Evidence of Evolution

What evidence do we have that life has evolved gradually from simple life forms to complex life forms over millions of years?

There are 4 major types of Evidence that Evolution has occurred.

1. Fossil Evidence

2. Comparative Anatomy and Vestigial Structures

3. Similar Embryonic Development

4. Biochemical similarities

Evidence of Evolution

Fossil Evidence

What is a fossil?The preserved or mineralized

remains (bone, tooth, or shell) or traces (footprints, burrow, or imprint) of an organism that lived long ago.

Dinosaur fossil - (bone)Ammonite fossil (shell)

Fossils come in many forms

Dinosaurfootprint

Shark teeth

Imprint of fish

Fossils are very old

Beetle fossil50 million years old

Stingray fossil95 million year old

Trilobite fossils445 million years ago

Bird egg fossil1 million years old

How do We Know How Old things Are?

Carbon dating half –life of carbon 14 is 5730 years.

How do fossils form?Most fossils are laid down in sedimentary

rock -(particles carried by streams and rivers that eventually settle to the bottom in layers)

Many fossils in theGrand Canyon

The oldest particles, and therefore the oldest fossils will be at the bottom, with new layers being added.

The deeper down you go, the simpler the life forms are.

This leads some to believe that life began as simple prokaryotic cells and gradually became more complex because…

Older, simpler fossils at the bottom

What is the “fossil record”

Over the years, paleontologists (scientists that study fossils) have collected millions of fossils. This groups of fossils is called the Fossil Record

The fossil record represents the preserved collective history of the the Earth’s organisms.

The fossil record shows that some organisms that once lived are now

extinct

archeopterous

triceratops stegosaurous

The fossil record can show that organisms changed gradually over time

60 millionyears ago

Today

Fossil record of the whale

Fossil record of the modern horse

55 millionyears ago

Today

Fossil record of the camel

Today

40 millionyears ago

Evidence of Evolution

Comparative Anatomy

&

Vestigial Structures

A. Comparative Anatomy: The limbs of all of these organisms are similar in structure even though their

function may be different

As vertebrates evolved, particular sets of bones were sometimes put to different uses…This may indicate a common ancestry

Some animals appear to have structures that no longer serve a function –

(called vestigial structures)

Vestigial leg bones in a python

Vestigial wings in a flightless bird

Ex a penguin and an ostrich

Human appendix is vestigialThe human appendix has no function in

humans but is very

important in horses

and other animals

Human tailbone is a vestigial vertebrate tail

Human tail bone consists of fused vertebrae that nolonger functionas a tail

Evidence of Evolution

Embryological Development

Similarities in Early Development

Similar development must mean similar genes at work

Similar genes indicated common ancestry.

Differences in development are caused by genes that have mutated during the course of evolution.

Biochemical Evidence of Evolution

Hemoglobin in the blood

The more similar two organisms are, the more similar their DNA is.

This would indicate that they animals evolved from a common ancestor.