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There is no grandeur to this view of life…that, whilst this planet has gone cycling on…endless forms most beautiful and most wonderful have been, and are being, evolved Evolution Natural selection Adaptations Mutations Differential reproduction Geographic isolation Reproductive isolation Largest reptile in North America, no natural predator 1930s: Hunters and poachers Importance of gator holes and nesting mounds 1967: endangered species 1977: comeback, threatened species Concept 4-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth. Variety of species and the genes they contain, ecosystems they live in and processes that sustain all life Do Now: Take 5 minutes to write everything you know and think about the topic of evolution Concept 4-2A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations. Concept 4-2B Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection). Evolution is the change in a population’s (not individual’s) genetic makeup over time Populations evolve by becoming genetically different. All species descend from earlier, ancestral species—theory of evolution. Over time, a population’s gene pool changes when mutations (beneficial changes) in DNA molecules are passed on to offspring Mutations are random changes in the structure/number of DNA molecules in a cell. 1) Gene DNA is exposed to external agents like X-rays, chemicals (mutagens), or radioactivity. 2) Random mistakes that occur in coded genetic instructions. Occurs when members of a population have genetic traits that improve their ability to survive and produce offspring with those specific traits. 1. The population must have genetic variability. 2. The trait must be heritable, capable of being passed from one generation to another. 3. The trait must enable individuals with the trait to produce more offspring than individuals without the trait; this is differential reproduction. Adaptation or adaptive traits are heritable traits that help organisms to survive and reproduce better under prevailing environmental conditions. Natural selection can only act on existing genes and is limited by reproductive capacity. Peppered Moth Online Hunt Natural Selection Directional selection favors individuals with traits that are at one end of a distribution (such as the peppered moth example). "It pays to be different.“ Ex: Industrial melanism in peppered moths © Brooks/Cole Publishing Company / ITP Natural Selection Stabilizing selection eliminates individuals at both ends in the spectrum of variation; the average remains the same. "It pays to be average.“ Ex: Human birth weights © Brooks/Cole Publishing Company / ITP Natural Selection Disruptive (diversifying) selection eliminates average individuals, but favors individuals at either extreme of the spectrum of variation. "It doesn't pay to be normal." © Brooks/Cole Publishing Company / ITP Evidence of ancient organisms (plants, animals etc) & internal structure Can provide clues as to past climate Fossil record incomplete…why? Do Now: What are some geologic processes that may separate individuals or populations of organisms? Shifting of tectonic plates Volcanic eruptions Earthquakes • All influence earth’s climate and in turn affect evolution by removing and/or isolating habitats and species. Volcano, Earthquakes & Plate Boundaries Types of Plate Boundaries Long-term climate changes relocate ecosystems, thus determining where certain species can live. Asteroids and meteorites have caused environmental stress and mass extinctions. YouTube - Species Extinction Video The Vanishing Frogs Part 1 The Vanishing Frogs Part 2 The Vanishing Frogs Part 3 Frogs: The Thin Green Line - Chytrid Fungus Natural selection can lead to development of an entirely new species. In speciation, two species arise from one when some members of a population cannot breed with other members to produce fertile offspring. • How might this occur?? 1. Geographic isolation, physical separation for long time periods. 2. Reproductive isolation. When population members cannot adapt to changing environmental conditions, the species becomes extinct. What are some species that have gone extinct? When local environmental conditions change, some species will disappear at a low rate; this is called background extinction “normal extinction” Before humans Mass extinction is a significant rise in extinction rates above the background extinction level. Usually, 25–70% of species are lost. Recent evidence suggests that there have been two mass extinctions on earth. There appear to have been five total mass extinctions on earth. Species diversity is the number of species (richness) combined with their relative abundance (evenness). Species rich communities tend to be more stable and more productive. Ecological niche is a species’ way of life in an ecosystem, everything that affects its survival and reproduction The niche includes the members’ adaptations; its range of tolerance for physical and chemical conditions, its interactions with other components of the ecosystem, and its role in energy flow and matter recycling The fundamental niche is the full potential range of conditions and resources a species could potentially use. Its realized niche is the part of the potential niche that allows a species to survive and avoid competition with other species for the same resources. Some species have broad ecological roles and are termed generalist species. Some species have narrow ecological roles and are termed specialist species. Number of individuals Niche separation Specialist species with a narrow niche Niche breadth Region of niche overlap Resource use Generalist species with a broad niche Silence of the Bees Keystone species have a large affect on maintaining balance within an ecosystem. 1. Can be, but are not necessarily, pollinators and top predators. 2. Foundation species create and enhance habitats that benefit other species. Niches can be occupied by native or nonnative species. Indicator species provide early warning of ecosystem damage because they have a narrow range of tolerance. Fruit Fly Artificial selection has been used to change genetic characteristics of populations by selecting one or more desirable genetic traits and selectively breeding them. Genetic engineering has been used to create genetically modified organisms (GMO’s) by transplanting genes from one species to the DNA of another. • Has great promise • Unpredictable—trial and error • Future problems that may results can’t always be anticipated Advantages: • Can result in: Increased nutritional value of food Greater crop yield—stop starvation Possible medicinal benefits such as addition of vaccines or removal of allergens from food Resistance of plants to pests so decreased used of pesticides Resistance of plants to herbicides so weed tilling can be decreased resulting in less soil erosion Disadvantages: • Negative effects may be: Possible production of new allergens or toxins by GMF’s due to mutation Decrease in genetic diversity by planting only a few “superfoods.” Cost of raising/growing food will increase due to high costs of creating and patenting GMF’s. This may drive out some independent farmers Pest populations may become resistant to some pesticides. Fruits, veggies, livestock certified organic. How? and eggs can all be • Avoidance of most synthetic chemicals: Antibiotics Pesticides Fertilizer Food additives • No GMO’s or irradiation • No use of sewage sludge for fertilization • Use of farmland that has been free from chemicals for a # of years