EVOLUTION:

Descent with modification

Age of the EarthAge of the Earth

Scientists estimate Earth to be 4.6 Scientists estimate Earth to be 4.6

billion years oldbillion years old Does not look today as it once did,Does not look today as it once did,

nor do the organisms on itnor do the organisms on it

Change over timeChange over time

Earth is very old! Earth is very old! Has changed a Has changed a great deal.great deal.

Different Different atmosphereatmosphere

Different temp.Different temp. Collisions from Collisions from

outer spaceouter space• Some organisms have stayed about the same as they were millions of years ago (sharks). Some have changed. Some have disappeared.

AdaptationAdaptation

Traits that an organism uses to survive and Traits that an organism uses to survive and reproduce in it’s environment. They are reproduce in it’s environment. They are passed on from parent to offspring.passed on from parent to offspring. Example: How are Polar bears adapted to life in Example: How are Polar bears adapted to life in

the Arctic? Why would they not be well adapted the Arctic? Why would they not be well adapted to life in Hawaii? to life in Hawaii?

Can include structures or behaviorsCan include structures or behaviors Sea Turtles bury their eggs in the sand.Sea Turtles bury their eggs in the sand.

How is this behavior an adaptation?How is this behavior an adaptation?

Species Living things that share the same Living things that share the same

characteristics and adaptationscharacteristics and adaptations Can mate with one another to produce Can mate with one another to produce

offspring that are fertile (can reproduce)offspring that are fertile (can reproduce) Species have changed over timeSpecies have changed over time

Species change too…Species change too…

Many different life forms have existed through Many different life forms have existed through Earth’s historyEarth’s history

Evidence for this comes from fossilsEvidence for this comes from fossils Why do species change? Due to evolutionWhy do species change? Due to evolution

Small changes in a species because of natural selection Small changes in a species because of natural selection add up over millions of years!add up over millions of years!

Mutations in an organism’s DNA, although most often Mutations in an organism’s DNA, although most often bad, can sometimes result in an adaptation. If this bad, can sometimes result in an adaptation. If this mutation helps the organism survive it will be selected mutation helps the organism survive it will be selected and passed on to its offspring.and passed on to its offspring.

Evidence!Evidence! Key evidence to support evolution comes from Key evidence to support evolution comes from

fossilsfossils Generally found in sedimentary rock (particles of Generally found in sedimentary rock (particles of

sand, dust and soil form layers, with oldest at the sand, dust and soil form layers, with oldest at the bottom)bottom)

Fossils tell us that some species have died out, Fossils tell us that some species have died out, while some have changed greatlywhile some have changed greatly

Why??Why??

Because of EVOLUTIONBecause of EVOLUTION

““Descent with Modification”Descent with Modification” Organisms change over time, to what suits Organisms change over time, to what suits

their survival the besttheir survival the best Example: GiraffeExample: Giraffe

Must Have:

"Struggle for Existence"

Variation (different traits

“Success = Reproduction and passing on the trait”

Overproduction (too many babies)

Giraffes with longer necks get better food, have more babies(have an advantage in the struggle for existence)

Longer necks make more long necks(so that trait gets inherited)

Results:

Over time, average neck length increases

Other conditions:**New species can form**Extinctions may occur,

which allow others to take over

Okapi (relative of the giraffe)

*Extinction happens when adaptations fail to keep up withchanges to the environment.

How do New Species Form?How do New Species Form?

Steps to a New Species1.1. SeparationSeparation

2.2. AdaptationAdaptation

3.3. Selection (reproductive isolation)Selection (reproductive isolation)

More evidence for evolutionMore evidence for evolution

1. Comparing Skeletons: Different organisms Different organisms

have same basic have same basic structure = common structure = common ancestorancestor

2. Fossil Evidence2. Fossil Evidence At first glance, whales may seem similar to fish. At first glance, whales may seem similar to fish.

But whales have all the characteristics of a But whales have all the characteristics of a mammal. mammal.

Scientists believe that the ancient ancestor of Scientists believe that the ancient ancestor of whales was a land mammal. A more recent whales was a land mammal. A more recent ancestor was a mammal that spent some time in ancestor was a mammal that spent some time in water and some time on land.water and some time on land.

There is fossil evidence to support this hypothesis.There is fossil evidence to support this hypothesis.

3. Vestigial Structures3. Vestigial Structures Physical structures or behavior that is no longer Physical structures or behavior that is no longer

necessary for an organism to survive or necessary for an organism to survive or reproduce in it’s environment.reproduce in it’s environment.

Things that have been left over as evolution takes Things that have been left over as evolution takes place.place.

Scientists Scientists

think that thethink that the

appendix mayappendix may

be a vestigialbe a vestigial

structure.structure.

Vestigial Structure

Vestigial Structure

4. Comparing DNA from different species4. Comparing DNA from different species All organisms have the same type of DNAAll organisms have the same type of DNA Organisms that are more closely related have more Organisms that are more closely related have more

similar sequences of DNA (example: humans and similar sequences of DNA (example: humans and chimpanzees, only 40 million chimpanzees, only 40 million base pair differencesbase pair differences

5. Embryonic Structures5. Embryonic Structures Early in development Early in development

all embryos look all embryos look amazingly similar amazingly similar

Common ancestor?Common ancestor?

Were you paying attention?Were you paying attention?1. What is evolution?1. What is evolution?

2. Organisms are considered members of the same 2. Organisms are considered members of the same species if….species if….

A.A. B. B.

Were you paying Attention Cont.Were you paying Attention Cont.

3. What are the 3 steps to speciation (the forming 3. What are the 3 steps to speciation (the forming of a new species)of a new species)

4. What are 5 examples of evidence in support 4. What are 5 examples of evidence in support of the Theory of Evolution?of the Theory of Evolution?

Branching Tree Diagrams Scientists use branching tree diagrams to show Scientists use branching tree diagrams to show

how they think organisms are related.how they think organisms are related. They are kind of like family trees.They are kind of like family trees. They use fossil evidence, comparative anatomy They use fossil evidence, comparative anatomy

(comparing skeletons), and DNA comparisons (comparing skeletons), and DNA comparisons

Which animal is most closely Which animal is most closely related to whales?related to whales?

Which groups of animals are still alive today?

How can you tell?

Why do the lines get wider or thinner?

What does the branching tree diagram tell us about snakes and lizards?