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Transcript
Evolution California Biology/Life Science Standard 7 3.a Quick Review Evolution is any change in time in the relative frequencies of alleles in a population. Evolution studies the varieties and interactions of living things across time. A great diversity of species increases the chance that at least some living things will survive in the face of large changes in the environment. Questions 1. What is a population? 2. Suggest a reason why the population of brown lizards decreased. 1. A group of individuals that belong to the same species and live in the same area. 2. Answers will vary. Students may suggest that environmental factors caused more brown lizards to be eaten. Evolution California Biology/Life Science Standard 7 3.b Quick Review During his travels, Darwin made numerous observations and collected evidence that led him to propose his theory of evolution. Geologists James Hutton and Charles Lyell helped scientists recognize that the Earth was very old and that the processes that changed Earth in the past were the same processes that operate today. Questions 1. What are some ways Earth has changed over time? 2. How did Hutton and Lyell influence Darwin’s thinking? 1. Students may suggest that mountains have been built up, or earthquakes have buried other rock 2. Darwin thought that if Earth could change, life could change as well. Evolution California Biology/Life Science Standard 7 3.c Quick Review Homologous structures provide evidence that all four-limbed vertebrates share a common ancestor. Limbs of different vertebrates have different functions but are structurally similar and develop from the same embryonic tissues. Fossils of ancient whale-like animals with legs suggest that whales and other mammals likely share a common ancestor. Questions 1. How are the bones similar across the four groups? 2. Would lighter bones be more advantageous for an animal that lived in the air or on land? 1. Similar arrangement and number 3. In air. (Lighter bones are easier to lift, such as in flight; heavier bones offer more structural support, as needed to bear weight on the ground.) Cell Biology California Biology/Life Science Standard BI 1.a Quick Review The phenotype of an organism is its physical characteristics. The genotype of an organism is its genetic makeup. Natural selection works on the phenotype of an organism. Questions 1. Why might the red lizard population have disappeared? 2. Which lizard population—brown or black—is more successful in this example? 1. They may have been more visible to predators 2. black Evolution California Biology/Life Science Standard BI 7.b Quick Review Organisms that have two identical alleles for a particular trait are homozygous. Organisms that have two different alleles for the same trait are heterozygous. A genetic disorder caused by a recessive allele, such as TaySachs disease, only appears if the individual inherits two recessive alleles for the trait. A heterozygous individual still contributes the allele to the gene pool even if the person doesn’t have the disorder. Question Both parents are heterozygous for Tay-Sachs disease. What is the chance that their offspring will have Tay-Sachs? (Hint: Use a Punnett square for help.) 1 in 4 chance. Evolution California Biology/Life Science Standard BI 7.c Quick Review The two main sources of genetic variation are mutations and the genetic shuffling that results from sexual reproduction. Plant breeders use several methods to increase genetic variation in plants and to produce new types of plants. A mutation is any change in the sequences of DNA. Some mutations affect an organism’s phenotype, while others do not. Questions 1. Describe one way in which natural selection could act on a plant characteristic. 2. Name one characteristic that plant breeders might select for. 1. Sample answer: If average temperatures in an area increase over time, plants with greater heat tolerance will be more likely to survive and reproduce. 2. Sample answer: Resistance to pests © Pearson Education, Inc., Publishing as Pearson Prentice Hall. All rights reserved. Evolution California Biology/Life Science Standard Bl 7.6 Quick Review Sample Population The number of phenotypes a given trait has is determined by how many genes control the trait. Genetic variation is studied in populations. A gene pool consists of all genes, including all of the different alleles that are present in a population. Genetic variation is present within and between species of animals. Questions Frequency of Alleles 1. Describe the characteristics of two breeds of dogs. What variation is present within the species? 2. Compare the characteristics of frogs and earthworms. What variation is present between the species? 1. Answers will vary. Students may compare any two types of dogs, noting the variation present between the types. 2. Sample answers: Students may note the presence of limbs on a frog or differences in body systems between the species. Evolution California Biology/Life Science Standard *BI 7.e Quick Review According to the Hardy-Weinberg principle, in order for genetic equilibrium to be maintained, five conditions must be met: 1. There must be random mating; 2. The population must be large; 3. There can be no movement into or out of the population; 4. There can be no mutations; and 5. There can be no natural selection. If all of these conditions are met, evolution will not occur. Questions 1. Why can there be no movement into or out of the population? 2. Is it likely that all five conditions can be meet for long periods of time? 1. New organisms moving into the population will bring new alleles 2. No Evolution California Biology/Life Science Standard *BI 7.f Quick Review The Hardy-Weinberg equation states: p+q=1 where p = the frequency of one allele and q = the frequency of another allele. The three genotypes possible are: pp (p2), pq, and qq (q2). The equation that shows this is: p2 + 2pq + q2 = 1. Questions 1. If p = 0.1, what does q equal? 2. What are the frequencies of the alleles p2, 2pq, and q 2? 1. q = 0.9 2. p2 = 0.01, 2pq = 0.18, q2 = 0.81 Evolution California Biology/Life Science Standard BI 8.a Quick Review An adaptation is a genetic change in an organism that helps it survive in its environment. The Galápagos finches likely descended from one population that became geographically isolated. Questions 1. What helped the finches adapt to local food sources? 2. During a dry season, which finches may have a better chance of survival? 1. Changes to their beaks 2. Seed-eating Evolution California Biology/Life Science Standard BI 8.b Quick Review A species’ traits may change over many generations due to environmental influences, such as changes in climate or landforms; interspecies interaction; and genetic mutations. Natural selection favors helpful traits in a way that increases the species’ fitness over time. Questions 1. Is a parrotlike beak better adapted to feeding on fruit or insects? 2. What would likely happen to the population size of the vegetarian tree finch if trees on the island did not produce fruit one year? 1. Fruit 2. The population size would probably decline. Evolution California Biology/Life Science Standard BI 8.c Quick Review Natural selection is not the only source of evolutionary change. Mutations, migration, genetic drift, and nonrandom mating can also result in evolution. In small populations, individuals that carry a particular allele may leave more descendants than other individuals, just by chance. Over time, a series of chance occurrences can cause an allele to become common in a population. Questions 1. How do the descendant populations in the diagram differ from the original population? 2. What is genetic drift? 3. What is the founder effect? 1. They are different colors and have different markings. 2. A random change in allele frequency 3. A situation in which allele frequencies change as a result of a migration of a small subgroup of a population Evolution California Biology/Life Science Standard BI 8.d Quick Review Reproductive isolation occurs when members of two populations cannot interbreed. There are three types of reproductive isolation: behavioral isolation, geographic isolation, and temporal isolation. Questions 1. What type of reproductive isolation has occurred when a barrier, such as a river, separates two populations? 2. When two populations are capable of breeding, but don’t because of different courtship rituals, what type of reproductive isolation has occurred? 1. geographic isolation 2. behavioral isolation Evolution California Biology/Life Science Standard BI 8.e Quick Review During the Paleozoic Era, the continents were one large landmass. As the continents drifted farther and farther apart, ancestors of mammal groups were isolated from one another. Mammals that feed on ants and termites evolved in five different regions. Question What characteristics do these mammals share? Front claws, long snout, and long tongue © Pearson Education, Inc., Publishing as Pearson Prentice Hall. All rights reserved. Genetics California Biology/Life Science Standard *BI 8.f Quick Review The exact sequence of nitrogen bases in DNA is unique to each species. Organisms with similar DNA sequences are more closely related than those with different sequences. Comparing genes of different species helps to determine possible relationships among species. Questions 1. Is the DNA of giant pandas more similar to the DNA of bears or lesser pandas? 2. When did all four groups share an ancestor? 3. Which have more similar DNA sequences, raccoons and lesser pandas or giant pandas and bears? 1. Bears 2. More than 40 million years ago 3. Giant pandas and bears Evolution California Biology/Life Science Standard *BI 8.g Quick Review Many genes are shared by a wide range of organisms. Cytochrome c is a protein found in most eukaryotic cells. The more closely two organisms are related, the more closely their genes resemble one another. Questions 1. Is a turkey more closely related to a chicken or to a rattlesnake? How can you tell? 2. With which animal does a donkey share the most recent ancestor? 1. a chicken because they have more amino acid sequences in common 2. horse