bi9 - Evolution Evolution and Darwin Evolution Evolution...

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Unformatted text preview: Evolution Evolution and Darwin Evolution Evolution • The processes that have transformed life on processes earth from it’s earliest forms to the vast earliest diversity that characterizes it today. diversity • A change in the genes!!!!!!!! change genes!!!!!!!! Old Theories of Evolution Old • Jean Baptiste Lamarck (early 1800’s) proposed: “The inheritance of acquired characteristics” • He proposed that by using or not using its body parts, an individual tends to develop certain develop characteristics, which it passes on to its characteristics passes offspring. offspring “The Inheritance of Acquired The Characteristics” Characteristics” • Example: A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring. Charles Darwin Charles • Influenced by Charles Lyell who published “Principles of Geology”. “Principles • This publication led Darwin to realize that Darwin natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times. Charles Darwin Charles • Darwin set sail on the H.M.S. Beagle (1831-1836) H.M.S. to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and and animals. • On the Galapagos Islands, Darwin observed species that lived no where else in the world. • These observations led Darwin to write a book. Charles Darwin Charles • Wrote in 1859: “On the Origin of Species “On by Means of Natural Selection” by • Two main points: 1. Species were not created in their present Species form, but evolved from ancestral species. form, 2. Proposed a mechanism for evolution: NATURAL SELECTION NATURAL Natural Selection Natural • Individuals with favorable traits are more favorable traits likely to leave more offspring better suited for their environment. environment • Also known as “Differential Reproduction” “Differential • Example: English peppered moth (Biston betularia) - light and dark phases Darwin’s 5 points 1. Population has variations. 2. Some variations are favorable. 3. More offspring are produced than survive 4. Those that survive have favorable traits. 5. A population will change over time. Artificial Selection Artificial • The selective breeding of domesticated selective plants and animals by man. • Question: What’s the ancestor of the domesticated dog? • Answer: WOLF WOLF Evidence of Evolution Evidence 1. Biogeography: Geographical distribution of species. 2. Fossil Record: Fossils and the order in which they appear Fossils in layers of sedimentary rock (strongest evidence). evidence). Eastern Long Necked Turtle Evidence of Evolution Evidence 3. Taxonomy: Classification of life forms. 4. Homologous structures: Structures that are similar because of Structures common ancestry (comparative anatomy) (comparative Evidence of Evolution Evidence 5. Comparative embryology: Study of structures that appear during Study embryonic development. embryonic 6. Molecular biology: DNA and proteins (amino acids) Population Genetics Population • The science of genetic change in science genetic population. • Remember: Hardy-Weinberg equation. Population Population • A localized group of individuals belonging individuals to the same species. same Species Species • A group of populations whose individuals populations individuals have the potential to interbreed and produce interbreed viable offspring. viable Gene Pool Gene • The total collection of genes in a collection population at any one time. Hardy-Weinberg Principle Hardy-Weinberg • The concept that the shuffling of genes that concept shuffling occur during sexual reproduction, by itself, cannot change the overall genetic makeup cannot of a population. Hardy-Weinberg Principle Hardy-Weinberg • This principle will be maintained in nature principle only if all five of the following conditions are five met: 1. 2. 3. 4. 5. Very large population Isolation from other populations No net mutations Random mating No natural selection Hardy-Weinberg Principle Hardy-Weinberg • Remember: If these conditions are met, the population is at equilibrium. equilibrium • This means “No Change” or “No Evolution”. Evolution”. Macroevolution Macroevolution • The origin of taxonomic groups higher than the species level. than Microevolution Microevolution • A change in a population’s gene pool population’s over a secession of generations. • Evolutionary changes in species over relatively brief periods of geological time. geological Five Mechanisms of Microevolution Five 1. Genetic drift: Change in the gene pool of a small Change population due to chance. population • Two examples: a. Bottleneck effect b. Founder effect a. Bottleneck Effect a. • Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces disaster population size. population • Examples: 1. Earthquakes 2. Volcano’s b. Founder Effect b. • Genetic drift resulting from the colonization colonization of a new location by a small number of individuals. • Results in random change of the gene pool. random • Example: 1. Islands (first Darwin finch) Five Mechanisms of Microevolution Five 2. Gene Flow: The gain or loss of alleles from a gain population by the movement of individuals movement or gametes. • Immigration or emigration. Five Mechanisms of Microevolution Five 3. Mutation: Change in an organism’s DNA that creates a new allele. 4. Non-random mating: The selection of mates other than by chance. 5. Natural selection: Differential reproduction. Modes of Action Modes • Natural selection has three modes of action: three 1. Stabilizing selection 2. Directional selection 3. Diversifying selection Number of Individuals Small Large Size of individuals 1. Stabilizing Selection 1. • Acts upon extremes and favors the extremes favors intermediate. intermediate Number of Individuals Small Large Size of individuals 2. Directional Selection 2. • Favors variants of one extreme. one Number of Individuals Small Large Size of individuals 3. Diversifying Selection 3. • Favors variants of opposite extremes. opposite Number of Individuals Small Large Size of individuals Speciation Speciation • The evolution of new species. evolution Reproductive Barriers Reproductive • Any mechanism that impedes two species mechanism impedes from producing fertile and/or viable hybrid offspring. offspring • Two barriers: 1. Pre-zygotic barriers 2. Post-zygotic barriers 1. Pre-zygotic Barriers 1. a. Temporal isolation: Breeding occurs at different times for different species. b. Habitat isolation: Species breed in different habitats. c. Behavioral isolation: Little or no sexual attraction between species. 1. Pre-zygotic Barriers 1. d. Mechanical isolation: Structural differences prevent gamete exchange. e. Gametic isolation: Gametes die before uniting with gametes of other species, or gametes fail to unite. 2. Post-zygotic Barriers 2. a. Hybrid inviability: Hybrid zygotes fail to develop or fail to reach sexual maturity. b. Hybrid sterility: Hybrid fails to produce functional gametes. c. Hybrid breakdown: Offspring of hybrids are weak or infertile. Allopatric Speciation Allopatric • Induced when the ancestral population ancestral becomes separated by a geographical separated barrier. barrier. • Example: Grand Canyon and ground squirrels Adaptive Radiation Adaptive • Emergence of numerous species from a common ancestor introduced to new and common diverse environments. • Example: Darwin’s Finches Sympatric Speciation Sympatric • Result of a radical change in the genome that produces a reproductively isolated subreproductively population within the parent population (rare). • Example: Plant evolution - polyploid A species doubles it’s chromosome # to chromosome become tetraploid. Parent population reproductive sub-population Interpretations of Speciation Interpretations • Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime. 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change. Convergent Evolution Convergent • Species from different evolutionary branches evolutionary may come to resemble one another if they live in very similar environments. very • Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert) Coevolution Coevolution • Evolutionary change, in which one species act as a selective force on a second selective second species, inducing adaptations that in turn act as selective force on the first species. first • Example: 1. Acacia ants and acacia trees 2. Humming birds and plants with flowers Humming with long tubes with ...
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This note was uploaded on 02/07/2011 for the course BSC 2010 taught by Professor Bowes during the Spring '08 term at University of Florida.

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