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

Theories vs. Laws in Science

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

EvolutionEvolution

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

Avis papyrus

Modeling Selection LabModeling Selection Lab

For today. . .For today. . .Remember there are Remember there are threethree birds for each birds for each

generation. generation. I expect that you will get through the F6 I expect that you will get through the F6

generation todaygeneration todayReuse the materials from the previous birds Reuse the materials from the previous birds

(paper strips, straws, tape)(paper strips, straws, tape)Think of ways that you can be more efficient Think of ways that you can be more efficient

(one person making new wings, two people (one person making new wings, two people testing the birds and recording, one person testing the birds and recording, one person taking apart the old birds) taking apart the old birds)

Natural SelectionNatural Selection1859 – Charles Darwin and Alfred Wallace1859 – Charles Darwin and Alfred Wallace

Not all individuals in a population are the sameNot all individuals in a population are the same

Differences are due to Differences are due to random mutationsrandom mutations

Traits are passed on from parent to offspringTraits are passed on from parent to offspring

Life is difficult, there is competition, not all survive

Organisms that are Organisms that are better adaptedbetter adapted to their to their environment survive environment survive

Survivors reproduce and pass on their genes to the Survivors reproduce and pass on their genes to the next generationnext generation

Evolution occurs through the process of Evolution occurs through the process of natural natural selectionselection

Evidence of Natural Selection:

• DDT resistant insects

• Bacteria resistant to antibiotics

• Industrial melanism -the peppered moths

• artificial selection

Evolutionary Evidence Evolutionary Evidence 1.1. Homologies- “similarities”Homologies- “similarities”

variations on a common variations on a common

structural theme. structural theme.

a.a. Anatomical MorphologyAnatomical Morphology– the study of – the study of the form and structure of the form and structure of organisms.organisms.

structural similaritiesstructural similarities Vestigial organs Vestigial organs – useless organs that were once – useless organs that were once

functional in some ancestral organismfunctional in some ancestral organism

exampleexample: wisdom teeth, human tail bone: wisdom teeth, human tail bone

b.b. EmbryologyEmbryology– the early study of – the early study of different bertebrate embryos are strikingly different bertebrate embryos are strikingly similar to each other.similar to each other.

c.c. Molecular BiologyMolecular Biology– similarity in all – similarity in all organism’s DNA, RNA, and amino acid organism’s DNA, RNA, and amino acid sequencessequences

d. Cellular biology – d. Cellular biology – cells are similar in all cells are similar in all organisms, same membrane and organellesorganisms, same membrane and organelles

2.2. Fossil RecordFossil Record A A fossilfossil is a trace of a long-dead is a trace of a long-dead

organism.organism. Using the Using the fossil record fossil record scientist can scientist can

see how life evolved in the past and see how life evolved in the past and compare it to life on Earth today.compare it to life on Earth today.

Through Through radioactive dating radioactive dating scientist scientist can determine the age of fossilscan determine the age of fossils• Oldest Fossil found 3.4 billion years oldOldest Fossil found 3.4 billion years old

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

4.4. BiogeographyBiogeography • animals and plants are NOT found animals and plants are NOT found

everywhere they could surviveeverywhere they could survive• exampleexample – alligators found only in – alligators found only in

rivers of SE U.S. and in China, rivers of SE U.S. and in China, kangaroos only found in Australia.kangaroos only found in Australia.

• Because… each species originates Because… each species originates only once and that place where it only once and that place where it originated is its center of origin. originated is its center of origin. Then they spread out until halted by Then they spread out until halted by a barrier.a barrier.

5.5. Convergent EvolutionConvergent Evolution – when – when unrelated or distantly related organisms unrelated or distantly related organisms possess similar adaptationspossess similar adaptations

• examplesexamples

• eyes evolved separately 8 timeseyes evolved separately 8 times

• plants unrelated to cacti have plants unrelated to cacti have similar characteristics to reduce similar characteristics to reduce water losswater loss

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

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

The Evolving EarthThe Evolving Earth

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

When do you see greater biological When do you see greater biological diversity?diversity?

Why do complex organisms appear so Why do complex organisms appear so late in our biologic and geologic late in our biologic and geologic history?history?