Ch 5: Evolution These lectures contain copyrighted images that are provided in the teacher materials for Friedland/Relyea Environmental Science for AP Textbook. By using these lectures, you guarantee that you have legal access to these images or that you have replaced the copyrighted images with images that you have the rights to use.
Big Ideas Species are constantly evolving to meet changing environmental conditions. The faster you reproduce, the faster you can evolve. Survival of a species is improved by having a large and varied gene pool: increases the chances that some species will have the right genes to survive changes and pass those genes on to future generations Humans are creating drastic changes in environmental conditions which may influence evolution in unexpected ways
Evolution is The gradual process by which the present diversity of plant and animal life arose from the earliest and most primitive organisms, which is believed to have been continuing for the past 3.5 Billion years
Natural Selection A process in which those members of a population BEST SUITED for the environmental conditions will SURVIVE and REPRODUCE at a greater rate than those less suited AKA: Survival of the fittest
Go to http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html and watch Video #4: How does evolution really work What are the four factors in Evolution? Put the following steps in order: o Environmental conditions change o Over time the population changes to have more individuals who are better suited to the new environment and less of those who are less suited. o Populations have genetic variation o Some species (due to variations) are better able to survive than others
Niches
Fundamental vs. Realized Niche Fundamental Niche The range of niches an organism could potentially fill Realized Niche The actual niche an organism fills based on the ecological structure of the ecosystem
Occupying the same niche Partial niche overlap both compete in the overlapping parts of the niche. If the overlap is minimal, both species can coexist by specializing. Called resource partitioning. Full niche overlap both compete directly for the same resources One specie will be more suited and outcompete the other specie Called the Competitive Exclusion Principle
Range of Tolerance Range of chemical and physical conditions that must be maintained for a population to grow, develop, and function normally. Different species have different ranges, for example some desert plants thrive with 7-10 cm of rain per year while some tropical trees thrive with 100 to 300 cm of rain per year. If environmental conditions are outside of the preferred range, reproduction rates will fall, weaker members of the species (usually the very young and the very old) will die, and eventually the species will either adapt, migrate or die out.
Theory of Island Biogeography Islands that are larger and closer to the mainland will have a greater biodiversity and population size than islands that are smaller and further away from the mainland. Immigration (in) and emigration (out) are determined by proximity to the mainland the closer the island, the more of both Extinction is determined by island size Larger island = lower extinction rate
Island Biogeography You are studying two islands located off the coast of California. One is very large and located over 500 miles off the coast. The second one is medium sized and located 3 miles off the coast. Predict which island will have more biodiversity. Explain why using the Theory of Island Biogeography.
Go to http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html and watch Video #6: Why does evolution matter now Why is the Russian prison system considered to be "ground zero" in the fight against TB? What is responsible for the evolution of TB strains that are resistant to multiple drugs? How does the misuse of antibiotics affect the evolution of disease-causing bacteria? Use the theory of natural selection to explain the growing resistance to antibiotics. What are the consequences of antibiotic overuse? How do we prevent drug resistant bacteria populations? Why should we care about a resistant strain of TB in Russia?
Artificial Selection A process that allows humans to select the genetic characteristics of a population Selective breeding selecting certain plants/animals that have desired traits and purposefully mating them to create offspring that have those same traits. Pros: Will eventually increase the frequency of the desired trait in a population Can be done by ordinary people Cons: Slow process depends on the reproductive rate of the population Can only be done between similar organisms Examples: Selectively breed your milking cows that produce the most milk to produce a line of cows that produce more milk Selectively breed trees that grow the fastest to create a line of trees that grow very fast Ranchers will pay to have a top bull travel to the farm to procreate with their cows to produce
Genetic Engineering Altering an organisms genetic material by adding, deleting or modifying segments of DNA The process creates Genetically Modified Organisms (GMOs) Pros Produces desirable traits very quickly Desirable genes can be moved from one specie to another Cons Must be performed by scientists in a laboratory Somewhat unpredictable (not all transformations will work, some will work in unexpected ways) Once the genes are out in nature, we are no longer in control of where they go Examples: Genetically modified corn (called Bt corn) that produces its own endotoxin to kill caterpillar larvae Eggs can be genetically modified to have less cholesterol Round-up ready crops are genetically engineered to be resistant to common herbicides so you can spray the herbicides to kill weeds without killing the crop.
Steps in Genetic Engineering 1. Select and cut out a desirable gene (using enzymes) 2. Paste the desired gene into a plasmid (using enzymes) 3. Allow the desired gene to reproduce, creating copies of the desired gene (using a fast reproducing bacterial cell) 4. Insert the desired gene into plant cells 5. Grow the new plant with the desired gene
Go to http://www.pbs.org/wgbh/harvest/engineer/ and try your hand at both artificial selection and genetic modification You might need to install a shockwave plugin to run the animation Selective Breeding (Create a larger ear of corn) How long does it take to get larger corn? Assume each generation is a year. How easy was it to pick the best seeds to use the next round? What are the limitations of artificial selection? Genetic Modification (Create a Bt Tomato) List the steps in genetic modification in your own words. How long does it take to genetically modify a plant?