5 Darwin collected fossils Some fossils looked like modern animals.
6 Some fossils were different: Giant Ground Sloth from Patagonia
7 Fossil Record = All fossils known to science Younger fossils lie above older fossils in undisturbed rock layersComparing fossils shows a gradual change from past to present lifeWe keep finding new fossils, but the fossil record will still have gaps
8 Layers of rock include fossils shows history of life over millions of years.
9 Fossils support Evolution From looking at the fossil record, Darwin suggested that whales may have come from a 4-legged land mammal.
27 According to Lamarck,this body builder’s offspring would be born buff.
28 Galapagos TortoisesDarwin noticed that the giant tortoises on different islands had different characteristic.How would Lamarck explain these differences?Galapagos tortoise closeup!
29 Why are the animals different? Each island has slightly different weather:lower islands are barren and dry,higher islands are wetterSo, different islands have different vegetation, different habitat.
30 Tortoises with longer necks could reach the higher vegetation in drier areas, so they survived and reproduced, passing their long-necked genes to their offspring.Tortoises in wetter areas had plenty to eat and didn’t need long necks to survive and reproduce.Galapagos tortoise
31 Natural Selection:Individuals that have traits better suited to their environment are more likely to survive and reproduce.“survival of the fittest”
33 Darwin’s steps of natural selection: Variation –inherited variation in every populationOverproduction – populations produce more offspring than can possibly survive (leads to competition for resources!)Selection – individuals with favorable traits leave more offspringAdaptation – over time, favorable traits become more common in a population
34 Darwin considered More Evidence: Artificial SelectionPopulation growth (Malthus)Age of the Earth (Lyell & Hutton)
35 Darwin’s Artificial Selection When breeding livestock, humans choose the parents with traits they want in the offspring.Ex: dogs, cows, horses, pigeons
36 Population growth:Thomas Malthus pointed out that food supplies were limited and the human population could not keep increasing exponentially.Darwin applied this to all populations: organisms must COMPETE for limited resources!
37 Age of the EarthIn Darwin’s time most Europeans believed in the biblical age of the Earth (a few thousand years).James Hutton and Charles Lyell were geologists who studied fossils and rock layers and suggested that theEarth was much older (millions of years)!…long enough for species to evolve gradually.
38 On the Origin of Species by Means of Natural Selection Darwin hesitated to publish his ideas because they conflicted with popular religious beliefs about the origin of life.He waited until 1858 when Alfred Wallace convinced him to go public with his book, On the Origin of Species.
39 Evolution:A change in an inherited characteristic of a population over time.Individuals DO NOT evolve!
40 Adaptation:An Inherited trait present in a population because it helps individuals survive AND reproduce in a given environment.Individuals may have adaptations, but they DO NOT CREATE adaptations through use. (That’s Loser Lamarck!)
41 Now, work with the person sitting next to you to think of a particular organism’s adaptation. Be prepared to explain how that adaptation might have evolved.
42 Macroevolution (forming new species) is a slowww process Macroevolution (forming new species) is a slowww process! It takes many generations to develop adaptations!!!
43 Microevolution is a change in the gene frequencies of a population. Can happen quicklyEx: antibiotic resistant bacterial colonies
44 Speciation:New species evolve and no longer interbreed with the ancestor.What is a species?Morphological (what they look like)Biological (reproduction)Molecular (DNA)
45 Evolution is a unifying theory Darwin brought together evidence from geology, biogeography, ecology, paleontology.Today Evolutionary Theory also includes evidence from developmental biology, genetics, and biochemistry.
47 Anatomy gives clues to evolutionary relationships: Homologous structures: traits that are similar in 2 or more species, inherited from a common ancestor.
48 BiogeographyStudy of the locations of organisms around the world.
49 Large, flightless birds are found in similar habitats, different locations.
50 Embryology - study of developing embryos Compare the development of embryos of different species.All vertebrate embryos have a tail at some point in development.
51 Genetics: Compare DNA sequences to find hereditary relationships. The more similar the genes, the more closely related the organisms.
52 Biochemistry: All life is built from the same 20 amino acids. compare differences in amino acids of same protein.
53 Darwin’s Theory Weakness: 1. Darwin didn’t know about genes. Strengths:1. Organized notes, observations, evidence.2. Showed the mechanism of change.3. Showed that variation was starting point of evolution.Weakness:1. Darwin didn’t know about genes.
54 Cladogram – a tree-like diagram that shows evolutionary relationships.
55 Evolutionary novelty: a characteristic shared by one branch of the cladogram