The Life and Times of Individual Animals
(^) This section is placed here because it is about modeling. The reader may want to
postpone study of it until after reading more about the zoology of zooplankton in
Chapters 6 through 8. To show that models can have a completely different form and
address completely different issues, we will consider some population-dynamical
problems using individual-based (IBM) models. These are also called agent-based
models.
A Simple Example
(^) Several lines of evidence suggest that some, possibly many, species of copepods have
environmental sex determination (ESD; see the copepod section of Chapter 6). In
brief, instead of genes clustered on one chromosome (for example, “Y” in Homo
sapiens) from one parent controlling development as male or female, sex is
determined at a receptive stage in development, sometimes very late, by some aspect
of the habitat. Sex in many reptiles is set by the temperature at which the embryos
develop. In the copepod genus Calanus, clutches of eggs can mature entirely as
females, which usually occurs in laboratory rearing, or as 90% males, which is
sometimes observed in the field. The controlling factors are not reliably identified,
and may differ among genera or species.
(^) With only that much background, and without fully proving that ESD operates, one
can ask what selective advantage could accrue to populations from having flexible sex