Evolution_readings

Assignment 6
Understanding Change in Organisms

Adapted from: National Academy of Sciences. 2003. Teaching about evolution and the nature of science. National Academy Press, Washington, D.C.

You studied various methods and types of evidence (e.g., geology, radiometric dating, fossils) used by scientists to develop an estimation of the age of the Earth and the age of prehistoric objects. You also learned that science is an ongoing process of inquiry and how to distinguish science from non-science. In today's assignment you will continue to develop your understanding of how science is conducted using a historical perspective.

Prior to today, you read three excerpts from original statements by individuals who contributed to a major revolution in the history of biology. In the 1800s, each of these individuals proposed an explanation for the changes that occur in organisms over generations of time. Explanations for the origin and diversity of life are not new. thayles

thayles

As soon as humans began asking questions about the natural world, it is likely that they wondered about different forms of life around them. By the time of the Greeks, explanations for life's origins and gradual changes had been proposed by individuals such as Thales (624 to 528 B.C., photo to the right) and Anaximander (611 to 547 B.C., photo below). The changes that occurred in proposed explanations for changes in living organisms is an excellent example

anaximander

of how scientific knowledge evolves over time, usually building on prior knowledge. The differing explanations for changes in living organisms are also due, in part, to the influences of society, culture, personal beliefs, and ways of viewing the world.

Before you begin discussions of the excerpts you read, you will review various characteristics of science and your knowledge of the theory of evolution. As a class, briefly discuss the questions below:

How do you think the society in which scientists live might influence their views?
What makes a person's explanation scientific?
Can scientific explanations change? If so, how? Why? In not, why not?
What do you know about Charles Darwin?
When did he propose his theory of evolution?
Did any other individuals propose theories about evolution?

jbl

giraffes

giraffes

Working in groups of four, discuss the excerpts you read. Begin with the statements by Jean Lamarck. Lamarck was a French biologist who proposed a new view of evolution in the early 19th century. Although Lamarck's views are not supported by scientists today, his ideas were of great importance historically because he questioned the then popular belief that species did not change over time. In your group answer the following questions:

What is the role of the environment in Lamarck's explanation?
What scientific approach is suggested by Lamarck's statement: "Nothing of all this can be considered as hypothesis or private opinion; on the contrary, they are truths which, in order to be made clear, only require attention and the observation of facts."
Was Lamarck's explanation scientific? Why or why not?
Can you propose any other explanations for Lamarck's observations about the disuse and use of organs?

wallace

wline

wline

Now focus on the excerpt by Alfred Russel Wallace. Wallace was an English teacher in England who also was interested in plant and animal life. While on expeditions to the Amazon River in Brazil and the Malay Islands, he asked questions about why different species occurred on different land masses. If species, never change, then wouldn't you expect the same species to occur on all of the Malay islands? In your group answer the questions below. As you develop your answers, think of ways in which the excerpt demonstrates science as a human endeavor and the nature of science.

How would you characterize Wallace's idea that "The life of wild animals is a struggle for existence?" How is Wallace's view scientific?
Wallace claims that "useful variations will tend to increase, unuseful or hurtful variations to diminish." How does this occur? What evidence does he cite?
How does Wallace's explanation differ from Lamarck's? What do you think of Wallace's critique of Lamarck's hypotheses?

For your final discussion examine the excerpt by Charles Darwin. Like Wallace, Darwin was an Englishman but he devoted his life to the study of nature. As a result of observations that he made while on the H.M.S. Beagle, especially while at the Galapagos Islands, Darwin wondered about the origin of different plants and animals and the variations in species he recorded in similar specimens. The conclusions that Darwin came to were similar to those made earlier by Wallace. Darwin published Wallace's and his ideas in On the Origin of Species by Means of Natural Selection. The publication stimulated great debate and what is now seen as a scientific revolution that has had significant impacts on society and culture. Your answers to the questions below should demonstrate application of concepts about the nature of science and the historical perspective you have developed in your previous discussions of Lamarck's and Wallace's hypotheses.
darein book

darein book

darwin

What led Darwin to formulate his ideas about the origin of species?
On what did he base his explanations?
What did Darwin propose as the origin of species?
What was the relationship of Lamarck's and Wallace's work to Darwin's?
Was Darwin's explanation scientific? Why or why not?
How did Darwin attempt to determine how modifications of a species are accomplished?
How did Darwin explain the incomplete nature of his ideas?

By now, you probably realize that your classmates have varying views about change in organisms over time or evolution. To gain some insight into why controversy about evolution exists in the United States, view video #7 by clicking on the icon below.

Why Is Evolution Controversial Anyway?

ASSIGNMENT! Type an essay (maximum of one single-spaced page) on the nature of scientific knowledge as demonstrated in the development of the theory of evolution. Your essay needs to clearly demonstrate your understanding of the concepts of adaptation, natural selection, and descent from common ancestors.