There is sometimes a misconception that a theory is a theory until it is somehow finally proven and then it “graduates” to a law. It is incorrect that there is a hierarchy from theory to law. In truth, laws and theories serve different purposes in science and one is not more important than the other. Both are based on tested hypotheses Both are supported by a large body of experimental data Both are widely accepted by a majority of scientists within a discipline Both could be shown to be wrong if future evidence brings new discoveries to light Theories vs. Laws in Science

A law tells us what nature does under certain conditions. For example, laws of motion tell us that if we apply a given amount of force to an object with a given mass we can expect a predicted resulting motion. A theory explains why and how nature works the way it does. For example, the germ theory of disease explains why the human body is adversely affected when contaminated with certain micro- organisms.

Evolution Scientific theory that living things change over the course of time and all living things, to some extent, are genetically related to one another.

Avis papyrus

For today... Remember there are three birds for each generation. I expect that you will get through the F6 generation today Reuse the materials from the previous birds (paper strips, straws, tape) Think of ways that you can be more efficient (one person making new wings, two people testing the birds and recording, one person taking apart the old birds)

Natural Selection 1859 – Charles Darwin and Alfred Wallace Not all individuals in a population are the same Differences are due to random mutations Traits are passed on from parent to offspring Life is difficult, there is competition, not all survive Organisms that are better adapted to their environment survive Survivors reproduce and pass on their genes to the next generation Evolution occurs through the process of natural selection

Evidence of Natural Selection : DDT resistant insects Bacteria resistant to antibiotics Industrial melanism -the peppered moths artificial selection

Evolutionary Evidence 1.Homologies- “similarities”  variations on a common structural theme. a. Anatomical Morphology– the study of the form and structure of organisms.  structural similarities  Vestigial organs – useless organs that were once functional in some ancestral organism  example: wisdom teeth, human tail bone

b.Embryology– the early study of different bertebrate embryos are strikingly similar to each other. c.Molecular Biology– similarity in all organism’s DNA, RNA, and amino acid sequences d. Cellular biology – cells are similar in all organisms, same membrane and organelles

2. Fossil Record  A fossil is a trace of a long-dead organism.  Using the fossil record scientist can see how life evolved in the past and compare it to life on Earth today.  Through radioactive dating scientist can determine the age of fossils Oldest Fossil found 3.4 billion years oldOldest Fossil found 3.4 billion years old

3.Organ Systems become more complex as we move up the phylogenetic tree

4.Biogeography animals and plants are NOT found everywhere they could surviveanimals and plants are NOT found everywhere they could survive example – alligators found only in rivers of SE U.S. and in China, kangaroos only found in Australia.example – alligators found only in rivers of SE U.S. and in China, kangaroos only found in Australia. Because… each species originates only once and that place where it originated is its center of origin. Then they spread out until halted by a barrier.Because… each species originates only once and that place where it originated is its center of origin. Then they spread out until halted by a barrier.

5.Convergent Evolution – when unrelated or distantly related organisms possess similar adaptations examplesexamples eyes evolved separately 8 timeseyes evolved separately 8 times plants unrelated to cacti have similar characteristics to reduce water lossplants unrelated to cacti have similar characteristics to reduce water loss

6.Divergent Evolution – each group spreads out and occupies as many different habitats and niches as possible. Ex: Galapogos finches

7. Co Evolution – Mutual evolution of two different species interacting with each other. Example:

The Evolving Earth Why did no life exist on Earth in the very beginning? Before the increase in atmospheric ozone, what did early bacterial life use to protect itself from the damaging UV radiation? Before life could successfully exist on land, what significant change in Earth’s atmosphere had to occur? At the end of the Mesozoic Era a massive asteroid impact occurred on Earth. Did the impact result in a mass extinction of all life on Earth?

When do you see greater biological diversity? Why do complex organisms appear so late in our biologic and geologic history?