Chapter 8 Notes (WEEK 4)
Chapter 8 Notes (WEEK 4) BIOL 101
Cal State Fullerton
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This 4 page Class Notes was uploaded by Xyvil Dapal on Wednesday February 17, 2016. The Class Notes belongs to BIOL 101 at California State University - Fullerton taught by in Winter 2016. Since its upload, it has received 17 views. For similar materials see Biology in Biology at California State University - Fullerton.
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Date Created: 02/17/16
CHAPTER 8 NOTES (8.6 – 8.9, 8.11 – 8.15, 8.18 – 8.22) 8.6 MUTATION – A DIRECT CHANGE IN THE DNA OF AN INDIVIDUAL – IS THE ULTIMATE SOURCE OF ALL GENETIC VARIATION. • MUTATION: an alteration of the base-pair sequence of an individual’s DNA, and when this alteration occurs, the DNA sequence may change an allele • Only mutations that affect reproductive cells can be inherited • “mutations are random” o cannot predict which individuals will have mutations o we cannot predict whether the consequences of a mutation will be bening, harmful or useful • is the ultimate source of genetic variation in a population 8.7 GENETIC DRIFT IS A RANDOM CHANGE IN ALLELE FREQUENCIES IN A POPULATION. • GENETIC DRIFT: a random change in allele frequencies in a population • Greater in small populations that larger ones • FIXATION: in genetics, the point in which the frequency of an allele in a population is 100% and thus there is no more variation in the population for this gene • FOUNDER EFFECT: a small no. of indiv can leave a population >> become founding members of new, isolated population; founder population has different allele frequencies than the original • POPULATION BOTTLENECK EFFECT: event causes deaths of a large proportion of individuals >> reduced to a small fraction of original size 8.8 MIGRATION INTO OR OUT OF A POPULATION MAY CHANGE ALLELE FREQUENCIES. • MIGRATION (GENE FLOW): the movement of some individuals of a species from one population to another • Influenced by the mobility of the organisms and barriers, i.e mountains or rivers 8.9 WHEN THREE SIMPLE CONDITIONS ARE SATISFIED, EVOLUTION BY NATURAL SELECTION IS OCCURING. • 3 conditions necessary for natural selection: 1. MUST have variation for the trait within a population 2. Variation must be heritable 3. Individuals with one version of trait must produce more offspring than those with a different version of the trait • Variation is not limited to physical features; can vary in physiological and biochemical ways • More organisms are born than can survive • organisms are continually struggling for existence • some organisms are more likely than others to survive and reproduce • DIFFERENTIAL REPRODUCTIVE SUCCESS: from all the variation existing in a population, individuals with traits most suited to survival and reproduction in their environments generally leave more offspring than do individuals with other traits 8.11 TRAITS CAUSING SOME INDIVIDUALS TO HAVE MORE OFFPSRING THAN OTHERS BECOME MORE PREVALENT IN THE POPULATION. • “Survival of the fittest.” • Fitness = everything to do with an organism’s reproductive success • FITNESS: a measure of the relative amount of reproduction of an individual with a particular phenotype compared with the reproductive output of individuals of the same species with alternative phenotypes • ELEMENTS TO AN ORGANIM’S FITNESS: 1. Individual’s fitness is measured relative to other genotypes or phenotypes in the population 2. depends on the specific environment in which the organism lives 3. depends on organism’s reproductive success compared with other organism in the population 8.12 ORGANISMS IN A POPULATION CAN BECOME BETTER MATCHED TO THEIR ENVIRONMENT THROUGH NATURAL SELECTION. • ADAPTION: process by which organisms become better matched to environment; specific features that make organism more fit 8.13 NATURAL SELECTION DOES NOT LEAD TO PERFECT ORGANISMS. 1. Environments change faster than natural selection process 2. Mutation doesn’t produce all possible alleles 3. Not always single, optimum adaptation for a specific environment 8.14 ARTIFICIAL SELECTION IS A SPECIAL CASE OF NATURAL SELECTION. • Animal breeders and farmers CHOOSE the traits that are to be inherited 8.15 NATURAL SELECTION CAN CHANGE THE TRAITS IN A POPULATION IN SEVERAL WAYS. • DIRECTIONAL SELECTION: individuals with one extreme of the range of variation in the population have higher fitness • Increased fitness at one extreme and reduced fitness at the other • STABALIZING SELECTION: take palce when individuals with intermediate phenotypes are the most fit • DISRUPTIVE SELECTION: individuals with extreme phenotypes experience the highest fitness and those with intermediate phenotypes have the lowest; rare in nature 8.18 THE FOSSIL RECORD DOCUMENTS THE PROCESS OF NATURAL SELECTION. • FOSSIL RECORD: physical evidence of organisms that lived in the past • BIOGEOGRAPHY: patterns in the geographic distribution of living organisms • COMPARATIVE ANATOMY AND EMBRYOLOGY: growth, development, and body structures of major groups of organism • MOLECULAR BIOLOGY: examination of life at the level of individual molecules • FOSSILS: the remains of an organism, usually its hard parts such as shells, bones, teeth that have been neturally preserved; also traces of such an organism, such as footprints. • RADIOMETRIC DATING: a method of determining both the relative and the absolute ages of ages objects such as fossils by measuring both the radioactive isotopes they contain, which are known to decay at a constant rate, and their decay products • Earth is very old • Reconstruct how organisms looked a long time ago and understand how groups of organisms evolved over time 8.19 GEOGRAPHIC PATTERNS OF SPECIES DISTRIBUTIONS REFLECT SPECIES’ EVOLUTIONARY HISTORIES. • BIOGEOGRAPHY: the study of the distribution patterns of living organisms around the world • Note similarities and differences on species that live close to each other, but habitats are very different, OR live in same habitat but far from each other 8.20 COMPARATIVE ANATOMY AND EMBRYOLOGY REVEAL COMMON EVOLUTIONARY ORIGINS • HOMOLOGOUS STRUCTURES: body structures in different organisms that, although they may have been modified over time to serve different functions in different species, are derived through inheritance from a common evolutionary ancestor • VESTIGIAL STRUCTURES: a structure, once useful to organisms, but which has lost its function over evolutionary time • CONVERGENT EVOLUTION: a process of natural selection in which features of organisms not closely related come to resemble each other as a consequence of similar selective forces 8.21 MOLECULAR BIOLOGY REVEALS THAT COMMON GENETIC SEQUENCES LINK ALL LIFE FORMS. • All living organisms share the same genetic code • Degree of similarity reveals relationship with other species
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