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Lecture 28th - BIOA01H3.docx

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Biological Sciences
Mark Fitzpatrick

BIOA01H3 – Lecture 28 th Chapter 17 17.1 Recognition of Evolutionary Change  Aristotle believed that both inanimate objects and living species had fixed characteristics; created ladder-like classification of nature from simplest to most complex: minerals  plants  animals  humans  gods of spiritual realm  14 century, Europeans merged Aristotle and biblical creationism; prevailing view was that all of diff. kinds of organism had been specially created by god, that species could never change or become extinct, and that new species could never arise  biological research dominated by natural theology  sought to name and catalogue all of God’s creation  careful study of each species will identify its position&purpose in Scala Naturae, or Great Chain of Being  Aristotle’s ladder of life called  this approach to nature and history seen in Carolus Linnaeus, whose efforts were ad majorem Dei gloriam (for the greater glory of God)  in western world, modern science began; Francis Bacon established importance of observation, experimentation, and inductive reasoning  George-Louis Leclerc, le Comte de Buffon noted useless structures like two toes of pig feet never touching the ground  Buffon proposed some animals must’ve changed since creation; suggested vestigial structures  useless body parts we observe today, must have functioned in ancestral organisms  Georges Cuvier observed layers of fossils represented organisms that had lived in past at successive times; developed theory of catastrophism  reasoning that each layer of fossils represented the remains of organisms that had died in a local catastrophe such as a flood. Somewhat diff. species than recolonized area & when another catastrophe hit, formed diff. set of fossils in next higher layer.  Jean Baptiste Lamarck proposed a metaphysical “perfecting principle” in which organisms evolved into complex ones, moving up ladder of life Theorized two mechanisms that fostered evolutionary change: 1. Principle of Use and Disuse 2. Inheritance of Acquired Characteristics Principle of Use and Disuse  Body parts grow in proportion to how much they’re used.  Unused structures get weaker and shrink Inheritance of Acquired Characteristics  Changes that an animal acquires during its lifetime are inherited by offspring 1 Although above theory not entirely true, Lamarck made 4 important contributions: 1. Proposed that all species change through time 2. Recognized that changes passed from one generation to next 3. Suggested that organisms change in response to environments 4. Hypothesized existence of specific mechanisms that caused evolutionary change 17.2 Changes in Earth  James Hutton (geologist) argued that slow and continuous physical processes, acting over long periods of time, produced Earth’s major geologic features Gradualism: view that Earth changed slowly over its history, contrasted sharply w/ Cuvier’s catastrophism.  Charles Lyell extended Hutton’s ideas in influential series of books, Principles of Geology; argued that geologic processes that sculpted Earth’s surface over long periods of times are exactly the same processes we observe today  uniformitarianism 17.3d Darwin Was an Innovator Four characteristics that distinguish Darwin’s theory from earlier explanations of biological diversity and adaptive traits: 1. Provided purely physical rather than spiritual explanations about origins of biological diversity 2. Recognized that evolutionary change occurs in groups of organisms rather than in individuals. Some members of group survive and reproduce more successfully than others do 3. Described evolution as multistage process. Variations arise within groups, natural selection eliminates unsuccessful variations, and the next generation inherits successful variations 4. Like Lamarck, Darwin understood evolution occurs b/c some organisms fnc better than others in a particular environment 17.3f Darwin Had a Huge Impact on Biological Thought and Society  Darwin argued that all organisms that ever lived arose through descent with modification  evolutionary alteration and diversification of ancestral species 17.4a How Old is That Fossil in Relative or in Absolute Time?  Scientists can assign relative and absolute ages to geologic strata & fossils they contain 2 Relative data  Sediments found in any place form distinctive strata that usually differs in colour, thickness, mineral composition, and particle size  If not disturbed, strata arranged in order in which forme  Geologists of nineteenth century deduced that fossils discovered in a particular sedimentary stratum, no matter where it’s found, represent organisms that lived and died at roughly same time in past  b/c each stratum formed at specific time, sequence of fossils from lowest to highest strata reveals relative ages  used sequence of strata and distinctive fossil assemblages to establish geologic time scale  provides relative dating system for sedimentary strata rather than actual ages of rocks and fossils Actual ages  radiometric dating involves use of isotopes and sometimes allows actual ages to be associated w/ diff. rock strata  radiometric dating exploits the fact that isotopes decay moment they form  isotopes decay at steady rates; rocks then dated when amounts of isotopes can be measured and rates of decay known  this approach limited by half-life of isotope 17.5a Continental Drift Involves Movements in Space and Time  according to theory of plate tectonics, Earth’s crust broken into irregularly shapes plates of rock that float on semisolid mantle  current in mantle cause plates and continents to move  phenomenon called continental drift Continuous and Disjunct Distributions  many species have continuous distribution  living in suitable habitats throughout large areas i.e. herring gulls live along coastlines of all northern continents; usually requires no special historical explanations  disjunct distributions  closely related species live in widely separated locations i.e. magnolia trees occur in parts of North, Central, and South America as well as in China and Southeast Asia, but nowhere in between  dispersal and vicariance create disjunct distributions Dispersal: the movement of organisms away from their place of origin; can create disjunct if new population becomes established on far side of geographic barrier. Vicariance: fragmentation of continuous geographic distribution by external factors. 17.5b Biogeographic Regions Influence Flora and Fauna  Pangea breakup powerful vicariant experience for species that were widespread in Mesozoic 3  Subsequent geographic isolation of continents fostered evolution of distinctive regional biotas  all organisms living in a region  Alfred Russel Wallace used biotas to define six biogeographic regions  Australian and Neotropical (now South America) realms have been geographically isolated since Mesozoic  Each contains endemic species (those that occur nowhere else on Earth) 17.5c Life Forms Evolves in Parallel and Convergent Ways  Distantly related species living in different biogeographic realms may appear similar but did not inherit shared similarities from shared ancestors; rather, overall appearance may’ve been result of convergent or parallel evolution  evolution of similar adaptations in distantly related organisms that occupy similar environments  i.e. T-rex, marsupial wolves, and grey wolves are all carnivores. T-rex is convergent with marsupial an
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