Geology 105 - Paleontology
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Speciation

Reading: Chapter 5 & Web

In Chapter 5, read p. 120-128, & p. 138.

On the Web, read the Speciation section of Evolution 101.

Background

Terms:

Key Concepts and Questions:

1. It's pretty obvious that there are different "kinds" of organisms. We call these basic "kinds" species - i.e., not squirrel, but fox squirrel; not snake, but timber rattlesnake. How do we define or recognize a species?

A. Find definitions for a biological and morphological species:

Biological species:

Morphological species:

B. What problems do biologists have in identifying species? (find what you can in the reading; we'll fill it out in class)

 

 

 

C. What problems do paleontologists have in identifying species? (find what you can in the reading; we'll fill it out in class)

 

 

 

2. How do new species form?

A. Species form by geographic isolation - allopatric speciation.

Cite some examples of how allopatric speciation can occur:

 

 

 

 

B. Species can form when species living in the same region become reproductively isolated - sympatric isolation.

In the reading find three ways sympatric speciation can occur.

 

 

 

 

In lecture we will look at at least two other ways sympatric speciation can happen.

 

 

 

 

 

3. Rate and tempo of speciation

A. Find definitions for phyletic gradualism and punctuated equilibrium:

Phyletic gradualism:

Punctuated equilibrium:

B. Is the tempo of speciation (i.e., phyletic gradualism vs. punctuated equilibrium) related to the mechanism of speciation (i.e. allopatric vs. sympatric speciation)? (find what you can in the book and we'll add to it in class)

 

 

 

 

 

 

 

C. Hawaii has the largest number of fruitfly species in the world, with the greatest concentration of species in the active volcanic areas on the Big Island. Is this most likely an example of allopatric or sympatric speciation?

 

 

 

 

 

 

4. Species selection. Your book is not great on this topic, so we'll do most of the work on it in class.

A. Species have varying rates of speciation and extinction. That is, some groups of organisms tend to throw off a lot of new species, while others don't. Some groups tend to go extinct more readily than others.

What is an example of species selection from your reading?

 

 

 

B. The characteristics that lead to rapid speciation need not be characteristics that are more adaptive within the species. In other words, characteristics that lead to reproductive isolation do not necessarily lead to reproductive success.

For example, broadcasting your offspring into the oceans where they drift away from predators and competitors may lead to greater reproductive success, but leads to fewer opportunities for reproductive isolation than having offspring that remain close to the parent.

 

 

C. If a characteristic increases the probability that a species will produce more species, soon that characteristic will become widespread in that lineage.

Most animals have segmented bodies and jointed appendages - they are insects (there are more insects alive to day than all other species of plants and animals put together). Explain this phenomena using two different mechanisms of species selection. Then explain this phenomena NOT using species selection.

 

 

 

Assessment

1. Short Answer

• Explain the difference between a biospecies and morphospecies.
• Examine the collection of fossils before you. They are all the same mophospecies. When we call these members of the same species, what assumptions are we making? What information do we have in defining biological species that we do not have in defining morphological species?
• Examine the fossil lineage you have been given (to be provided). Do you see evidence for punctuated equilibrium, phyletic gradualism, or some combination of the two? Define the two patterns of evolution, then cite specifically where you see either or both of them in the lineage.
• Define species selection. What factors of the biology of organisms impact this process?
• What is the difference between allopatric and sympatric speciation? Give an example of how each might occur.
• Under what circumstances may I choose the name of a new species? What must I do to make that name "official"?

2. Essay

• Phyletic gradualism and punctuated equilibrium represent different models of the pace and tempo of speciation. Each model is more consistent with a particular view of how environments change and about how speciation occurs. Explain each model of speciation, including what it implies about environments, allopatric and sympatric speciation.