How Populations Evolve Charles Darwin and Alfred Wallace are the fathers of the theory of evolution. Darwin's main ideas centered on ------------------------, how species change over time, and the ----------------------------------------------. " Origin of Species" which mainly proposes ------------------------- as a mechanism for evolution (survival of the fittest) Jean Baptiste Lamarck:( before Darwin) suggested that life evolves but the mechanism he suggested was mistaken. He proposed the -----------------------------------------------------------------------------Evolution: Origins of Earth: earth is approx. 4.6 billion years old(BYBP) - oldest fossil of prokaryotic cells 3.5BYBP - oldest fossils of eukaryotic cells 2.2BYBP - humans ~ 1.8MYBP First cells were --------------------------------, eating organic molecules in oceans first autotrophs were -------------------------, blue - green algae cells became more specialized, had organelles for certain functions all living organisms have same characteristics, composed of cells, take energy, reproduce, evolve all living things are related, common ancestor, became diverse because of the different environments and ways of life. Evidence of Evolution: 1. Fossils: remains or trace of -------------------------------, footprints, imprints, bones, teeth, shells, skeletons, usually ------------------------------------. We have a missing record of things, like studying a book with missing pages. Fossils give us ideas of older versus younger organisms. We have a fossil record that is ----------------------------------------------------------------------. Sedimentations occur in layers called ----------------, where the -------------------------- are found in the bottom strata and the ------------------------------ are contained in the upper strata. Get a view of different species that might have become extinct over time. Ex: The "Ice Man" was preserved in ice 5000 yrs. ago. 2. Biogeographical evidence: 3. Comparative anatomical evidence: comparison of body structures in different species. 4. Embryological evidence: Related organisms have similar stages during embryonic development. 5. Molecular evidence: Population Evolution Population: Species: gene pool: Microevolution is the change in a population's gene pool over time. The frequencies of the alleles encoding the various traits can change over time. The gene pool of a non-evolving population remains --------------------------------------------------------------------Hardy - Weinberg Law of genetic equilibrium: allele frequencies in a population will remain stable over time IF there --------------------------------------------------------------------------------p+q=1 p = % dominant alleles in a population p2 + 2pq + q2 = 1 q = % of recessive alleles in a population p2 = % homozygous dominant individuals 2pq = % of heterozygous individuals q2 = % homozygous recessive individuals In real life, these conditions are never met and thus allele frequencies change creating evolution. Four factors cause evolution: 1. Mutations: 2. Genetic drift: - founder effect - bottleneck effect: 3. Gene flow: 4. Natural selection: . There are many types of outcomes for natural selection: - Stabilizing selection: - Directional selection: - Diversifying selection Evolution leads to Speciation: Species: a group of populations that share a gene pool, the members can breed and produce fertile offspring. Best Example: Charles Darwin in Galapagos islands: 13 different species of finches descended from mainland finches. Birds look similar to each other but have very different beaks depending on where they live and what they eat.