Aim: What evidence do we have that Evolution took place?
I. Evolution – living things have changed from ancestors
that they have in common.
A. Evidence of Evolution
1. Fossils – a fossil is any record of an organism that
lived in the geologic past. Remains, impressions, and
traces of organisms of past geologic ages have been
preserved in the earth’s crust as fossils.
Question. Are all dead organisms preserved as fossils?
Answer: NO! Hard parts of organisms such as bones,
teeth, and shells are more resistant to weathering. Also,
dry environments help preserve fossils better.
a. Types of Fossils – animals can be created by
refrigeration (wooly mammoth), imprints in soft mud, casts,
insects trapped in amber, petrification. Coal is an
example of fossilized plant remains. Tar pits(La Brea in
Los Angeles).
b. Determining the Age of Fossils – older fossils are
found at deeper layers of earth than younger ones, index
fossils, and radioactive dating.
c. Evidences of Relationships - examination of rocks
and fossils indicate that there was:
• a change from simple to complex forms
• change from marine to land forms
• presence of intermediate forms
• presence of transitional series
• sufficient time for evolution to have occurred
Insect in
Amber
Imprints
Preserved
bones
Casts
Bony Tail
Teeth
Link between reptiles and birds
2. Evidence from comparative cytology (the study of
cells) - Most organisms are composed of cells, but even
their organelles (tiny organs) are similar in structure and
function.
3. Evidence from comparative biochemistry (the
chemical reactions in living things) - The structure of
DNA and RNA and the way they function is similar in all
living things. Many different organisms have similar
proteins and enzymes
4. Evidence from comparative anatomy
a. Analogous structures – have the same
function but different evolutionary origins.
Example: The wing of a fly and the wing of a bird.
Fly wing is a membrane and the bird wing is bony
covered with feathers.
b. Homologous structures – same basic
structure and evolutionary origin. Example: human
arm, wing of a bat, and the flipper of a whale.
Bird Wing
Insect wing
5. Evidence from immunology
a. Similarities in blood proteins of various animals
(ex: vaccines from horse)
6. Evidence from Embryology
a. Examine early stages of embryos and
found great resemblance. See photo.
b. These embryos then develop differently as
they grow.
What evidence do scientists have that evolution
took place?