Theories and Evolution Objective: SWBAT explain what makes a good scientific theory Catalyst: How does speciation (one species splitting into two) occur? When you hear the word theory, what do you think? What are the two criteria of a good scientific hypothesis?

What is a scientific theory? Key Point #1: A scientific theory is a testable explanation of observations Not just a hunch! Has been supported by many, many experiments Can be disproved or modified

How is a THEORY different from a HYPOTHESIS? I THINK I have an idea! HYPOTHESIS Tentative explanation based on observations ONE SCIENTIST Experiments must still be conducted to test hypothesis

How is a THEORY different from a HYPOTHESIS? Explanation supported by many, many experiments MORE THAN ONE SCIENTIST Takes time!

Where did evolution start? Evolution is a theory: it has been revised many times because of new evidence. One of the first evolution theorists was Jean-Baptiste Lamarck, who had some pretty crazy ideas.

This reading is TOUGH… Instead of me re-writing it, let’s see if we can work this out together…

What was wrong with Lamarck’s theory? Key Point #2: Lamarck’s theory was tested and proven wrong. Organisms cannot force themselves to adapt (random mutations are required!) Acquired characteristics are not inherited (my children won’t be born with tattoos!)

Thanks, Darwin! Charles Darwin rejected Lamarck’s theory of evolution, and created the modern theory of evolution in 1859 Random mutation Environmental pressure Natural selection for heritable traits Evolution

Giraffe Giraffes eat leaves on tall trees. Since they stretch their necks so often, the neck grows. Children inherit the stretched out necks. Why is this wrong (Lamarck)? Can’t make your neck grow by stretching it! Children wouldn’t inherit stretched out necks, anyways. What really happened (Darwin)? Random mutations produced some giraffes with longer necks than others. The ones with long necks had more children. This caused the mutation to become more common. Eventually, all giraffes have long necks.

Wolves Wolves need to run to catch food. Since they run so often, they get faster. Children are born fast because the parents are fast. Why is this wrong? (Lamarck) Children aren’t born fast just because parents exercise! If I lift weights, are my kids born with big biceps? NO! What really happened? (Darwin) Random mutations produced some fast wolves. The fast ones had more children. This caused the mutation to become more common. Eventually, all wolves have long necks.

Elephants Larger elephants are more difficult to kill. Elephants got big from eating a lot. Children were born large because their parents ate a lot. Why is this wrong? (Lamarck) Children aren’t born big just because parents eat lots! If I eat a lot, are my kids going to come out 200 lbs? NO! What really happened? (Darwin) Random mutations produced some larger elephants. The large ones had more children. This caused the mutation to become more common. Eventually, all elephants were large.

Intelligent Design Intelligent design = some organisms did not evolve, they were created in their final form by an intelligent designer Key Point #3: Intelligent design cannot be tested, so it is not a scientific theory There is no way to prove, modify, or disprove the theory It is not science!

Guided Practice Mr. LY’s roommate, Mr. McElligott, keeps trying to convince Mr. LY to teach intelligent design in biology class. Write one paragraph to answer… What is intelligent design? Why is intelligent design not a scientific theory? Why is intelligent design not taught in biology class?

Key Point Wrap-Up Key Point #1: A scientific theory is a testable explanation of observations Can be disproved or modified by new evidence Key Point #2: Lamarck’s theory was tested and proven wrong Key Point #3: Intelligent design cannot be tested, so it is not a scientific theory

Why is Intelligent Design not a scientific theory? Exit Questions Why was Lamarck’s theory of evolution rejected? Be specific: what is wrong with it? Why is Intelligent Design not a scientific theory? Write in complete sentences! Don’t talk during the Exit Question!