Keith S. Taber
Bert was a participant in the Understanding Science Project. In Y11 he reported that he had been studying about the environment in biology, and done some work on adaptation. he gave a number of examples of how animals were adapted to their environment. One of these examples was the polar bear.
…our homework we did about adapting, like how polar bears adapt to their environments, and camels….
And so a polar bear has adapted to the environment?
Yeah.
So how has a polar bear adapted to the environment?
Erm, things like it has white fur for camouflage so the prey don't see it coming up. Large feet to spread out its weight when it's going over like ice. Yeah, thick fur to keep the body heat insulated.
Bert gave a number of other examples, including dogs that were bred with particular characteristics, although he explained this in terms of inheritance of acquired characteristics: suggesting that dogs that have been taught over and over to retrieve have puppies that automatically have already got that sense. Bert realised that his example was due to the work of human breeders, and took the polar bear as an example of a creature that had adapted to its environment.
Yeah, so how does adaption take place then? …
I don't know. It may have something to do with negative feedback.…Like you have like, you always get like, you always get feedback, like in the body to release less insulin and stuff like that. So in time … organisms, learn to adapt to that. Because if it happens a lot that makes a feedback then it comes, yeah then they just learn to do that.
Okay. Give me an example of that. I'm trying to link it up in my head.
Okay, like the polar bear, like I don't know. It may have started off just like every other bear, but because it was put in that environment, like all the time the body was telling it to grow more fur and things like that, because it was so cold. So after a while it just adapted to, you know, always having fur instead of, you know, like dogs shed hair in the summer and stuff. But like if it was always then they'd just learn to keep shedding that hair.
So if it was an ordinary bear, not a polar bear, and you stuck it in the Arctic, it would get cold?
Yeah.
But you say the body tells it to grow more fur?
Erm, yeah.
How does that work?
I'm not sure, it just … I don't know. Like, erm, like the body senses that it's cold, it goes to the brain, and the brain thinks, well how is it going to go against that, you know, make the body warmer. And so it kind of, you know, it gives these things.
So Bert seemed to have notion of (it not the term) homoeostasis, that allowed control of such things as levels of insulin. He recognised thus was based on negative feedback – when some problematic condition was recognised (e.g. being too cold) this would trigger a response (e.g., more insulation) to bring about a countering change.
However, in Bert's model, the mechanism was not initially automatic. Bert thought that this process which initially was based on deliberation became automatic over many generations…
I see. So the bear has already got a mechanism which would enable it to have more fur, but it's turned on to some extent by being put into the cold?
Yeah.
And then over a period of time, what happens then?
Erm I guess it just it doesn't really need that impulse of being cold, it's just naturally there now, to tell it to do it more.
So how does that happen? Is this the same bear or is this many generations later?
I would probably think many generations later.
Right, so if it was just one particular bear, it wouldn't eventually just produce more hair automatically itself, but its offspring eventually might?
Yeah.
So how does that happen then?
I don't know. Probably from DNA or something. We haven't gone over that yet.
So for Bert, the individual bear could change its characteristics through activating a potential mechanism (in this case for keeping year-round thick fur) through a process of sensing and responding to environmental conditions. Over many generations this changed characteristic could become an automatic response by eventually being coded into the genetic material. As with his explanation of selective breeding, Bert invoked a model of evolution through the inheritance of acquired characteristics, rather than the operation of natural selection on the natural range of characteristics within a breeding population.
Like many students learning about evolution, Darwin's model of variation offering the basis for natural selection was not as intuitively appealing as a more Lamarckian idea that individuals managed to change their characteristics during their lives and pass on the changes to their offspring. This is an example of where student thinking reflects a historical scientific theory that has been discarded rather than the currently canonical scientific ideas taught in schools.
