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EVOLUTION is change over time Macroevolution –long-term large-scale evolutionary changes among species. Chemical Evolution ---Lasted about 1 billion years Earth formed 4.6 billion years ago Primitive atmosphere contained CO2, N2, and H2O. Trace amounts of CH4, NH3 and H2S. Energy from electrical discharges, radioactivity, solar radiation, and heat from earth combined to form first organic molecules Biological Evolution ---3.7 billion years 1st organisms were heterotrophs who ate all the organism compounds, leading nature to select for those organisms which could photosynthesize their own food-Prokaryotic cells Example: Cynanobacteria Photosynthesis removed CO2 from air and led to oxygen build up and the presence of ozone layer, protecting earth from UV radiation—Oxygen revolution Eukaryotic Cell, which were heterotrophic and could reproduce sexually, leading to genetic diversity Macroevolution includes all of the following: Genetic persistence –Common DNA present in all cells today indicates common ancestor to all cells Genetic divergence –long-term changes in species giving diversity of life Genetic losses –background extinction is steady loss and mass extinction of lineages. Evidence for Macroevolution Fossils Comparative anatomy—homologous parts Comparative embryology Comparative biochemistry MICROEVOLUTION –Changes in gene pool of a population over time Changes in the gene pool (sum total of all genes in a population)of a population overtime Source of new alleles is by o Mutations in DNA of gametes Random changes in DNA due to X-rays, mutagenic chemicals, radioactivity Random mistakes made in DNA o Recombination during meiosis NATURAL SELECTION –environmental conditions select those organisms that have favorable variations allowing them to survive and reproduce more offspring than those without the variation. Called “differential reproduction” VARIATION Raw materials upon which natural selection acts A difference in some characteristic within a population May aide in surviving long enough in an environment to reproduce and pass on their genes to next generation. Color of fur in housecats Length of claws Number and size of teeth ADAPTATION A heritable trait that helps the population to survive and reproduce better under current conditions Products of evolution by natural selection Needles on pine tree Binocular vision Opposable thumb TYPES OF ADAPATIONS Structural Adaptations –those involving structure or anatomy o Shape of tooth o Hoof of horse o Snout of pig Physiological Adaptations –functioning parts of organisms o Venom in snakes o Enzymes in stomach o Brain synapses o Pheromones Behavioral Adaptations o Squirrels store nuts for winter o Plant stems grow toward light o Migration of animals in winter/summer Environmental Changes challenge organisms to: Adapt to the new conditions Migrate to an area which is more favorable Become extinct Three Types of Natural Selection Stabilizing –eliminates the outliers of group and all organisms become more alike “It pays to be average.” Diversifying –environmental conditions favor individuals at both extremes “It doesn’t pay to be normal.” Directional –changing environment causes shift in favor of one direction “It pays to be different” Limits to Adaptation Changes in environment can only work on variations that are present in gene pool Adaptations are compromises –sickle cell anemia Population’s ability to adapt is limited by its reproductive capacity. Populations that reproduce quickly can often adapt quickly Populations that reproduce slowly take a long time to adapt by natural selection For a new favorable trait to predominate, most of an existing population would have to die prematurely Survival of the fittest means those organisms that leave the most descendants SPECIES –A group of organisms that can interbreed and produce fertile offspring Horse & Donkey mate to produce Mule which is sterile Tigers & Lions mate to produce Ligers. SPECIATION –The development of a new species through evolution. Allopatric speciation is most common: Geographic isolation –some physical feature separates the population so they can’t interbreed. o Landslide o Flood o Road Reproductive Isolation –When the sperm of one species cannot fertilize the eggs of another species or the chromosomes are so different that the embryo cannot develop. Sympatric speciation –less common Two species live closely together but cannot interbreed due to a mutation or subtle changes in behavior DIVERGENT EVOLUTION –when one species evolves into two or more species with different characteristics Darwin’s Finches Galapagos Tortoises Dog Pine trees CONVERGENT EVOLUTION –species not closely related evolve similar traits. Usually due to similar roles in similar environments. Dolphin—mammal with lungs Sea Bass –fish with gills COEVOLUTION –species evolve depending on the interactions with other members of their ecosystem Predator & Prey—Predator hunts and eats the prey o Prey develops faster run so predators that can run faster eat more, live longer, reproduce and pass on these genes. o Predator has better eyesight to see motion better, so prey runs faster, better camouflaged, EXTINCTION –a species cannot adapt to environmental conditions and disappear Background Extinction Rate –normal loss of species over time Mass Extinction –significant rise in extinction rates above the background level o Usually 25-70% of all species lost o Two mass extinctions and three mass depletions ADAPTIVE RADIATION –a variety of new species arise through divergent evolution in new habitats Takes one to ten million years to recover Ancestral form must reach the new environment Ancestral form must have basic adaptations suited to new environment New environment must have no competition o After mass extinctions, adaptive radiation of mammals and insects occurred TWO THEORIES ON RATE OF EVOLUTION GRADUALISM –evolution occurs at a slow but steady pace PUCTUATED EQUILIBRIUM –little or no evolution occurs while environment is stable, but when a large change occurs in the environment, many species become extinct and other rapidly evolve to fill the empty habitats. BIODIVERSITY = SPECIATION – EXTINCTION o Humans causing premature extinction above the background level o Predictions of extinction of half the present species on Earth by end of this century Humans have changed ecosystems to cause some of the following problems: Simplifying ecosystems –monocultures Strengthening populations of pest species by producing genetic resistance Eliminating predators Introducing new species –cloning Overharvesting resources Interfering with chemical cycles in ecosystems. FUTURE OF EVOLUTION Artificial Selection instead of natural selection Selective Breeding—specific traits Cross breeding –takes a long time to develop desired traits Genetic engineering –recombining genes from different organisms to give new traits that would never appear in nature Genetically Modified Organisms or “transgenic” –result of gene splicing o Takes have the time as cross breeding o Cloning produces genetically identical individual o Biopharming –genetically engineered animals are biofactories to produce drugs Genetic Engineering raises ethical, moral, legal, and environmental issues Success is 1% Questions Who benefits Who should be notified What happens when things turn out harmful Who should pay Should we use the precautionary principle Who gets to decide