1) Fossil records, anatomy, DNA, and embryology provide evidence for evolution. Fossils show transitional forms and tracks of ancient organisms. Comparing DNA between species shows greater differences the more distantly related they are. 2) Anatomical evidence like whales having vestigial hind limbs and DNA comparisons support the theory that whales evolved from land mammals. Transitional whale fossils dating back 50-35 million years show the evolution of whales from land to sea dwellers. 3) Embryos of different species resemble each other more closely in early stages of development, providing further evidence they share a common ancestor and have evolved over time from that ancestor.

1. The Evidence for
Evolution

2. Evidence Supporting Darwin
 1) Fossil records
 2) Anatomy
 3) DNA
 4) Embryology

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.

7.  35 mya
 42 mya
 50 mya
 60 mya

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.

10. Comparative Anatomy

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.