Here is a little exercise I use in my evolution class. I post a segment of a news story that describes an evolutionary process in sloppy terms and then ask the students to translate it into language that accurately describes what is going on.
Here’s one from today’s Discovery News.
Lizards Evolved Quickly to Avoid Death by Ants
It takes some effort for fire ants to get under the hard scales of an unsuspecting lizard. When the insects finally penetrate the reptile’s fleshy core, the attackers inject a toxin that paralyzes their victim. Then, they tear the lizard to pieces, which they carry back to their nest.
…
It’s an unpleasant way to die, and one that at least one species of lizard is rapidly evolving to avoid. In just 70 years, according to a new study, eastern fence lizards in parts of the United States have developed longer hind limbs and new behaviors that help them escape the clutches of the venomous ants.
Have at it!
(Hint: Start your answer with “Within a population of lizards…”)
________________________
Get your Darwin Year gear here.
How about:
Eastern fence lizards have relatively recently become the prey of invasive fire ants. Lizards with longer limbs (thus able to run faster) and who actively attempt to repel ants on their bodies are more likely to get away and avoid the ants fatal sting, whereas ones with short limbs who hope the ants will just leave them alone are more likely to fall victim. In 70 years, this predation pressure has selectively acted against the shorter limbed lizards who sit and wait. In areas where fire ants have been present the longest, the average limb length of the population is significantly longer than where the ants have not colonized, and lizards are more likely to have the tendency to fight and flee when ants attack. This is a great example of how invasive species can introduce new selective pressures against native populations, affecting both their physiology and behaviors.
Although I’m not sure it has the same pizzaz as “Hey look! The Lizards have figured out to grow longer limbs and act funny to avoid ants!”
A very good start…
You’ve covered variation and selection. One other component should be discussed explicitly.
Wait… do you mean adding “thus the longer limbed, flighty lizards produce more offspring than the shorter limbed complacent ones where fire ants attack lizards” somewhere after the explanation as to how longer limbs, the behavior, and fire ants are variable? Or am I missing something else…
Where’s my evolution checklist…
Precisely. We need heritability and non-random reproduction.
Ooo Ooo! Do I get a cookie or something now?