Transcript Chapter 16
EVOLUTION Students know and understand the characteristics and structure of living things, the processes of life, and how living things interact with each other and their environment. Benchmark 3.18: Organisms change over time in terms of biological evolution and genetics. Darwin, the Beagle and Finches: 3:59 Darwin’s Discoveries: 10:10 Gene frequency, natural selection, speciation: 29:00 What do you get when you cross a mouse with a mango? 4:15 Why did the woolly mammoth become extinct? 2:17 Total time: 49:41 min. (approximately) Before Darwin, most people believed that each species was created once and stayed the same forever. The modern theory of evolution began when Charles Darwin presented evidence that evolution happens and offered an explanation of how evolution happens. Darwin, the Beagle and Finches (3:59) Through breeding pigeons, Darwin gained a new insight. Through artificial selection, breeders can produce individuals that will pass on desirable traits. Darwin took a voyage in 1831 from Europe around S. America, Australia and Africa with a stop at the Galapagos Islands off the western coast of S. America. It was in the Galapagos Islands that Darwin noticed that some species resembled those found in S. America, but were slightly different. Darwin was influenced by ideas from the fields of natural history, economics, and geology. The ideas of Lamarck, Malthus, Culvier and Lyell were especially important. In 1809, French scientist, Jean Baptiste Lamarck proposed that organisms change over time as they adapt to their environment. He also incorrectly proposed that use or disuse of a characteristic would be passed on to future generations. If you did not exercise your right arm all your life and had wimpy muscles, would that trait be passed on to your offspring? What can you conclude about Lamarck’s proposal, and why would it have been important to Darwin? Darwin Develops a Non-Random Theory of Evolution: Natural Selection and Adaptation (4:41) Thomas Malthus was an English economist who wrote an essay in 1798 where he observed that human populations were growing faster than food supplies. While food growth increased linearly, populations grew exponentially. Darwin observed that all kinds of organisms tend to produce more offspring than can survive, so he applied this to his theory that populations are limited by their environments. Geologist(s) Theory Georges Cuvier Species change over time but not gradually, he thought the changes were sudden. James Hutton and Charles Lyell Both Hutton and Lyell thought that geologic processes work gradually and constantly. They showed that Earth’s history was long enough that it supported the idea that species changed gradually over long periods of time. Cuvier Lyell Hutton Darwin formed a key idea: Individuals that have traits that better suit them to their environment are more likely to survive. Individuals that have certain traits tend to produce offspring with those same traits . Those differences are part of natural selection, which Darwin proposed is a cause of evolution. 1. Overproduction: Every population is capable of producing more offspring than can possibly survive. 2. Variation exists within every population. Much of this variation is in the form of inherited traits. 3. Selection: In a given environment, having a particular trait can make individuals more or less likely to survive and have successful offspring. So, some individuals leave more offspring than others do. 4. Adaptation: Over time, those traits that improve survival and reproduction will become more common. Darwin published “Origin of Species by Means of Natural Selection” in 1859. The fossil record reveals a pattern of gradual change from past to present. Biogeography shows that environments shape the evolution of organisms. Developmental Biology shows that the ancestry of organisms are similar such as the development of multicellular organisms from embryos. Anatomy or body structure shows how some species are the same or different. There is a hypothesis that all vertebrates descended from one common ancestor. When comparing modern vertebrates, the differences in the size, number and shape of bone is clear, yet the basic pattern is the same. Strengths: His theory is supported by data and helps explain that data. He presented a logical and testable theory for the process of evolution. He changed the way scientists think about the diversity of life. Weaknesses: His theory lacked a clear mechanism fro inheritance because he knew very little about genetics. Today, an understanding of genetics is integral to the understanding of evolution. The link between microevolution and macroevolution is speciation. Speciation is the formation of a new species as a process of genetic change or as a pattern of change in the form of organisms. What do you get when you cross a mouse with a mango? (4:15) Natural selection Migration Mate Choice Mutation Genetic Drift ◦ Causes an increase or decrease in certain alleles in a population. ◦ The movement of individuals into, out or between populations. Changes the types of alleles in a population. ◦ Random pairing of mates increases the assortment of traits. ◦ Changes the numbers and types of alleles from generation to generation. ◦ Random effects of everyday life can affect the survival and reproduction in populations, thus some alleles can become more or less prevalent. Convergent evolution is strongly directed by environment— species living in the same type of environment should evolve similar adaptations. Coevolution: Species that live close together can affect one another’s evolution. Species that live in close contact often have clear adaptations to one another’s existence. Coevolution between the yucca moth and the yucca plant. A female yucca moth (Tegeticula yuccasella) pushing pollen into the stigma tube of the yucca flower while visiting the flower to deposit her eggs. Over time, species may split into two or more lines of descendants or lineages. As the splitting repeats, one species can give rise to many new species. Darwin’s finches Adaptive Radiation (13:04) If all members of a lineage die off or fail to reproduce, the species is said to be extinct. Evolution and Sexual Reproduction Why did the Wooly Mammoth become extinct? (2:17) Gradualism is a model used to describe the formation of a new species through small, gradual changes as opposed to large-scale changes. Punctuated equilibrium is where new species “suddenly” appear in response to environmental changes. Chapter 16 Lab pg. 387: Selection Model