1. Evidence for Evolution
By Dr. J. Suris Soto
SC.912.L.15.1

2. Objectives By the end of this lesson you should be able to
List several examples of evidence for evolution.
Explain how fossils, and the fossil record document the descend of modern species from ancient ancestors.
Describe what homologous, analogous, vestigial structures and embryology suggest about the process of evolutionary change.
Explain how geologic distributions of species relate to their evolutionary history.

3. Organize your thoughts
EVIDENCE FOR EVOLUTION is seen in the following ways:
Direct observation
The fossil record
Homology and Convergent Evolution
Biogeography
Evolutionary theory
Provides a cohesive explanation for many kinds of observations

4. Direct Observation of Evolutionary Change
Insect populations can rapidly become resistant to pesticides such as DDT.
Evolution of drug-resistant viruses
and antibiotic-resistant bacteria

5. How does resistance come about?
Mutations in insect populations lead to a resistance allele (R) which is dominate over other alleles that code for susceptibility to a particular chemical.
Genetics and intensive application of insecticides are responsible for the rapid development of resistance in many insects and mites.

6. The Fossil Record Fossils provide evidence for the theory of evolution
Fossils are remains or traces of organisms from the past. Found in sedimentary rock
They show evolutionary changes have occurred over time.
They show the origins of major new groups of organisms.
Paleontologists have discovered fossils of many such transitional forms
Paleontology is the study of fossils.

7. The Fossil Record The Darwinian view of life
Predicts that evolutionary transitions should leave signs in the fossil record

8. How do fossils demonstrate evidence of evolution?
a. They show that ancient species share similarities with species now on Earth. b. They show evidence of species that are now extinct. c. They show evidence of transitional anatomical forms. d. Fossils reveal that many species have remained unchanged for millions of years e. They are the primary source of evidence of natural selection.

9. Homology Is similarity resulting from common ancestry It includes:
Homologous structures
Embryonic Homologies
Molecular Homologies
Vestigial Organs

10. Homologous structures Are anatomical signs of evolution
Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor
Example: forelimbs of mammals that are now used for a variety of purposes.
Human
Cat
Whale
Bat

11. Embryonic Homologies
Comparison of early stages of organisms reveal additional anatomical homologies not visible in adult organisms
Example: All vertebrate embryos have a post-anal tail, and pharyngeal pouches.
Pharyngeal
pouches
Post-anal
tail
Chick embryo
Human embryo

12. Embryonic Homologies

13. Molecular Homologies
Biologists also observe homologies among organisms at the molecular level
Such as genes that are shared among organisms inherited from a common ancestor

14. Vestigial organs Are some of the most intriguing homologous structures
Are structures of marginal, if any, importance to the organism
They are remnants of structures that served important functions in the organism’s ancestors
Examples: the pelvic and leg bones found in some snakes

15. Convergent Evolution
Convergent evolution explains why distantly related species can resemble one another.
Convergent evolution has take place when two organisms developed similarities as they adapted to similar environmental challenges, not because they evolve from a common ancestor.
The likeness that results from convergent evolution are considered analogous rather than homologous.

16. Convergent Evolution Similar problem = similar solution
The torpedo shape of a penguin, dolphin and shark are the solution to move through an aqueous environment.
Sugar gliders (marsupial mammals) and flying squirrels (eutherian mammals) occupy similar niches in their respective habitats.

17. STUDY TIP Homologous structures show evidence of common ancestry.
Analogous structures are similar solutions to similar problems but do not indicate close relatedness.

18. Homologous structures
Analogous structures
similar problem= similar solutions
but do not indicate close relatedness
It leads to
show evidence of common ancestry.
It leads to
Convergent Evolution
Divergent Evolution

19. Biogeography
Is the study of the distribution of species and ecosystems in a geographic space and through geological time.
Species in a discrete geographic are tend to be more closely related to each other than to species in distant geographic areas
Example: In South America , desert animals are more closely related to local animals in other habitats, that they are to the desert animals of Asia.
This reflect evolution, not creation.
Sugar
glider
AUSTRALIA
NORTH
AMERICA
Flying
squirrel
Some similar mammals that have adapted to similar environments
Have evolved independently from different ancestors

20. Biogeography
Continental drift and the break-up of Pangea can explain the similarity of species on continents that are distant today.

21. Biogeography
Endemic species are found at a certain geographic location and nowhere else.
Example: Marine iguanas are endemic to the Galapagos
Darwin’s theory of evolution through natural selection explains the succession of forms in the fossil record.
Transitional fossils have been found that link ancient organisms to modern species, just as Darwin’s theory predicts.

22. What Is Theoretical about the Darwinian View of Life?
In science, a theory
Accounts for many observations and data and attempts to explain and integrate a great variety of phenomena

23. Organize your thoughts
Evolution is change in species over time.
There is overproduction of offspring, which leads to competition for resources.
Heritable variations exist within populations.
These variations can result in differential reproductive success.
Over generations, this can result in changes in the genetic composition of the population.
And remember….Individual do not evolve! Populations evolve.

24. Let’s Practice

25. Biogeography is the study of the location of organisms around the world. Which of the following best explains how biogeography can provide evidence for evolution?
A. It shows that organisms have structures that serve no purpose but that resemble structural roles in related organisms. B. It shows that there are similarities and differences among the DNA of different species. C. It shows that organisms have changed gradually over millions of years. D. It shows that some organisms that are unrelated have developed similar adaptations to similar environments.

26. A. It provides information about the organisms' habitats.
The scientific theory of evolution is supported by different types of evidence. The diagrams below show the skeletons of two different animal species. How does comparing the skeletons of these animals provide support for the scientific theory of evolution?
A. It provides information about the organisms' habitats.
B. It shows possible common ancestry between organisms.
C. It provides information to determine the organisms' ages.
D. It shows possible chromosomal similarities between organisms.
Answer
B. It shows possible common ancestry between organisms.
Animals that evolved from a common ancestor will often have similar structures and organs.

27. D. evolution by natural selection
According to fossil records, the horses that lived 50 million years ago were much smaller, weaker and slower than modern horses.
Which process is most likely responsible for the changes that have led to the increased size, strength, and speed in horses?
A. commensalism
B. inbreeding
C. migration
D. evolution by natural selection
Answer
Natural selection is the mechanism of evolution, where animals that are more “fit” for a certain environment will naturally be selected to reproduce more often. Over time, new species have evolved from similar ancestral species.

28. The diagram illustrates an embryonic stage of two organisms
The diagram illustrates an embryonic stage of two organisms. Which of the following can be determined by observing the embryos shown in the diagram?
A. The organisms share a common ancestry.
B. The organisms belong to the same genus.
C. The organisms are native to the same geographic areas.
D. The organisms will grow into anatomically similar adults.
Answer
During the embryonic stage, before organisms develop many specialized structures, embryos with common ancestry will tend to have many of the same characteristics.

29. D. Reproductive Strategies
Scientists are studying the evolutionary history of a group of plants in the United States, and they developed an evolutionary tree, as shown below.
What information about the organisms best helps the scientists to determine the evolutionary relationships among them?
A. DNA sequences
B. Anatomical features
C. Habitat types
D. Reproductive Strategies
Answer
A. DNA Sequences
Since DNA is passed from parents to offspring, it is the most accurate way of determining evolutionary relationships between species.

30. A marsupial living in Australia has evolved to eat tree leaves, be diurnal, and raise its young until they are of reproductive age. A grazing placental mammal has also evolved to eat tree leaves, be diurnal, and raise its young until they are of reproductive age. Which pattern of evolution is this an example of ?
Answer: B Convergent Evolution

31. In his trips to the Galapagos Islands, Charles Darwin observed that 4 of the 13 species of the islands' finches have beaks adapted to eating specific foods. Which best explains how these facts provide evidence for divergent evolution?
A. The finches were different species but resemble each other because of how they evolved in a similar environment.
B. The finches descended from similar ancestors and have evolved adaptations in response to each other's influences.
C. The finches descended from the same ancestor but evolved along their own lines in isolation from each other.
D. The finches descended from a common ancestor but evolved differently in response to their environment.

32. Which of the following statements correctly compares a scientific theory and a scientific law?
A. A law is a fact and a theory is an opinion.
B. A law is a theory that has been proven to be true.
C. A law is a description and a theory is an explanation.
D. A law is always true and a theory is sometimes true