The polar bear is the largest extant species of bear and land carnivore, with adult males weighing 300–800 kg (660–1,760 lb). The species is sexually dimorphic, as adult females are much smaller. The polar bear is white- or yellowish-furred with black skin and a thick layer of fat.

2024年8月13日 · Lineages leading to the 6 distinct living bear species in Ursus radiated from a common ancestor 6.3 million years ago (Pliocene). Distant ancestors: Molecular data indicate that the procyonid (raccoons, koatis, ringtails, kinkajous and others) and bear families diverged from each other about 30 million years ago (Oligocene).

There are several distinct characteristics which place the polar bear in the animal kingdom. Polar bears, like all other animals are eukaryotic, multi-cellular organisms. They are heterotrophic, meaning that they get their food and energy from consuming other organisms.

The polar bear (Ursus maritimus) is a large bear which lives in the Arctic. [3] It has black skin under the white fur. They are strong and fast, and can run as fast as 25 miles (40 km) an hour for a short distance. [4] [5] In 2022, there were around 22,000 polar bears in the world. [6] There is an extinct subspecies called Ursus maritimus tyrannus.

2006年2月9日 · The polar bear (Ursus maritimus) is the largest of the extant bear species and is classified as a marine mammal. Polar bears are protected under the Endangered Species Act and Marine Mammal Protection Act.

The polar bear is the only bear considered to be a marine mammal. It is only partially aquatic though, and the least aquatic of all marine mammals. Fossil Record. Ursids in the fossil record date back to the early Miocene in Asia, and the late Miocene in North America. The oldest known polar bear fossil is approximately 130,000 years old.

2021年7月4日 · Polar bears are members of the family Ursidae and are closely related to brown bears. Since their divergence from brown bears ~400 Kya, polar bears have evolved from terrestrial omnivores into marine carnivores in the Arctic sea ice environment.

In this chapter, I provide an overview of polar bear taxonomy and evolution, genetic diversity, historical distribution, population status, and genetic evidence of positive selection for the sea ice habitat and a carnivorous diet.

A polar bear learns the seasonal pattern of movements as a cub during the 2 years it remains with its mother (Stirling and Guravich 1990, p 68). Description: A polar bear has an elongated body, with low, well-developed shoulders. They have a long thin but well developed neck, highly developed hindquarters and a straight profile (Brown 1993, p 51).

Polar bears are mammals, and all mammals belong to the taxonomic domain of Eukarya, which are characterised by having cells with nuclei. Eukarya covers all organisms in the Kingdom Animalia, as...