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Connect these two together! Earth: Just-right, Resilient Planet Temperature 0-100 Liquid water Orbit-right distance Rotation/Tilt Size and gravity Ozone layer-bacteria DO NOT POST TO INTERNET Fig. 5-1, p. 92 Life has been around for 3.7 billion years • Avg. surface temp. has been between 50-68o • Even with a 30-40% increase in the sun’s output EVOLUTION & BIODIVERSITY Chapter 5 Origins and Early Evolution of Life Chemical evolution Biological evolution Fig. 5-2 p. 93 How did life evolve? a. Two Hypotheses of Evolution: 1) Chemical Evolution - @ 4.7 billion years ago, lasted 1 billion years Formation of early molecules small proteins large proteins complex organic molecules first protocells 2) Biological Evolution – started 3.7 billion years ago, up to present Single-celled Prokaryotes Single-celled Eukaryotes diversification multicellular organisms in sea then land b. Types of Evolution 1) Microevolution Small genetic changes in a population such as the spread of a mutation, or the change in the frequency of a single allele due to selection ex. peppered moths 2) Macroevolution Long-term, large-scale changes in organisms. Usually involves major changes among groups of species (development of new genera) ex. horses Modern humans (Homo sapiens) appear about 2 seconds before midnight Biological Evolution Over Geologic Time Age of mammals Age of reptiles Insects and amphibians invade the land midnight Origin of life (3.6–3.8 billion years ago) Plants invade the land First fossil record of animals Plants begin invading land noon Evolution and expansion of life Fig. 5-3, p. 94 Recorded human history begins 1/4 second before midnight A. Evolution 1. Species Theory • What is a species? – Two populations of sexually reproducing organisms can be considered separate species if they cannot interbreed (or are reproductively isolated) What is a species? • Distinct type of organism –physically similar –can produce viable offspring –biochemical traits –DNA –behavioral (least efficient) 2. Evolution • What two things are needed for evolution to occur? -time -death 1) Microevolution works through a combo of processes that change genetic makeup of a population: a) Mutation - random changes in DNA structure or number in a cell -external and internal b) Natural Selection - some populations have traits that cause them to survive and produce offspring more than others c) Gene Pool – set of all genes in a population that reveals the change. Page 109 Microevolution, continued e) Differential reproduction – organisms best adapted to a given environment will be most likely to survive to reproductive age and have offspring of their own. 3. Natural Selection Definition - nonrandom breeding of individuals where the individuals that have the highest reproductive success are those that are most suited to the environment Types a) Directional b) Stabilizing c) Diversifying a. Directional Selection • Individuals from just one side of the distribution reproduce • population looks different over time • mean changes • range does not change b. Stabilizing Selection • Individuals from the center of the distribution are the only ones to reproduce • individuals look more similar over time • mean does not change • range narrows • animation c. Diversifying Selection (AKA Disruptive selection) • Individuals from the ends of the distribution are the only ones to reproduce • produced 2 separate phenotypes • mean does not change (but few individuals at mean) • range increases • animation 4. Co-evolution- Occurs when populations of two different species interact over a long time, changes in the gene pool of one species can lead to changes in the gene pool of the other species. B. ECOLOGICAL NICHES – Range of tolerance of enviro – Resource use 1. Niche Breadth a. Fundamental niche is the full potential range of physical, chemical, and biological conditions and resources it could theoretically use if there were not direct competition from other species b. Realized niche- a species usually occupies only part of its fundamental niche in a particular community or ecosystem Herring gull is a tireless scavenger Black skimmer seizes small fish at water surface Flamingo feeds on minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation 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 Adaptation • Adaptation - heritable trait that enables organisms to better survive and reproduce under a given set of environmental conditions (competitive advantage) 1. What are the limits to adaptation? a. Limited genetic variability in population – traits must already exist in gene pool b. Reproductive capacity and time delays c. Most of population must die or not reproduce for desirable trait to become dominate and be passed on Misconceptions About Evolution • “Survival of the fittest” means “survival of the strongest” – fitness is a measure of reproductive success • Evolution involves a grand plan of nature where species become more perfect – there is no plan or goal D. How do New Species Evolve? 2. Speciation - two species arise from one. a. Geographic isolation - physically separated (mountains, water) b. Reproductive isolation - when mutation and natural selection operate independently in two geographically isolated populations and change the allele frequencies in different ways. Process is called divergence divergent evolution What determines biodiversity? Biodiversity = Speciation - Extinction (number of species on the planet) creation of new species removal of species 4. Extinction - The elimination of all individuals in a species from the earth a. Two major types: 1) Background extinction rate - relatively constant rate of extinction in the fossil record – – average lifespan = 4 million yrs extinction = 3-30/yr 2) Mass extinction - major loss of species – climate change, humans, catastrophic events – – average lifespan - thousands of years extinction = thousands/yr Chicxulub Crater – 112 miles wide, 3,000 feet deep LAURASIA 120°80° 40° 80° 120° 120°80° GONDWANALAND 80° 120° 135 million years ago 225 million years ago EURASIA AFRICA 120°80° 120° 120° 0° MADAGASCAR 65 million years ago Present 40° 120° b. Adaptive Radiation – extinctions open up gaps in niches so new species can evolve to fill niches b. Adaptive Radiation – after a mass extinction, over the next 10 million years, new species evolve to fill in new or abandoned niches How do we affect extinction rates? 1) Simplify ecosystems (monocultures/disturbed habitats) 2) Strengthening pest populations (resistance to pesticides) 3) Eliminating predators (can create new pests) 4) Introducing new species (starlings) 5) Over-harvesting 6) Interfering with chemical cycling and energy flow (UV/ozone, heat pollution)