Introduction to Evolution

Part 1: Introduction:

View video clip: Isn't Evolution Just a Theory

1. How does a scientific theory differ from the use of the word theory in

every day language?

2. State in your own words what you understand by 'The theory of

evolution'

3. Share your ideas with a small group and write in one or two sentences what you understand about evolution.

Part 2: Who was Charles Darwin?

View video clip: Who was Charles Darwin?

1. What characteristics made Darwin especially well-suited to for science?

2. What did Darwin see and do on his five-year voyage on the Beagle?

3. Why was the publication of On the Origin of Species a courageous act?

4. Why was it simply good science?

Part 3: Evidence for Evolution

View video clip: How do we know evolution happens?

1. How do fossils give us a picture of change over time?

2. What distinguishing feature of the fossil Pakicetus skull identified it as related to a whale? Why was this surprising?

3. Why do scientists seek fossils that are intermediate in form and time between modern forms and their probable earliest ancestors?

Part 4:

View video clip: “Fish with fingers”.

  1. Activity: Examining the Fossil Record

Part 5: How does evolution work?

View video clip: How does evolution really work?

1. What are the four components of natural selection?

2. What determines an individual hummingbird’s beak length?

3. What factors in the environment might select for beak length and shape within hummingbird populations?

4. How can hummingbird DNA help Dr. Schneider determine the evolutionary history of hummingbirds?

Part 6: Sex and the Single Guppy

1. Complete the Evolution Web Feature“Sex and the Single Guppy”.

2. Fill in the attached worksheet.

Part 7: Why does evolution matter now?

View video clips: “Cholera: Domesticating Disease” and “Double Immunity”

  1. How does an understanding of evolution help doctors manage infectious diseases?
  1. What factors affect the evolution of disease organisms to make them become more virulent?
  1. What is the relationship between HIV and the Black Death?
  1. How have disease organisms coevolved with humans?

View video clip: Why does evolution matter now?

  1. How does the misuse of antibiotics affect the evolution of disease-causing bacteria like TB? Describe in terms of natural selection.
  1. What is responsible for the evolution of TB strains that are resistant to multiple drugs?
  2. Why is the Russian prison system considered to be “ground zero” in the fight against TB?
  1. How does globalization affect the transmission of diseases? Give an example that includes the way TB is transmitted.

Part II. Examining the Fossil Record

Objectives:

  • analyze characteristics of fossils
  • compare placement of fossils and determine relative ages
  • develop a model evolutionary tree based on the morphology and age of fossils

Fossils are traces of organisms that lived in the past. When fossils are found, they are analyzed to determine the age of the fossil. The absolute age of the fossil can be determined though radiometric dating and determining the layer of rock in which the fossil was found. Older layers are found deeper within the earth than newer layers.

The age and morphologies (appearances) of fossils can be used to place fossils in sequences that often show patterns of changes that have occurred over time. This relationship can be depicted in an evolutionary tree, also known as a phylogenetic tree.

There are two major hypotheses on how evolution takes place: gradualism and punctuated equilibrium. Gradualism suggest that organisms evolve through a process of slow and constant change. For instance, an organism that shows a fossil record of gradually increased size in small steps, or an organism that shows a gradual loss of a structure. Punctuated equilibrium suggests that species evolve very rapidly and then stay the same for a large period of time. This rapid change is attributed to a mutation in a few essential genes. The sudden appearance of new structures could be explained by punctuated equilibrium.


Speciation

The fossil record cannot accurately determine when one species becomes another species. However, two hypotheses regarding speciation also exist. Phyletic speciation suggests that abrupt mutations in a few regulatory genes occur after a species has existed for a long period of time. This mutation results in the entire species shifting to a new species. Phyletic speciation would also relate to the Punctuated Equlibrium hypothesis regarding evolution. Divergent speciation suggest that a gradual accumulation of small genetic changes results in subpopulation of a species, that eventually accumulate so many changes that the subpopulations become different species. This hypothesis would coincide with the gradualism model of evolution. Most evolutionary biologists accept that a combination of the two models has affected the evolution of species over time.


Time Period / Began (years ago)
Wyomington (oldest) / 995,000
Ohioian / 745, 000
Nevadian / 545,000
Texian / 445,000
Oregonian / 395,000
Coloradian / 320,000
Montanian / 170,000
Californian / 80,000
Idahoan
(the present) / 30,000

Procedure:

Arrange the fossils by age. On your data chart, place each fossil next to the period from which the fossil came from. The term "upper" means more recent and should be placed lower in the low. The term "lower" means an earlier time period, fossils from a "lower" time period should be place toward the older time periods. In each fossil column, you may have 3 specimens, one from the main time period, one from the upper and one from the lower. Not all fossils are represented, illustrating the incompleteness of any fossil record.
While keeping the fossils in the proper age order, arrange them by morphology (appearance). To help you understand the morphology of the specimen, view the diagram. Arrange the fossils using the following steps.
Center the oldest fossil at the top of the fossil column (toward the oldest layer)
Through the chart, those fossils that appear to be the same (or close to the same) as the fossils preceding them should be placed in a vertical line
During a certain period, the fossils will split into two branches. In other words, one fossil from that period will show one type of change, and another fossil will show a different change. When this happens, place the fossils side by side in the appropriate time period. From this point on you will have two lineages.

Analysis

1. Give a brief description of the evolutionary changes that occurred in the organism.

2. During which time period did the fossils differentiate into two branches?

3. Phyletic speciation is the transformation of a species into a new species through the accumulation of genetic changes within a single gene pool. Biological diversity results from divergent speciation, the splitting of a gene pool into two or more separate pools, each of which gives rise to one or more species. Explain how the fossil record in this activity provides evidence for both processes.

Part III. Sex and the Single Guppy
The purpose of this activity is to analyze how guppy populations change over time. The simulation activity allows you to start with a pool of guppies and your choice of predators, you will be able to watch what happens to your guppy population and how the introduction of predators can affect the guppy's appearance. The simulation will help you understand what pressures drive guppy evolution.
*Activity adapted from PBS -
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Open the Guppy Sex Simulator!!!

Introduction:

1. If being flashy and colorful attracts predators, why do you think guppies are so colorful?

2. After viewing the guppy gallery, pick the fish you find most interesting. What is the fish’s scientific name, origin and average size? Describe the coloration of the fish you chose.

3. After viewing the predator gallery, pick the fish you find most interesting. What is the fish’s common name, scientific name, and origin?

4. View the guppy’s habitats, what habitat conditions would affect the predator populations?

Endler’s Discovery and Variations of Guppy’s in Pools

5. Who is John Endler? What did he study and where did he study it?
6. For each of the three stream areas, describe the guppy coloration:
Pool 1:
Pool 2:
Pool 3:
7. Develop your own hypothesis about guppy coloration. The hypothesis should answer the questions: Why do guppies in different areas of the stream have difference in coloration? (You can choose from the list on the simulation, or make up your own)

Guppy Simulation

In this part of the project, you will run 3 experiments and collect data about guppy populations. This data will then be analyzed to determine whether your hypothesis was correct or not. Make sure each simulation runs through at least 5 generations.
8. Trial 1
Guppy Color Types ______
Predator Species and Numbers ______
Results and Analysis:
Percentage of Brightest Guppies after 5 generations ______
Percentage of Bright Guppies after 5 generations ______
Percentage of Drab Guppies after 5 generations ______
Percentage of Drabbest Guppies after 5 generations ______
Analysis of the data: (What happened in this simulation, did the guppy coloration change over time? Did the predators seem to affect guppy Coloration? )

9. Trial 2
Guppy Color Types ______
Predator Species and Numbers ______
Results and Analysis:
Percentage of Brightest Guppies after 5 generations ______
Percentage of Bright Guppies after 5 generations ______
Percentage of Drab Guppies after 5 generations ______
Percentage of Drabbest Guppies after 5 generations ______
Analysis of the data: (What happened in this simulation, did the guppy coloration change over time? Did the predators seem to affect guppy Coloration? )

10. Trial 3
Guppy Color Types ______
Predator Species and Numbers ______
Results and Analysis:
Percentage of Brightest Guppies after 5 generations ______
Percentage of Bright Guppies after 5 generations ______
Percentage of Drab Guppies after 5 generations ______
Percentage of Drabbest Guppies after 5 generations ______
Analysis of the data: (What happened in this simulation, did the guppy coloration change over time? Did the predators seem to affect guppy Coloration? )

Summary

11. Describe how predators influence guppy coloration.
12. Was your hypothesis correct, use your data to justify your answer.
13. What does it mean that “male guppies live in a crossfire between their enemies and their would be mates”?
14. Why do you think guppies in different areas of the stream have different coloration?
15. How does the number of predators affect the number of brightly colored guppies?