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Lecture 4 (biology)
Listen to part of a lecture in a biology class.
Professor
Now James, you said that you’ve been to state of Maine right?
James
Yeah, actually I lived in western of Maine till I was about 16.
Professor
Right. So why aren’t you tell everybody what it’s like there in the winter?
James
In the winter? Well, it’s cold and there is lots of snow. You wouldn’t believe how much snow we used to get.
Professor
Actually, I would. I did a few research up there couple of winters and there really is incredible environment. And to survive in that sort of environment, animals have to adapt to evolve and response to their surroundings. As you were cold and adaptation is any feature, em physical or behavioral feature of this species that helps it survive and reproduce. And in adapting to extreme climates, like Maine in the winter time, animals can involved in pretty interesting ways. Take for example, the snowshoe hare.
Ok the snowshoe hare and of course that’s H A R E, like a rabbit. Although I probably should mention that technically a hare is not exactly the same as a rabbit. Even though is very similar, the primary differences is that a rabbit’s young are born blind and without fur, while a hare’s babies are born with a full coat and able to see. Now the snowshoe hare…Tommy what sort of adaptations do you think is developed that help to survive in the Maine winters. I’ll give you a hint: food isn’t an issue. The hare actually has abundant food and small twigs it finds.
Tommy
Well, I don’t know. I mean I know we used to try to look for these rabbits…er…hares, when we went hiking in the winter but it was often hard defined them and the snow.
Professor
Yes. That’s exactly right. The major concern of the snowshoe hare in the winter is predators. And now that include humans. So one of this adaptation is basically camouflage, in other words it’s coat, it’s fur, turns from brown in the summer to white in the winter, which makes it harder of the hare’s predators to see it against the white snow.
Tommy
Yeah, but I could swear I remember seen rabbits on the snow a couple times, I mean hares, that were brown.
Professor
Well, you may well have, timing is really important. But the snowshoe hare doesn’t always get it exactly right. Its chances for survival the best if it turns white about the time of the first snow fall, and it’s demand of daylight, the triggers that changing the hare’s coat. As the days get shorter, that is as the sun is up for shorter and shorter time each day, the snowshoe hare starts growing white fur and shedding its brown fur. The hare does pretty good job with this timing but sometimes winters were really early or late snow its sounds out. Plus, it takes a month for the snow shoe hare’s coat to completely change color. So if there is a particularly early snow fall, it’s very likely that the hare’s fur would not yet be totally white. And that will make this particularly dangerous time for the hare.
Ok. What else? Other adaptations? Susan?
Susan
Well, it’s called the snowshoe hare, so aren’t feet somehow protected from the cold?
Professor
Well, this animal’s name does have to do with an adaptation of its feet, er, though not like it has warm furry boots or something to keep its feet from getting cold. You probably never need to wear snow shoes, but, well, snowshoes are not like thick furry shoes designed to keep the feet warm, they’re actually quite thin but very white. What they do is spread out the weight of the foot coming down on the snow. See the problem is walking on snow is that you sink in with every step, but with snowshoes you don’t sink in, you walk on top of the snow. It makes walking though the main countryside in the winter much easier. Anyway, the snowshoe hare hasn’t adaptation the place on the same idea; it has hind feet that act like snowshoes. I mean its paws are wide and they allow the hare to hop and run just at the surface of the deep snow. And this is a huge advantage of the snowshoe hare since by contrast the feet of its predators usually sink right down into the snow. Now another advantage relate to this is that unlike many animals in winter, snowshoe hares can stay lean and light weight, they accumulate essentially no body fat. Can anyone guess why this is so?
Susan
They don’t need very much?
Professor
Well, yes. But not because there is enough food around. It’s because, like I said, food is almost always within rich and they don’t have to store up a lot of food energy for the harsh winters.