The document provides evidence for evolution from the fossil record, geology, comparative anatomy, biogeography, embryology, and biochemistry. It discusses how fossils are formed through various processes like compression and petrification. Dating methods like relative dating examine rock layers while radiometric dating uses radioactive isotopes to determine absolute ages. Comparisons of homologous and analogous structures in organisms support common descent. Similarities in embryonic development and DNA across species also provide evidence that organisms share a common ancestry.

1. Evidence of Evolution
Chapter 12

2. Geologic
Time Scale

4. Fossil Record
• Evidence of organisms
from long ago
• Formed in many ways
• Layers of earth
show relative age
of fossils

5. Formation of Fossils
• Compression fossil - fossil preserved in
sedimentary rock that has undergone physical
compression.

6. Formation of Fossils
• Petrification -
organic material
converted into
stone through
replacement of
original material
with minerals

7. Formation of Fossils
• Impression – 2-
dimensional imprint
of organism without
any organic material
left

8. Formation of Fossils
• Molds and Casts - original
bone or shell dissolves
away, leaving behind empty
space.
• Depression = mold
• Cast = space filled with other
sediments in the shape of
the original organism

9. Formation of Fossils
• Intact Preservation -
Oozing tree sap traps
insects and other
organisms
• Amber - When the
sap (or resin)
fossilizes

10. Dating Fossils
• Relative Dating - based on where in layers of
rock it is.
– Does NOT assign an exact age
• Absolute Dating - test fossil or sediment
around it to get a date range
– Radiometric Dating - uses radioactive isotopes
• Based on half life—amount of time it takes for half the
substance to decay
• Ex. Carbon-14

11. Carbon 14 Dating
• Carbon dating - used to date samples to the relative
dates that the sample was from
• Half-life - amount of time it takes for half the
radioactive nuclei in a sample to decay
• Carbon-14 = 5,700 years

12. Biogeography
• Biogeography – the study of past and present
distributions of organisms
• Continental Drift – movement of major land
masses due to plate tectonics

13. Continental Drift
PANGEA
280 million years ago

14. Comparative Anatomy
• .
• Analogous structures - structures that look
similar, but have different origins (e.g. wings
in birds and insects).

15. Comparative Anatomy
• Homologous Structures - structures that have
a common origin, but may be used for
different things

16. Comparative Anatomy
• Analogous Structures - structures that look
similar, but have different origins

17. Comparative Anatomy
• Convergent Evolution - similar structures due
to similar environmental pressures
– Body shape of fish, dolphins and ichtyosaurs
(extinct).

18. Embryology
• Embryos show common ancestry
– Gill slits in human, chick, fish, amphibian embryos

19. Biochemistry
• DNA/RNA - All organisms use DNA/RNA and
proteins as basis of inheritance
– Similar species have similar DNA
– Can use whole genomes or single/groups of
genes
– Mitochondrial DNA – does not degrade as
quickly as nuclear DNA
– Y Chromosome – accumulates changes more
slowly than X
– Can use DNA as a molecular clock to estimate
when organisms diverged (became different)

20. Biochemistry—Molecular Clock

21. Biochemistry
• Proteins – cytochrome c used in electron
transport chain of cellular respiration