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Chapter 2

Chapter 2- The Pattern of Evolution.docx

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University of Waterloo
BIOL 359
Jonathan Witt

BIOL 359 Lecture 3 Janice Wong Evolution Evidence for Evolution Chapter 2: The Pattern of Evolution Theory of Special Creation • Set of assertions 1. Species do not change through time 2. They were created independently of one another 3. They were created recently (Earth and life are young) • The process that is responsible for producing the pattern: separate and independent acts of creation by a designer Theory of Descent with Modification (Charles Darwin) 1. Species are not immutable, but change through time 2. Species are derived not independently, but from common (shared) ancestors 3. The Earth and life are considerably more than 6000 years old The Theory of Special Creation and the Theory of Descent with modification make different assertions about whether species can change, where species came from and the age of the Earth and life. Jean-Baptiste Lamark • All species, including humans, are derived by gradual evolution from other species • Inheritance of acquired characteristics • Inherent tendency for all organisms to progress from simple to complex form • The continued existence of simple life forms is due to the spontaneous generation from nonliving matter 2.1| Evidence of Change through Time Microevolution: small evolutionary changes in gene frequencies and trait distributions that occur within populations and species Macroevolution: large evolutionary change, usually in morphology; typically refers to the evolution of differences among populations that warrant their placement in different genera or higher-level taxa • Ex. Bodies of living organisms Evidence from Living Species Soapberry bugs • Feed by using their long beaks to attack the inflated, balloon-like fruit capsules • When the bug reaches the seed, it liquefies it contents and suck them up • Florida started to plant flat-capsule golden rain fruit trees • On average, the population of bugs living on the flat-capsule host had much shorter beaks • Soapberry bug population evolved following their switch to a new host • One alternative interpretation: perhaps as the bugs grow, they develop a beak that just long enough to reach the seeds of the fruits they find themselves feeding on. BIOL 359 Lecture 3 Janice Wong Evolution Evidence for Evolution o Wrong: the bugs that develop in Key Largo grew long beaks and bugs from Lake Wales grew short beaks regardless of the fruits they grew of with. • The short-beaked Lake Wales bugs have descended with modification from long-beaked ancestors • Observations on living organisms provide direct evidence of microevolution by showing that populations and species change over time • Characteristics of soapberry bugs are not immutable, but change over time Vestigial Organs • Vestigial structures: a useless or rudimentary version of a body part that has an important function in other, or closely allied species • Reduced or useless body parts are evidence of both microevolution and macroevolution Animals • Apteryx mantelli o Flightless bird that has tiny stubby wings • Rubber boa o Remnant hind limbs, represented internally by rudimentary hips and leg bones and externally by minute spurs • These vestigial structures show that they are descended, with modification, from ancestors in which wings or hind legs were fully formed and functional Humans • Have a tiny tailbone called the coccyx • Muscles attached to our hair follicles that contract to make our hair stand up when we are cold or frightened • If we were hairy like chimpanzees, the contraction of our hair follicles would keep us warm or intimidate others • Instead we get goosebumps, which imply that we are descended from ancestors what were hairier than us Chickens • Adult chickens have 3 digits in their wings and 4 in their feet • During development, an extra digit appears for a short time • The evolutionary explanation is that birds are descended from ancestors that, like tetrapods, had 5 digits in all their limbs • Modifications in development that transformed these ancestral limbs into wings and birds’ feet take place after the fourth and fifth digits begin to form • But before the structure of the limb is fully defined Evidence from the Fossil Record • Fossil: trace of any organisms that lived in the past • Fossil Record: the total, worldwide collection of fossils, scattered among thousands of thousands of different institutions and individuals The Fact of Extinction BIOL 359 Lecture 3 Janice Wong Evolution Evidence for Evolution • The fact that many species have gone extinct suggests that Earth’s flora and fauna have changed over time • Ex. Irish Elk: huge ice-age deer, an extinct species, found throughout northern Europe and the British Isles. It was neither moose nor reindeer, it was a species itself. • Extinct species are the relatives of living organisms The Law of Succession • Fossils and living organisms from organisms found in the same geographic region are related to each and are distinctly different from the organisms found in another area • The resemblance between living and fossil forms in the same region suggests that living organisms are descended with modification from earlier species • Ex. Armadillos of Argentina • Today’s species are descended with modification from ancestors that lived in the same region Transitional Forms • The fossil record should capture evidence of transformations in progress; • Transitional species showing a mix of features, including traits typical of ancestral population and novel traits seen in later descendants • Archaeopteryx: A bird with modern feathers and a dinosaur like skeleton o Skeleton was so reptilian, with teeth, 3-clawed hands and long bony tail, that it was mistaken as the dinosaur Compsognathus o Represents an extinct side branch on the evolutionary tree that connects dinosaurs to birds o A transitional fossil because it demonstrates the past existence of species intermediate in form between dinosaur and bird o Indicates with its fully modern feathers and dinosaurian skeleton, that birds evolved their birdness piecewise. • Sinosauropteryx: a dinosaur with bristly structures on its neck, back, flanks, and tail are believed to be down-like feathers o There are many feathered dinosaurs depicting a model of feather evolution based on how feathers develop o Shows how modern feathers developed, and that birds evolved from dinosaurs • Bird: if it has feathers and can fly, or descended from an animal that had feathers and could fly • Transitional fossils document the past existence of species displaying mixtures of traits typical of what are today of organisms • They are evidence of macroevolution • Transitional forms in the evolution of whales o Some whales have a vestigial femur and pelvis, suggesting that the ancestor of whales also lived on land o Between the terrestrial ancestors and modern whales, there should be an intermediate form that have functioning limbs and are ocean-dwelling species o Basilosaurus was an aquatic animal and had tiny and fully formed hind limbs that may have served as grasping organs during copulation Evidence of Descent with Modification • Microevolution: soapberry bugs evolved shorter beaks BIOL 359 Lecture 3 Janice Wong Evolution Evidence for Evolution • Macroevolution: birds evolved from dinosaurs 2.2| Evidence of Common Ancestry An Introduction to Tree Thinking • Phylogenic Trees: a visual representation of descent with modification from a common ancestor • It is the order of the branching that is important A Ring Species • Evidence of common ancestry that one species can split into two • Some species appear to be in the process of splitting into 2 • Freely interbreeding populations connect the entire species, but members of certain populations do not interbreed • Example: Siberian greenish warbler • The bird’s geographic range forms a ring surrounding the Tibetan Plateau • The warblers song complexity increases from south to north around both sides of the rings • Individuals recognize each other as members of the same species by interbreeding •
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