4Galapagos IslandsDarwin studied anatomy of insects, reptiles, birds and flowering plants
5Galapagos TortoisesThe inhabitants...state that they can distinguish the tortoise from different islands; and that they differ not only in size, but in other characters. Captain Porter has described those fromCharles and from the nearest island to it, namely Hood Island, as having their shells in front thick and turned up like a Spanish saddle, whilst the tortoises from James Island are rounder, blacker, and have a better taste when cooked.---Charles Darwin 1845
6Species Change Over Time Darwin was convinced that evolution occursSpecies Change Over Time
7Darwin Concluded...That there must be a struggle for existence among all individualsOrganisms must struggle forFoodSpacePrey
8Ideas that shaped Darwin's thinking From ancient times, most people believed all living things were created by a divine being at the same time and remained unchanged.By the time Darwin set sail, numerous discoveries, including a rich fossil record, had turned up importance evidence that caused some scientists to question these ideas.
9Ideas that shaped Darwin's thinking Geologists James Hutton and Charles LyellAfter examining Earth in great detail, recognized that Earth is many millions of years old, and the processes that changed Earth in the past are the same processes that operate in the present.Ex: volcanoes, earthquakes, erosion, continental drift, etc.The Grand Canyon, with its many layers of rock, was formed over millions of years by the Colorado River (erosion).
10Ideas that shaped Darwin's thinking Jean-Baptiste Lamarck - French naturalistPublished hypothesis of Inheritance of Acquired Characteristics same year Darwin was bornProposed that by selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime.Traits could then be passed on to offspringOver time would lead to change in species
13Ideas that shaped Darwin's thinking Thomas Malthus - English economistReasoned that if the human population continued to grow unchecked, eventually there would not be enough space and food for everyoneForces such as war, famine and disease work against the growthDarwin realized this was even more true for plants and animals because humans produce far fewer offspring
14Upon returning to England, Darwin began studying his specimens and filling notebooks with ideas. Shared ideas with friends but reluctant to publish -- understood his ideas challenged scientific and religious beliefs of his dayAfter more than 25 years -- published On the Origin of Species in 1859
15Charles Darwin Published: “On the Origin of Species” 1859
17Survival of the Fittest Only some of the population survive long enough to produce offspringSurvival of the Fittest
18Which ones survive?Darwin’s observations led to the conclusion that individuals have different variations of traits that can be inheritedDarwin bred pigeons with desirable variations and he was able to produce offspring with the same features
19Artificial Selection Breeder selects the particular traits Darwin wondered if there was some force in nature similar to artificial selection
20Darwin's Explanation for Change... NATURAL SELECTION
21Natural SelectionMechanism for change in populations that occurs when organisms with favorable variations for a particular environment survive, reproduce and pass variations on to the next generationOrganisms with less favorable variations are less likely to survive and pass on traits to the next generation
23Tendency toward Overproduction For example: Fish lay thousands of eggsMost of these eggs will not survive
24Individuals Exhibit Variations Example: Fishes may differ slightly in color, fin and tail size and speed
25Individuals with favorable traits survive and pass on those genes Ex: A fast fish with camouflaged skin will be more likely to survive and reproduce. Thus, passing along the more desirable traits to future offspring.
26Populations evolve, or change over time Gradually, the offspring of the survivors make up a larger portion of the population. After many generations the population may look entirely different.
28Changes in structure or body parts that aide in survival AdaptationChanges in structure or body parts that aide in survival
29To copy the appearance of another species MimicryTo copy the appearance of another species
30CAMOUFLAGEColor adaptation so organism blends with its surroundings
31Adaptations....May take millions of years to develop or they may be rapidEx: Slow---Sightless mole ratFast: Antibiotic resistance
32Evidence for Evolution The Fossil RecordFossils show change over time
33Geographical Distribution Organisms live in different areas of the world, but have similar adaptationsDifferent ancestors, but similar environmental pressures acting against itDescent with modification
34Homologous Structures Modified structure that is seen among different groups of descendantsLimbs and Wings
35Analogous Structure Similar in function, but different in structure Ex: Bird Wing/Butterfly Wing
36Vestigial Structure Appendix Eyes of a sightless mole rat Any body structure that is reduced in function in a living organism but may have been used in an ancestorAppendixEyesof a sightless mole rat
37Embryological Development Fish, reptiles, birds and mammals look similar during embryological development
39Populations Evolve; Individuals Do Not If you know the genotypes of all the organisms in a population, you can calculate the allelic frequency.A population in which the frequency of alleles does not change is in genetic equilibrium.
42Stabilizing Selection Favors Average Individuals in a population
43Directional Selection Favors either of the extreme forms of a trait
44Disruptive SelectionBoth extreme forms of a trait are favored
45Evolution of a SpeciesSpeciation, or the formation of new species, can only occur when either interbreeding or the production of fertile offspring is somehow prevented: Reproductive IsolationGeographic isolationTemporal isolationBehavioral Isolation
46BehavioralIsolationOccurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.Ex. Eastern and Western MeadowlarksHabitat overlaps, but will not mate with each other because they do not respond to each others song!
47Geographic IsolationTwo populations are separated by geographic barriers such as rivers, mountains, or bodies of water.Ex. Colorado River separating the Abert squirrel and the Kaibab squirrel (about 10,000 years ago).
48Temporal Isolation Two or more species reproduce at different times. Example: Orchids. Release pollen on different days, so they cannot pollinate each other.