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Comparing Theories

Comparing Theories Compilation of images of Lamarck, by Charles Thévenin [Public domain], and Darwin, by George Richmond [Public domain], via Wikimedia Commons

Introduction

The theory of evolution revolutionized the way we view the history of the human species and other life on earth. Darwin was not the first one to propose the theory of evolution but his description of the mechanism for it, natural selection, has proven to be more plausible and therefore accepted by the scientific community today. Use the resources found here to help you compare Darwin’s theory of natural selection with Larmarck’s proposed mechanism for evolution.


Exploration

Open the BrainPOP movie, Natural Selection. While the movie is loading, read this:

BrainPOP is a subscription site. However, it will allow you to see the movie if you take a free trail. You will not be able to view any other BrainPOP movies if you are not subscribed to the site. Use the following technique to watch the movie and then answer the questions below. Write the answers to the questions on your Natural Selection student sheet.

  • First read through the questions you will be asked about natural selection that are based on this movie.
  • Play the movie to answer all the questions. As you watch, use the four control buttons on the lower right hand of the viewing screen. You can use your mouse on these buttons to skip back a section or pause, rewind, and fast-forward the film as you are watching it.
Questions:
  1. How did Darwin explain his observations of the diversity of island finches?
  2. Describe the types of environmental pressures faced by living organisms.
  3. What are mutations?  Describe the relationship between mutations and variations in organisms.
  4. Describe the term "survival of the fittest."
  5. Why does Moby call natural selection the driving force behind the theory of evolution?
  6. How does the theory of natural selection explain the observed diversity of life?

Developing Scenarios

On the Hawaiian Islands, there are today numerous species of honeycreepers, a family of birds. All of these different species share the same common ancestor: a single finch-like species that scientists estimate arrived on the Hawaiian Islands about 5 million years ago. PBS describes a fictitious group of birds called pollenpeepers, based on what scientists know about the Hawaiian honeycreepers. With your partner, write a similar pair of scenarios describing how a particular species of pollenpeeper bird evolved from the ancestral species.

Go to An Origin of Species. At the "Map of Pollenpeeper Homes," choose one of the four islands. In your scenarios, describe the evolution of a new bird species on your chosen island using the information provided by the website and the timeline. Your scenarios must be detailed and describe the environmental pressures faced by the bird species over time. Concentrate on describing how and when the new species evolved, new physical features, and how the birds survived and reproduced while being faced with particular environmental challenges. Be sure to state the name of the ancestral species, the island chosen, and the name of the new species.

Write one scenario using a Lamarkian explanation and the second scenario using a Darwinian explanation.


Knowledge Check

Consider this problem:
Many insular species of both plants and animals have lost defense mechanisms that are frequently found on their continental relatives. Several species of birds and insects have become flightless and many plant species have lost defense mechanisms such as thorns or toxic chemicals. How would an evolutionary biologist explain how these losses came about?

Your assignment is to answer this question in short answer format using your knowledge of evolutionary theory. Your teacher will provide writing guidelines.

As you think critically about this problem, you might want to turn to some resources, including textbooks and other books. Here are some online resources that you might find helpful:


This esheet is a part of the Comparing Theories: Lamarck and Darwin lesson.

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Esheet Details

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