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Evolution and the History of Life Part 2 MLK Fall 2005

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Presentation on theme: "Evolution and the History of Life Part 2 MLK Fall 2005"— Presentation transcript:

1 Evolution and the History of Life Part 2 MLK Fall 2005

2 Natural Selection Darwin theorized that evolution occurs through a process he called natural selection 1.______________ – Each species produces more offspring that will naturally survive. 2.______________ – individuals will be slightly different from one another. 3.____________ – competition for resources Abiotic and Biotic factors 4.___________________ – fitness (Survival of the fittest) Overproduction Genetic Variation Survival Struggle Successful Reproduction

3 Genetic Variation Two important words: 1.Genotype: The actual genetic code of an individuals DNA. 2.Phenotype: The physical characteristics of an individual.

4 Genotype versus Phenotype In many cases the phenotype is dominated by the genotype. In other cases, the environment exerts strong controls on the outward appearance of an organism. There might be the genetic potential, but it is not expressed. Thus, in general the phenotype represents some combination of genetic and environmental factors.

5 Chapter 8.3 Natural Selection in Action Insecticide Resistance Adaptation to Pollution Formation of New Species Separation Adaptation Division

6 Insecticide Resistance Insects that cause economic or health damage are becoming more difficult to kill due to insecticide resistances. Insecticides are compounds designed to kill insects (cidal – to kill). Insects that are resistant to a particular insecticide can survive and reproduce while those that do not have the genotype that infers resistance will die and will not reproduce.

7 Resistance The application of the harmful material (by humans) results in an artificial selection for those insects that are resistance. The same, unfortunately occurs to disease causing bacteria and virus, creating super bugs which often times results in incurable situations or death because antibiotics (against life) are no longer effective. This is why it is so important when prescribed an antibiotic to complete the treatment to avoid mutation during treatment of a pathogen creating a resistant pathogen that can survive – generation times of bacteria and virus is measured in minutes.

8 Adaptation to Pollution Peppered moths are the classic case. Dark moths were low in population because they did not blend well with the environment and so where eaten by predators. The pale moths were high in population because they were camouflaged. Then comes along the Industrial Revolution with coal burning to fuel factory machines and heat homes. The results of burning coal are sooty smoke, acid rain, and mercury contamination.

9 Well, the sooty smoke coated the vegetation made those pale moths stand out like a sore thumb and the dark moths became camouflaged. So what do you think happened? The population of dark moths increased and the population of pale moths decreased.

10 Match each statement about the peppered moth population (1-4) with the appropriate step in natural selection (a-d). 1. Moths that live to maturity may mate and produce offspring. a. Genetic variation 2. A population of peppered moths contains some light-colored moths and some dark-colored moths. b. Successful reproduction 3. Many moths do not survive because they are eaten by birds. c. Overproduction 4. Peppered moths lay many eggs. d. Struggle to survive B A D C

11 Formation of New Species Steps: Separation, Adaptation, Division (speciation). Separation allows the gene pool to be come isolated where no mixing of the populations occur. Adaptation are mutations that help the species to be successful in the new environment. Division occurs over time these mutant changes result in a separate species that cannot interbreed, speciation.

12 Chapter 8 Review One species evolves into another through the process of _____________________. A group of similar organisms that can mate with one another to produce fertile offspring is known as ________________. A(n) __________ helps an organism survive better it its environment. ____________is the process by which populations change over time speciation species adaptation Evolution

13 In ______________________________, humans select traits that will be passed from one generation to another. A change in a gene at the DNA level is called a __________________. The theory of evolution combines the principles of _________________________ __________________. The fact that all organisms have DNA as their genetic material is evidence that all organisms ______ __________________________. Everything had to start somewhere. Artificial selection Mutation Natural selection and genetic inheritance desended from a common ancestor.




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