Dept of Biology, Lewis and Clark College		Dr Kenneth Clifton
	Biology 141 Lecture Outline

Natural Selection, Life History, and Ecology

 

I. Consider the ecology of individuals

A. Any discussion of ecology is ultimately based on prinicples of:

1. Natural Selection

2. Adaptation

3. Evolution

 

 

II. Refresher on Natural Selection

A. Variation in heritable traits..

B. ....confers differential reproduction....

C. ...such that some traits are better represented in subsequent generations

D. We call these traits adaptations...

E. ...and changes in these traits over time is evolution.

 

 

 

III Adaptation and evolution are a response to the environment....hence the obvious link to ecology

 

A. So we can learn a lot about individuals and their ecology by studying how they get on with their lives

 

IV. To study individuals and their ecology is easy... justremember three things:

A. Food.

B. Sex.

C. Death

 

Acknowledging the role that these factors play in the behavioral, morphological, and developmental traits expressed by an individual can teach us a great deal about their relationship to their environment.

Now let's think about how natural selection shapes how an organism allocates energy to life functions:

The study of Life History

V. Getting on with life given a limited energy budget

A. How should energy be allocated

1. Maintenence

2. Reproduction

3. Survival

 

(what about growth?)

 

B. With a finite amount of energy available to an individual, think about trade-offs.

 

C. The challenge of optimizing allocation to survival and reproduction

 

1. Minimizing the risk of dying

2. Maximizing "lifetime reproductive output"

3. How to balance these given that they are inversely related

 

 

VI. Basic patterns of survivorship:

Hypothetical survivorship curves for three different reproductive strategies. Type I: large-young strategists that nurture their young; Type II: populations that have a steady rate of mortality; Type III: small-young strategists with low, or no, investment in nurturing. (After R. Pearl, 1928.)

A. Type I: low juvenile mortality

B. Type II: constant mortality over a lifetime

C. Type III: high juvenile mortality

 

VII. What does this mean in term of scheduling reproduction?

VIII. What about investment in each offspring?

IX. The timing and intensity of reproduction may play very important ecological roles

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