Chapter 13 The Theory of Evolution

Occam’s Razor (The simplest explanation is usually the right one.) Many scientists have adopted or reinvented Occam's Razor, as in Leibniz's "identity of observables" and Isaac Newton stated the rule: "We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances."

What facts are used to refine the theory of evolution?

Science of Geology Dating rocks Mountains and the movement of the tectonic plates.

600 Million Years PLANET EARTH

Evidence for Evolution Theory Different types of Fossils

Evidence for Evolution Theory Casts – When a mold of an organism is created it is sometimes filled with minerals that produce a replica of the organism.

Evidence for Evolution Theory Trace fossils – Markings of evidence of an organism, footprints, trails, and burrows.

Evidence for Evolution Theory Amber – Preserved or frozen fossils in tree sap or ice.

Evidence for Evolution Theory Petrified fossils – The hard parts of an organism is replaced atom by atom with minerals, making an exact copy.

Evidence for Evolution Theory Molds – Organism is buried and then decays leaving a mold.

Dating Fossils and Geological Material Relative dating – If the material closest to the surface is the most recent, then age should increase as the depth increases. Relative dating only gives age in relation to surrounding material.

Radioactive Isotopes Elements with unstable nuclei, which break down over time forming new elements. The half-life determines the percent of the isotope and can be measured. Ex. Potassium – 40  1.3 billion yrs  Argon - 40

Age of the Earth Scientists also use radiometric dating to determine the age of rocks, fossils, etc. By measuring the proportion of different radioactive isotopes the age can be determined.

Radiometric dating Imagine a bucket filled with 8 gallons of water. Each day you must pour out half the water. How much water is left after 4 days?

Radiometric Dating (cont) When an organism dies, it stops taking in new carbon. The ratio of C -12 to C -14 at the moment of death is the same as other living things. The C -14 decays with a half-life of 5,700 yrs, the C -12 remains constant. By looking at the ratio of C -12 to C -14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing fairly precisely.

4 points to be understood Write these down!!! Variations exist within the genes of all populations or species, and are the result of random mutation.

4 points to be understood In a particular environment, certain individuals of a species are better suited to survive and have more offspring. This can be referred to as “survival of the fittest”. Like This!

4 points to be understood Over time and generations, the traits that give certain members of a species an increased ability to survive and reproduce spread throughout the population.

4 points to be understood There is clear proof from fossils and many other sources that living species evolved from organisms that are now extinct.

Jean Babtiste Lamark – Law of Use and Disuse In 1809 he proposed a mechanism that would allow organisms to evolve. He stated that if an organism used a particular structure frequently during its lifetime, the structure increased in size.

Jean Babtiste Lamark – Law of Use and Disuse Likewise, disuse caused the structure to reduce in size. This would be passed on the offspring. If this theory were correct what would a body builder’s child look like?

Charles Darwin In 1831, at 21, Darwin set out on the HMS Beagle for a 5 yr voyage. He was hired as the ship’s naturalist, to study the wildlife, plants, geography, and even other cultures.

Galapagos Islands

Charles Darwin The ship eventually made its way to the Galapagos Islands off the west coast of South America. There Darwin found species of animals that where very similar to species found in Central and South America.

Charles Darwin Darwin theorized that these species were descendents from organisms that migrated to the islands years ago.

Charles Darwin He returned to England in 1836 and studied his notes and his observations trying to determine a mechanism that could explain the various species.

What is "Natural Selection?" Charles Darwin In 1859 he published On the origin of species by natural selection. What is "Natural Selection?"