Download Evolution Theory: Understanding Natural Selection, Genetics, and Speciation and more Lecture notes Evolutionary biology in PDF only on Docsity! Theory of Evolution Module B, Anchor 3 Basic Evolutionary Theory: 1. Explain what the term “evolution” means. Provide an example. Evolution – change in species over time. Example – whales evolved from a land mammal into a marine mammal. 2. What is natural selection? How does natural selection relate to evolution? The process by which some organisms survive and reproduce and others do not. Natural selection is the mechanism by which evolution occurs. 3. Describe the conditions necessary for natural selection to occur. Struggle for existence – some organisms live, others die Variation and adaptation – organisms are not all alike, organisms that are well-suited to survive in their environment possess adaptations Survival of the fittest – those organisms best adapted will survive and reproduce at higher rates than those who are not. 4. How does natural variation affect evolution? What are the sources of genetic variation within populations? Explain how each increases genetic variation. Without natural variation, all organisms would be identical. Therefore, no organism would have an advantage over another. If a change occurred in the ecosystem the entire species would be wiped out. Genetic variation arises from: Recombination during sexual reproduction – genes are put into new combinations during Meiosis, producing new phenotypes Mutation – mistakes are made in the copying of DNA Lateral gene transfer – genes are passed between prokaryotic organisms 5. How does natural selection account for the great diversity of organisms on the Earth today? Organisms adapted to their environments, creating a wide variety of organisms suited to various niches within various environments. 6. An inherited characteristic that increases an organism’s ability to survive and reproduce in its specific environment is called a(n) B. adaptation 7. How well an organism survives and reproduces in its environment can be described as its A. fitness 8. How are fitness and adaptation related? Fitness is the ability to survive and reproduce. This is made possible through the use of adaptations which make an organism better suited to its environment. 9. Why is reproduction, as opposed to simply survival, needed for fitness? An organism cannot affect the species as a whole without producing offspring 10. What is the role of the environment in determining fitness? The environment determines what traits make an organism more fit. For example, a trait allowing organisms to store water would increase fitness in a desert environment. In a rainforest, this trait would not be advantageous. 11. Why does natural selection work only on heritable characteristics, as opposed to acquired characteristics? Acquired characteristics cannot be passed on to offspring, therefore they cannot affect the genetic make-up of the population. For example, dying your hair purple does not give you genes for purple hair. Therefore, your children will not have purple hair. 12. What is the principle of common descent? All life is descended from one common ancestor. 13. Use the theory of natural selection to explain how two unrelated organisms, such as sharks and dolphins, come to possess very similar physical adaptations. The organisms occupy similar niches in similar environments. Therefore, the same types of adaptations are advantageous to them. This would lead to the possession of very similar physical traits. Natural Selection and Genetics: 1. The combined genetic information of all members of a particular population forms a: A. gene pool 2. How is evolution defined, genetically speaking? Change in allele frequency. 3. Explain what the term relative frequency means, include an example illustrating your answer. The frequency of an allele in relation to the other alleles in the gene pool. For example, fur color in rabbits comes in grey and white. There are 65 grey alleles and 35 white alleles. The frequency of the grey allele is .65; the frequency of the white allele is .35. How does evolution change the relative frequency of alleles in a gene pool? Why does this happen? Natural selection selects against particular phenotypes. The frequency of the alleles controlling those phenotypes is decreased. The frequency of other alleles in the gene pool goes up in response. 4. The frequency of a particular allele changes from 30% to 10%. Is this population evolving? Why or why not? Yes. The allele frequency has changed significantly. 5. Does natural selection work directly or indirectly on genotype? Explain your answer. Phenotype. An albino rabbit dies because it is white and stands out to predators more than a brown rabbit. It does not die because it has a white allele.
