3. 1) Fossils
Footprints of
dead organisms
Tracks
Insects trapped
in tree sap
Impressions of
skin
Traces of dead
organisms.
4. Conditions to create fossils
Must be buried by sediments
Swamps, mud, tar pits, ocean
bottoms
Hard stuff most likely to be
fossilized.
5. How are Fossils Dated?
Scientists determine the age of fossils by
measuring the amounts of radioactive
decay.
Half-life describes how long it takes for one-
half of the radioactive atoms in a sample to
decay.
The rate of radioactive decay is constant
Scientists can use the amount of radioactive
element remaining in a rock or fossil to
determine its age. This technique is
6. 2) Anatomy
Transitional Species
– Evolutionary transitions/ intermediate
forms of the organism.
Whales-
– Are descendants of 4 legged land
animals that are also ancestors of
horses and cows.
8. Whales- Vestigial Structures
-Remnants of an organisms
Hind limbs
evolutionary past.
became
smaller
Eventually lost
Modern whales
have a pelvis
but, no rear
limbs.
9. Structural Evidence cont.
Vestigial
Structures:
Remnants of an
organisms
evolutionary
past. Structures
reduce in size
and have no
present function.
11. Structural Evidence
Comparing the way
two organisms are
put together.
Homologous
structures:
Modified versions of
the same structure.
Similar in structure
differ in functions.
12. 3) DNA Evidence
Structural, fossils, and developmental
evidence still posed many questions.
DNA evidence supports the other three.
If species change over time, their DNA
will also change.
Similar organisms = similar DNA
Genes accumulate more alterations in
their nucleotide sequence over time.
13. DNA Evidence con’t
Compare: chimp, dog, rattlesnake,
human
Protein- look at amino acid sequence.
When comparing a.a. sequences
chimps vs. humans 0 a.a. differences
– Dog vs human 13 a.a. differences
– Rattlesnake vs. human 20 a.a.
difference
14. 4) Embryology
Early stages of development are similar
between organisms.