Evidence of Evolution
ßWhat 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?
ßThe preserved or mineralized
remains (bone, tooth, or shell) or
traces (footprints, burrow, or imprint)
of an organism that lived long ago.
Ammonite fossil (shell)
Dinosaur fossil - (bone)
Fossils come in many forms
Shark teeth
Dinosaur
footprint
Imprint of fish
Fossils are very old
Trilobite fossils
445 million years ago
Beetle fossil
50 million years old
Stingray fossil
95 million year old
Bird egg fossil
1 million years old
How do We Know How Old things
Are?
ß Carbon dating half –life of carbon 14 is 5730
years.
How do fossils form?
ß 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 the
Grand Canyon
ß The oldest particles, and therefore the
oldest fossils will be at the bottom,
with new layers being added.
ß The deeper down you go, the simpler
the life forms are.
ß 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”
ß Over the years, paleontologists
(scientists that study fossils) have
collected millions of fossils. This
groups of fossils is called the Fossil
Record
ß 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
triceratops
stegosaurous
archeopterous
The fossil record can show that
organisms changed gradually over time
60 million
years ago
Today
Fossil record of the whale
Fossil record of the modern horse
Today
55 million
years ago
Fossil record of the camel
Today
40 million
years 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
ß 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)
ß Vestigial leg bones in a python
ß Vestigial wings in a flightless bird
Ex a penguin and an ostrich
Human appendix is vestigial
ß The 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 no
longer function
as a tail
Evidence of Evolution
Embryological
Development
Similarities in Early
Development
ß Similar development must mean
similar genes at work
ß Similar genes indicated common
ancestry.
ß Differences in development are caused
by genes that have mutated during the
course of evolution.
Biochemical Evidence of
Evolution
ß
Hemoglobin in the blood
ßThe more similar two organisms
are, the more similar their DNA is.
ßThis would indicate that they
animals evolved from a common
ancestor.