Natural Selection 4.1.2 Outline the mechanism of natural selection as a possible driving force for speciation.

Evidence? (for or against) What is evolution? What does it mean to you? Do you think it happens? Evidence? (for or against) http://evolution.berkeley.edu/evolibrary/article/evo_25

DEFINITIONS: Evolution are the changes in the gene pool of a population over time. Natural selection process by which individuals that are better suited to their environment survive and reproduce most successfully. Adaptation is an inherited characteristic that increases an organism’s chance of survival.

Darwin and Evolution 1809-1882

Sailed around world 1831-1836 Galåpagos Islands Darwin Wolf Pinta Isabela Darwin Wolf Pinta Marchena Genovesa Fernandia Santiago Bartolomé Råbida Pin zon Seymour Baltra Santa Cruz Santa Fe Tortuga Española San Cristobal Floreana EQUATOR Galåpagos Islands

Each island had its own type of tortoises and birds Through his travels he found that species diversity was much greater than previously known.

Marine Iguana Land Iguana

His observations led to the development of the theory of evolution.

What is a Theory? Supported by multiple sources of evidence A well tested idea that explains an observed phenomena Supported by multiple sources of evidence

Darwin’s Postulates Populations have natural Variation Overproduction of offspring. Struggle for existence. Unequal survival and reproduction rates. (Those with traits more likely to help them survive will pass traits to their offspring)

What is a species? A group of individual organisms that are capable of reproducing and produce viable offspring. When organisms can no longer reproduce or do not produce viable offspring then they are no longer the same species.

insect and nectar eaters FOUNDER SPECIES insect and nectar eaters fruit and seed eaters KAUAI AKIALAOA AMAKIHI IIWI APAPANE KONA FINCH extinct LAYSAN FINCH AKIAPOLAAU MAUI PARROTBILL

Based on his observations, Darwin proposed that EVOLUTION occurs by NATURAL SELECTION.

Population of organisms Mutations & Sexual reproduction produces variations among offspring. Overproduction of offspring Limited resources leads to a struggle for survival between offspring. Survivors reproduce more successfully. Population changes over time.

The Genetic Makeup of a Population Can Change Populations evolve by becoming genetically different Genetic variations First step in biological evolution Occurs through mutations in reproductive cells Mutations in other cells can happen , but only reproductive cell mutations are passed on Sometimes a mutation can result in a new genetic trait that gives it a better chance to survive, sometimes not.

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring Natural selection: acts on individuals Second step in biological evolution Adaptation may lead to differential reproduction Genetic resistance in bacteria, cockroaches When environmental conditions change, populations Adapt Migrate Become extinct

A group of bacteria, including genetically resistant ones, are exposed to an antibiotic Normal bacterium Resistant bacterium Eventually the resistant strain replaces the strain affected by the antibiotic The genetically resistant bacteria start multiplying Most of the normal bacteria die

Evidence Supporting Evolution Fossil Record

Evidence Supporting Evolution Homologous Structures

Evidence Supporting Evolution Vestigial Structures

Evidence Supporting Evolution Embryo Development

Opposing Theory at the Time Lamark: Theory of Acquired Traits Lamark believed that organisms acquired traits by using their bodies in new ways These new characteristics were passed to offspring Why was Lamark’s theory refuted???

Can a fish species willfully grow limbs and fingers if they are needed to crawl out of the water onto dry land?

Origin of Species Darwin published his book The Origin of Species in 1859 His findings are still supported today by further evidence and the scientific community.

Activity: Choose two online natural selection simulations. Work through the simulation and discuss the strengths and weaknesses of the simulation with regard to modeling natural selection. Which simulation do you believe does a better job modeling natural selection? Justify your answer. In your own words, explain how a new species forms. http://phet.colorado.edu/en/simulation/natural-selection (requires shockwave) http://sepuplhs.org/high/sgi/teachers/evolution_act11_sim.html http://biologyinmotion.com/evol/ http://www.techapps.net/interactives/pepperMoths.swf (requires flash) http://www.sciencechannel.com/games-and-interactives/charles-darwin-game.htm