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Chapter 2

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BIOL 359
Jonathan Witt

BIOL359 - Evolution Winter 2013 Chapter 2: The Pattern of Evolution - Theory of Special Creations o Species are immutable, independent & recent - Darwin’s Theory of Evolution o Species are not immutable, but changes through time o Species are derived not independently, but from common/shared ancestor o Earth and life are more than 6,000 years old 2.1. Evidence of Change through Time - Theory of Special Creation: Species, once created, are immutable - Evidence from Living Species o Microevolution: Small scale changes (monitor natural populations)  E.g. Soapberry bugs evolved shorter beaks o Macroevolution: Dramatic change (monitor bodies of living organisms)  E.g. Birds evolved from dinosaurs o Direct Observation of Change through Time  Soapberry bugs, uses long beaks to penetrate the inflated balloon like fruit capsules on their host plants(Balloon vine) to reach the seeds  After the import of the flat-podded golden rain tree, soapberry bugs began to exploit it  The lengths of the bugs’ beaks was much shorter for bugs living on flat-capsuled host than round-capsuled hosts (short-beaked bugs are descendants of long-beaked bugs)  The bug from balloon vine developed long beaks regardless, same for the bugs from golden rain trees (The 2 populations are genetically different)  The characteristics of soapberry bugs are not immutable, but changed over time o Vestigial Organs: A useless version of a body part  Vestigial structures  Humans tiny bone “coccyx” – Descendants of ancestors with tails  Arrector pili muscles attaching to hair – Descendants of ancestors with hair  Vestigial developmental trait  Chickens have 3 forelimbs & 4 hindlimbs, but during development, there’s 4 forelimbs & 5 hindlimbs – Extra digit later disappears  Vestigial genes:  Humans’ gene for encoding enzyme CMAH on chromosome 6, disabled by a 92 bps deletion (CMAH produced in abundance in other mammals) o CMAH converts an acidic sugar into surface cell displays  Humans & chimps are immune to each other’s malaria parasites - Evidence from Fossil Record o Fossil: Trace of any organism in the past  fossil record o Fossil record: Total collection of fossils worldwide o The Facts of Extinction: Extinct animals are relatives of living organisms, this is evident that Earth’s flora and fauna have changed through time o The Law of Succession: The resemblance between living and fossil forms in the same region suggests that living organisms are descended with modification from earlier species living in the same region o Transitional Forms: Species showing a mix of features, traits of ancestral population & novel traits seen from later descendants  E.g. Archaeopteryx (Crow sized, 145-150 million years ago)  Contains feathers, teeth, 3-clawed hands & long bony tail  E.g. Sinosauropteryx prima, Caudipteryx zoui & Microraptor gui – long feathers  E.g. Whales with vestigial pelvis & leg bones BIOL359 - Evolution Winter 2013 Box 2.1. A brief history of ideas on evolution - The Origin of Species by Means of Natural Selection (1859) – Charles Darwin o To provide evidence on the fact of evolution o To identify natural selection as the mechanism responsible - The Fact of Evolution o It was Darwin that convinced the scientific community that Earth’s species are the products of descent with modification from a common ancestor o Darwin worked on The Origin of Species for 20+ years o The presentation of evidence of evolution was persuasive, and was accepted within a decade of publication o The mechanism of evolution by natural selection however, was not well accepted - The Mechanism of Evolution o Alfred Russel Wallace independently discovered natural selection before Darwin o Lamarck’s theory was widely accepted until the 1930s, where natural selection became popular o Gregor Mendel’s work on the mechanism of inheritance, rediscovered in 1900, lead to the development of population genetics, which merged with natural selection “combination is used to explain gradual evolution” o Genetics and the Origin of Species – 1937 2.2. Evidence of Common Ancestry - Phylogenetic/Evolutionary tree: Visual representation of descents with modification from a common ancestor - Ring Species: Documentation for common ancestry, where one common ancestor splits into 2 species with space & time o Phylloscopus trochiloides @ Tibetan Plateau, interbreeds freely unless the northeastern form encounters the northwestern form  Too much expansion over many generations “sufficiently modified” - Homology: Likeness “fundamental similarities” between species o Structural & Developmental Homology: Organisms show curious similariti
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