Morphology

Reading: Chapter 6

You can skim the sections on Morphospaces and Ecological Niches, and on Diversity and Disparity - we won't be using these. The section on Functional Constraints reviews some material we already covered in Natural Selection.

Background

Terms: find definitions

Key Concepts and Questions:

1. What are the sources of variation within a population (we'll do this in class)?

A. Ecological pressures: From lab, think of an example of a marine invertebrate where morphology is shaped by environment during the organisms lifetime (NOT from genetic variability):

 

B. Sexual Dimorphism: What evidence can we use to infer sexual dimorphism in fossil species?

 

C. Individual genetic variability in neutral characters: how could we recognize this?

 

D. Ontogeny: How are juveniles and adults different?

 

C. Taphonomic variability: How is our understanding of fossil populations altered by post-mortem distortion?

 

2. Can we recognize distinct patterns of growth in organisms?

A. Rates of Growth

1. What is the difference between allometric and isometric growth?

 

 

 

2. Why is allometric growth more common than isometric?

 

 

3. Why does allometric growth place limits on the maximum size of organisms?

 

B. From lecture:Find definitions and an example for each of the four patterns of growth:

Growth pattern	Definition	Example
accretion
addition
molting
modification

B. How does an organism's growth pattern affect the information we can get from the fossil record about that organism? (You can start this from the book and we'll finish it in class.)

Growth pattern	How is information affected?
accretion
addition
molting
modification

 

 

3. How can developmental influence evolution of a lineage?

This is a review of heterochrony and how large morphologic change can occur with minimal mutation.

What is heterochrony and why does it metter in evolution?

 

 

How can Hox genes impact evolution?

 

 

4. How do we know what ancient organisms used specific structures for?

Here are the four methods we looked at in class:

• Find an analogy among living organisms.
• Analyze the biomechanics of the organism
• Build a physical model
• Build a mathematical model

What other methods are described in the chapter?

 

 

5. We did this in lab: Representing morphology in theoretical morphospace

One way to analyze the shapes organisms have is to compare the range of actual shapes with the range of possible shapes.

Molluscs:

What are the mathematical constraints of mollusc shell formation? Define each one in your own words and give an example of what a shell would look like with a low and high value of each variable:

Variable	Definition	Low Value	High Value
W
D
T

Now examine Fig. 13.4. Why are there some areas of the graph where there are no organisms?