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Transcript
Chap 6 Evolution • Species- a group of organisms that share similar characteristics and can reproduce among themselves to produce fertile offspring • Evolution- the change of the inherited characteristics of a species over time Charles Darwin • On a journey exploring the South American coast, Charles Darwin recorded observations about the plants and animals he saw • He hypothesized that the plants and animals on the Galapagos Islands originally must have come from Central and South America, but the islands were home to many plants and animals he had never seen there Darwin • Observed 13 species of finches on the Galapagos Islands • All 13 were similar, except for differences in – Body size – Beak shape – Eating habits • He reasoned that the finches must compete for food. Finches with beak shapes that allowed them to eat available food allowed them to survive longer and produce more offspring than finches without those beak shapes Darwin • Developed a theory of evolution based on his observations and experiments • Described his ideas in book On the Origin of Species in 1859 • His ideas on evolution still accepted today Natural Selection • Organisms with the traits best suited to their environment are more likely to survive and reproduce. Their traits are passed to their offspring • Members of a large population compete for living space, food, and resources. Those best able to survive are more likely to reproduce and pass on their traits to next generation Variations • Variations- an inherited trait that makes an individual different from other members of its species – Result from permanent changes, or mutations, in organism’s genes – Over time, more and more individuals may inherit these variations, and if they continue to survive and reproduce, can create new species Adaptations • Any variation that makes an organism better suited to its environment – Can involve organism’s color, shape, behavior, or chemical makeup – Ex: camouflage • This video describes the journey of Charles Darwin and showcases the animals he studied HOMEWORK 2/10 • What adaptations would be helpful for an animal that moved to the Arctic? Geographic Isolation • Sometimes mountains, a lake, or other geographic features isolate some individuals from the rest of the population. • Over several generations, variations that were not present in the main population become more common in the isolated group • Over time, the two groups may become so different that they can no longer breed with each other, therefore becoming two different species Speed of Evolution • Gradualism- describes evolution as a slow, ongoing process by which one species changes. A continuing series of mutations and variations over time will result in a new species • Punctuated equilibrium- rapid evolution comes about when the mutations of a few genes results in the appearance of a new species over a relatively short period of time Clues about Evolution • Scientists can use fossils to study organisms no longer present on earth – Can also determine age of organism from the rock • Using this information, scientists can piece together how current animals and plants may have evolved from their ancestors. Fossil Record • Sedimentary rock- formed when layers of sand, silt, clay, or mud are compacted and cemented together, or when minerals are deposited from a solution. • Radioactive element- gives off steady amount of radiation as it slowly changes to nonradioactive element. Each one gives off radiation at a different rate – Scientists can estimate the age of a rock by comparing the amount of radioactive element with the amount of nonradioactive element in the rock More Clues about Evolution • Evolution can be viewed directly through 1. cross breeding plants to produce genetic changes 2. Antibiotic resistance in bacteria 3. Pesticide resistant insects • What is similar about these three examples that allows us to view evolution directly? Embryology • Embryo- the earliest growth stage of an organism • Embryology- the study of embryos and their development – What conclusions can you draw from this picture? Homologous Structures • Homologous body parts- body parts that are similar in origin and structure. Can also be similar in function. Indicate that species share common ancestor Vestigial Structures • Structures that don’t seem to have a function – Human appendix not used, but used to have similar function to a cecum, a part of the digestive track of many mammals • Provide evidence for evolution – We know snakes used to have legs because they still have pelvic bones ( a vestigial structure) MATERIAL FOR QUIZ ENDS HERE LAB • Complete the pedigree tutorial on http://www.phschool.com/atschool/phsciexp/ active_art/pedigree/index.html • Due Tuesday February 23, complete a pedigree of your family tree that tracks whether or not your family members can roll their tongue. – Must include your parents and siblings – Can be done on computer or hand drawn Dad Mom Mr. Powers Mrs. Powers Jen Jimmy Kerry Danny Henrik Amalia Pedigree Key Girl, can roll tongue Boy, can roll tongue Boy, can’t roll tongue Girl, can’t roll tongue Girl, carrier Boy, carrier Dad Mom Mr. Powers ????? Mrs. Powers ???? Kerry Jimmy Jen Danny Henrik Amalia Is it possible for Mr. and Mrs. Powers to have children that can curl their tongues? First, we have to figure out the Powers’ possible genotypes. To do that, we must create a Punnett square for Mom and Dad T t Tt tt t Tt t tt Dad Mom Mrs. Powers Mr. Powers Jen Danny Jimmy Kerry Henrik Amalia Mrs. Powers must be heterozygous! But we have no idea what genotype Mr. Powers has. What genotypes are possible? Tt or TT! Because both of these display the phenotype of not being able to curl tongue! Now, we must create a punnett square for both possible phenotypes. T TT Tt t TT Tt Tt tt T T TT T T t Tt t Dad Mom Mrs. Powers Mr. Powers Kerry Jen Jimmy Danny Henrik Amalia Can the Powers have a child that can curl his or her tongue? Yes, as long as Mr. Powers is heterozygous for the trait. T TT Tt t TT Tt Tt tt T T TT T T t Tt t There is a 25% chance of having a child that can curl his or her tongue if Mr. Powers is Tt. Primates • A group of mammals that include humans, monkeys, and apes – All have opposable thumbs, binocular vision, and flexible shoulders • Hominids- 4-6 million years ago, humanlike primates that ate both meat and plants and walked upright on two legs. A larger brain separated them from the apes Early Humans • Lucy- one of the oldest hominids discovered. Had humanlike jaw and teeth, a small brain, but walked UPRIGHT. • Homo sapiens- evolved about 400,00 years ago. Two groups – Neanderthals- short, heavy bodies, with thick bones, small chins, and heavy browridges. Lived in caves and used tools. Probably not direct ancestor of humans – Cro-magnon humans- similar physical appearance to modern humans. Lived in caves, made stone carvings, buried dead. Painted animals and people on cave walls. Thought to be direct ancestors of modern humans Homo Sapiens Neanderthal Cro-magnon