Feb. 6-12, 2014, Current Events Lesson Plan
Current Event:
Polar bears live in some of the coldest climates on Earth. In a recent scientific paper, researchers revealed a trick polar bears use to stay warm–their shiny white fur reflects waves of heat energy back into their bodies. Their research also helps solve the mystery of why polar bears are nearly invisible on infrared cameras. Their white fur–like a white t-shirt on a sunny day–scatters more of the sun‘s heat than it absorbs. However, the sun is not the only object that radiates heat energy. All warm objects give off thermal radiation. This radiation is largely in the infrared range of the electromagnetic spectrum, beyond visible red light. Warm-blooded polar bears stand to lose a great deal of their body’s warmth via thermal radiation. Scientists found that as thermal radiation leaves the polar bear’s body, some gets scattered through the fur, and some gets absorbed. The fur works much like the reflective coating on the inside of insulated vacuum bottles that can keep coffee and soup warm for hours.
Objective:
Polar bears are large, white bears of the North. They live in regions where the sea freezes in winter, chiefly along the northern coasts and islands of Alaska, Canada, Greenland, Norway, and Russia. They range throughout the Arctic Ocean as far north as the North Pole but remain more common near land. A polar bear has a long body and neck. Its head appears long and narrow with short, furry ears. Sharp teeth and curved claws help polar bears to catch their prey. From nose to tail, adult male polar bears measure from 7.5 to 8.5 feet (2.3 to 2.6 meters) long. Some weigh more than 1,300 pounds (590 kilograms). Most adult female polar bears are about 6.5 feet (2.0 meters) long and weigh from 330 to 550 pounds (150 to 250 kilograms). Polar bears have dense, yellowish-white fur that hides black skin. Their large size, fur, and the thick layers of fat beneath their skin protect polar bears from the bitter cold. Their fur also serves as camouflage for hunting. Polar bears feed mainly on seals. However, they will eat many other things, including berries and grasses, birds’ eggs, ducks, geese, lemmings, reindeer, seaweed, walrus, certain whales, and sometimes other polar bears. The Behind the Headlines news stories and related World Book articles explore polar bears and other animals.
Words to know:
- Arctic Ocean
- Bear
- Fur
- Heat
- Infrared rays
- Polar bears
- Seal [Ocean mammal]
- Spectrum
- Warm-blooded animal
Discussion Topics:
1. Ask your students to name other species of bear besides polar bears. (The other 7 species of bear are American black bears, Asiatic black bears, brown bears, giant pandas, sloth bears, spectacled bears, and sun bears.)
2. Global warming and hunting threaten the survival of polar bears. Ask your students to debate, “Humans have the responsibility to protect animals from extinction.”
3. In 2011, a Canadian senator launched a campaign to have the polar bear replace the beaver as his nation’s emblem. Ask your students which animal they think would make a better symbol. Why?