EVOLUTION

EVIDENCE OF CHANGE

•The idea that life has and is changing is not new.

•Evolution is the process by which modern organisms have descended from ancient organisms.

Charles Darwin Born Feb 12,

1809, died 1882. Grew up in

England Had a strong

interest in natural history.

Hi, I’m Darwin

At 22 years old, Darwin was invited to sail on the HMS Beagle.

The Beagle sailed around the world. Whenever the ship anchored, Darwin went ashore to observe and

collect animal and plant specimens.

DARWIN’S OBSERVATIONS

Organisms come in a very wide variety of sizes, shapes, and habits.

In one day, he collected 68 kinds of beetles.

There are approximately 10 million species today.

Estimates that 99.9% of all species that have ever lived on Earth are now extinct.

AFTER VOYAGE, DARWIN HAD 2 QUESTIONS…

Where did all the species come from?

Why have so many disappeared?

2 QUESTIONS COME TO MIND….

I wonder if it was a good idea to

marry my cousin?

OBSERVATIONS

Darwin noticed that most animals and plants were very well suited to do the things they do.

The combination of physical traits and behaviors that helps an organism survive and reproduce is called FITNESS

HERE’S SOME QUESTIONS:

1. How did the organisms develop structures that give them their fitness?

2. Why are there such a variety of techniques for survival?

1859

Darwin publishes The Origin of Species by Means of Natural Selection

Proposed that modern organisms have been produced through evolution.

EVOLUTION

A long, slow process of change in a species over time.

HERE’S SOME QUALITY INFO:

Alfred Wallace, a naturalist in the Far East, also came up with the idea of natural selection. He wrote to Darwin about his idea, only to then have Darwin quickly publish the idea first!

Now I’m not

going to get any credit

TWO IMPORTANT DEFINITIONS:

COMMON DESCENT: species have descended from common ancestors.

ADAPTATION: a process that causes fitness (better able to survive and reproduce).

Adaptations Long legs and

neck of giraffe are adaptations

Long legs and neck allow giraffes to eat leaves too high for other grazing animals.

Age of Earth

Earth is approximately 4.6 Billion years old.

Life has changed dramatically over time.

Common descent has taken place

IN THE PAST, PEOPLE BELIEVED:

The Earth was a few thousand years old

Earth remained unchanged

Humans, rarely, if ever, witnessed the earth changing

The Earth is a few

thousand years

old..tops

BUT THEN SOME INTELLIGENT SCIENTISTS

CAME ALONG…Scientists in the 18th and 19th

Centuries examined the Earth and suggested that the Earth is 1) very

old and 2) changed slowly by forces such as weather.

JAMES HUTTON

1788: Proposed that rocks, mountains, and valleys had been changed gradually by rain, heat, cold, and the activity of volcanoes.

A non-changing Earth…absurd!

While scientists were hypothesizing about Earth’s age:

Geologists began to discover fossils. Fossils:

preserved remains of ancient organisms.

Two Methods to Date Fossils:

Relative Dating

Absolute Dating

GEOLOGIC TIME SCALE: A CLOCK IN THE ROCKS

Forms a record in the rocks. Scientists noticed that certain layers

appeared in the same vertical order wherever they were found.

It is the position of the layers relative to each other that tells how old rocks and fossils within them are.

RELATIVE DATING

Technique to determine age of fossils by comparing the layers they are found in

The lower layer is the OLDEST.

Cannot tell actual age, just RELATIVE to other layers.

RADIOACTIVE DATING

By the mid 1900s, our understanding of radioactivity gave scientists a tool to determine the actual age of rocks.

Radioactive elements break down, or decay, into non radioactive elements at a constant rate.

ERNEST RUTHERFORD

Every element has a HALF-LIFE. This is the length of time required for half of the

element to decay. In 1 half life: ½ radioactive

element broken down2 half lives: ¾ broken down

3 half lives: 7/8 broken down.

REMEMBER:

Each element has a different rate of decay, and therefore a different HALF-LIFE!

Hmmm….if a fossil has potassium in it, I can

figure out how old it is by knowing the half life

of potassium!

Radioactive Decay:

Potassium 40: Half life is 1.3

Billion years. In one half life of

P-40,one half of the atoms decay to argon-40

Uranium 238: Half life of 4.5

Billion years. In one half life,

one half of the atoms decay to lead-206.

RADIOACTIVE DECAY CHART

Using radioactive decay, scientists can accurately date fossils.

This is known as ABSOLUTE DATING.

QUALITY QUESTIONS:

What does the X axis (number of shakes) correspond to?

The number of half lives.

THE FOSSIL RECORD

The history of life is recorded by the remains from the past.

Animals and plants can be preserved by natural means

Can be trapped in tree sap-amber

Trapped in sedimentary rock

When a fossil is formed:

Minerals replace the organic components (usually the shell or bone)

Most fossils are found in sedimentary rock

How do fossils form?

Sand, mud and small rocks settle down and COMPACT together, forming layers upon layers.

Unfortunately…

The fossil record is not complete.Not every organism leaves a

fossil.For every organism that does

leave a fossil, many do not leave anything.

Also…

Becoming a fossil depends on where an organism lives.

Thank goodness we didn’t live in the

mountains where it is hard to become a fossil!

Sometimes Nature Helps:

Weather or water may erode newer layers to expose fossils.

But Remember:

Some fossils are not as well preserved as others.

In some fossils, you can see microscopic detail…in others, not so much!

Paleontologists:

I’m a scientist who studies

fossils.

My job is to collect a fossil

record that represents a preserved

collective history of Earth’s organisms.

Horse Fossil Record:

Remember:Changes in species follow

changes on Earth!

As Earth’s conditions changed, species had to either adapt or become extinct!

In case fossil evidence wasn’t enough….

There’s Evidence in Structure!

Homologous Structures

Structures in species that have the same evolutionary origin.

Vestigial Organs

Small or incomplete organs that have no apparent structure.

Tailbone, appendix, ear muscles, pink lump in the corner of your eye….all vestigial organs!

Snakes have some bones that serve no apparent function, but other reptiles with legs ALSO have similar bones.

Hypothesis:…..What do you think???

Amphibian Evolution:

Evidence From Development

In organisms that have common ancestors:The early stages of development have embryos that look similar.

Ontogeny Recapitulates Phylogeny

Evidence of a Common Ancestor:

Fish, reptiles, birds and humans all have gill slits in the embryonic stages.

Molecular Biology Evidence

Amino Acid sequences of proteins in organisms.

Cytochrome C: protein involved in the electron transport chain of ALL aerobic organisms. Humans and Chimpanzees: Cytochrome C is

identical! Humans and fish have an average of 22

different amino acids