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Intro to Evolution Objective 9 • What is Evolution? • EVOLUTION-- Intro to Evolution Objective 9 Why Should We Study Evolution? • Scientists use evolution to ______________ organize biology. • It helps us understand relationships between ecosystems species in ________________. • It explains the development of _______________ antibiotic resistance and ___________________ resistance. insecticide • It explains how viruses such as _____________________________ can change. AIDS and the Flu • Understanding relationships between organisms can help us make conclusions in _______________ ___________. Medical research Intro to Evolution Objective 9 2 Types of Evolution: Law of Evolution)— • Microevolution (______ change that occurs within any given species over time. Example: A population of bacteria Antibiotic resistance develops ______________________. Theory • Macroevolution (_____________ of Evolution) refers to the changes among species over time. Example: the replacement of dinosaurs by Mammals ___________________). Natural Selection Objectives 7-9 Charles Darwin proposed his theory of evolution in 1844. **Evolution works at the POPULATION level—NOT individual level** at the ________________ 2 Types of Evolution: • Microevolution (______ Law of Evolution)—change that occurs within any given species over time. Example: A population of bacteria develops ______________________________. Antibiotic resistance • Macroevolution (_____________ of Evolution) refers to the changes among species over time. Theory Example: the replacement of dinosaurs by ___________________). Mammals Natural Selection Objectives 7-9 How does Natural Selection (Microevolution) work? MAIN IDEA: Natural selection changes the frequency of certain Genes ______________within a population ______________________ as the Gene Pool Adapts population ____________________ to its environment. Natural Selection Objectives 7-9 1. All species have natural genetic ____________ asvariation a result of ____________ mutation. random • Variation-Differences in characteristics within a species Question: What causes variation within a species? Mutations and Crossing Over Natural Selection Objectives 7-9 2. The environment presents many challenges (selective pressures) to _________________. Examples: predator-prey interactions, Survival ________________ shortage, changes in _______________________ conditions) resource environmental Natural Selection Objectives 7-9 3. There is a struggle for survival. Struggle = competition fittest __________________. The _________ individuals will be able to survive (those genes whose ____________ give them an advantage). • Question: Are the fittest individuals the same in all environments? No!! – different traits provide an advantage in different environments Natural Selection Objectives 7-9 Traits (Genes) from the survivors are passed 4. _______________ on to their offspring. The frequency of the survivors’ genes will increase in the population over time as the population _____________ to adapts its environment. • Adaptation—any variation that allows an organism to ___________________ successfully. reproduce What are the adaptations here? Natural Selection Objectives 7-9 5. Individuals (and species) that are not able to survive and reproduce will die off (become Extinct Their _____________ ________________). will become extinct with them. Traits (Genes) Natural Selection Objectives 7-9 Example of Natural Selection In 1973 Peter and Rosemary Grant began a study of the finches on the Galapagos Islands. They noticed that some finches had large beaks while others had smaller more slender beaks. Both birds with small beaks and those with large beaks seemed to feed primarily on small, soft seeds. While the Grants were on the Islands a drought occurred. During a drought, plants produce only a few seeds. These seeds tend to be larger and tougher. Birds with small beaks are not able to eat these seeds. The Grants found that after several dry years the average size of the birds’ beaks had increased. Natural Selection Objectives 7-9 • Questions: 1. In this example what variation was present in the finches? Size of the beaks in Finches 2. What was the selective pressure? Drought causing the absence of seeds 3. What change occurred within the population during the dry years? The size of the beaks 4. Use the theory of natural selection to explain how this change occurred. The Larger beak gene became more popular in the population and the thin, small beak genes decreased. Behavior Objective 11 Behavior – refers to the actions and mannerisms made by organisms, systems, or artificial entities in conjunction with their environment Behavior Objective 11 What is the affect of natural selection on behavior? Behaviors will be maintained or removed based on their overall contribution to the _____________ offitness an individual. The behavior must be ____________________genetic because natural selection changes the frequency of that _____________ (alleles)gene in the gene pool. Behavior Objective 11 Example: Read the passage below and answer the questions that follow. Animals display various behaviors for many reasons. Generally, behaviors can be linked to a goal of survival or reproduction. One famous biologist, Niko Tinbergen, noticed that Common Black-headed Gulls would meticulously remove the eggshell fragments from their nests after their offspring hatched. In an attempt to understand this behavior, he painted chicken eggs so that they were camouflaged into the backgrounds where the gulls lived and nested. He then placed some broken eggshells near them. He then noted how many eggs were discovered and eaten by Carrion crows. He observed that crows were able to easily notice the white interiors of the broken shells and consumed many more of the camouflaged eggs near the broken shells than camouflaged eggs with no broken shells near them. (Taken from Holt Biology Skills Worksheet p13) Behavior Objective 11 1. What question was Tinbergen attempting to answer with his experiment? Why do gulls remove the shells? 2. Why did Tinbergen set up one area with camouflaged eggs and no shell fragments? Experimental control Behavior Objective 11 3. Explain how you would interpret the behavior of the gulls based on this experiment. Gulls remove shells to keep predators from eating the other eggs 4. How is the behavior of the gulls linked to natural selection? Gulls who remove shells have more offspring live so the gene that makes them remove shells is passed on. The Genetics of Natural Selection Objective 10, 15-18 Natural selection changes the frequency of certain _________within a population Genes _______________ as the population Gene pool ____________________ to its environment. adapts **Evolution works at the POPULATION level— NOT the _________________ level** Gene Pool—The individual entire collection of genes among a _______________. population The Genetics of Natural Selection Objective 10, 15-18 Remember that there can be different versions of a gene. Each version of a gene is called an allele. You inherit one allele for each gene from each parent. The Genetics of Natural Selection Objective 10, 15-18 Allelic Frequency—the % of a particular allele Gene pool (choice) within a _______ ______. The Genetics of Natural Selection Objective 10, 15-18 Example: Sickle Cell Anemia—a recessive genetic disease that affects red blood cells. A-dominant allele S-recessive allele 30 people AA 15 people AS 5 people SS What are the allelic frequencies of A and S? A = 75/100 or 75% S= 25/100 or 25% The Genetics of Natural Selection Objective 10, 15-18 • If allelic frequencies remain the same from generation to generation, the population is Static ???___________ and said to be in ___________ the population is NOT evolving. • If the allelic frequencies are changing from generation to generation then we can conclude that Frequencies are changing??? ________________________________. The Genetics of Natural Selection Objective 10, 15-18 • Natural selection is the MAJOR mechanism for changing allelic frequencies. However, there are other mechanisms of evolutionary change. These include genetic drift, gene flow, mutation and recombination. • Genetic Drift—Random change of allelic frequencies in a small population due to chance. The Genetics of Natural Selection Objective 10, 15-18 The Genetics of Natural Selection Objective 10, 15-18 Gene Flow—transfer of genes from one population to another due to immigration or emigration. ***Explain how gene flow can lead to evolutionary change. Gene flow can show how genes move into or out of a population, thus changing the frequencies. The Genetics of Natural Selection Objective 10, 15-18 Mutation—any change in a sequence of DNA. ***Explain how mutation can lead to evolutionary change. Mutations can introduce “new” genes into a population and thus changing the Gene Frequencies. The Genetics of Natural Selection Objective 10, 15-18 Recombination—exchange of genetic material that occurs due to crossing over. ***Explain how recombination can lead to evolutionary change. Recombination can make new gene combinations and this can change the gene frequencies in a population. Speciation Objective 13 How can you tell members of 2 different species apart? Physical characteristics, DNA, Behavior What is a species? A group of organisms that can mate and produce fertile offspring Speciation Objective 13 How can natural selection produce a new species? 1. Natural selection causes changes in _____________ _______________ of a Allelic Frequencies population. 2. Different parts of a population might Change _________________ in different ways. Speciation Objective 13 3. Due to these changes, the 2 parts of the mate population are now unable to __________ Any factor that keeps Reproductive Barrier— fertile offspring from being produced. mate this 4. If the 2 parts can no longer _____________ species means a new ___________ has evolved. The evolution of a new species from old ones is called ______________ speciation or macroevolution. Speciation Objective 13 An Example of Speciation: About 50,000 years ago, the region now known as Death Valley had a rainy climate and many lakes and rivers that were interconnected. About 10,000 years ago, the climate began to get much drier and by 4000 years ago the area had become a desert. Lakes and rivers that were once connected were reduced to isolated springs, mostly found in deep clefts between rocky walls, separated by vast expanses of desert. The water in each spring varies in temperature and salinity. Today, many of the springs are inhabited by a tiny fish called a pupfish. Each spring is home to a different species of pupfish that is adapted to that particular pool and found nowhere else in the world. Speciation Objective 13 • Describe the reproductive barrier that has separated the various species of pupfish. They are too far apart to mate with each other • Use natural selection to explain how these various species of pupfish could have evolved from a single species. Phylogeny Objectives 4, 14 Phylogeny— An organism’s evolutionary history An organism’s phylogeny can be diagramed using a phylogenetic tree. A phylogenetic tree is a branching diagram that shows evolutionary relationships. Phylogeny Objectives 4, 14 Phylogeny Objectives 4, 14 How is the phylogeny of an organism determined? Scientists classify organisms based on their DNA ______________, similarities in ________, Anatomy and _______________. Behavior Phylogeny Objectives 4, 14 Common Ancestor-- A species from which 2 or more species separated Diversity— The number of different species in an ecosystem Phylogeny Objectives 4, 14 Why is a more diverse ecosystem more stable? There is more than 1 organism to fill a role, so if one dies there is a “back up”. Example- an ecosystem with only one producer will fall apart thatnatural speciesselection goes extinct How ifcan increase diversity? Natural selection provides a way for new species to evolve which can raise diversity. Evidence of Evolution Objectives 1-3, 5-6 1. Fossils- any evidence of an organism __________________ that lived long ago. sedimentary Most fossils form in __________________ rock. This type of rock is formed when sediments ( ) form layers and areand compressed Dirt sand together. Organic matter trapped between the layers decays slowly and a fossil is left behind. Evidence of Evolution Objectives 1-3, 5-6 Examples: Whole bodies,shells, bones, waste How do fossils show evidence of evolution? They show us what species used to look like in the past. Evidence of Evolution Objectives 1-3, 5-6 2. Biochemistry-- Nearly all organisms share _________, ATP, and many enzymes among DNA their biochemical molecules The more closely related organisms are, the more similar their ________ (and therefore, DNA ___________ __________) will be. Their Traits Evidence of Evolution Objectives 1-3, 5-6 Example: The enzyme, cytochrome c, occurs in bacteria and organisms as diverse as ______________ bison. Biologists compared the differences that exist among species in the Amino acid _____________ __________ sequence of cytochrome c. Organisms that are biochemically similar have fewer differences in Amino Acid their_________ ________ sequences. Evidence of Evolution Objectives 1-3, 5-6 3. Homologous Structures- Are similar structure in different species Examples: Arms, wings, fins • How do homologous structures show evidence of evolution? Organisms that posses the same Homologous structures have common ancestors. Evidence of Evolution Objectives 1-3, 5-6 4. Vestigial StructuresStructures that had a use in ancestors but that have no use in present day organisms. Examples: Pelvic bones in whales and snakes Tailbones in humans • How do vestigial structures evidence of evolution? They show past ancestral traits Evidence of Evolution Objectives 1-3, 5-6 5. Embryology- The study of characteristics of embryos • How does embryology show evidence of evolution? Organisms with similar embryonic traits have a common ancestor.