Aim: Does Evolution Happen Today?

Evolution - Review Evolution is a change in a population of organisms over a period of time. Within every population, there are individuals who are slightly different. These differences are the results of mutations in the DNA. These mutations lead to new traits that can help or hinder an individual chances to survive. “Survival of the fittest” and “natural selection” means that individuals who have better traits will survive and pass on these traits to their offspring. If the individual does not reproduce, then those traits become extinct.

Evolution - Review An individual’s behavior can also help with natural selection. If the behavior helps the individual to survive, the behavior may be pass on to offspring (instinct or teaching).

Evidence for Evolution - Review Although evolution is only a theory, there are lots of evidence that support it. Fossils show a gradual changes in species Similar anatomy show common body structures that are shared by different animals Embryo development seem to be similar in many animals. Similar proteins are found in different animals using the same amino acids. Similar DNA are found in different organisms.

Reading Phylogenic Trees Phylogenic trees shows how organisms change over time. The oldest part of the tree is always where there is only one line. As the line splits, time become closer to our time. A transition species occurs at the point where the line split. Sometime the lines make it to the top, which means that the organism still exist today. Sometime the line ends before it reaches the top. This means that the organism became extinct.

Antibiotic Resistant Bacteria Doctors use antibiotic (medicines) to kill infections that occur in the body. The antibiotic is designed to kill bacteria. But because within every population, there are individuals who are slightly different; some bacteria may have a mutation that makes them resistant the antibiotics. The antibiotics kills all the bacteria except for these mutated bacteria. These bacteria reproduce and pass on their mutated genes to their offspring. Now all the new bacteria are resistant to the medicine and the medicine does not work. New antibiotics are needed to kill the new bacteria.

Pesticide Resistant Insects. Farmers use pesticides to kill unwanted insects that eat their crops. The pesticides are designed to kill insects. But because within every population, there are individuals who are slightly different; some insects may have a mutation that makes them resistant to the pesticide. The pesticide kills all the insects except for these mutated insects. These insects reproduce and pass on their mutated genes to their offspring. Now all the new insects are resistant to the pesticide and the pesticide does not work. New pesticides are needed to kill the new insects.

The Key to a Species Chances to Survive The environment is always changing. (climate, amount of resources) Populations that have the most variety will have a better chance of some individuals surviving sudden environmental changes. These surviving individuals will reproduce and keep the species from becoming extinct. Populations that have few or no variety will die out if the environment changes too quickly.

What is the best way to reproduce? Asexual reproduction is fast. Only one parent is needed. Little variation (clones) If a mutation occurs, the mutation will quickly move through the population. Sexual reproduction is slow. Needs two individuals Lots of variations (Chromosome combinations) Mutations move slow through a population. (mutation has to occur in the egg or sperm cells in order to be passed on to offspring).