Hold Your Breath
This is Andrew Matheson again. I need to share a secret with you, but I think it's going to upset you greatly. So I'm trying to think of a way to gently ease you into what's really going on here. Because you need to know.
Last November, my ninth-graders were studying Darwinian evolution in the biology classes I used to teach. One morning we were discussing how natural selection working across many generations will tend to result in optimized organisms that fit well within their particular habitats. Sometimes we describe this as "survival of the fittest."
You politely interrupt to ask, "What are you talking about, Andrew? How does survival of the fittest work?"
I'm very glad you asked because as I mentioned, up until about a year ago, I was a high school biology teacher. Now things are getting kind of crazy, and I suppose I'm technically unemployed. But I used to greatly enjoy explaining this foundational principle of evolutionary theory. So let me bring you up to speed on survival of the fittest.
First, let's refer to all the organisms of a particular species as a population. Within each population, individual organisms may exhibit small variations in phenotype. (Phenotype is the observable characteristics of the organism—on the outside. Genotype is what is coded into the organism's DNA—on the inside.) So for example, maybe Organism A can hold its breath underwater for 22 seconds, and Organism B can hold its breath underwater for 27 seconds.
Maybe holding your breath underwater longer doesn't seem like a big deal, but what if maybe it is sometimes? Like what if there are juicy, delicious fish over there in that river? What if because of her breath-holding prowess, Organism B can catch more fish than hapless old Organism A? Organism B is able to feed her offspring better, and more of them survive to adulthood and reproduce. What if her offspring carry the longer-breath-holding trait in their genotypes? They pass it along to their offspring, while poor old Organism A's offspring struggle to compete for fish from the river.
After just a few generations, the whole population is holding their breath underwater longer. Get it? That's survival of the fittest!
Now you politely ask, "Andrew, what are you talking about? Are Organisms A and B bears? Because it sounds like you're describing bears."
Natural selection has quietly worked in the background over thousands of generations of bears. As a result, this magnificent creature fits well within her habitat.
Oh really? Well, maybe I just wanted you to think I was describing bears, okay? What if I was actually describing, um, sea turtles? What about that, hmm? Some sea turtles can hold their breath underwater for hours, you know! I'd like to see a dumb old bear try to do that! Good luck with that, Mrs. Bear! Yeah, it's not going to happen for you, which we all know.
Natural selection has quietly worked in the background over thousands of generations of sea turtles. As a result, this serene creature fits well within its underwater habitat.
Okay, I admit it. They were bears. Organisms A and B, that is. But sea turtles are an even better example of organisms that can hold their breath for a long time. And both examples show how natural selection working across many generations will tend to result in optimized organisms that fit well within their particular habitats, which we describe as "survival of the fittest."
TO BE CONTINUED...
(Images courtesy of wix.com)