In this question, you will listen to a lecture. Then you will be asked to su

Okay, let’s get started here. Today’s lecture is going to give an example of the effects of climate change on animals, particularly those living in the North. Now, some of you may already know that the effects of climate change are strongest at the North and South Poles. We know for a fact that temperatures have been rising in the Arctic in recent years, as evidenced by the collapse of a huge polar ice shelf in 2002. Satellite pictures recently showed us that a 15 kilometer-long crack has formed near Ellesmere Island, the most northerly point in Canada.
    Scientists have been worried for a few years about polar bears in particular. The main concern is that the sea ice is melting, and that’s where polar bears find most of their food, usually seals. That means the bears have to swim further and further away from land to hunt seals, and we’re beginning to see some very skinny bears.
    What we didn’t know until very recently is that grizzly bears are being sighted more and more frequently in polar bear territory. In fact, a hunter recently shot and killed what he thought was a polar bear, only to have authorities bring it to a wildlife research center because it looked a bit like a grizzly. Researchers analyzed the DNA of the dead bear and came to the conclusion that it was a hybrid of a polar bear and grizzly. This proves that the two kinds of bears could have the opportunity--very, very rare opportunity--to mate. Then how could this happen? Well, due to the global warming, polar bears are migrating further north in search of food and colder weather and grizzlies in less cold areas are taking up the territory abandoned by polar bears. So somewhere in their migration routes, the two kind of bears must have met ... you know what I mean?