Eidence for rvolution

1. Evidence for Evolution
1

2. Evidence
Evidence of
common
ancestry
among species
comes from
many sources.
2

3. #1 Fossil Evidence
 Fossils
o Earth is Millions of
years old!
o Fossils in older layers
are more primitive than
those in the upper
layers.
o Extinct Fossils resemble
modern animals.
o This shows a common
ancestry.
3

4. What are fossils and how are they formed?
 Fossils are evidence of
organisms that lived in the
past. They may be actual
remains like burrows,
nests, and dinosaurs’
footprints or even the
ripples created in our
prehistoric shore.
4

5. Types of Fossils
 Permineralization
occurs when minerals
carried by water are
deposited around a
hard structure
A natural cast forms
when flowing water
removes all of the
original tissue, leaving
an impression. 5

6. Types of Fossils
Amber-preserved fossils are
organisms that become trapped in
tree resin that hardens after the
tree is buried.
Fossilized insects
6

7. Types of Fossils
 Impressions are imprints left in
rock
 Preserved remains form when an
entire organism becomes encased in
material such as ice, ash, tar …
7

8. Dating Fossils
8

9. Relative Dating of Fossils
 Estimates the time
during which an
organism lived
 It compares the
placement
of fossils in layers of
rock
 Scientists infer the
order in which species
existed 9

10. Radiometric Dating of Fossils
 Measures the half-life of the isotope
– the time it takes for ½ of the
isotope to break down
 Carbon-12 stable; Carbon-14
radioactive (carbon in ALL organisms)
 Example:
– Carbon-14 has a half-life of 5730 years;
decays into Carbon-12
– Compare ratio of C-14 to C-12 to age
fossil
10

11. Radiometric Dating of Fossils
 Uses Radioactive Isotopes: atoms of
the same element with differing
neutrons
 Example:
– 12C and 14C
– 12C = 6 protons + 6 neutrons
– 14C = 6 protons + 8 neutrons
11

12. Radiometric Dating of
Fossils
12

13. PALEONTOLOGY
13
• the study of fossils
• has revealed to us both the
great variety of organisms
(most of which, including
trilobites, dinosaurs, and the
woolly mammoth, have died off)
and the major lines of
evolution.

14. #2 Geographical Distribution
of Living Organisms
 Geography & environment gives
evidence for evolution
 Island species most closely resemble
nearest mainland species
 Populations can show variation from
one island to another
14

15. Biogeography
• is the study of the geographical
distribution of fossils and living organisms
and of how and why plants and animals live.
• Organisms usually arise in areas where
similar forms already exist. It provides
information about how and when species
may have evolved.
• The evolution of unique species on islands is
an example of how evolution and geography
intersect.
15

16. #3 Embryology
 Embryo (early developmental stage) gives
evidence of evolution
 Identical larvae, different adult body
forms
 Similar embryos, related but diverse
organisms
 Shows
common
ancestry
Larva
Adult barnacle
Adult crab
16

17. #3 Similarities of
Embryology
17
Vertebrates
all share gill
slits and a
tail in their
early
embryo
stage;
Share a
common
ancestor

18. #4 Comparative Anatomy
 The study of anatomy provides
evidence of evolution
 Homologous structures are
similar in structure but
different in function.
 Homologous structures ARE
EVIDENCE of a common
ancestor.
18

19. Structures in different organisms can be
compared to infer common lineage.
19
• HOMOLOGOUS
Structure is an organ
or a bone with the
same underlying
anatomical features in
different animals.
They appear different
and have various
functions

20. Homologous Structures
ARM LEG Flipper Wing
20

21. #4 Comparative Anatomy
 Analogous structures are similar
in function but differ in structure
 Analogous structures DO NOT
show common ancestry
Fly wing
Bat wing 21

22. 22
• ANALOGOUS STRUCTURES are forms that
perform the same function but have very
different embryological development or set of
structures like bones. Examples are the
insect’s wing, bird’s wing and bat’s wing.

23. Structural patterns are clues
to the history of a species.
Vestigial structures are remnants of
organs or structures that had a
function in an early ancestor.
Examples include ostrich wings, human
appendix, and wisdom teeth, whale
and snake pelvis/hind legs
23

24. 24
• VESTIGIAL STRUCTURES are structures that have
no apparent function and appear to be residual parts
from the past ancestor. Examples of vestigial
structures in humans are the following: a tail bone/
the coccyx, Sinuses, Wisdom teeth, a muscle in the
external ear, Erector pili muscles, Tonsils, Male
nipples, a palmar grasp reflex of infants,

25. Pythons have tiny
femurs (leg bone)
25

26. #5 Molecular and Genetic
Evidence
 AKA Biochemical
Evidence
 Two closely-related
organisms will have
similar DNA, RNA, and
protein (amino acid)
sequences.
 This also gives
evidence of a common
ancestor. 26

27. 27

28. 28
Molecular Biology
• is a branch of biology that deals with the structure
and function of the macromolecules (e.g., proteins
and nucleic acids) essential to life.
• Molecular biology gives complete and strong proof
available for biological evolution.
• The nucleic acids (DNA, and RNA) and the proteins
are constructed using the genetic instructions encoded
in the molecules.
• Similarities and differences among biological molecules
can be used to determine species’ relatedness. Like
structural homologies, similarities between molecules
can reflect shared evolutionary ancestry. (Evidence
for evolution, Khan Academy).

29. Five examples of Evidence
for Evolution
1.Fossils
2.Geographical Distribution of
Living Things
3.Similarities of Embryology
4.Comparative Anatomy
5.Molecular and Genetic
29

30. 30