Chapter 15 Theory of Evolution

Transcription

1 Chapter 15 Theory of Evolution 15-1 History of Evolutionary Thought Evolution- the development of new species form pre-existing species. -change over time. In the 1800 s scientists began to present evidence that the species on Earth had changed over time, and that the Earth was much older than previously thought. Scientists had begun to study strata or rock layers lower strata formed first and are therefore older. Georges Cuvier ( ) -began reconstructing organisms from fossil bones -found many unique species and different organisms in different layers. -he contributed to the acceptance of geologic change and extinction. Charles Lyell ( ) -wrote Principles of Geology -stated that the processes that formed the Earth continue to occur Jean Baptiste Lamarck ( ) - supported the idea of evolution, he stated: - A) populations of organisms change over time (correct) - B) acquired traits were passed on to offspring (incorrect) Acquired traits - a trait that is not determined by genes it arises during the organism s lifetime. - only genetic traits can be passed on. Charles Darwin-( ) s- a 5 year journey to South America -He studied organisms in S. America and the Galapagos Islands -read Lyell s Principles of Geology - it made Darwin realize that geologic time is very slow, so modifications in the environment might also be very slow. -he developed the idea of Natural Selection. Darwin and Alfred Wallace presented their hypothesis at the same time. But Darwin s Origin of Species was published first. Darwin proposed: A. Descent with modification B. Modification by Natural Selection Page 1 of 5

2 Descent with Modification -newer organisms are modified descendants of older species (ex. Galapagos tortoises) Modification by Natural selection- P ) Overproduction- species produce too many offspring (Darwin used Thomas Malthus s ideas on human population. The idea of competition among organisms 2) Genetic variation- within a species, individuals have different traits or variations 3) Struggle to Survive- those organisms that are best suited to their environments will survive 4) Differential reproduction- those with the best adaptations survive and reproduce (pass on their traits) Fitness - ability to adapt, survive and reproduce. A favorable trait gives the organisms an adaptive advantage The Fossil record Fossils-traces of long dead organisms often form in sedimentary rock. Ex. Molds, casts, tracks, amber. Superposition -lower layers (strata) are the oldest Relative age -age compared to other fossils Absolute age -age in years. Can be done by radiometric dating of the rock. The age in inferred from the age of the rock The fossil record is not complete -not all organisms form fossils -fossils can only form under certain conditions Page 2 of 5

3 -not all fossils have been found by humans From the fossil record scientists can infer: 1. organisms lived at different times. 2. today s organisms are different from those of the past. (ex. Trilobites) 3. fossils found in adjacent layers are more alike than those found in layers farther apart. 4. when and where organisms existed (they compare fossils from around the world. Transitional species- P organisms that have features between a hypothesized ancestor and a later species. -some groups of organisms have many transitional species that have been discovered (whale, horse) others do not. Biogeography - study of geographical distributions of fossils and living organism. Living organisms are usually in areas where their ancestors lived. The study of anatomy and embryology support the idea of descent with modification. Homologous Structures- P 305 -similar structures that are found in a common ancestor showed species shared an ancestor. Page 3 of 5

4 Analogous Structure -structures that serve the same purpose, but have a different evolutionary development. Ex. Bat wing and butterfly wing. Vestigial structures -structures that seem to serve no useful purpose. Part of our evolutionary history. Ex. Human appendix, human tail bone, whale pelvis. Embryology -early stages of vertebrates appear very similar -can infer that vertebrates share a common ancestor. Page 306 Similar macromolecules -similar DNA, RNA, and amino acid sequence between closely related organisms Scientists use many types of evidence to form, challenge and refine the hypothesis and theories about evolution. Ex. Developing a phylogenic diagram. P. 307 Page 4 of 5

5 15-3 Evolution in Action Evolution is a continuing process, ex. Anole Lizards P Convergent Evolution -the environment selects similar phenotypes, even though the ancestors were different Ex. Body shape of dolphins and sharks. Divergent Evolution -two or more related populations or species become more dissimilar. -usually due to different habitats (adaptive radiation) or human intervention (artificial selection) Adaptive Radiation -many related species evolve from one single ancestral species. Ex. Darwin s finches- a small number of finches were blown to the Galapagos Islands. They moved into different habitats, and developed different beaks and plumage in response to their different environments. Artificial Selection -animals and plants are bred by humans for certain phenotypic characteristics Ex. Dogs, cows, chickens, corn. Coevolution -changes in two species in association with each other Ex. Flowers and the length of hummingbird s beaks. Page 5 of 5