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Biology 160 Week 1 Notes

by: Emily Swafford

Biology 160 Week 1 Notes BIL 160

Marketplace > University of Miami > Biology > BIL 160 > Biology 160 Week 1 Notes
Emily Swafford
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Chapter 22 Notes from the book
Evolution and Biodiversity
Van Dyken
Class Notes
Evolutionary Biology




Popular in Evolution and Biodiversity

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This 7 page Class Notes was uploaded by Emily Swafford on Tuesday January 26, 2016. The Class Notes belongs to BIL 160 at University of Miami taught by Van Dyken in Fall. Since its upload, it has received 40 views. For similar materials see Evolution and Biodiversity in Biology at University of Miami.

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Date Created: 01/26/16
Biology 160 Notes Chapter 22: Descent with Modification: A Darwinian View of Life Intro:  Evolution – descent with modification  The Origin of Species by Charles Darwin published in 1859  Evolution is a change in the genetic composition of a population from generation to generation  The pattern of evolution – observations about the natural world  The process of evolution – the mechanisms that produce the observed pattern of change  Evolution explains and connects a vast array of observations about the living world  We test our theory of evolution by examining whether it can account for new observations and experimental results 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species  Aristotle believed species were fixed and unchanging; believed in scala naturae (scale of nature); consistent with creationism  Carolus Linnaeus – developed binomial naming system; described the pattern of the species creation  Darwin drew work from studying fossils (the remains or traces of organisms from the past)  New layers of sediment cover old ones and compress them into layers of rock called strata  The stratum provides a glimpse of some of the organisms that populated the earth at the time that the layer formed  Paleontology – the study of fossils; developed by Georges Cuvier  Cuvier had observed that one layer to the next, species disappeared and others appeared; yet he still opposed evolution  Darwin was influenced by Hutton and Lyell (geologists) who thought that slow, continuous actions (at the same rate) occurred and similar slow process produced substantial biological change as well  French biologist, Jean – Baptiste de Lamark proposed HOW life changed 1. Use and disuse: the idea that the parts of the body that are used become larger and stronger while the parts that aren’t used deteriorate 2. Inheritance of acquired characteristics: an organism could pass these modifications to its offspring  Darwin rejected this, but thought that variation was introduced into the evolutionary process in part through inheritance of acquired characteristics  Today, we also refute these mechanisms. Traits are not inherited based on how often they are used. 22.2: Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life  Charles Darwin (1809-1882) - from England; father = physician who sent Darwin to medical school in Edinburgh, but Darwin quit and enrolled at Cambridge to become a clergyman; became a botany professor  Darwin embarked on the Beagle in December of 1831 to chart stretches of the South American coastline  Darwin noticed plants in temperate South American climates resembled those of tropical South American climates more so than plants in temperate European climates.  In the Galapagos, he noticed several kinds of mocking birds that were similar but different species  Darwin hypothesized that the Galapagos had been colonized by organisms that had strayed from South America and then diversified  During the voyage, Darwin observed adaptations (inherited characteristics of organisms that enhance their survival and reproduction in specific environments)  Darwin perceived that adaptation and origin of new species were related: New species arise from an ancestral form by the gradual accumulation of adaptations to a different environment  Natural selection – a process in which individuals that have a certain inherited trait tend to survive and reproduce at higher rates than other individuals BECAUSE of those traits  In 1844, Darwin wrote a long essay on descent with modification and its underlying mechanism: natural selection  Alfred Russel Wallace (1823-1913) worked in South Pacific islands of Malay Archipelogo; had developed a hypothesis nearly identical to Darwin’s Natural Selection and published first; however, he admired Darwin and allowed Darwin to be known as the main architect of evolution  In the Origin of Species, Darwin made 3 Main Observations: 1. The unity of life 2. The diversity of life 3. The match between organisms and their environments  They all resulted from Descent with Modification  Darwin never said “evolution” he only said “descent with modification”  Descent from common ancestor  Tree of Life – each fork represents the most recent common ancestor; explains morphological gaps  Scientists estimate that 99% of species that have ever lived are extinct  Artificial selection- modifying species over many generations by selecting and breeding individuals that possess desired traits  Darwin’s observations and inferences: 1. Observation: Members of a population often vary in their inherited traits 2. Observation: All species can produce more offspring than their environment 1. Inference: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals 2. Inference: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations  Darwin read Thomas Malthus’s essay to draw these inferences  When traits are favored, they are likely to appear at a greater frequency in the next generation.  Thus, over time, natural selection resulting from factors such as predators, lack of food, or adverse physical conditions can lead to an increase in the proportion of favorable traits in a population  If artificial selection can bring about dramatic change in a relatively short period of time, then natural selection should be capable of substantial modification of species over many hundreds of generations  Even if the advantages of some heritable traits over others are slight, the advantageous variations will gradually accumulate in the population, and the less favorable will diminish  Over time, the process will increase the frequency of individuals with favorable adaptations and hence refine the match between organisms and their environment  Summary: 1. Natural selection is a process in which individuals that have certain heritable traits survive and reproduce at higher rates than other individuals because of those traits. 2. Over time, natural selection increases the match between organisms and their environment 3. If an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species 4. Although natural selection occurs through interaction between individual organisms and their environment, INDIVIDUALS DO NOT EVOLVE! The POPULATION evolves. 5. Natural selection can amplify or diminish only those heritable traits that DIFFER among individuals of a population. (Thus if a trait is heritable, if all the individuals in the population are genetically identical for that trait, evolution by natural selection CANNOT occur. 6. A trait that is favorable in one place may or may not be favorable in another 22.3: Evolution is supported by an overwhelming amount of scientific evidence.  4 types of data that document the pattern of evolution: Direct observations, homology, fossil records, and biogeography 1. Direct Observation:  Natural selection in response to introduced species:  The soapberry bug (Jadera haematoloma) feeds on seeds of the balloon vine (Cardiospermum corundum). In Florida, balloon vines became rare, so soapberry bugs started feeding on goldenrain tree (Koelreuteria elegans). Soapberry bugs feed best when their beak length matches the depth at which the seeds are found. Goldenrain tree fruit have seeds much closer to the fruit’s surface. Beak lengths are shorter in populations that feed on goldenrain tree.  The size of the soapberry bug’s food source can result in evolution by natural selectioin for matching beak  Drug-resistant bacteria: Staphylococcus aureus  methicillin-resistant Staphylococcus aureus (MRSA)  In two years, S. aureus became resistant to penicillin. With each new drug, came a new strain of pathogen  Overtime, the resistant individuals became increasingly common, leading to the spread of MRSA  Multidrug-resistant strains of today may have emerged over time as MRSA strains that were resistant to different antibiotics exchanged genes  Natural selection is the process of editing not creating  A drug does not CREATE a resistant pathogen. It SELECTS a resistant pathogen already present in the population  Natural selection depends on time and place. Selects that have advantages in the current, local environment 2. Homology  Comes from analyzing similarities among different organisms  Related species have characteristics that have an underlying similarity yet function differently  Similarity resulting from common ancestry = homology  Anatomical and Molecular Homologies  The forelimbs of all mammals show the same arrangement of bone from shoulder to tip of the digits even though the appendages have different functions  The underlying skeletons of the arms, forelegs, flippers, and wings of different mammals are homologous structures that represent variations on a structural theme that was present in their common ancestor  At some point in development, all vertebrate embryos have a tail located posterior to the to the anus and pharyngeal arches (gills)  Vestigial structures are remnants of features that served as a function in the organism’s ancestors  All forms of life use the same genetic code  Humans and bacteria share genes from a common ancestor  Homologies and “Tree Thinking”: All life shares the deepest layer, and each successive smaller group adds its own homologs to those it shares with larger groups  Biologists represent the pattern of descent from common ancestors with an evolutionary tree (a diagram that reflects evolutionary relationships among groups of organisms)  Mammals are more closely related to birds than amphibians  The tree is supported by both anatomical and DNA sequence data  A Different Cause of Resemblance: Convergent Evolution – the independent evolution of similar features because they adapt to similar environments in similar ways  Example: Sugar glider is similar to a flying squirrel. A sugar glider is a marsupial and a squirrel is an eutherian.  Species that share function because of convergent evolution = analogous (share function, not ancestry)  Homologous features share ancestry not necessarily similar function. 3. Fossil Record  Example: Pelvic bone in stickleback fish  Fossils can shed light on the origins of new groups of organisms (ex. cetaceans)  Cetaceans are closely related to even-toed ungulates (pigs, deer, camels, and cows). Earliest cetaceans lived 50-60 million years ago (before that, only terrestrial)  Fossil records show that over time, descent with modification produced increasingly large differences among related groups of organisms, ultimately resulting in the diversity of life we see today 4. Biogeography  Biogeography is the scientific study of the geographic distributions of species; influenced by the continental drift (the slow movement of the Earth’s continents over time)  Pangaea ~ 250 million years ago  200 mil years ago, the continents we know today were roughly in the same place  Examples: Horses (Equus) originated 5 mil years ago in North America;  Islands generally have many plant and animal species that are endemic (found no where else in the world). But many are closely related because they had a common ancestor from the nearest mainland before the land separated. That explains why 2 islands with similar environments do not have similar species. The species on each island are closer to species of the nearest mainland, where the environment is quite different.  Theory: The pattern of evolution (the observation that life has evolved over time) has been documented directly and is supported by a great deal of evidence.  The process of evolution (that natural selection is the primary cause of the observed pattern of evolutionary change) makes sense of massive amounts of data  The effects of natural selection also can be observed and tested in nature  A theory accounts for many observations and explains and integrates a great variety of phenomena.  A unifying theory does not become widely accepted unless its predictions stand up to the thorough and continual testing by experiment and additional observation  Evolutionary biologists recognize that natural selection is not the only mechanism responsible for evolution  Although Darwin’s theory attributes life’s diversity products of evolution are nevertheless elegant and inspiring


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