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Chapter 17, 18 and 19 Evolution Unit Earth: The Just-Right, Adaptable Planet • During the 3.7 billion years since life arose on Earth, the average surface temperature of the earth has remained within the range of 10-20oC Figure 4-1 The consistent temperature range has allowed life to Evolve, Flourish and create the Diversify on Planet Earth Our Home Evolution of Life On Earth Chemical Evolution Biological Evolution (1 billion years) (3.7 billion years) Formation Large Variety of First Single-cell Single-cell of the Small organic multicellular protocells prokaryotes eukaryotes earth’s organic molecules organisms form in the form in form in early molecules (biopolymers) form, first seas the seas the seas crust and form in form in in the seas atmosphere the seas the seas and later on land Fig. 4-2, p. 84 Stanley Miller’s Experiment Or- How we figured our how life evolved from non-living components http://highered.mcgraw- hill.com/sites/9834092339/student_view0/chapter26/an imation_-_miller-urey_experiment.html Stanley Miller’s Experiment Vial of Material from Original Experiments Found (youtube) 1.5 mins Bill Nye Explains Stanley Miller’s Experiments Creating the Potential for Life (united streaming) 8 mins Time Line -1953 Miller’s Experiments 1977 Undersea vent discovery Time Frame of Human Evolution • Time Scales Demonstration-string Modern humans (Homo sapiens sapiens) appear about 2 seconds before midnight Age of Recorded human history mammals begins about 1/4 second Age of reptiles before midnight Insects and amphibians invade the Origin of life land (3.6-3.8 billion years ago) First fossil record of animals Plants begin invading land Evolution and expansion of life Fig. 4-3, p. 84 • If the diagram of Evolution were a clock, at what time would Fish have evolved? • What time are flowering plants present? • What time do humans evolve? Evolution and Geological Time • Over the last billion years, the location of the continents has changed. This has led to the evolution of similar species on different continents… 225 million years ago 135 million years ago 65 million years ago Present Fig. 4-5, p. 88 http://contintental drift theory pangae Changes in climate throughout the earth’s history have shifted where plants and animals can live Figure 4-6 Asteroids and meteorites hitting the earth have wiped out large numbers of species and created evolutionary opportunities for Natural Selection of new species Ex: KT Meteorite killed off dinosaurs and gave rise to the “age of mammals” Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis NATURAL SELECTION • Evolution by natural selection involves the change in a population’s genetic makeup through successive generations • Through either: –genetic variability –Mutations: random changes in DNA that can be inherited by offspring Natural Selection and Adaptation: 3 conditions are necessary for evolution: 1. Genetic variability 2. Traits must be heritable 3. Trait must lead to differential reproduction Types of Natural Selection • Stabilizing: occurs when the most common phenotype is selected for. • Disruptive: occurs when changes favor individuals at both extremes of the distribution, individuals at the extremes contribute more offspring than those in the center, producing two peaks. • Directional: occurs when natural selection favors a single phenotype and therefore allele frequency continuously shifts in one direction. http://wps.pearsoncustom.com/wps/media/obje cts/3014/3087289/Web_Tutorials/17_A02.swf Directional Selection Microevolution occurs when allele frequencies change from one generation to the next Ex. Industrial melanism Moth Populations: Directional Selection PLAY ANIMATION Wrap Up of Natural Selection Types Adaptive Trait Game PLAY ANIMATION Limits on Adaptation through Natural Selection • A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce. Coevolution • Interacting species can engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the other. This often happens between predators and prey species Example: Toxic Newts Every species in an ecosystem has a specific role or Niche 1. Fundamental niche: the potential range conditions and resources a species could theoretically use 2. Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche 2 Species of Barnacles- 2 niche In the previous diagram the two species of barnacles grow on different parts of the rocks. When the lighter coloured (Balanus sp.) were removed from the rocks the darker coloured (Chthamatus sp.) was able to move down onto the unoccupied surface. But when the Chthamatus sp. was removed from the upper areas of the rock Balanus sp. was not able to move up and occupy these upper areas, because Balanus sp. can't stand to be exposed to the air for a long time, which is the case with rocks close to the high tide mark. Balanus can only occupy the lower niche. Generalist and Specialist Generalist species Specialist tolerate a species can wide range only of tolerate a conditions. narrow range of conditions. Figure 4-7 Cockroaches: Nature’s Ultimate Survivors • 350 million years old • 3,500 different species • Ultimate generalist – Can eat almost anything. – Can live and breed almost anywhere. – Can tolerate radiation. 4-A Figure Specialized Feeding Niches • Resource partitioning reduces competition and allows sharing of limited resources. Figure 4-8 Avocet sweeps bill through mud and surface water in search of small crustaceans, Ruddy insects, and seeds Herring gull is a turnstone tireless scavenger searches Brown pelican under shells dives for fish, and pebbles which it locates Dowitcher probes deeply for small Black skimmer from the air into mud in search of invertebrates seizes small fish at water surface snails, marine worms, and small crustaceans Louisiana heron wades into water to seize small fish Piping plover feeds Flamingo Scaup and other Oystercatcher feeds on on insects and tiny feeds on diving ducks feed clams, mussels, and crustaceans on minute on mollusks, other shellfish into which sandy beaches organisms crustaceans,and it pries its narrow beak in mud aquatic vegetation Knot (a sandpiper) picks up worms and small crustaceans left by receding tide (Birds not drawn to scale) Fig. 4-8, pp. 90-91 SPECIATION • Speciation: A new species can arise when member of a population become isolated for a long period of time Pre-zygotic Barriers Mechanical isolation: Structural differences prevent gamete exchange. Gametic isolation: Gametes die before uniting with gametes of other species, or gametes fail to unite. Post-zygotic Barriers Hybrid inviability: Hybrid zygotes fail to develop or fail to reach sexual maturity. Hybrid sterility: Hybrid fails to produce functional gametes. Hybrid breakdown: Offspring of hybrids are weak or infertile. Allopatric Speciation • Induced when the ancestral population becomes separated by a geographical barrier. • Example: Grand Canyon and ground squirrels Adaptive Radiation • Emergence of numerous species from a common ancestor introduced to new and diverse environments. • Example: Darwin’s Finches Sympatric Speciation • Result of a radical change in the genome that produces a reproductively isolated sub-population within the parent population (rare). • Example: Plant evolution - polyploid A species doubles it’s chromosome # to become tetraploid. Parent population reproductive sub- population Evolutionary Divergence • Each of the finches evolved into a new species, from a common ancestor, to fill a niche Figure 4-9 Animation: Evolutionary Tree Diagrams PLAY ANIMATION Geographic Isolation • …can lead to reproductive isolation, divergence of gene pools and speciation. Figure 4-10 Extinction: • Extinction occurs when the population cannot adapt to changing environmental conditions. The golden toad of Costa Rica’s Monteverde cloud forest became extinct because of climate change. Figure 4-11 Bar width represents relative Species and families Era Period Millions of experiencing years ago number of living species Cenozoic mass extinction Quaternary Today Extinction Current extinction crisis caused by human activities. Tertiary Extinction 65 Cretaceous: up to 80% of Cretaceous reptiles (dinosaurs) Mesozoic Jurassic Extinction Triassic: 35% of animal families 180 Triassic 250 Extinction Permian: 90% of animal families Permian Carboniferous 345 Extinction Devonian: 30% of animal Paleozoic families Devonian Silurian Ordovician Extinction 500 Ordovician: 50% of animal Cambrian families Fig. 4-12, p. 93 II. Mass Extinctions A. Paleozoic Era between Ordovician/ Silurian 438 mya (million years ago): First Ice Age=75% of all species extinct Paleozoic Era between Devonian/ Carboniferous 360 mya: Sea levels rising=70% of all species extinct Paleozoic Era between Permian/Triassic 245 mya: all land masses colliding together to form Pangaea and single world ocean=90% of all species extinct Mesozoic Era between Triassic/ Jurassic 214 mya: comets hitting the Earth (theory) 60% of all species extinct-first extinction of some dinosaurs Mesozoic/Cenozoic Era: Cretaceous/Tertiary 65 mya: Volcanic lava, maybe an asteroid hitting the earth. 2nd and final extinction of most dinosaurs GREATEST EXTINCTIONS THROUGHOUT HISTORY Current Day Cretaceous Ordovician Devonian Permian Jurassic Dinosaurs go extinct Terrestrial Number of families Marine Millions of years ago Fig. 4-13, p. 94 Effects of Humans on Biodiversity • The scientific consensus is that human activities are decreasing the earth’s biodiversity. Figure 4-13 GENETIC ENGINEERING • We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding. (Cows are an example of this) • We have used genetic engineering to transfer genes from The mouse on the right has been one species to engineered to be obese. another. Figure 4-15 Genetic Engineering: Genetically Modified Organisms (GMO) recombinant DNA: genes from different organisms are combined. Figure 4-14 How Did We Become Such a Powerful Species so Quickly? • We lack: – strength, speed, agility. – weapons (claws, fangs), protection (shell). – poor hearing and vision. • We have thrived as a species because of our: -opposable thumbs, ability to walk upright, and complex brains (problem solving).
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