Transcript Powerpoint
The Theory of Natural Selection Biology I 1 I. Early Biology • Scientists knew that organisms had changed • Fossil evidence • Age of the Earth 2 Lamarck • Changes from simple to complex • Organisms want to adapt or change • Acquired characteristics were inherited (passed on) 3 Lamarck • Later disproved 4 5 II. Darwin • At 21, took a job as a naturalist on the HMS Beagle • Collected specimens, took notes of different organisms 6 His voyage: 7 II. Darwin • Sailed to Galapagos Islands • All new species, but similar to those found elsewhere 8 • Finches most famous • Had slightly different beaks from island to island • Differed by their diet 9 II. Darwin • Darwin 22 years developing theory of natural selection • Pressured into publishing by Wallace • Published On the Origin of Species by Natural Selection 10 III. Natural Selection 4 Requirements •1. Variation exist • 2. Differential Reproduction • • 3. Heredity Best suited survive and reproduce 4. Lots of Time 11 1. Variation • Variations exist – Color, size, speed, etc. • Variations are genetically linked 12 2. Differential Reproduction • Organisms produce more offspring than can survive – creates competition and Survival of the Fittest = Only the best are going to survive 13 Heredity • Beneficial variations survive, pass traits to offspring • Passed through DNA 14 Natural Selection • Over time variations become more frequent in population • Results in population being different than ancestors 15 Evolution Evolution is the change in a population over time Natural Selection - Remember the Giraffe? How did it get the long neck? 16 Evidence of Change • • • • Fossil Record Anatomy & Physiology Embryology Biochemistry 17 Fossils • Remains or traces of living organisms 18 Physiology Mimicry-An adaptation • Enables one species to resemble another species. • Ex.-harmless species looks like a harmful one, good tasting vs. bad tasting. 19 20 21 Camouflage-An adaptation • A species blends in with its environment to avoid predators. • Ex.- peppered moth, leaf frog 22 Anatomy- Homologous Structures • Common evolutionary origin. Similar in arrangement or function or both. • Example: forelimbs of a whale, a crocodile and a bird wing. 23 24 Anatomy- Analogous Structures • No common evolutionary origin, but similar in function. • Wings of a bat and wings of a butterfly. 25 26 Anatomy- Vestigial Structures • No function now but was probably useful to an ancestor. • Ex. A whale has leg bones, a snake has leg bones 27 28 Embryology • Earliest stage of growth and development • Embryos of a fish, a chicken, a pig, a cow, a rabbit, and a human are almost identical. • They all have gill slits and a tail. 29 30 Biochemistry • Comparisons of DNA and RNA • Now monera (prokaryotes) is divided into two separate kingdoms based on their biochemistry. 31 V. Mechanisms of Evolution • Genetic Drift • Gene Flow • Artificial Selection • Natural Selection Sexual Selection 32 Genetic Drift • Change in allele frequency by CHANCE 33 GENE FLOW • Bottleneck effect • Founders effect 34 Gene Flow • Change in allele frequency as a result of MIGRATION 35 Sources of Variation • GENE FLOW moves genes among populations • SEXUAL REPRODUCTION introduces new gene combinations • Random MUTATIONS in DNA lead to the formation of new alleles (sound familiar?) 36 Mutations • Can be beneficial, neutral, or harmful for the organism • Only mutations in gametes are inherited by offspring 37 Bell: • What is the difference between Analagous structures, Homologous Structures, and Vestigial Structures? • What are the 4 requirements of Natural Selection? AGENDA •Intro to Classification •Natural Selection Today •Antibiotics 38