WHAT IS EVOLUTION? General definition: a change or modification through time (e.g., galaxies and language evolves)

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1 WHAT IS EVOLUTION? General definition: a change or modification through time (e.g., galaxies and language evolves) biological or organic evolution: change in the properties of organisms that transcend the lifetime of a single individual : in biology, more specifically, changes that are heritable : changes in allele frequency HISTORICAL DEVELOPMENT OF EVOLUTION I. Classical Thinking Greeks thought that the world changes, but by Plato s time the idea of a static world came into prominence 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

2 HISTORICAL DEVELOPMENT OF EVOLUTION II. Pre-Darwinian Thinking A. ( ) 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 ( ): 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

3 HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm 1. Homology b) Structural: 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 2. Change Through Time: a) fossil record: old things resembled new and transitional animals

4 HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm 2. Change Through Time: b) vestigial parts: parts that are now useless were once useful other examples: whale femur, human appendix HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm 2. Change Through Time: c) extinction in fossil records -creationist: extinct due to flooding -biologist: extinct species are relatives of extant species

5 HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: A. Basic types of evidence that challenged old paradigm 2. Change Through Time: d) marine fossils in arid areas: earth itself is dynamic! (grand canyon, see figure) coral fossil in Anza- Borrego State Park (desert in CA) 3. Age of the earth: Geology earth is old (4.6 by) Evolution was really accepted, but the mechanisms is what was controversial (and the idea of no design!) HISTORICAL DEVELOPMENT OF EVOLUTION III. Darwin's time: B. Darwin Charles Darwin: joined the crew of the HMS Beagle to travel around the world as the ship's naturalist. 1844: he wrote an essay on Natural Selection 1858: another biologist, Alfred Wallace ( ), 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 In 1858, he published his seminal abstract -- On the Origin of Species.

6 C. Natural Selection HISTORICAL DEVELOPMENT OF EVOLUTION a. Darwin proposed 4 steps, how Natural Selection drives evolution: 1. individuals need to be variable 2. traits that are variable are heritable -- passed on to next generation 3. excess offspring is produced 4. differential production or survival linked to specific traits (see 2) IV. Neo-Darwinian How are traits passed on? A.Lamarckism HISTORICAL DEVELOPMENT OF EVOLUTION 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

7 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. One of Mendel s basic outcomes: inheritance of genes is discrete, no mixing 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?

8 1. Individuals need to be variable - Medium ground finch (Geospiza fortis) on Isla Daphne Major 2. Traits that are variable are heritable

9 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

10 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??

11 V. Example of Evolution by NS B. Type of Natural Selection 1. DIRECTIONAL SELECTION w w = fitness (how well an animal does) e.g., larger trait results in higher fitness trait f w = frequency of animal with specific trait trait V. Example of Evolution by NS B. Type of Natural Selection 2. STABILIZING SELECTION w trait f trait

12 V. Example of Evolution by NS B. Type of Natural Selection 2. STABILIZING SELECTION: EXAMPLE BIRTH WEIGHT IN HUMANS By Karn and Penrose 13,730 birth records at University College Hospital between 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 ( ) FOUND A 4-FOLD DECREASE IN INTENSITY OF SELECTION V. Example of Evolution by NS B. Type of Natural Selection 3. DISRUPTIVE SELECTION w trait f trait

13 V. Example of Evolution by NS B. Type of Natural Selection Beak Size in Seedeater Finches, Pyerenestes ostrinus By T. B. Smith 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 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 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

14 VI. Forces that Drive Evolution A. Natural Selection B. Genetic Drift e.g., Clegg and colleagues work on Silvereyes (Zosterops lateralis) -populations have colonized islands off Australia -founder populations lose alleles VI. Forces that Drive Evolution A. Natural Selection B. Genetic Drift C. Mutation D. Gene Flow

15 VII. SOURCES OF GENETIC VARIATION A. MUTATION TRUE SOURCE OF VARIATION MISTAKES DURING REPLICATION OF DNA RESULTS IN MUTATIONS THAT ARE HERITABLE 1. TYPES OF MUTATIONS a) Point Mutation: Substitution of single base pair VII. SOURCES OF GENETIC VARIATIONa) POINT MUTATION b) DELETION: REMOVAL OF 1 OR MORE NUCLEOTIDES IN A DNA SEQUENCE c) INSERTION: ADDITION OF ONE OR MORE NUCLEOTIDES IN A DNA SEQUENCE

16 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) VII. SOURCES OF GENETIC VARIATION MECHANISMS OF DELETION AND INSERTION 1) unequal crossing over during recombination 2) transposition 3) slippage

17 VII. SOURCES OF GENETIC VARIATION d) INVERSION: 180 DEGREE ROTATION OF DNA e) POLYPLOIDY: INHERITING EXTRA COPIES OF CHROMOSOMES -COMMON IN PLANTS VII. SOURCES OF GENETIC VARIATION A. MUTATION B. RECOMBINATION -DURING METAPHASE, HOMOLOGOUS CHROMOSOMES EXCHANGE C. GENE FLOW Copyright 2002 Pearson Education, Inc.

18 VIII. Sexual Selection Peahen and chick drab and cryptic Peacock elaborate Peacocks highly conspicuous and vulnerable to predators Why does this evolve? Sexual Selection: Differential Reproduction Related to Elaborate Male Display Traits VIII. Sexual Selection A. Causes of Sex Differences 1. Anisogamy: DIFFERENTIAL INVESTMENT IN GAMETES Male Birds: Fairywren: 8 billion sperms at one time Female Birds: 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! HUMANS: FEMALES PRODUCE ONE VIABLE EGG PER MONTH MALES CAN FERTILIZE THE ENTIRE WORLD WITH 1 EJACULATION

19 VIII. Sexual Selection A. Causes of Sex Differences 1. Anisogamy: DIFFERENTIAL INVESTMENT IN GAMETES 2. Parental Investment (post gametes) -females typically invest more than males e.g., mammals: females nourish and carry embryo, nurse offspring vs. males fertilize eggs and leave VIII. Sexual Selection B. Effects of Sex Differences 1. Reproductive Potential Bateman s Rule reproductive success males females number of mates -males increase their mating success with more females -females do not necessarily increase their mating success with more males

20 VIII. Sexual Selection 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! VIII. Sexual Selection C. Test Differential Parental Investment Dictates Which Sex is Choosy 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

21 VIII. Sexual Selection Differential Parental Investment Dictates Which Sex is Choosy 2. Australian Katydids Lab Experiment By D. Gwynne Different food quality: Shaded = high quality Unshaded = low quality -FEMALES MATED MORE OFTEN WHEN FOOD QUALITY IS LOW; MALES MATED MORE OFTEN WHEN FOOD QUALITY IS HIGH -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 VIII. Sexual Selection C. Test Differential Parental Investment Dictates Which Sex is Choosy 3. Australian Katydids Field Experiment By D. Gwynne and L. Simmons Placed 8 fiberglass cages in the field Four extra food, Four intact/control CAGE CONTROL 1 CONTROL 2 CONTROL 3 MEAN NO. OF CALLING MEAN NO. OF MATINGS PER % INTERACTION S WITH - COMPETITION males, 24 females released in each cage CONTROL 4 EXTRA FOOD EXTRA FOOD EXTRA FOOD EXTRA FOOD

22 IX. Modes of Sexual Selection A. Intrasexual Competition B. Intersexual Choice - Differential Mating Success Among Individuals IX. Modes of Sexual Selection A. Intrasexual Competition: Elephant Seal work by T. S. McCann (also B. LeBoeuf) Size dimorphic: Males 3x > Females Females gather at beaches for 3 months breed Males fight to dominate these harems

23 IX. Modes of Sexual Selection 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 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: 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 -longer tails = more females -shorter tails = lost females

24 IX. Modes of Sexual Selection B. Intersexual Choice: 2. Postcopulatory Female Choice e.g. jungle fowl work by Westneat -dimorphic -females prefer males with redder comb -females prefer dominant males -force copulations are common -female preferentially eject sperm low ranking males X. MALE MATE CHOICE SEX ROLE REVERSAL e.g., fish family Syngnathidae seahorses and pipefish, where male pregnancy occurs Rosenqvist s work on broad-nosed pipefish -male provide all of parental care -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

25 X. MALE MATE CHOICE SEX ROLE REVERSAL Rosenqvist s work on broad-nosed pipefish a) Bateman s Principle comparing Bateman s Drosophila work in 1948 with current work on pipefish pipefish test by Jones, Rosenqvist, Berglund and Arnold in barrels: 4 males and 4 females or 2 male and 6 females (results same, so pooled) As predicted, female reproductive success increases more steeply with more mates than for males Drosophila Pipefish 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, male provide all of parental care -not energetically costly, but time is the key cost -males more valuable, so females should compete over males, and males should be choosy N. ophidion: females are larger and have dark blue stripes and skin folds on their bellies S. typhle: same size, but females court (zigzag)

26 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