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Introduction to Darwinian Evolution. Chapter 18. Learning Objective 1. What is evolution ?. Evolution. Accumulation of inherited changes within a population over time Unifying concept of biology links all fields of life sciences into a unified body of knowledge. Learning Objective 2.
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Introduction toDarwinian Evolution Chapter 18
Learning Objective 1 • What is evolution?
Evolution • Accumulation of inherited changes within a population over time • Unifying concept of biology • links all fields of life sciences into a unified body of knowledge
Learning Objective 2 • Discuss the historical development of the theory of evolution
Jean Baptiste de Lamarck • Proposed that organisms • change over time by natural phenomena, not divine intervention • had vital force that changed them toward greater complexity over time • could pass traits acquired during lifetime to offspring
Charles Darwin • Theory of evolution • Based on observations during voyage of HMSBeagle • Found similarities between organisms • on arid Galápagos Islands • on humid South American mainland
Darwin • Influenced by artificial selection • variety of domesticated plants and animals • Applied Thomas Malthus’s ideas • on human populations to natural populations • Influenced by geologists (Charles Lyell) • idea that Earth was extremely old
Genetic Variation • Artificial selection • Natural Variation
KEY CONCEPTS • Ideas about evolution originated long before Darwin’s time
Learning Objective 3 • What are the four premises of evolution by natural selection as proposed by Charles Darwin?
4 Premises of Evolution by Natural Selection 1. Genetic variation • exists among individuals in population 2. Reproductive ability of each species • causes populations to geometrically increase over time
4 Premises of Evolution 3. Organisms compete with one another • for resources: food, living space, water, light 4. Offspring with most favorable characteristics • most likely to survive and reproduce • pass genetic characteristics to next generation
Natural Selection • Results in adaptations • evolutionary modifications • improve chances of survival and reproductive success in a particular environment • Over time • accumulated changes in geographically separated populations produce new species
KEY CONCEPTS • Darwin’s voyage on the Beagle provided the basis for his theory of evolution by natural selection
Animation: The Galapagos Islands CLICKTO PLAY
KEY CONCEPTS • Natural selection occurs because individuals with traits that make them better adapted to local conditions are more likely to survive and produce offspring than are individuals that are not as well adapted
Learning Objective 4 • What is the difference between the modern synthesis and Darwin’s original theory of evolution?
Modern Synthesis • Or synthetic theory of evolution • combines Darwin’s theory of evolution by natural selection with modern genetics • Explains • why individuals in a population vary • how species adapt to their environment
Mutation • Provides genetic variability • that natural selection acts on during evolution
KEY CONCEPTS • The modern synthesis combines Darwin’s theory with genetics
Learning Objective 5 • What evidence for evolution can be obtained from the fossil record?
Fossil Record • Fossils • remains or traces of ancient organisms • provide direct evidence of evolution
Fossil Record • Sedimentary rock • layers occur in sequence of deposition • recent layers on top of older ones • Index fossils • characterize specific layer • Radioisotopes • in rock accurately measure rock’s age
Mesonychid Fig. 18-8a, p. 399
Ambulocetus natans Fig. 18-8b, p. 399
Rodhocetus Fig. 18-8c, p. 399
Basilosaurus Fig. 18-8d, p. 399
Balaenoptera Fig. 18-8e, p. 399
Learning Objective 6 • What evidence for evolution is derived from comparative anatomy?
Homologous Features • Basic structural similarities • structures may be used in different ways • Derived from same structure • in common ancestor • Indicate organism’s evolutionary affinities
HUMAN BAT WHALE CAT Humerus Radius Ulna Humerus Carpal Radius 5 Metacarpal Ulna Carpal 4 1 Radius Ulna 1 5 Carpal 1 Metacarpal 3 2 Phalanges 4 2 1 2 3 4 3 Phalanges 5 5 2 4 3 Fig. 18-10, p. 401
Humerus Radius Ulna Humerus Carpal Radius 5 Metacarpal Ulna Carpal 4 1 Radius Ulna 1 5 Carpal 1 Metacarpal 3 2 Phalanges 4 2 1 2 3 4 3 Phalanges 5 5 2 4 3 HUMAN BAT WHALE CAT Stepped Art Fig. 18-10, p. 401
Spine Fig. 18-11a, p. 401
Tendril Leaflet Leaf petiole Stipule Stem Fig. 18-11b, p. 401
Homoplastic Features • Evolved independently • similar functions in distantly related organisms • Demonstrate convergent evolution • organisms with separate ancestries adapt similarly to comparable environments
Aardvark (Orycteropus afer) Fig. 18-12a, p. 402
Giant anteater (Myrmecophaga tridactyla) Fig. 18-12b, p. 402
Pangolin (Manis crassicaudata) Fig. 18-12c, p. 402