6The Facts….99% of everything that has ever lived no longer exists on the Earth – it is extinctSome modern organisms look very similar to other unrelated organisms (ex. Ant-eaters & Echidnas)Some modern organisms look very similar to ancient organisms that are now extinct (ex. fossils)For centuries, people looked at these fossils and tried to EXPLAIN what they are, and what they meanWhat hypotheses could you propose for the diversity of life?What evidence could you gather?What do you ALREADY KNOW about inheritance?
7“EVOLUTION” – what’s all the fuss about?! Theory = “a scientific explanation of natural phenomena, based on empirical evidence”A theory brings together all the research into a single cohesive, testable explanationEvolution = “change over time”A scientific explanation for the origin, diversity and continued change observed within living thingsDefined more specifically in Biology as “descent with modification” (ie. The things alive today are modified versions of their ancestors…just like you and me!)Physical traits are passed-on to offspringSome traits are beneficial, others aren’tThe beneficial traits remain in the population, and become more common over time – THIS IS “EVOLUTION”…
8Let’s back up: “In The Beginning…” Most scientists in the early 1600’s believed that life was a force carried in the air, and that life was spontaneously generated from non-living matterRedi’s simple experiment with maggots and meat proved this to be false…Pasteur filled a flask with growth medium, heated it to kill all life, and then drew out the neck of the flask into a long S. This prevented dust & microorganisms in the air from entering the flask, but allowed air to flow freely. If the swan neck was broken, microbes could enter the flask and growThe Result? Bacteria only grew in the broken flasks…Therefore, microbes come from OTHER microbes…
9ALEXANDER OPARIN - FORMATION OF MACROMOLECULES WITHOUT OXYGEN STANLEY MILLER AND HAROLD UREY EXPERIMENT“Created” amino acids from simulated early Earth conditions…creative commons copyright
13Summary of Darwin’s Theory of Evolution 1. Individual organisms in nature differ from one another
142. Organisms produce more offspring than can survive. Turtle eggsLobster eggsTurtle eggs:Lobster eggs: 8, ,000 for maine lobster; up toInsect eggsFrog eggs
153. Members of each species must compete for limited resources.
164. Each organism has different advantages and disadvantages for the struggle of existence.
175. Individuals best-suited to their environment survive and reproduce 5. Individuals best-suited to their environment survive and reproduce. Those not suited will be less likely to breedSurvival of the fittest!
18Nature (the environment) will determine which organism is the fittest to Survive
196. Species change over time, by passing on their useful (and harmful) traits to their offspring
207. All species alive today have therefore descended with modifications from ancient ancestors
228. Ultimately, ALL organisms on Earth are united into a single tree of life… Darwin’s original sketchbook drawing
23Darwin’s Theory is supported by…. ARTIFICIAL SELECTION Nature provides variation but humans decide what traits are selected and passed on.Hybridization brings about new variations
24Descent with Modification Darwin proposed that after long periods of time, offspring of ancient organisms spread out through the environment, and natural selection then results in organisms with traits that are very different from their ancestorDifferent structuresDifferent nichesDifferent habitatsWe call this Adaptive Radiation
26Evidence of Evolution Did you know???? Fossil Records-fossils being discovered were evidence that the world was much older that once thought.Did you know????Some fossils were very similar to modern day creatures99% of species that once lived are now extinct!!!!!!
27Fossils show history of life on Earth Relative Dating -The layering of rock can show which fossils are older.
28Fossils show history of life on Earth Radioactive Dating -using the half-life of radioactive elements scientists can tell approx. how old a fossil is…
29What Does The Fossil Record Tell Us About Evolution? Sedimentary rocks can be dated by studying the decay of radioactive isotopes they contain.In some cases, successive layers of rocks of different ages are so well-preserved that families of similar fossils can be traced through the layers, over several million years of historyThis apparent transition suggests a pattern of development, and allows scientists to infer changes from one form to another and construct a diagram called a Phylogenetic Tree…
30Trilobite EvolutionPhylogenetic trees show the evolutionary ancestry of organisms, based on their inferred relationships to ancestral species
31The History Of LifeThe fossil record has allowed scientists to locate the “first appearance” of different organisms within rocks of a specific ageThe pattern of change & progression suggests that recent organisms might be modified forms of ancient organisms that previously existed
32The Geological Timescale Based ONLY on the fossil evidence, it appears that the nature and diversity of life on our planet has changed dramatically throughout Earth’s historyBut HOW have these changes occurred?How? We’ll look at Macroevolution on Wednesday