1. Evidence of Evolution
Chapter 15-3

2. I. Darwin’s Evidence
A. For millions of years living things have been evolving
B. 4 areas of evidence:
1. Fossil Record
2. Geographical Record Distribution of living species
3. Homologous Structures
4. Similarities in Embryology
5. Molecular Biology

3. II. Fossil Record
A. Shows how different organisms & species have changed over time
B. Paleontologists study fossils
C. Fossils are preserved remains of dead organisms

4. 1. Its used to determine the absolute age of fossils
D. Radioactive Dating
1. Its used to determine the absolute age of fossils
2. Half-life = time it takes for ½ of the radioactive isotopes to decay
a) Isotope= an atom with an abnormal # of protons or neutrons

5. E. Relative Dating
1. aging of fossils by comparing its placement among other fossils in rock layers.
2. Older rock layers are found under younger rock layers

6. Types of Fossils
Trilobites preserved in sedimentary rock
The term fossil refers to any parts or impressions of an organism that may survive after its death.
Fossils form best when organisms are buried quickly in conditions that slow the process of decay.
Fossils are most commonly found in sedimentary rock.
A layer of shell still covers the stone interior of this ammonite
Bird bones preserved in a tar pit

7. Formation of Sedimentary Rock

8. III. Geographic Distribution Of Living Species
A. Different species lived in different areas.
B. Similar environments had species with similar characteristics or anatomies.

9. Continental Drift

10. Biogeography – distribution of species

11. Biogeography

13. C. Darwin’s Theory: Decent with Modification
1. Organisms are related to one another through a common ancestor
2. Over time natural selection produces organisms with different structures or behaviors causing changes in species

14. IV. Homologous Body Structures
A. Structures that vary in form and function but are constructed from the same basic bones.
1. Ex: arms & legs of reptiles & mammals

15. Comparative Anatomy – Homologous Structures
Wings
Comparative Anatomy – Analogous Structures

16. B. Vestigial Structures
1. organs that have reduced in size and are traces of homologous organs in other species.
2. Ex: Hind legs in whales

17. Vestigial Organs in Whales
Ex: Whales are the descendants of large, four-legged land mammals that existed some 60 million years ago.
Over many years, the pelvis & femur have become very small & no longer fulfill a locomotory function.
Pelvis
Femur
Hindlimb
Forelimb

18. C. These provide strong evidence that organisms have descended, with modifications, from common ancestors.

19. V. Similarities in Embryology
A. Early stages of embryos of many animals are similar
B. It is clear that the same groups of embyronic cells develop in the same order and in the same pattern.
C. It is these similarities that give rise to homologous structures.

20. Comparative Embryology
Developmental Stage
Amphibian
Bird
Monkey
Human
Fertilized egg
Late cleavage
Body segments
Limb buds
Late fetal
Gill slits

21. VI. Molecular Biology
A. Closely related organism have very similar DNA sequences
B. Organisms that are not closely related do not have similar DNA Sequences

22. Molecular Biology

23. Summary of Darwin’s Theory
1. Organisms produce more offspring than can survive
2. Because more organisms are produced than survive, there is competition for resources
3. Individual organisms are different & this variation is heritable

24. 4. “Unique” organisms have advantages & disadvantages.
5. Those best suited for their environment will survive and reproduce most successfully.

25. 7. All organisms trace back to a single common ancestor organism.
6. Species alive today are descendants with modifications from relative species that lived in the past.
7. All organisms trace back to a single common ancestor organism.
THIS IS EVOLUTION!