Bears: They can walk upright, see in color — unlike most other mammals — and most are ominivores like us. Yes, we are distantly related to bears — bears and humans share a common, rat-like ancestor from about 100 million years ago. The American black bear, pictured here, ranges across North America and is an excellent tree climber. Black bears can also be cinnamon or even platinum in color.

Brown bears, or Ursus arctos, are the most widely distributed bear in the world, ranging across Eurasia and North America. These bears tend to be solitary, but sometimes congregate to feast on fish. Ahead of hibernation, brown bears gorge themselves on fat to prepare for winter. Brown bears living inland in the lower 48 US states are known as grizzly bears — an iconic symbol of wilderness.

Although brown bears have been hunted to extinction in portions of their native habitat, they continue to survive in Europe in isolated pockets. Above, a mother bear watches over her cub as it struggles through thick snow in Finland. Bears' summer feasting creates a thick layer of fat they survive off in winter, typically in hibernation. But changing weather is also altering hibernation patterns.

In addition to being able to walk upright, brown bears can also run very quickly on all fours — up to 30 miles per hour (64 kph). This helps them hunt down other animals to eat. The anatomy of bear paws is so remarkably similar to that of human hands and feet that skeletal remains, and footprints, are often mixed up. Above, a brown bear gets a tooth operation in Germany.

South America even gets its "own" bear: the spectacled or Andean bear. Per its name, the species often sports light-colored fur around its eyes. The IUCN classifies this species as "vulnerable" — the bear has lost its wooded habitat on the slopes of the Andes due largely to forest-clearing for crops and cattle farming.

Sun bears, or Malayan sun bears, have a bib-shaped golden patch on their chests, which for some cultures represents the rising sun. Indeed, the sun bear lives in the Far East, making its home in tropical forests of southern Asia. The IUCN classifies sun bears as "vulnerable" — it's among the rarest bear species, and is under threat due to habitat loss, the pet trade and hunting for "medicine."

Moon bears, also known as Asiatic black bears, are likewise threatened due largely to poaching. Demand for bile from the gall bladders of black bears is driving widespread hunting, capture, captivity and trade — moon bears are even kept on mostly illegal "bile farms." Although there is no scientifically proven human health benefit from consuming bear bile, the trade continues.

The sloth bear is also "vulnerable," as its lowland forest in the Indian subcontinent disappears. Sloth bears survive on insects and have particularly shaggy fur — they are also targets for poaching and the pet trade. Pictured above, "Buddu" the sloth bear was adopted by a family in India after wandering into the village after a herd of goats. Wildlife officials later rescued the bear.

We all know and love pandas — panda cubs are particularly cute. Giant pandas were upgraded from "endangered" to "vulnerable" in 2016 due to vigorous efforts by the Chinese government to preserve the iconic animal. Such efforts include a captive breeding program, which achieved record success in 2017 with 42 pandas born.

Like many other bears, pandas are threatened above all from loss of habitat. Infrastructure projects in particular are cutting into what's left of the cool, humid bamboo forest high in the mountains of western China where pandas make their home. Since bamboo is so nutritionally poor, the bears have to eat up to 84 pounds (38 kilograms) per day — giant pandas spend much of their waking time eating.

Last but not least ... another icon. Technically classified as a marine mammal, polar bears are carnivorous. For hunting seals and other ocean animals, polar bears rely on sea ice, which is declining as the Arctic melts due to climate change. The plight of the polar bear has become synonymous with the fight against global warming. As the planet heats up, time is running out for these bears.