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Darwin and Natural Selection

by: Rebbecca Taing

Darwin and Natural Selection BIOL1362

Marketplace > University of Houston > Science > BIOL1362 > Darwin and Natural Selection
Rebbecca Taing
GPA 3.0

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Chapter 19
BIOL 1362
Ann Oliver Cheek
Class Notes
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This 4 page Class Notes was uploaded by Rebbecca Taing on Thursday August 4, 2016. The Class Notes belongs to BIOL1362 at University of Houston taught by Ann Oliver Cheek in Fall 2016. Since its upload, it has received 11 views. For similar materials see BIOL 1362 in Science at University of Houston.


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Date Created: 08/04/16
Darwin and Natural Selection Thursday, January 21, 2016 10:04 PM Chapter 19 1795 1812 1830 Hutton Cuvier Lyell 1707-78 1798 1809 1831-36 1859 Linneaus Malthus Lamarck Darwin on Beagle Darwin: On the Origin of Species Compare artificial selection and natural selection in the table below. Artificial selection Natural selection Variation in heritable trait[1] Selection pressure [2] humans predators, climate Trait[3] Frequency of trait [4] [1] Present/absent [2What is causing selection of particular individuals for survival & reproduction? [2What is causing selection of particular individuals for survival & reproduction? [3] What kind of trait is being selected for – desirable or favorable for survival & reproduction? [4How does frequency of the trait change in response to selection? Increase/decrease/nochange From <> I. Ideas about Life on Earth A. Species are permanent 1. Aristotle (350 bce) ○ Spp fit on a scale of increasing complexity 2. Linnaeus (1707-78) ○ Binomial nomenclature: Turdus migratorius ○ Grouped similar species into hierarchical categories based on morphology- body form ○ Kingdom, phylum, class, order, family, genus, species B. Earth is changing 1. Hutton ○ Earth's physical features formed by gradual processes that are still operating, radical idea 2. Lyell ○ Geologic processes operate today @ the same rate as in the past Hutton and Lyell inference: earth older than 6000 yrs old C. Species change 1. Cuvier (1769-1832) ○ Species go extinct due to catastrophes 2. Lamarck (1744-1829) 2. Lamarck (1744-1829) ○ Species can change into new species ○ Proposed mechanisms -use & disuse -inheritance of acquired characteristics ex. Arnold Schwarzenegger muscles passed to offspring, appendix, giraffe's neck stretched II. Darwin proposes that species change by natural selection A. Darwin's observations & inferences • 1830- Voyage of the Beagle- originally a mapping expedition • First hand observation of geologic processes • Earthquake while on land • Finding fossils of ocean organisms high in Andes mntns • Conclusion: Lyell is right, earth is old • Observations -spp in temperate S Amer were more similar to spp in tropical S Amer than to temperate spp in Europe -spp on Galapagos resembled S Amer mainland but were diff from mainland & world -members of a pop vary in their inherited traits -all spp can produce more offspring than their envmt can support • Inference -distribution of species can be explained by Earth's geologic history -individ whose inherited traits give them a higher probability of surviving leave more offspring, "survival of the fittest" -differential selection & reproduction lead to an accumulation of favorable traits in pop over many generations -freq (commonness) of a trait can increase in a pop if that trait is favorable for survival/reprod • Adaptation -def'n: inherited trait that enhances survival & reproduction in the current, local envmt -inference: new species could develop from ancestral species by gradual accumulation of adaptations to a different envmt B. Descent w/ modification • All living species are descended from one another, heresy • History of life is like a tree -multiple branches form a common tree -like a family tree • Branch point is most recent common ancestor Natural selection • Mechanism of descent w/ modification • Individs that inherit certain traits survive better & reproduce more offspring in the current local envmt Artificial selection: pigeons Artificial selection: cruciferous veg, mustard common ancestor Selection pressure- conditions that affects S&R • Ex. Predators, type & amount of food, female preference for male characteristics Implications of Darwin's idea • Earth is very old & changing • Species weren't created individually all at once • Species are changing due to natural selection & new ones are created • All species descended from a common ancestor • Leftover adaptation- a structure that may have aided S&R in an ancestral species or past envmt but doesn’t anymore doesn’t anymore • By-products of another characteristic -vertebrate blood is red b/c of the light reflecting properties of hemoglobin III. Evidence A. Living organisms 1. Change in structure between populations of same species ○ Soapberry bug -native to FL -native food: balloon vine seeds -"beak" long enough to dig down seeds 2. Changes in structure between species ○ Homology- different spp have similar structural characteristics b/c they descended from a common ancestor ○ Fxns differ due to different selection pressures in envmt B. Fossils • Are there transitional forms? • Tikaalik- close ancestor of terrestrial vertebrates • Ex. Varition in inherited traits more offspring than envmt can support C. Biogeography Reading: Chapter section 1.2, Chapter 19 Concept Check Questions: Section 19.1 Q1; Section 19.2 Q1, Q3 Summary of Key Concepts: Q at end of Concept 19.1 Test Your Understanding: 2, 3, 4, 6a & 6b


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