Polar bears are in danger of extinction in the future if globalwarming continues, as their habitat, Arctic sea ice, is shrinkingevery year, making it difficult for bears to have enough food tolast through the lengthening summers.With a population of nearly 25,000, the polar bear is not in dangerof extinction now.
1 In general, anything that is good for your heart is great for your brain. 2  Aerobic exercise is great for body and brain: not only does it improve brain function, but it also acts as a first aid kit on damaged brain cells.
To benefit most from aerobic exercise, you should work out hard enough to raise your heart rate to its training zone (target heart rate) for at least 20 minutes on most days. This enhances your aerobic capacityâthat is, the ability of your cardiovascular system to deliver oxygen to the bodyâs cells during exercise.