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WHAT IS EVOLUTION? HISTORICAL DEVELOPMENT OF EVOLUTION General definition: a change or modification through time (e.g., galaxies and language evolves) I. Classical Thinking biological or organic evolution: change in the properties of organisms that transcend the lifetime of a single individual Greeks thought that the world changes, but by Plato’s time the idea of a static world came into prominence : in biology, more specifically, changes that are heritable : changes in allele frequency A. Static World by Plato (427 to 347 BC) -there is the “essence” or “form” that doesn’t change, and things on earth are a reflection of this -so things on earth can show variation, but the form never changes. B. Purpose in Life: Natural Order "Will of God" Scala Naturae or “the ladder of life” HISTORICAL DEVELOPMENT OF EVOLUTION II. Pre-Darwinian Thinking A. (1500-1700) No purpose in physical world: Newton and Copernicus B. Geologist: Earth is old!! James Hutton (1788): uniformitarianism Charles Lyell (1830) Based on rocks, earth is billions of years old (about 4.6), not 5668, according to Archbishop James Usher, who used lineages in the Old Testament to estimate this. C. Jean Baptiste de Lamarck (1744-1829): evolve to be better by design of God (in his book Philosophie Zoologie, 1809); use and disuse of traits, then passed on to the next generation HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm 1. Homology: the study of likeness a) ontogeny: development of embryo to adult HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm 1. Homology b) Structural: HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm 2. Change Through Time: a) fossil record: old things resembled new and transitional animals so why similar? Creator or because of common descent HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm 2. Change Through Time: 2. Change Through Time: c) extinction in fossil records b) vestigial parts: parts that are now useless were once useful -creationist: extinct due to flooding -biologist: extinct species are relatives of extant species other examples: whale femur, human appendix HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: B. Darwin 2. Change Through Time: Charles Darwin: 1809-1882 1831-1836 joined the crew of the HMS Beagle to travel around the world as the ship's naturalist. d) marine fossils in arid areas: earth itself is dynamic! (grand canyon, see figure) 1844: he wrote an essay on Natural Selection coral fossil in AnzaBorrego State Park (desert in CA) 3. Age of the earth: Geology – earth is old (4.6 by) 1858: another biologist, Alfred Wallace (1823-1913), sent Darwin a manuscript outlining natural selection, identical to his! So at the urging of his colleagues, Darwin presented his work, along with Wallace's, at a meeting of the Linean Soceity of London in 1858. In 1858, he published his seminal “abstract” -- On the Origin of Species. Evolution was really accepted, but the mechanisms is what was controversial (and the idea of no design!) HISTORICAL DEVELOPMENT OF EVOLUTION C. Natural Selection a. Darwin proposed 4 steps, how Natural Selection drives evolution: 1. 2. 3. 4. individuals need to be variable traits that are variable are heritable -- passed on to next generation excess offspring is produced differential production or survival – linked to specific traits (see 2) HISTORICAL DEVELOPMENT OF EVOLUTION IV. Neo-Darwinian How are traits passed on? A.Lamarckism B. Mendelian Genetics: Gregor Mendel, in 1854 carried out breeding experiments in a monastery using the garden pea Pisum sativum In 1865 he reported his results, but his results were not widely read until the 1900's HISTORICAL DEVELOPMENT OF EVOLUTION IV. Neo-Darwinian How are traits passed on? B. Mendelian Genetics Experiment: smooth x wrinkled seeds. The f1: all smooth The f2: 3/4 smooth and 1/4 wrinkled. NATURAL SELECTION V. Example of Evolution by Natural Selection A. Observations: Galapagos Finches by Grants and colleagues - Galapagos Archipelago, dramatic differences among finch “species”’’ Is this evolution in action? One of Mendel’s basic outcomes: inheritance of genes is discrete, no mixing 2. Traits that are variable are heritable 1. Individuals need to be variable - Medium ground finch (Geospiza fortis) on Isla Daphne Major 3. Excess offspring is produced 4. Differential reproduction or survival V. Example of Evolution by NS A. Observations: Galapagos Finches by Grants and colleagues Remember, NS works: 3. Excess offspring is produced 4. Differential reproduction or survival – linked to specific characters V. Example of Evolution by NS A. Observations: Galapagos Finches by Grants and colleagues Remember, NS works: 3. Excess offspring is produced 4. Differential reproduction or survival – linked to specific characters V. Example of Evolution by NS A. Observations: Galapagos Finches by Grants and colleagues Are populations evolving?? V. Example of Evolution by NS V. Example of Evolution by NS B. Type of Natural Selection B. Type of Natural Selection 2. STABILIZING SELECTION 1. DIRECTIONAL SELECTION w = fitness (how well an animal does) w e.g., larger trait results in higher fitness w trait trait w = frequency of animal with specific trait f f trait trait V. Example of Evolution by NS V. Example of Evolution by NS B. Type of Natural Selection B. Type of Natural Selection 2. STABILIZING SELECTION: EXAMPLE 3. DISRUPTIVE SELECTION BIRTH WEIGHT IN HUMANS w By Karn and Penrose trait •13,730 birth records at University College Hospital between 1935-1946 •7037 males and 6693 females •Survivorship (to 28 days), weight, gestation time and mother •Stabilizing Selection for birth weight •Stabilizing Selection for gestation time and age of mother (not shown) MORE RECENT SURVEY IN ITALY (1954-1985) FOUND A 4-FOLD DECREASE IN INTENSITY OF SELECTION f trait V. Example of Evolution by NS Beak Size in Seedeater Finches, Pyerenestes ostrinus B. Type of Natural Selection 3. DISRUPTIVE SELECTION Two forms: large and small billed Feed on two species of sedge: hard and soft shelled (10 fold difference in hardness) Consumption of seeds (handling time) related to bill morphology Two rainy seasons, split by dry season – survival across dry season is low By T. B. Smith VI. Forces that Drive Evolution A. Natural Selection B. Genetic Drift: changes in gene frequencies occur because of chance events (sampling errors) that occur when populations are finite in size (small). Population could be small due to founder event or bottle neck •Banded and measured > 2500 birds •Found (in general) 20% survival across seasons •Bill morphology heritable – discrete and dominant raised in zoo s x s = all small l x l = 3:1 large to small s x l = 1:1 VI. Forces that Drive Evolution VI. Forces that Drive Evolution A. Natural Selection A. Natural Selection B. Genetic Drift B. Genetic Drift e.g., Clegg and colleagues work C. Mutation on Silvereyes (Zosterops lateralis) -populations have colonized islands off Australia -founder populations lose alleles D. Gene Flow VII. SOURCES OF GENETIC VARIATION A. MUTATION VII. SOURCES OF GENETIC VARIATIONa) POINT MUTATION “TRUE” SOURCE OF VARIATION b) DELETION: REMOVAL OF 1 OR MORE NUCLEOTIDES IN A DNA SEQUENCE MISTAKES DURING REPLICATION OF DNA RESULTS IN MUTATIONS THAT ARE HERITABLE 1. TYPES OF MUTATIONS a) Point Mutation: Substitution of single base pair c) INSERTION: ADDITION OF ONE OR MORE NUCLEOTIDES IN A DNA SEQUENCE VII. SOURCES OF GENETIC VARIATION VII. SOURCES OF GENETIC VARIATION MECHANISMS OF DELETION AND INSERTION 1. unequal crossing over during recombination 2. transposition: jumping of genetic material from one position to another chromosome (transposable elements) MECHANISMS OF DELETION AND INSERTION 1) unequal crossing over during recombination 2) transposition 3) slippage VII. SOURCES OF GENETIC VARIATION VII. SOURCES OF GENETIC VARIATION d) INVERSION: 180 DEGREE ROTATION OF DNA A. MUTATION B. RECOMBINATION -DURING METAPHASE, HOMOLOGOUS CHROMOSOMES EXCHANGE C. GENE FLOW e) POLYPLOIDY: INHERITING EXTRA COPIES OF CHROMOSOMES -COMMON IN PLANTS Copyright © 2002 Pearson Education, Inc. VIII. Sexual Selection Peahen and chick drab and cryptic VIII. Sexual Selection Peacock elaborate A. Causes of Sex Differences 1. Anisogamy: DIFFERENTIAL INVESTMENT IN GAMETES Male Birds: Female Birds: Fairywren: 8 billion sperms at one time One egg = 15-20% of body weight In Kiwi, it’s 25%, 1 lbs SALMON: FEMALES LAY 3500 EGGS DURING SPAWNING, MALES FERTLIZE THEM WITH 400,000,000,000 SPERM! Peacocks highly conspicuous and vulnerable to predators Why does this evolve? Sexual Selection: Differential Reproduction Related to Elaborate Male Display Traits HUMANS: FEMALES PRODUCE ONE VIABLE EGG PER MONTH MALES CAN FERTILIZE THE ENTIRE WORLD WITH 1 EJACULATION VIII. Sexual Selection VIII. Sexual Selection A. Causes of Sex Differences B. Effects of Sex Differences 1. Reproductive Potential – Bateman’s Rule 1. Anisogamy: DIFFERENTIAL INVESTMENT IN GAMETES 2. Parental Investment (post gametes) e.g., mammals: females nourish and carry embryo, nurse offspring vs. males fertilize eggs and leave males 9 reproductive success -females typically invest more than males females 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 0 0 0 2 4 6 8 10 0 2 4 6 8 number of mates -males increase their mating success with more females -females do not necessarily increase their mating success with more males VIII. Sexual Selection VIII. Sexual Selection C. Test Differential Parental Investment Dictates Which Sex is Choosy B. Effects of Sex Differences 2. Operational Sex Ratio (by Emlen and Oring) The ratio of available males to available females NOT just the ratio of males to females -note: if a female is mated, she is no longer available for mating while males after being mated are still available for mating -as season progresses, skew towards more males than available females FEMALES ARE CHOOSY SEX BECAUSE OF THESE TWO FACTORS! 1. Mormon Cricket Observations By D. Gwynne MALES PRODUCE SPERMATOPHORES: NUTRIENT RICH PRODUCTS SPERMATOPHORE IS UP TO 25% OF MALES WEIGHT! IN AREAS WHERE FOOD IS SCARCE AND OSR IS FEMALE BIASED, MALES ARE THE CHOOSY SEX 10 VIII. Sexual Selection Differential Parental Investment Dictates Which Sex is Choosy 2. Australian Katydids Lab Experiment By D. Gwynne VIII. Sexual Selection C. Test Differential Parental Investment Dictates Which Sex is Choosy 3. Australian Katydids Field Experiment By D. Gwynne and L. Simmons •Different food quality: CAGE Shaded = high quality •Placed 8 fiberglass cages in the field Unshaded = low quality -FEMALES MATED MORE OFTEN WHEN FOOD QUALITY IS LOW; MALES MATED MORE OFTEN WHEN FOOD QUALITY IS HIGH •Four – extra food, Four – intact/control •24 males, 24 females released in each cage -WITH HIGH QUALITY FOOD, SPERMATOPHORE PRODUCTION IS EASY (LOW PI FOR MALES), SO FEMALES BECOME MORE VALUABLE AND CHOOSY -WITH LOW QUALITY FOOD, MALES BECOME CHOOSY IX. Modes of Sexual Selection A. Intrasexual Competition MEAN NO. OF CALLING ♂ % INTERACTION S WITH ♀-♀ COMPETITION CONTROL 1 0.4 1.4 15 CONTROL 2 0.7 1.2 22 CONTROL 3 0.1 1.4 27 CONTROL 4 0.3 1.3 30 EXTRA FOOD 1 8.1 0.6 0 EXTRA FOOD 2 4.7 0.7 0 EXTRA FOOD 3 5.7 0.8 0 EXTRA FOOD 4 7.9 0.6 0 IX. Modes of Sexual Selection B. Intersexual Choice MEAN NO. OF MATINGS PER ♀ A. Intrasexual Competition: Elephant Seal work by T. S. McCann (also B. LeBoeuf) - Differential Mating Success Among Individuals •Size dimorphic: Males 3x > Females •Females gather at beaches for 3 months – breed •Males fight to dominate these “harems” IX. Modes of Sexual Selection IX. Modes of Sexual Selection B. Intersexual Choice: A. Intrasexual Competition: Elephant Seal work by T. S. McCann (also B. LeBoeuf) 1. Combat: * Largest and oldest males win male-male combats *Winner of combats are the dominant males in a harem: 8 most dominant males inseminated 348 females 1. Premating Female Choice e.g. widowbird work by Andersson -dimorphic, males with long tails and red epaulet - males defend territories for female nesting -alter tail length 2. Endurance Rivalry - Males stay on the beach for 90 days without feeding = lose over 40% of body weight by end IX. Modes of Sexual Selection B. Intersexual Choice: -longer tails = more females -shorter tails = lost females X. MALE MATE CHOICE – SEX ROLE REVERSAL 2. Postcopulatory Female Choice e.g., fish family Syngnathidae – seahorses and pipefish, where male “pregnancy” occurs e.g. jungle fowl work by Westneat Rosenqvist’s work on broad-nosed pipefish -male provide all of parental care -dimorphic -females prefer males with redder comb -females prefer dominant males -force copulations are common -female preferentially eject sperm low ranking males -males have brood pouches where females deposit eggs, and male provide oxygen, nutrients, protection until they hatch -females can produce eggs much quicker than males rearing eggs to hatchling, so PI greater in males X. MALE MATE CHOICE – SEX ROLE REVERSAL Rosenqvist’s work on broad-nosed pipefish X. MALE MATE CHOICE – SEX ROLE REVERSAL Drosophila a) Bateman’s Principle -not energetically costly, but time is the key cost -males more valuable, so females should compete over males, and males should be choosy pipefish test by Jones, Rosenqvist, Berglund and Arnold 2000 -in barrels: 4 males and 4 females or 2 male and 6 females (results same, so pooled) open, solid line=male filled, dashed line=female X. MALE MATE CHOICE – SEX ROLE REVERSAL e.g., pipefish by Rosenqvist and colleagues two species: Syngnathus typhle and Nerophis ophidion in both species, males choose in Nerophis, use female traits in Syngnathus, use “parasite” infestation two species: Syngnathus typhle and Nerophis ophidion -In both species, male provide all of parental care comparing Bateman’s Drosophila work in 1948 with current work on pipefish As predicted, female reproductive success increases more steeply with more mates than for males e.g., pipefish by Rosenqvist and colleagues N. ophidion: females are larger and have dark blue stripes and skin folds on their bellies Pipefish S. typhle: same size, but females court (zigzag)