What is the difference between a scientific law, theory, and hypothesis?

There is no “proof” in science Hypothesis A statement that is based on observation that can be tested. Theory A well supported explanation of natural phenomenon Law Describe how things happen but don’t explain them. There is no “proof” in science New observations can change current understanding

LaMarck Organisms are adapted to their environments through acquired traits change in their life time Use & Disuse organisms lost parts because they did not use them — like the missing eyes & digestive system of the tapeworm Perfection with Use & Need the constant use of an organ leads that organ to increase in size — like the muscles of a blacksmith or the large ears of a night-flying bat transmit acquired characteristics to next generation Lamarck noted how well-adapted organisms were to their environments, and believed that fossils could be understood as less perfect forms which had perished in the struggle for increasing perfection. He explained adaptation as a result of change caused by environmental pressures.

Voyage of the HMS Beagle Travels around the world 1831-1836 makes many observations of natural world main mission of the Beagle was to chart South American coastline Robert Fitzroy After graduation Darwin was recommended to be the conversation companion to Captain Robert FitzRoy, preparing the survey ship Beagle for a voyage around the world. FitzRoy chose Darwin because of his education, his similar social class, and similar age as the captain. Darwin noted that the plants and animals of South America were very distinct from those of Europe

How did Darwin come up with this?

Cut to the videotape… Darwin: ”The black Lava rocks on the beach are frequented by large (2-3 ft), disgusting clumsy Lizards. They are as black as the porous rocks over which they crawl & seek their prey from the Sea. I call them 'imps of darkness'. They assuredly well become the land they inhabit.”

Correlation of species to food source Seed eaters Flower eaters Insect eaters Adaptive radiation

In historical context Other people’s ideas paved the path for Darwin’s thinking competition: struggle for survival population growth exceeds food supply land masses change over immeasurable time

Natural Selection Overproduction … Variation Competition

Overproduction

Variation

Competition

How does it work? Overproduction Variation Competition Selection… Organisms have more offspring than can survive Variation Not all organisms are the same Competition There isn’t enough for everyone, so who will get what they need? Selection…

The “selection” part of Natural Selection Variation in traits Selection Heredity End result? More organisms with the successful trait

Example: Peacocks

E. coli long-term evolution experiment 50,000 generations - 25 years 1 strain Evolved the ability to use citrate

This is not just a process of the past… It is all around us today Artificial Selection This is not just a process of the past… It is all around us today

Lots of hidden variation comes out! Selective Breeding Lots of hidden variation comes out! AP Movie—Ch 22: Artificial Selection

Evolution Descent with modification The process of change in all forms of life over generations Change in the frequency of a trait Eo: 52-45 mya Plio: 12-6 mya

Bellwork 2/5/2013 What is the primary mechanism of evolution? How do we know if evolution is happening in a species or population?

Evolution Descent with modification Millions of years ago 50 100 150 200 250 300 350 400 450 500 550 60 55 45 40 35 30 25 20 15 10 5 Equus Hyracotherium Mesohippus Merychippus Nannippus Body size (kg) Evolution Descent with modification The process of change in all forms of life over generations Change in the frequency of a trait Eo: 52-45 mya Plio: 12-6 mya

Where does Variation come from? Mutation random changes to DNA errors in mitosis & meiosis environmental damage Sexual reproduction mixing of alleles genetic recombination new arrangements of alleles in every offspring new combinations = new phenotypes

LaMarckian vs. Darwinian view in reaching higher vegetation giraffes stretch their necks & transmits the acquired longer neck to offspring Darwin giraffes born with longer necks survive better & leave more offspring who inherit their long necks 

Other mechanisms of evolution Migration Mutation Genetic Drift

Keep in mind Evolution does not always mean a new species Some changes are minor When speciation occurs, it happens over millions of years

Evolution Descent with modification The process of change in all forms of life over generations Change in the frequency of a trait Eo: 52-45 mya Plio: 12-6 mya

Evolution: What it doesn’t describe The origin of life The definition of species The age of the earth The beginning of the universe

Evidence Fossils Tiktaalik roseae

Fossil Record Shows organisms transitioning from less complex to more complex

Evidence Relative Dating Radiometric dating

Transitional Species Ambulocetus Ambulocetus – walking and swimming – 50 million years ago Doradon– swimming – 35 million years ago Evidence of a gradual change between a newer species and its ancestor

Transitional Species Doradon– swimming – 35 million years ago Evidence of a gradual change between a newer species and its ancestor

Vestigial Structures Structures that do not serve a function and are similar to those found earlier organisms

Homologous Structures Structures that related species have inherited from a common ancestor

Homologous Structures Structures that related species have inherited from a common ancestor

E. coli long-term evolution experiment 50,000 generations - 25 years 1 strain Evolved the ability to use citrate

DNA

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