What is evolution?
Evolution is a change in frequencies of inherited characters in
a population over time.
Unbeknownst to the teachers, the dish filled with different types
of candy was part of an experiment to illustrate selective pressures
at work. At the start of the session, there were a variety of candies
available in the dish; there was an equal number of each type of
candy. At the end of the session, the bowl contained the following
amounts of each type:
|Good & Plenty's
||12 and 14
|Candy necklaces, rings, watches
||1 of each (started with 2 of each)
a) What were the traits of the candies that you ate?
Chocolate, creamy, size, location in the bowl, nostalgia, wrapped
b) What were the traits that led you to avoid certain candies?
Age, cavity-causing potential, flavor, lack of chocolate, camouflage
Discussion can look at variation of traits and differential survival
rates. The traits listed in (a) led to the disappearance of certain
types of candy while the traits listed in (b) led to the continued
survival of the candies in the bowl. If there were no variation,
however, we wouldn't see this difference in selection. The activity
can be extended by having all "surviving" candy "reproduce" to exaggerate
the effect; then discussion can focus on change in frequencies in
populations and changes over time.
Variation leads to different "survival" rates, which leads to changes
in frequencies in a population, which is evolution.