Presentation on theme: "Lecture #3 Evidence of Evolution"— Presentation transcript:
1 Lecture #3 Evidence of Evolution Unit 6: Evolution
2 Evidence of Evolution Based on a large amount of evidence, most scientists agree on the following three majorpointsEarth is about 4.5 billion years old.Organisms have inhabited the Earth for most of its historyAll organisms living today evolved from earlier, simpler life forms.
3 There are 4 major areas of evidence that exist for evolution 1. Fossil EvidenceFossils provide an actual record of Earth’s past life forms. Change over time (evolution) can be seen in the fossil record.Fossils - Remains or traces of a once-living organismFossil specimens found in older rocks are different from those found in newer rocks.
4 Evidence for Evolution – The Fossil Record Darwin and His TheoryEvidence for Evolution – The Fossil Record4/22/2017G. Podgorski, Biol. 1010
5 Darwin predicted that intermediate forms between the great groups of organisms would eventually be found.Since Darwin’s time, many of these links have been found.Ex: Archaeopteryxlinks birds andreptiles
6 The fossil record is far from complete. Finding fossils is no easy task. Not all organisms lived in areas where fossils form.Paleontologists - scientists who study fossils.They can determine the age of fossils using different techniques.
7 Radiometic dating is used to get an actual age (absolute age) You can also compare a fossils position in the rock strata to the position of another fossil (relative age).
8 How does this help us? When fossils are organized from oldest to youngest,orderly patterns ofevolution can beseen.ExampleEvolution of the horse
10 2. Molecular Evidence (Comparative biochemistry) Darwin could only study traits that could beseen but molecular genetics supports histheoryAll living organisms have the same molecular codeMany organisms have homologous genesExample: Hox gene directs growth of limbs; theprotein hemoglobin carries oxygen
11 Prediction: A species that descended from a common ancestor in the distant past should have more differences in the amino acid sequences of the same protein than do species that shared a common ancestor more recently. Common ancestor - species from which two or more species have diverged.
12 Comparing ProteinsThis predication was tested by analyzing the amino acid sequences of hemoglobin in humans and several other species.The data supported the prediction. Humans and gorillas have fewer differences than do humans and chickens.
13 Comparing DNAScientists can compare the # of nucleotide changes in a given gene as well. Closely related organisms = fewer base differences in the same genePhylogenetic tree
14 Phylogenetic trees branching diagram which shows how organisms are related through evolution. These provide strong evidence supporting evolution because they show the same relationships indicated by the fossil record.
15 Cladogram- a diagram used in which shows ancestral relations among organisms. It is based on shared characteristics.
16 Humans and Chimpanzees are 97% genetically identical. This supports the claim that chimpanzees and humans have a common ancestor
17 3. Homology‘Same structure, different function’Homologous Structures Structures found in organisms that share a common ancestry but have since evolved for different functions.ExampleThe forelimbs of ALL vertebrates are made from the samebasic groups of bones, hooked up in the same way.
18 ‘Same function, different structure’ Analogous structures –Similar features oforganisms that evolveindependently.Example - Wings of afly and the wing of abird‘Same function, different structure’
19 Vestigial Structures – Structures that are reduced in size and function.They are considered to be evidence or an organism’s evolutionary past.These structures have no apparent function. (evolutionary leftovers)Examples- human appendix, wisdom teeth, tailbone