Transcript Chapter 16
Evolution of Populations Chapter 16 (M) Evolution a continuing process of change in a population of organisms over long periods of time History 1700s Scientists believed that “Species are Fixed” and do not change Mid 1700s fossil records lead Georges Buffon to say Earth is older than 6000years Different species arose from variation from a common ancestor 1800s Lamarck explained fossil records & species diversity Lamarck Proposed the theory of “Inheritance of Acquired Characteristics” body changes developed during an organisms life time could be passed on to the offspring Short neck ate up grass had to stretch neck to reach trees Lamarck Acquired characteristics would have to modify DNA to be inherited no evidence of this Lamarck’s theory was rejected Set the stage for Darwin Variation in the population long & short necks Long necked survived reproduced population was gradually changed to long necked animals Darwin(1809-1882) Started his voyages at the age of 22 on the HMS Beagle Was responsible for collecting specimens of fossils He was aware of geological formations of land masses could explain fossils of snails from mountains Studied his collections for the next 22 years Darwin’s Key Observations 1. 2. 3. 4. Fossils & fossil records show that organisms simpler complex Overproduction of offspring Limited supply of resources in an environment Survival in a limited environment depends in part on features inherited from parents Information that influenced Darwin Charles Lyell geologist proposed that the Earth was very old and had slowly been changing for millions of years Thomas Malthus economist social problems as a result of the exponential growth of the human population Artificial selection by breeders Darwin Concluded 1. Descent with Modification 2. Natural Selection Descent with Modification All present day organisms are related through descent from unknown ancestors in the past. These descendants of earliest organisms spread into different habitats adapted to diverse ways of life Natural Selection Individuals whose inherited characteristics adapt them best to their environment are most likely to survive and reproduce Basic Mechanism of Evolution Natural Selection Natural Selection Occurs over a vast period of time Individuals undergo selection, but do not evolve Populations Evolve Evidence of Evolution Section 16.4(M) Evidence 1. 2. 3. 4. Fossil Records Comparative Anatomy Embryonic Structures DNA Homology Fossils Remains, traces or imprints of an organism preserved in the earth’s crust Imprint Mold Cast Petrified Fossil Records 1. 2. Fossils & the order in which they appear in layers of rocks Fossil records show that animals & plants have appeared in a historical sequence, fossils found in rocks of different ages differ because life on Earth has changed through time Each Layer represents a particular time period Comparative Anatomy The comparison of body structures in different species Homologous Structures Analogous Structures Vestigial Structures Ex: common descent evident in anatomical similarities between species in the same taxonomic group Homologous Structures Structures that are similar & have been derived from a common ancestor, but have been adapted to different functions. ex: humans, cats, whales, bats all mammals Whales’ flipper does not have the same function as a bat’s wing Homologous Structures Analogous Structures Body parts similar in function but have different structures Ex: wings of insects and birds Vestigial Structures Body parts reduced in size & appear to serve no function Embryonic Structures Embryos of closely related organisms often have similar stages in development DNA Homology Comparison of genes and proteins shows the relationships between species Darwin’s Natural Selection : A Mechanism of Evolution Natural Selection Regional and timely Adapts organisms to their local environment Environmental factors vary from place to place & time to time adaptation in one situation may be useless in another Example: Biston betularia peppered moth Peppered Moth England two varieties dark & light 1850 almost all were light industrial revolution pollution tree trunks turned black light moths became easy prey Dark survived & reproduced End of century almost all were dark Biston betularia : peppered moth Populations A group of individuals of the same species living in the same place at the same time Mainland animal species colonizes a chain of distant and isolated islands separate population. These populations adapt to their local environments. Over time, the isolated populations would become more and more different. And over many generations, the populations could become different enough to be separate species. Darwin’s Finches adapted to different food sources beak Structures Variation Differences among members of the same Species Adaptation Inherited trait that Improves the Chances Of Survival & Reproduction Structural mimicry organism copies the appearance of another species 2. Physiological changes in the organisms metabolic process penicillin drug resistant bacteria 3. Behavioral inherited behavior pattern that allows organism to survive 1. Adaptation- Mimicry Monarch tastes bitter birds avoid them because they get sick Viceroy(extra black lines on wings) not bitter, look & act like Monarchs birds avoid them Adaptation: Camouflage Protective adaptation that allows an organism to blend into its surroundings The better the camouflage, the more likely it is for the organism to survive and reproduce Adaptation: Camouflage Artificial Selection Selective breeding of domesticated plants and animals to produce offspring with genetic traits that humans value. From Wild Mustard to our Table Pesticides- Natural Selection in Action Spraying crops kill insect pests favored the reproduction of insects with inherited resistance to the poisons