (gene flow) Fitness: having alleles suited to an environment Unequal reproductive success o The more fit, the more reproduction Production of New Alleles- 3 gene mutation types: Beneficial- bestows an advantage, confers fitness. Neutral. And Harmful- typically results in death Sexual Selection Julia Delaluz BIOL 120 Week 7 Notes 3/28-4/1 Through nonrandom mating, the alleles for preferred traits prevail over the generations Sexual dimorphism is particularly striking among mammals and birds Often, females are the agents of selection Gene Flow- Migration Gene flow: a physical flow of alleles between populations, tends to counter genetic difference that we expect to arise through mutations and natural selection Emigration (move out) Immigration (move in) It helps keep separated populations genetically similar Genetic Drift Chance of alteration of allele frequency in a population Bottleneck Effect: disease kills off members Founder Effect: small part of the population moves to a new area and they bring only a portion of the gene pool. Can give rise to dangerous disorders Natural Selection Results from Current Environmental Conditions…Results: Directional o Traits move in a particular direction Ex: towards larger beak sizes in birds Stabilizing o Extremes are selected against and the traits of the population remain the same because the average condition is the most fit Birth weight of babies Disruptive (or Diversifying) o Average condition is least fit, extremes are preferred o Increases the diversity- tow or more variants are fit HIVV particles, better to evade the immune system Hardy-Weinberg Equilibrium States that there will be no change in allele frequencies if: o He population is large o Mating is totally random o No immigration or emigration o No mutations, no natural selection Artificial VS. Natural Selection Julia Delaluz BIOL 120 Week 7 Notes 3/28-4/1 Artificial: o Humans act as environment o Seen in animals (dogs) o Seen in plants (crops) Natural: o Depends on environment o Fitness o Unequal reproductive success MacroEvolution Large changes, new species, occurs over a super duper long time Species: a group of individuals that, in nature, can interbreed and produce fertile offspring by cannot reproduce with members of other species o A single species makes up an impermeable container for its gene pool 3 Conditions for Speciation (macroevolution) 1) Separation of population into 2 groups 2) Environmentally different in the 2 areas causing genetic divergence 3) Development of mechanisms for reproductive isolation Isolation of populations leads to divergence of traits; migration leads to speciation Physical separation leads to Speciation Reproductive Isolation: Are viable fertile offspring produced? Temporal Isolation: o Different breeding seasons o No mating Behavioral Isolation: o No mate attraction due to behavioral differences o No mating Ecological Isolation: o Different microclimates o No mating (Difference in the timing of reproduction can lead to speciation) Mechanical Isolation: o Physical incompatibility of reproductive structures o Attempted mating Julia Delaluz BIOL 120 Week 7 Notes 3/28-4/1 Gamete Isolation: o Mating o No fertilization o Games don’t fuse- sperm does not penetrate egg Hybrid Inviability: o Mating o Fertilization o Hybrid doesn’t survive long after conception Hybrid Infertility: o Mating o Fertilization o Hybrid offspring survives o Hybrid is sterile Does Evolution Occur Gradually? Gradualism: slowly and smoothly over time (ramp) OR Punctuated Equilibrium: long static periods then quickly (staircase) HUMAN RACES ARE NOT BIOLOGICAL GROUPS No race-specific alleles have been identified Populations classified in the same race do not have similar allele frequencies Populations within “races” are not necessarily more similar to each other than they are to populations of different races…we are all the same Human races have never been truly isolated
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