Change through Time

White board activity Discuss the definition of a scientific theory On your white boards, write the definition you all agree upon

Theory A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. If enough evidence accumulates to support a hypothesis, it moves to the next step—known as a theory—in the scientific method and becomes accepted as a valid explanation of a phenomenon. A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of knowledge that has been repeatedly confirmed through observation and experiment Most people today use "theory" as just a hunch, guess, belief, or proposal. Science uses the original meaning of "theory": a logical, systematic set of principles or explanation that has been verified—has stood up against attempts to prove it false.

Isn’t evolution just a theory? Let’s look at some of the evidence

Earth has been home to living things for about 3.8 billion years. 6.1 Earth has been home to living things for about 3.8 billion years. Fossil records inform humans about the development of life on Earth. Information from fossils can help scientists reconstruct Earth's history. 250 million years ago 70 million years ago 55 million years ago VISUALIZATION CLASSZONE.COM Explore how fossils form.

Fossils - The remains of organisms preserved in the earth Age of fossils: Absolute age tells you when it was formed, determined by radioactive decay Relative age is determined by a fossils location More complex organisms develop over time

Unicellular organisms 3.8 billion years ago single-celled organisms lived in the ocean and were responsible for creating the oxygen in our atmosphere

Multicellular organisms 1.2 billion years many celled organisms appeared in the ocean

Life on land The first land dwellers were simple plants and fungi

Mass extinctions Huge numbers of species died or became extinct in a very short period of time Permian extinction – 250 million years ago, 90% of the species living in the ocean became extinct and many land dwelling animals disappeared Cretaceous extinction – 65 million years ago, dinosaur fossil record ends. At the same time, more than half of the other species living on Earth became extinct.

Evolution Process through which species change over time

Theories Lamarck – acquired traits are inherited Example: giraffes had to stretch their necks to reach leaves. Passed on the trait to the next generation Darwin – natural selection: members of the same species that are better suited to their environment will survive to pass on their traits Example: tortoises, finches

Species change over time. Darwin's theory of natural selection explains evolution. Four principals of natural selection are • Overproduction - Organisms produce more offspring than will survive Overproduction adult salmon eggs CHAPTER RESOURCES SECTION OUTLINE

Species change over time. 6.2 Species change over time. Darwin's theory of natural selection explains evolution. Four principals of natural selection are • overproduction Variation curve • variation – all offspring vary slightly due to differences in their genetic make-up CHAPTER RESOURCES SECTION OUTLINE

Species change over time. 6.2 Species change over time. Darwin's theory of natural selection explains evolution. Four principals of natural selection are • overproduction Adaptation • variation • adaptation – some differences allow for better survival rate CHAPTER RESOURCES SECTION OUTLINE

Species change over time. 6.2 Species change over time. Darwin's theory of natural selection explains evolution. Four principals of natural selection are • overproduction Selection • variation • adaptation • selection – those preferable differences get passed on to the offspring CHAPTER RESOURCES SECTION OUTLINE

Speciation Evolution of a new species from an existing species Isolation Contributes to a new species

Salamander evolution What were the two strategies used by the salamanders to adapt to their environment? What was the problem with the hybrid?

Interactives Tree of life video Tree of life interactive Simple tree of life

Do Now April 29 What are the three types of evidence for evolution?

Evidence for evolution Genetic – comparing DNA for similarities Fossil – sharing a common ancestor Biological – similarities in structure, similarities in development

Genetic – Comparison of chimp and human chromosomes

Fossil evidence From Wolf to Whale

Similarities in structure Vestigial organs – structures that at one time had a function but no longer do Homologous structures – structures or organs that are similar from one species to another

Biological evidence Homologous structures

Vestigial organs Top ten

Embryological

Even a caveman can do it! brainpop Evolution of humans Cave man challenge Evolution of humans What is the difference between relatives and ancestors? What is one common way new traits are introduced? Why Does Evolution Matter Now?