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Evolution and Biodiversity Chapter 4 Key Concepts Origins of life Evolution and evolutionary processes Ecological niches Species formation Species extinction How Did We Become Such a Powerful Species So Quickly? Adaptive traits Human weaknesses Opposable thumbs Walk upright Intelligence Environmental impacts p. 67 Origins of Life Chemical evolution Biological evolution How Do We Know Which Organisms Lived in the Past? Fossil record Radiometric dating Ice cores DNA studies Fig. 4-2, p. 65 Biological Evolution of Life Modern humans (Homo sapiens) appear about 2 seconds before midnight Recorded human history begins 1/4 second before midnight Origin of life (3.6–3.8 billion years ago) Fig. 4-3, p. 66 Biological Evolution Evolution Theory of evolution Microevolution Macroevolution Microevolution Gene pool Genetic variability Mutations Mutagens Natural selection A human body contains trillions of cells, each with an identical set of genes. Genetic Materials There is a nucleus inside each human cell (except red blood cells). Each cell nucleus has an identical set of chromosomes, which are found in pairs. A specific pair of chromosomes contains one chromosome from each parent. Each chromosome contains a long DNA molecule in the form of a coiled double helix. Genes are segments of DNA on chromosomes that contain instructions to make proteins—the building blocks of life. The genes in each cell are coded by sequences of nucleotides in their DNA molecules. Fig. 2-5 p. 33 Natural Selection Differential reproduction Adaptation (adaptive trait) Coevolution Ecological Niches and Adaptation Ecological niche Habitats Fundamental niche Realized niche Specialized Feeding Niches for Birds Black skimmer seizes small fish at water surface Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation Flamingo feeds on minute organisms in mud Herring gull is a tireless scavenger Brown pelican dives for fish, which it locates from the air Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Louisiana heron wades into water to seize small fish Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Ruddy turnstone searches under shells and pebbles for small invertebrates Knot (a sandpiper) picks up worms and small crustaceans left by receding tide Piping plover feeds on insects and tiny crustaceans on sandy beaches Fig. 4-10, p. 72 Broad and Narrow Niches and Limits of Adaptation Generalist species Specialist species Limits of adaptation Number of individuals Niches of Specialist and Generalist Species Specialist species with a narrow niche Niche separation Generalist species with a broad niche Niche breadth Region of niche overlap Resource use Fig. 4-4, p. 68 Cockroaches: Nature’s Ultimate Survivors Fig. 4-A, p. 69 Evolutionary Divergence of Honeycreepers Fruit and seed eaters Insect and nectar eaters Greater Koa-finch Kuai Akialaoa Amakihi Kona Grosbeak Crested Honeycreeper Akiapolaau Maui Parrotbill Unknown finch ancestor Apapane Fig. 4-6, p. 70 Misconceptions of Evolution “Survival of the fittest” “Progress to perfection” Speciation What is speciation? Geographic isolation Reproduction isolation Geographic Isolation can Lead to Speciation Arctic Fox Northern population Early fox population Spreads northward and southward and separates Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Different environmental conditions lead to different selective pressures and evolution into two different species. Gray Fox Southern population Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Fig. 4-9, p. 70 Factors Leading to Extinction Plate tectonics Climatic changes over time Natural catastrophes Human impacts Extinctions Background extinctions Mass extinctions Mass depletions Human impacts “Continental Drift” (Plate Tectonics): The Breakup of Pangaea LAURASIA 225 million years ago 135 million years ago EURASIA AFRICA 65 million years ago Present Fig. 4-8, 4-9 p. 69 Mass Extinctions of the Earth’s Past Fig. 4-9, p. 73 Changes in Biodiversity over Geologic Time Terrestrial organisms Cretaceous 400 Quaternary Marine organisms Tertiary Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician 800 Cambrian 1200 Pre-cambrain Number of families 1600 0 3500 545 500 440 410 355 290 250 205 145 65 1.8 0 Millions of years ago Fig. 4-10, p. 74 Future of Evolution Artificial selection Genetic engineering (gene splicing) Genetic modified organisms (GMOs) Cloning Ethical concerns Genetic Engineering Phase 1 Make Modified Gene E. coli Cell Extract plasmid Extract DNA Gene of interest Identify and extract gene with desired trait DNA Identify and remove portion of DNA with desired trait Genetically modified plasmid plasmid Remove plasmid from DNA of E. coli Insert extracted DNA (step 2) into plasmid (step3) Insert modified plasmid into E. coli Grow in tissue culture to make copies Fig. 4-11, p. 75 Genetic Engineering Phase 2 Make Transgenic Cell E. coli A. tumefaciens (agrobacterium) Foreign DNA Host DNA Nucleus Transfer plasmid copies to a carrier agrobacterium Transfer plasmid to surface microscopic metal particle Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell Use gene gun to inject DNA into plant cell Fig. 4-11, p. 75 Genetic Engineering Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Transfer to soil Transgenic plants with new traits Fig. 4-11, p. 75 Genetically Engineered Mouse p. 71