chapter 17 outline
chapter 17 outline BIOL 1110
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This 6 page Class Notes was uploaded by Caitrín Hall on Tuesday January 26, 2016. The Class Notes belongs to BIOL 1110 at University of Connecticut taught by Bernard Goffinet in Summer 2015. Since its upload, it has received 17 views. For similar materials see Introduction to Botany in Biology at University of Connecticut.
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Date Created: 01/26/16
Biological Evolution 17.1 Pre-Darwinian science held that species were unchanging Creationism – all species were created simultaneously in their present forms and have remained unchanged to the present; each species has ideal form Paleontology arose Geology recognized fossils – remains/impressions of old, dead plants or animals Younger rock layers contained fossils that resembled more present-day organisms George Cuvier – first scientist to recognize extinct species; “series of catastrophes” Hutton & Lyell o Uniformitarianism - rock layers result of normal geological processes over long periods of time o Revealed age of earth (4.5 billion years) important to Darwin’s theory of evolution by natural selection Evolution BEFORE Darwin LeClerc suggested that original creation produced few founder species from which modern species arose by some natural process Lamarck – organisms evolve through inheritance of acquired characteristics; giraffe neck example 17.2 During the voyage of the Beagle, Darwin made observations that revolutionized biology Studied plants, animals, fossils, and geological formations of coastal/inland areas Galápagos Islands discoveries o Plants and animals resembled those in nearby South America, but entire groups of continental organisms were absent o Different islands had different species o Tortoises differed in form on different islands influenced cacti growth o Many types of finches differed in size and shape of beaks Parrot-like, large, small, and straight beaks served different purposes “Adaptive radiation” Theory of evolution by natural selection o Artificial selection produces significant changed in domesticated species over a few generations all species vary in characteristics of their individuals selection of some individuals and elimination of others was key to evolutionary changes o All species reproduce in a manner that would overflow environment if growth went unchecked, but naturals populations remain constant because of survival of the fittest o Natural selection – differential survival and reproduction of individuals with different inheritable characteristics; nature is selective mechanism o Malthus’s Essay on the Principle of Population influenced Wallace and Darwin (concept that growth is controlled) Wallace collected plants and animals in Malaysia while Darwin studied his; also came up with theory of evolution by natural selection Both fathers of evolutionary biology o Darwin/Wallace theory of evolution by natural selection 1. Every species is capable of producing more offspring than can survive to maturity 2. The sizes of natural populations remain constant over time 3. There is competition for survival and reproduction 4. Individuals in a population vary in traits that affect their chances for survival and reproduction 5. Individuals with the most advantageous traits are more likely to survive to produce the most offspring 17.3 Many areas of science provide evidence for evolution Artificial selection demonstrates that species can be modified o Intense artificial selection of variation observed in a single species (Brassica oleracea) gave rise to broccoli, Brussels sprouts, cabbage, cauliflower, kale, and kohlrabi Comparative anatomy reveals many evolutionary relationships o Descent by modification – structure can be changed to improve fitness of individual population o Homologous organs share common origin but may differ in function o Analogous organs perform similar functions but have different origins 17.4 Evolution occurs when forces change allele frequencies in the gene pool of a population Fundamental basis for evolution = mutation Synthetic theory of evolution combines Darwinism and modern genetics; gave rise to population genetics o Examines genes and their allelic frequencies in entire populations o Gene pools and how/why they change over time o Individuals with higher frequency of more favorable combination of alleles increase in next generation o Microevolution – forces of mutation, nonrandom mating, genetic drift, migration, or natural selection (small-scale changes) in the frequency of alleles from one generation to the next; results from the accumulation over time of small-scale changes in gene pools of populations Mutation provides new variation to a gene pool o Mutation – any change in the hereditary material of an organism; must affect reproductive cells to be heritable o Occur at gene or chromosome level o Gene mutations: allele changes into another form of the same gene; involves one or few nucleotides; occur randomly due to errors in transcription OR induced by chemical reagents; beneficial, harmful, or neutral o Chromosome mutations: can involve pieces of chromosomes, single whole chromosomes, or entire sets of chromosomes; deletions/duplications Single chromosome added = aneuploidy Entire set duplicated = polyploidy Nonrandom mating alters frequency of alleles – self-fertilization In small populations, genetic drift can cause alleles to be lost o Genetic drift – removal on an allele by chance alone o Affects endangered species o Founder effect – result when a small number of seeds forms a new population or colony on an isolated area; colonizing seeds may contain fewer alleles than parental generation gene pool remains different Migration causes alleles to flow into or out of a population o Species exist as # of separate local populations over a range o Seeds and pollen f plants may move between local populations o Migrating individuals reproduce with members of local population new gene pool = gene flow between populations o Counteracts the effects of natural selection and genetic drift Natural selection – allele frequencies change such that populations become better adapted to their environment o Selective agent = environment o Directional selection – shift in dominant alleles o Stabilizing selection – loss of infrequent alleles, and dominance of average alleles increases o Disruptive selection – extreme alleles become dominant **graphs** 17.5 New plant species originate through reproductive isolation and polyploidy Allopatric speciation – geographic isolation differential evolutionary forces o Adaptive radiation – species undergoes a sudden diversification into many new species o Key to the discovery of evolution by natural selection Sympatric speciation – occurs without geographic isolation; “same homeland” o Fostered by polyploidy (more than 2 sets of chromosomes in sporophyte cell o Autopolyploidy - # chromosomes doubles because of failure of chromosomes to separate during meiosis, producing diploid gametes tetraploid individuals; sterile hybrids may become fertile and sexual o Allopolyploidy – 2 distinct species produce fertile hybrid; cannot produce fertile offspring with parental species but can breed with other similar allopolyploids; 2 species hybrid o Both require doubling of chromosome # at some point so the resulting polyploidy is fertile Chapter Wrap-up Examine and Discuss Self Test 1. Molecular data (DNA) from flowering plants has indicated that carnivorous plants with pitcher-type traps have evolved at least three times in separate lineages of flowering plants. Which of the following statements is true about the pitcher trap structure and its evolution? a. Within each of the three pitcher plant lineages, the pitcher trap structure is an homologous structure among the carnivorous species of that lineage. b. When comparing the pitcher plants of the three carnivorous plant lineages, the pitcher plant structure is an analogous structure derived by convergent evolution in the three separate lineages. c. The pitcher trap structure is an homologous structure both within and among the three different plant lineages. d. Both a and b are true. 2. Which of the following statements describe problems with the application of the morphological species concept? a. Some species are so morphologically variable that individuals within the species might be classified as separate species. b. Numerous microorganisms and plants can reproduce asexually. c. Many species may interbreed if brought together in a greenhouse or zoo but will not interbreed in nature. d. Because of convergent evolution, individuals belonging to different species may look like they belong to a single species. e. Both a and d are true. 3. In the process of allopatric speciation, geographic isolation of populations is essential because it stops ______ between populations, which would prevent gene pools from diverging. a. mutationb. genetic driftc. migrationd. natural selection 4. Which of the following situations would not likely lead to al- lopatric speciation? a. fragmentation of a large forest into many smaller forested areas b. a large lake drying down into a number of small lakes under an increasingly arid climate c. islands arising by volcanism in an ocean d. a large area of grassland slowly changing to desert 5. Among the flowering plants called petunias, Petunia integrifolia has purple, scentless flowers visited by bumblebees and P. axil- laris has white, fragrant flowers visited by hawkmoths. Inser- tion of a single allele called AN2 into P. axillaris converted the white flowers to purple and caused bumblebees to visit them while hawkmoths avoided them. In this case a change in a single allele could lead to pollinator-mediated ______ and ______ speciation. a. polyploidy, allopatricb. reproductive isolation, allopatric c. polyploidy, sympatricd. reproductive isolation, sympatric 6. Charles Darwin proposed that evolution would require thousands of generations of organisms for change to occur. Experiments with microorganisms, however, indicate that very different microbes can develop from a single strain in as little as ten days. Which statement best explains this observation? a. Microorganisms do not follow the same rules as multicellular organisms. b. The rate of mutation in microorganisms may be higher than in multicellular organisms. c. Microorganisms can trade genes by horizontal gene trans- fer and change faster than multicellular organisms. d. Microorganisms have very short generation times and hundreds of generations can pass in just 10 days. Applying Concepts 1. In 1898 an extremely powerful winter storm killed many spar- rows around Providence, Rhode Island. An ornithologist named Hermon Bumpus at Brown University collected many of the dead birds and compared several of their traits with those of birds that had survived the storm. His studies revealed a ten- dency for the dead birds to possess characters at the extremes of the character ranges, while the surviving birds possessed traits clustering closer to the norm. What type of selection had Bumpus found? Would this type of selection be the basis for evolutionary change?
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