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Biological Evolution 1 Evolutionary Bush -thousands of earlier and later branches. 2 At any given moment (e.g. the ‘present’), all we see is current diversity… all extinct forms are gone (99.9%) 3 Four Causes of Evolution 1. Mutation: fundamental origin of all genetic (DNA) change. 4 Four Causes of Evolution 1. Mutation: fundamental origin of all genetic (DNA) change. Point mutation …some at base-pair level 5 Four Causes of Evolution 1. Mutation: fundamental origin of all genetic (DNA) change. Crossing-over …others at grosser chromosome level 6 Four Causes of Evolution 1. Mutation: fundamental genetic shifts. 2. Genetic Drift: isolated populations accumulate different mutations over time. In a continuous population, genetic novelty can spread locally. 7 Four Causes of Evolution 1. Mutation: fundamental genetic shifts. 2. Genetic Drift: isolated populations accumulate different mutations over time. Local spreading of alleles 8 Four Causes of Evolution 1. Mutation: fundamental genetic shifts. 2. Genetic Drift: isolated populations accumulate different mutations over time. Local spreading of alleles 9 Four Causes of Evolution 1. Mutation: fundamental genetic shifts. 2. Genetic Drift: isolated populations accumulate different mutations over time. Spreading process known as ‘gene flow’. 10 Four Causes of Evolution But in discontinuous populations, gene flow is blocked. 11 Four Causes of Evolution Variations accumulate without inter-demic exchange 12 Four Causes of Evolution Of course, this works at many loci simultaneously 13 Four Causes of Evolution 1. Mutation: fundamental genetic shifts. 2. Genetic Drift: isolation accumulate mutations 3. Founder Effect: sampling bias during immigration. When a new population is formed, its genetic composition depends largely on the gene frequencies within the group of first settlers. 14 Founder Effect.-- Human example: your tribe had to live near the Bering land bridge… 15 Founder Effect.-- …to invade & settle the ‘New World’! 16 Galapagos Finches 17 Audeskirk & Audeskirk, 1993 Four Causes of Evolution 1. Mutation: fundamental genetic shifts. 2. Genetic Drift: isolation accumulation of mutations 3. Founder Effect: immigrant sampling bias. 4. Natural Selection: differential reproduction of individuals in the same population based on genetic differences among them. 18 Four Causes of Evolution 1. Mutation: fundamental genetic shifts. 2. Genetic Drift: isolation accumulation of mutations 3. Founder Effect: immigrant sampling bias. 4. Natural Selection: reproductive race These 4 interact synergistically 19 Evidence of Evolution 20 Evidence of Evolution 1. Biogeography: Geographical distribution of species Evidence of Evolution 2. Fossil Record: Fossils and the order in which they appear in layers of sedimentary rock (strongest evidence) Fossils • Oldest fossils are the approximately 3.465 billion-year-old microfossils from the Apex Chert, Australia – colonies of cyanobacteria (formerly called bluegreen algae) which built real reefs 23 Fossils 1600's - Danish scientist Nicholas Steno studied the relative positions of sedimentary rocks – Layering is the most obvious feature of sedimentary rocks • formed particle by particle and bed by bed, and the layers are piled one on top of the other • any sequence of layered rocks, a given bed must be older than any bed on top of it – Law of Superposition is fundamental to the interpretation of Earth history, because at any one location it indicates the relative ages of rock layers 24 and the fossils in them. 25 Relative and Absolute Dating • Relative Dating • Absolute Dating • Can determine the age of fossil with respect to another rock or fossil. • You compare the depth of a fossils position, layers. • Some drawbacks include limitations on accuracy. • Can determine the age of a fossil IN YEARS. • You determine the age by finding the amount of radioactive and nonradioactive isoptope in a specimen. • Some drawbacks are that it is difficult to perform in a lab. 26 Types of Radioactive Isotopes • Carbon 14 • Potassium 40 • Use for more recent fossils (60,000 yrs old) • Can be used with high accuracy • Half life of 5,730 years • Decays into Nitrogen • Used for older fossils • Half life of 1.3 billion years • Decays into Calcium • Less common element 27 28 Half-life for a given radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay 29 Half-life for a given radioisotope is the time for half the radioactive nuclei in any sample to undergo radioactive decay 30 Evidence of Evolution 3. Taxonomy: Classification of life forms. 32 4. Homologous structures: Structures that are similar because of common ancestry (comparative anatomy) Evidence of Evolution Turtle Alligator Bird Typical primitive fish Mammals Evidence of Evolution 5. Comparative Embryology: Study of structures that appear during embryonic development Evidence of Evolution 6. Molecular biology: DNA and proteins (amino acids) History of Theories of Evolution 36 Old Theories of Evolution • 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 characteristics, which it passes on to its offspring. 37 “The Inheritance of Acquired 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. 38 39 Charles Darwin • Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants 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 40 41 Giant Tortoises of the Galápagos Islands Pinta Pinta Island Intermediate shell Fernandina Isabela Tower Marchena James Santa Cruz Santa Fe Hood Island Floreana Hood Saddle-backed shell Isabela Island Dome-shaped shell 42 43 http://www.galapagosislands.com Charles Darwin Wrote in 1859: “On the Origin of Species by Means of Natural Selection” Two main conclusions: 1. Species were not created in their present form, but evolved from ancestral species. 2. Proposed a mechanism for evolution: NATURAL SELECTION 44 Darwin’s Observations 1. Most species produce more offspring than can be supported by the environment 2. Environmental resources are limited 3. Most populations are stable in size 4. Individuals vary greatly in their characteristics (phenotypes) 5. Variations that survive are inherited. (genotypes) 45 Natural Selection • Individuals with favorable traits are more likely to leave more offspring better suited for their environment • Also known as “Differential Reproduction” Example: English peppered moth (Biston betularia) Modes of Action • Natural selection has three modes of action: 1. Stabilizing selection 2. Directional selection 3. Diversifying selection Number of Individuals Small Large Size of individuals 1. Stabilizing Selection • Acts upon extremes and favors the intermediate. Number of Individuals Small Large Size of individuals 2. Directional Selection • Favors variants of one extreme. Number of Individuals Small Large Size of individuals 3. Disruptive Selection •Favors variants of opposite extremes. Number of Individuals Small Large Size of individuals Evidence for Natural Selection 51 Artificial Selection • The selective breeding of domesticated plants and animals by man. • Question: What’s the ancestor of the domesticated dog? Biodiversity 53 54 Biodiversity • Biodiversity – increases with speciation – decreases with extinction • Give-and-take between speciation and extinction changes in biodiversity • Extinction creates evolutionary opportunities for adaptive radiation of surviving species 55 Interpretations of Speciation • Two theories: 1.Gradualist Model (NeoDarwinian): Slow changes in species overtime 2.Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change 57 Adaptive Radiation Emergence of numerous species from a common ancestor introduced to new and diverse environments. Example: Hawaiian Honeycreepers Convergent Evolution • Species from different evolutionary branches may come to resemble one another if they live in very similar environments. • Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert) 60 Coevolution • Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species. Example: 1. Acacia ants and Acacia trees 2. Yucca Plants and Yucca moths 3. Lichen 62 Extinction • Extinction of a species occurs when it ceases to exist; may follow environmental change - if the species does not evolve • Evolution and extinction are affected by: – large scale movements of continents – gradual climate changes due to continental drift or orbit changes – rapid climate changes due to catastrophic events 63 64 Extinction • Background extinction - species disappear at a low rate as local conditions change • Mass extinction - catastrophic, widespread events --> abrupt increase in extinction rate • Five mass extinctions in past 500 million years • Adaptive radiation - new species evolve during recovery period following mass extinction 65 http://www.geog.ouc.bc.ca/physgeog/contents/9h.html Mass Extinctions Date of the Extinction Event Percent Species Lost 65 mya (million years ago) 85 213 mya 44 Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals, birds, turtles, crocodiles, lizards, snakes, and amphibians were unaffected. Marine vertebrates and invertebrates 248 mya 380 mya 450 mya 75-95 70 50 Marine vertebrates and invertebrates Marine invertebrates 66 Marine invertebrates Species Affected Community Relationships 67 Niche a species’ functional role in its ecosystem; includes anything affecting species survival and reproduction 1. Range of tolerance for various physical and chemical conditions 2. Types of resources used 3. Interactions with living and nonliving components of ecosystems 4. Role played in flow of energy and matter cycling 68 Niche is the species’ occupation and its Habitat location of species (its address) 69 Niche Fundamental niche: set of conditions under which a species might exist in the absence of interactions with other species Realized niche: more restricted set of conditions under which the species actually exists due to interactions with other species 70 Species Interaction 71 Competition any interaction between two or more species for a resource that causes a decrease in the population growth or distribution of one of the species 1. 2. 3. 4. Resource competition Preemptive competition Exploitation competition Interference competition 72 73 Competition 74 Competition 75 76 77 78 79 80 81 82 83 84 85 86 87 Predation: prey adaptations • Avoid detection – camouflage, mimics, – diurnal/nocturnal • Avoid capture – flee – resist – escape • Disrupt handling (prevent being eaten) – struggle? – protection, toxins 88 89 90 91 92 93 94 95 96 97 98 99 Rewards of Mutualism • Food: energy and nutrients • Protection: – from other species (competition, predation) – from the physical environment (shelter) • Gamete or zygote dispersal (the most common of all) • Pollination and fruit dispersal (between plants and animals). 100 Pollination (hummingbird/bee and flowering plants) • animals visit flowers to collect nectar and incidentally carry pollen from one flower to another • animals get food and the plant get a pollination service 101 Yucca moth and yucca • Yucca’s only pollinator is the yucca moth. Hence entirely dependent on it for dispersal. • Yucca moth caterpillar’s only food is yucca seeds. • Yucca moth lives in yucca and receives shelter from plant. 102 Lichen (Fungi-algae) • Symbiotic relationship of algae and fungae…results in very different growth formas with and without symbiont. • What are the benefits to the fungus? 103 Seed Disperser • Many birds and mammals consume fruits and incidentally disperse the seeds contained in those fruits – Animals get food and the plant gets seed dispersal (often with fertilizer) 104 Ant-tended plants • Ants live inside swollen Acacia thorns or hollow stems, e.g. Cecropia trees. • Patrol for caterpillars or leaf predators and storm out to repel intruders…including you! 105 Commensalists • Benefit from the host at almost no cost to the host • Eyelash mite and humans • Us and starlings or house sparrows • Sharks and remora 106 Parasites Parasites: draw resources from host without killing the host (at least in the short term). 107 Bibliography 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. Miller 11th Edition http://abandoncorporel.ca/medias/evolution.jpg http://www.ne.jp/asahi/clinic/yfc/fetus.html rob.ossifrage.net/images/ http://www.mun.ca/biology/scarr/Five_Kingdoms_Three_Domains.htm http://www.gpc.peachnet.edu/~ccarter/Millerlec5/Millerlec5.PPT http://www.dnr.state.md.us/education/horseshoecrab/lifecycle.html http://www.falcons.co.uk/mefrg/Falco/13/Species.htm http://www.sms.si.edu/irlspec/NamSpecies.htm http://www.falcons.co.uk/mefrg/Falco/13/Species.htm http://www.globalchange.umich.edu/globalchange1/current/lectures/complex_life/complex_life.html http://nsm1.nsm.iup.edu/rwinstea/oparin.shtm http://www.angelfire.com/on2/daviddarling/MillerUreyexp.htm http://exobiology.nasa.gov/ssx/biomod/origin_of_life_slideshow/origin_of_life_slideshow.html http://www.geo.cornell.edu/geology/classes/Geo104/HistoryofEarth.html http://astrobiology.arc.nasa.gov/roadmap/objectives/o2_cellular_components.html http://pubs.usgs.gov/gip/fossils/ http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/halfli.html http://www.accessexcellence.org/AE/AEPC/WWC/1995/teach_rad.html http://biology.usgs.gov/s+t/SNT/noframe/pi179.htm http://www.npca.org/magazine/2001/march_april/nonnative_species.asp http://www.bagheera.com/inthewild/spot_spkey.htm Biology, 2003, Prentice Hall http://www.nearctica.com/ecology/habitats/island.htm 108 http://www.valdosta.edu/~grissino/geog4900/lect_1.htm