Fossil Record and Evolution

Day 126

DN 126

• Can new species result from evolution? Why or why not? HOW?

Let’s Review Kettlewell’s Experiments

• Think back to yesterday…• TRUE or FALSE:

Moths that lived in forests near polluted areas turned black from the soot and coal dust. This changed the color of their wings and they passed this genetic information on to their offspring, which is why there are more dark moths in polluted forests.

Charles Darwin: another old, white, important male scientist

•12 February 1809 – 19 April 1882• Wrote On the Origin of Species in 1859 that proposed theory that natural selection was the basic mechanism of evolution• This theory was not widely accepted until the 1930s, long after his death

Darwin’s 5 year voyage (a three hour tour…)

• In 1831, Darwin left on the HMS Beagle to study biology. He didn’t return until 1836.

Darwin goes on vacay!

Islands, as it turns out, are a great place to study biology.

Why???

Islands are great…• They are separated

from the mainland by some body of water

• This provides a barrier, and prevents many (most) organisms from traveling in between

• Because there is a limit to the organisms that can reproduce, genetic variation is limited.

• “What happens on the island, STAYS on the island!”

Easter Island, Chile

Darwin collects dead birds• Darwin collected many species on his trip,

including many different birds from the Galapagos Islands.

• He didn’t realize the importance of his discovery until he had returned to England.

The story goes like this…

1. Some finches leave the mainland on a dangerous voyage, and reach one of the islands (separation)

2. The finches reproduced and adapted to the environment (adaptation)

3. Some finches flew to a second island (separation)4. The finches reproduced and adapted to a different

environment (adaptation)5. Some finches flew back to the first island, but could no

longer interbreed with the finches there (division, speciation)6. This process occurs over and over again as finches flew to

other islands.

What differences do you see?

If these are only 4 of the finches Darwin found on the islands, what genetic variations do you see?

What environmental factors do you think made these genetic variations successful?

How they work…• Large ground finch has a

wide, strong beak for cracking open big, hard seeds. The beak works like a nutcracker

• The cactus finch has a tough beak used for eating cactus parts and insects. This beak works like a pair of needle-nose pliers

• The warbler finch has a small narrow beak that it uses to catch small insects. This beak works like a pair of tweezers.

Not just birds!

• The Galapagos Islands are well-known for another animal…

Galapagos Tortoises

• Darwin found similar variations among the giant tortoises on the islands.

• http://www.youtube.com/watch?v=BaEezIUzhlI

• How might shell shape have changed?• WHY might shell shape have changed?

Now let’s talk FOSSILS

• Fossils help prove Darwin’s theory• Fossils: the remains or imprints of once-living

organisms found in layers of rock• Fossil Record: a timeline of life that organizes

fossils by their estimated ages and physical similarities.

• Present-day organisms are most similar to organisms found in the newer (shallowest) layers of Earth’s crust.

The Fossil Record

• Scientists examine the fossil record to figure out the relationship between extinct and living organisms

• They draw branching diagrams to illustrate their hypotheses

Among carnivores, felines broke off before the canine species existed

Fossil Record, con’t

• Scientists think that whales and hoofed animals have a common ancestor. This was probably a land mammal that lived between 50 million and 70 million years ago.

• During this time period, dinosaurs died out, and ocean dwelling mammals first appeared in oceans

• Scientists think that all mammal species alive today evolved from a common ancestor

• A more recent ancestor for whales was probably a mammal that spent time on both land and in water

• Scientists have several pieces of evidence to indicate similarities between organisms – molecular and anatomical evidence (DNA and BONES!)

• Look at all the things we have in common!

• Take out a sheet of paper, turn your voices off, and clear everything else off your desk.

• When you are done with the Exit Slip, you may pack up.

• You’ll hand your Exit Slip to me on the way out the door.

• Reminder: QUIZ TOMORROW!

ES 126

1. What was the ship Darwin sailed on for five years?

2. True or False: The book Darwin wrote was called Evolution: A Process of Natural Selection.

3. Why would finches have had to adapt to different surroundings when they moved between islands?

4. What two forms of evidence do we have to indicate similarities between organisms?