1. 15.2 Evidence of Evolution
Main idea: Multiple lines of evidence support the theory of evolution.
Objectives:
Describe how fossils provide evidence of evolution.
Discuss morphological evidence of evolution.
Explain how physiology and biochemistry provide evidence of evolution.
New Vocabulary
Derived trait
Ancestral trait
Homologous structure
Vestigial structure
Analogous structure
Embryo
Fitness
Mimicry
Camouflage

2. Support for Evolution
The theory of evolution states that all organisms on Earth have descended from a common ancestor.
The fossil record offers some of the most significant evidence of evolutionary change.
Fossils provide a record of species that lived long ago.
Fossils show that ancient species share similarities with species that now live on Earth.

3. Support for Evolution
The Fossil Record
The giant armadillo-like Glyptodon is an extinct animal that Darwin thought must be related to the living armadillos of today.
The fossil record provides information for determining the ancestry of organisms and the patterns of evolution.

4. Support for Evolution Two major classes of traits:
The Fossil Record
Two major classes of traits:
Derived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors.
Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms.

5. Support for Evolution
The Fossil Record
Transitional fossils provide detailed patterns of evolutionary change for ancestors of many modern animals, including mollusks, horses, whales and humans.
Example:
Archeopteryx
Shares features of both dinosaurs and birds.

6. Support for Evolution
Comparative Anatomy
Homologous structures are anatomically similar structures inherited from a common ancestor.
The forelimbs of vertebrates are adapted for different uses, but they all have similar bones.
Similar structure; different function.

7. Support for Evolution Comparative Anatomy
Vestigial structures are the reduced forms of functional structures in other organisms.
Evolutionary theory predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost.
Same structure; reduced function
Examples: Snake pelvis, human appendix, blind fish and salamanders that live in caves but have eyes.

8. Support for Evolution Comparative Anatomy
Analogous structures can be used for the same purpose and can be similar in construction, but are not inherited from a common ancestor.
Analogous structures show that functionally similar features can evolve independently in similar environments.
Different structure; same function

9. Support for Evolution Comparative Anatomy
Analogous structures example:
Human eye and squid eye
Similarities
The iris to regulate light entering the lens
Each eye is filled with fluid
Both eyes use a lens to focus
function;

10. Support for Evolution
Comparative Embryology
An embryo is an early pre-birth stage of an organism’s development.
Vertebrate embryos exhibit homologous structures during certain phases of development but become totally different structures in the adult forms.

11. Comparative Biochemistry
Support for Evolution
Comparative Biochemistry
Common ancestry can be seen in the complex molecules that many different organisms share.
Molecules are similar because the organisms have a common ancestor
Species
Sequence of Amino Acids in the same part of Hemoglobin Molecules
Human
Lys-Glu-His-Iso
Horse
Arg-Lys-His-Lys
Gorilla
Lys-Glu-His-Lys
Chimpanzee
Lys-Gu-His-Iso
Zebra
Arg-Lys-His-Arg
The genomes of humans and chimpanzees differ by only about 1% of their genetic makeup
Scientists now use similarities in DNA and RNA sequences to determine relationships between species

12. Geographic Distribution
Support for Evolution
Geographic Distribution
The distribution of plants and animals that Darwin saw during his travels first suggested evolution to Darwin.
Rabbit in Europe Mara in S. America

13. Support for Evolution
Geographic Distribution
Scientists have confirmed and expanded Darwin’s study of the distribution of plants and animals around the world in a field of study now called biogeography.
Evolution is intimately linked with climate and geological forces.

14. Adaptation
An adaptation is a trait shaped by natural selection that increases an organism’s reproductive success.
Fitness is a measure of the relative contribution an individual trait makes to the next generation. It is often measured as the number of reproductively viable offspring that an organism produces in the next generation.

15. Adaptation Types of Adaptation
Camouflage allows organisms to become almost invisible to predators. Some species have evolved morphological adaptations that allow them to blend in with their environments.
Mimicry is another morphological adaptation that allows one species to evolve to resemble another species.

16. Adaptation
Types of Adaptation
Can you see the peppered moth?

17. Adaptation Types of Adaptation
When disturbed, this octopus flashes and intensifies its stripes, resembling a poisonous sea snake. Unlike the sea snake, the octopus venom is harmless

18. Adaptation Types of Adaptation Antimicrobial resistance
An antibiotic is a medicine that slows or kills the growth of bacteria.
Bacteria originally killed by antibiotics like penicillin have evolved quickly into populations of resistant bacteria.
For most antibiotics, at least one species of resistant bacteria exists.
People infected with resistant bacteria can never get rid of it.

19. Adaptation Types of Adaptation Traits may decrease fitness
Some features arise as a consequence of other evolutionary changes.
Human babies are born helpless at an earlier developmental stage than other primates as a consequence of the mother’s narrow birth canal.
Narrow birth canal is an adaptation that enables walking on 2 legs instead of 4.
Early birth is not an adaptation but instead a consequence of evolution.