Transcript evolution
Some Evidence of Evolution • • • • Geographic Locations Anatomical Similarities Developmental Similarities Molecular (biochemical) Similarities Some Evidence of Evolution • Geographic Locations Some Evidence of Evolution • Anatomical Similarities –Homologous Structures = structural features with a common evolutionary origin. Similar in arrangement, function or both. Some Evidence of Evolution • Anatomical Similarities –Homologous Structures Some Evidence of Evolution • Anatomical Similarities –Homologous Structures http://www.ucmp.berkeley.edu/ –Analogous Structure = A structural or functional similarity of a body feature, but not related. Example: Insect & bird wings are similar in function, but not structure Some Evidence of Evolution • Anatomical Similarities –Vestigial Structures = a body structure that has no function in a present-day organism but was probably useful to an ancestor. Some Evidence of Evolution • Anatomical Similarities –Vestigial Structures http://www.tpwd.state.tx.us Some Evidence of Evolution • Anatomical Similarities –Fossils http://www.earthhistory.org.uk/wp-content/crayfish.jpg 1. Trace Fossils https://courseware.e-education.psu.edu/courses/earth105new/graphics/L02_fossil_hpl922.jpg 2. Casts http://www.activityvillage.co.uk/cast-fossils.jpg 3. Imprints http://www.hopefossils.co.uk/Fossil%20photos/Trilobite%20under%20x10%20magnification%20-%20Placoparia%20cambriensis.JPG 4.Amber-Preserved & Frozen http://dsc.discovery.com/news/2007/10/08/gallery/amber_zoom.jpg 5. Petrified http://www.legendsofamerica.com/photos-arizona/PetrifiedWood.jpg 6. Molds http://www.ammonoid.com/mcE-m.jpg Some Evidence of Evolution • Developmental Similarities –Comparative embryology • Early developmental stages are compared. • Related embryos look similar. Some Evidence of Evolution • Developmental Similarities –Comparative embryology Some Evidence of Evolution • Molecular (biochemical) Similarities http://www.genome.gov/15515096 Natural Selection 1. Variations exist in a population Natural Selection 2. Some variations improve the ability to survive and reproduce in the particular environment Sweet! I’m better at surviving because I blend into my surroundings! Boo! Natural Selection 3. The individuals with the adaptive traits are more likely to pass on their genes to Boo! future generations I have more fitness than you! Natural Selection 4. Over time, the frequency of adaptive alleles increases = evolution. Question Break 1. True or False? Individual organisms evolve. 2. Which of the following is NOT needed for natural selection to occur? a. b. c. d. Heritable variation Competition Fossil evidence Different levels of fitness Speciation • One species splits into two due to isolation (geographic, reproductive, etc…) • Also known as Divergent Evolution… results in homologous structures between groups Speciation Hurricane http://evolution.berkeley.edu Speciation The populations diverge: Ecological conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does. Morphology, food preferences, and courtship displays change over the course of many generations of natural selection. http://evolution.berkeley.edu Speciation So we meet again: When another storm reintroduces the island flies to the mainland, they will not readily mate with the mainland flies since they’ve evolved different courtship behaviors. The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations. The lineage has split now that genes cannot flow between the populations. http://evolution.berkeley.edu Speciation http://evolution.berkeley.edu Speciation The first steps of speciation have been produced in several laboratory experiments involving “geographic” isolation. For example, Diane Dodd took fruit flies from a single population and divided them into separate populations living in different cages to simulate geographic isolation. Half of the populations lived on maltose-based food, and the other populations lived on starch-based foods. After many generations, the flies were tested to see which flies they preferred to mate with. Dodd found that some reproductive isolation had occurred as a result of the geographic isolation and selection in the different environments: “maltose flies” preferred other “maltose flies,” and “starch flies” preferred other “starch flies.” What is a species? A group of interbreeding populations that cannot breed with other groups. Giraffes and Elephants? German Shepards and Poodles? Maintaining Species Individuality • Ecological (geographic) Isolation – not around each other • Behavioral isolation – different species don’t understand each other’s mating rituals • Temporal isolation – different breeding seasons • Mechanical isolation – structural differences preventing mating Speciation may lead to extreme genotype survival • What is a genotype? • Environment may favor extreme genotypes. • Over time, extremes thrive, middle genotype extinct. Direction of Natural Selection and Species Formation • Stabilizing – extremes not favored (example – human birth weight) • Disruptive – extremes favored (example short or long beaks not medium beaks) • Directional – extremes at one end favored Convergent Evolution – when species become more alike • Animals live apart but in similar environments • Desirable traits are same • Example – rabbit and squirrel color