New research shows that polar bears (survive) in the past through warm periods. And a few scientists say they (do) so again in the future.
A study of polar bears and brown bears indicates that the two (split) around five million years ago. There (be) interbreeding between the two throughout their evolutionary history.
Polar bears (be) now very different from the grizzly bears. Polar bears are very specialized to a sea ice environment. Grizzly bears are very well-adapted to a land environment. A few scientist believe they (interbreed and survive).
Other scientists believe that if they do interbreed, the new creature would no longer resemble a polar bear. The genes would be passed on, but the bear (be) something very different.
The fact that they have survived in the past does not mean they (survive) through this next global warming, at least not as large, white, sea-hunting bears.
Unless we take action to decrease greenhouse gas emissions, polar bears (face) an uncertain future in which the climate continues to warm. If temperatures rise higher than ever before, polar bears (not survive).
environment (n.) – the area around
gene (n.) – the DNA; a part of a cell in a living thing that controls what it looks like, how it grows, and how it develops
interbreed (v.) – breed or mate with a closely related individual, as in a small, closed population.
species (n.) – related individuals that resemble one another, are able to breed among themselves, but are not able to breed with members of another species.
split (v.) – broke apart; became different
survive (v.) – to continue to live after an accident, war, illness, or natural disaster