1. Why do behavioral isolating mechanisms between species evolve?  Isn’t sterility enough to keep species from mixing?

(1 pt) Behavioral isolating mechanisms arise to prevent organisms that would not be able to produce viable or fit offspring from attempting to mate with each other.

            **Credit received if this is implied in your answer.

(1 pt) This evolves because individuals who can recognize potential mates who would allow them to have fit vs. unfit offspring experience higher fitness themselves than those who cannot recognize such differences in potential mates.

(2 pts) Individuals with behavioral isolating mechanism have higher fitness than individuals without such mechanisms through both increasing numbers of viable offspring and by saving time and energy otherwise wasted on producing sterile offspring for other tasks.

(1 pt) Therefore, behavioral isolating mechanisms evolve because they can invade a population that does not have behavioral isolating mechanisms—behavioral isolation is an ESS.

2. Describe the central assumption underlying optimal foraging theory. How would a student of the adaptationist programme modify his/her assumptions if he/she did not find that an animal was foraging optimally?

(2.5 pts) The central assumption is that energy maximization or optimization is in some way related to fitness maximization (e.g., stabilizing selection on the trait of interest).

            (1.5 pts) for mentioning energy and fitness maximization, but not the                                           correlation between them.

                        (0.5 pts) for mentioning either fitness or energy maximization.

            (1.5 pts) for mentioning stabilizing selection, but not energy and fitness.

(2.5 pts) The assumption might be modified by considering:

1. other traits that cause a tradeoff,
2. mechanisms that influence the function of the trait (e.g., hardness of prey)
3. constraints arising from time limitations, or
4. biotic agents (e.g., predators or competitors) that might influence the decision making.

(1.25 pts) for mentioning tradeoffs or constraints but not what specific types of       tradeoffs or constraints should be considered OR for mentioning considerations       (e.g. time, biotic factors, etc) but not mentioning how these are constraints or       tradeoffs.