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Transcript
Lecture #1 – Darwinian Evolution 1 Key Concepts: • Evidence for evolution • Darwin’s theory • The Modern Synthesis 2 Spiritual vs. Intellectual Different, but not necessarily in conflict The human emotional experience The human intellectual experience “The Bible tells us how to go to Heaven, not how the heavens go”3 Galileo Reality Check: The world’s major religions and the dominant religion in the world’s four most populous countries Religious Affiliation World China India United States 8 6 82 Muslim 33 21 2 14 2 13 77 Nonbelievers 14 50 1 12 2 Hindu 13 12 6 ~0 ~0 73 1 3 32 6 1 4 9 1 1 1 ~0 ~0 2 ~0 Christian Other Buddhist Jewish SOURCE – National Geographic, December 2007 Indonesia 4 There are many equally valid ways “to go to Heaven” • We rely on our religious texts for moral, emotional and spiritual guidance • We rely on science and other intellectual pursuits to gain knowledge about the natural world There need be no conflict in these different ways of thinking and learning 5 Defining Evolution: • A process of change over time • Cannot deny that this occurs • Evidence is overwhelming: Historical – within the span of recorded human history Fossils – the very long term geological record Comparative morphology and anatomy Biogeography – the geographic distribution of species The unity of life 6 Historical Evidence: observed character displacement Changes in beak size recorded over about 2 decades after a natural migration event Image – finches on the Galapagos Resident species shifted to smaller beak size 7 Photographs by B. Rosemary Grant/Science, 2006 Big-beaked invader All of agriculture is based on human selection events • The domestication of grass ~12,000 years ago • Led to the first cultural shift in human civilization Image – wheat Nomadic hunter-gather tribes villages based on agricultural production • Other plants and animals as well…. 8 Artificial Selection – Brassica oleracea in all its forms Image – cabbage, kale, cauliflower, broccoli, Brussels sprouts 9 Farm Animals – different breeds Images – different breeds of cattle and chickens 10 Cats and Dogs A great dane is the same species as a toy poodle! Images – different breeds of cats and dogs 11 The development of pesticide resistance • Resistance to insecticides, herbicides, antibiotics….. • All natural responses to human generated changes in the environment Diagram – development of pesticide resistance due to use of insecticides 12 Defining Evolution: • A process of change over time • Cannot deny that this occurs • Evidence is overwhelming: Historical – within the span of recorded human history Fossils – the very long term geological record Comparative morphology and anatomy Biogeography – the geographic distribution of species The unity of life 13 The fossil record extends back BILLIONS of years Images – fossils of plants and fish 14 Most form in marine sediments Diagram – formation of sedimentary rocks with fossils embedded 15 Fossil substrates – can you think of others??? Images – other fossil substrates 16 Formation of sedimentary rocks is not uniform in time or space Same diagram as #15 17 Critical Thinking • The formation of sedimentary rocks is not uniform in time or space • Why not??? 18 Critical Thinking • The formation of sedimentary rocks is not uniform in time or space • Why not??? 19 Formation of sedimentary rocks is highly dynamic • Varies with geological activity Tectonic movements, mountain building, erosion Varies with climate Rain, wind, freeze/thaw cycles, water temperature – all affect erosion and sedimentation • Varies with the depositional environment Finer sediments in still water, coarser sediments with more wave action or other energy 20 The earth’s crust is very dynamic Diagram – dynamic geological processes: tectonic movements, mountain building, erosion 21 Formation of sedimentary rocks is highly dynamic • Varies with geological activity Tectonic movements, mountain building, erosion • Varies with climate Rain, wind, freeze/thaw cycles, water temperature – all affect erosion and sedimentation • Varies with the depositional environment Finer sediments in still water, coarser sediments with more wave action or other energy 22 Climate is naturally dynamic on a geological time scale Graph – benthic carbonates; analogous to climate change over the past 5 million years Benthic carbonates parallel atmospheric temperature changes 23 Critical Thinking • How could water temperature affect the formation of sedimentary rocks??? 24 Critical Thinking • How could water temperature affect the formation of sedimentary rocks??? 25 Formation of sedimentary rocks is highly dynamic • Varies with geological activity Tectonic movements, mountain building, erosion • Varies with climate Rain, wind, freeze/thaw cycles, water temperature – all affect erosion and sedimentation • Varies with the depositional environment Finer sediments in still water, coarser sediments with more wave action or other energy – WHY??? 26 Play with the “ocean” • In high energy environments (waves) only the heaviest sediments can settle Coastal environments produce sandstones • In off-shore environments (no waves) finer sediments can settle Off-shore environments produce siltstones, slates, limestones… 27 Sediment size depends on the energy level at the site of deposition Diagram of different depositional environments 28 Formation of sedimentary rocks is highly dynamic • THUS sediments tend to be deposited in identifiable layers • THUS organisms trapped in sediments form a time sequence The earliest organisms are in the bottom layers and the most recent organisms in the upper layers 29 The Grand Canyon – a time sequence Image – the Grand Canyon 30 Formation of sedimentary rocks is highly dynamic • THUS sediments tend to be deposited in identifiable layers • THUS organisms trapped in sediments form a time sequence The earliest organisms are in the bottom layers and the most recent organisms in the upper layers Dating these fossils reveals the history of change 31 Study the geological time scale – it’s the history of life on earth! The geological time scale Use a search engine to find the geological time scale 32 Of course the fossil record is incomplete! • Organisms must be trapped in the right place under the right conditions – a rare event • Fossils must survive geological processes such as subduction, metamorphosis and erosion • Fossils must be found! Have you ever found a fossil??? • But what we do have is irrefutable evidence of change over time 33 Fossil Evidence Shows Progression Over Time – new species…. Diagram – evolution of elephant lineages 34 ….new traits…. Diagram – limbs developing from bony fins in tetrapods 35 ….transitional forms…. Diagram – transition from bony fins to limbs 36 Defining Evolution: • A process of change over time • Cannot deny that this occurs • Evidence is overwhelming: Historical – within the span of recorded human history Fossils – the very long term geological record Comparative morphology and anatomy Biogeography – the geographic distribution of species The unity of life 37 Comparative morphology – homologous structures are derived from a common ancestor Diagram – forelimbs of various mammals showing identical bone structure with variation in bone size 38 Fish SalamanderTortoise Chicken Pig Cow Rabbit Human Stage of Development Early Diagram – similarities in the embryos of a wide variety of vertebrates Later 39 Strickberger, 1996 Images – orchid floral structure 40 Comparative morphology – vestigial traits • Structures that are physically or functionally reduced but clearly similar to functional structures in related organisms Tiny limb bones in some snakes and aquatic mammals Non-flying wings in ostriches emus, kiwis, penguins Blind eyes in cave-dwelling animals Vestigial tails in humans 41 Defining Evolution: • A process of change over time • Cannot deny that this occurs • Evidence is overwhelming: Historical – within the span of recorded human history Fossils – the very long term geological record Comparative morphology and anatomy Biogeography – the geographic distribution of species The unity of life 42 Biogeography – Darwin observed patterns of species distribution during his voyage on the Beagle Diagram – the voyage of the Beagle 43 Sloths – found only in South America, even though similar habitats exist on other continents Image – modern and fossil sloths 44 Marsupials – almost restricted to Australia …though convergent evolution has resulted in many similar eutherian mammals on other continents Diagram of marsupial and eutherian mammals showing similar forms Convergent evolution – similar traits in unrelated organisms that evolved under similar selection pressures….more later 45 The Galápagos and other volcanic islands Many closely related endemic species….that are similar to those found on the closest mainland Darwin’s conclusion – species migrated and evolved new adaptations in their new home Diagram of Darwin’s finch lineages 46 Defining Evolution: • A process of change over time • Cannot deny that this occurs • Evidence is overwhelming: Historical – within the span of recorded human history Fossils – the very long term geological record Comparative morphology and anatomy Biogeography – the geographic distribution of species The unity of life 47 Uniformity and Diversity: same DNA, same ATP, same amino acids, same membranes, same aerobic respiration…. Image – frog in the center of a bromeliad 48 Critical Thinking • What is the implication of this uniformity in the basic building blocks of life, even though there are many millions of organisms both extant and extinct??? 49 Critical Thinking • What is the implication of this uniformity in the basic building blocks of life, even though there are many millions of organisms both extant and extinct??? 50 Defining Evolution: • A process of change over time • Cannot deny that this occurs • Evidence is overwhelming: Historical – within the span of recorded human history Fossils – the very long term geological record Comparative morphology and anatomy Biogeography – the geographic distribution of species The unity of life Step 1: accepting that evolution occurs….Step 2: 51 HOW??? Historical Context The development of ideas about biological evolution and the age of the earth began in the 1700’s – Darwin was just the first to publish! Timeline – the development of thought on evolution 52 Darwin’s voyage on the Beagle, 18311836…..publication of his theory, 1859 Map – the voyage of the Beagle 53 Darwin’s Theory of Evolution by Natural Selection based on observation + logical inference • OBSERVATION #1 – all species have the reproductive potential for exponential population growth • OBSERVATION #2 – populations tend to remain stable OBSERVATION #3 – environmental resources are limited INFERENCE #1 – excess of offspring leads to a struggle for existence • OBSERVATION #4 – significant variation exists between individuals of the same species • OBSERVATION #5 – some variation is heritable INFERENCE #2 – individuals that are best adapted to their environment contribute more offspring to the next generation = differential reproductive success = Darwin’s natural selection INFERENCE #3 – TIME X CHANGE = DIVERSITY Don’t panic – this is just a summary slide for you to look at later 54 Observation #1: All species have the potential for exponential population growth Images – examples of high reproductive potential in various organisms 55 Observation #2: Populations tend to remain stable (though sometimes within a fluctuating range) not exponential Graphs – examples of actual population growth patterns 56 Observation #3: Environmental resources are limited Image – lynx chasing rabbit food…. 57 water…. Image – desert landscape 58 habitat…. Images – various animals in habitat 59 Inference #1: Excess offspring in a resource-limited environment leads to a “struggle for existence” Image – resource competition between aquatic plants 60 Observation #4: Variation exists in all natural populations Diagram – natural variation in beetles 61 Image – natural variation in plants 62 Image – natural variation in mollusks 63 Images – natural variation in humans 64 Observation #5: Some variation is heritable Images – heritable variation in various animals 65 Inference #2: Best adapted individuals reproduce the most Differential Reproductive Success!!! Image – polar bears fighting 66 Inference #3: Darwin’s Big One Over long periods of time and many generations the incremental results of differential reproductive success will lead to divergence between populations in different environments and eventually to the development of new species 67 Key Conclusion Small changes over long periods of time result in adaptations to different environments and to the emergence of new species Image – orchid mantis 68 Same as #68 69 Same as #68 70 Images – additional cryptic animals; through slide #78 71 72 73 74 75 76 77 78 Critical Thinking • What other testable explanation is there for an insect or other animal that evades predation by mimicking its habitat??? • How else might this cryptic form and coloration benefit the animal??? 79 Critical Thinking • What other testable explanation is there for an insect or other animal that evades predation by mimicking its habitat??? • How else might this cryptic form and coloration benefit the animal??? 80 Critical Thinking • What other testable explanation is there for an insect or other animal that evades predation by mimicking its habitat??? • How else might this cryptic form and coloration benefit the animal??? 81 Darwin originally predicted gradual speciation from a common ancestor….. • Now we know that abrupt changes are also possible • Also, some gradual changes may not be recorded in the fossil record Diagram – mammal lineages 82 Questions Remain • We don’t, and may never, know exactly how life originated on this planet • But we do have a pretty good explanation for how diversity developed and why diversity changes over time Conditions change Organisms adapt Images – more cryptic animals; same on next slide 83 Questions Remain • We don’t, and may never, know exactly how life originated on this planet • But we do have a pretty good explanation for how diversity developed and why diversity changes over time Conditions change Organisms adapt 84 The Modern Synthesis • Darwin’s concepts of natural selection and differential reproductive success leading to adaptations and speciation • Mendel’s work on heredity and hypothesis of a particulate method of hereditary transfer • Microscopic revelation of chromosomes as that particle in the late 1800’s – early 1900’s • Discovery of the structure of the DNA molecule in the early 1950’s 85 The Theory of Evolution A comprehensive body of knowledge that describes a known fact of nature 86 Key Concepts: • Evidence for evolution • Darwin’s theory • The Modern Synthesis Questions??? 87