Bear

Bears were mammals native to the planet Earth.

Terrestrial bears
The Doctor, his companions and acquaintances encountered bears on several occasions.

About 120 AD, the Tenth Doctor found himself opposing lions, tigers and bears in a Roman amphitheatre. When the bear approached, the Doctor quickly climbed up a tree, losing his sonic screwdriver in his haste. He dropped on the back of the bear, scooped up his screwdriver and gave the beast a burst at the right frequency. The bear meandered away. (NSA: The Stone Rose)

While in Windsor of 1988, Richard Maynarde thought he heard a bear. Lady Peinforte reassured him that it would not follow them because such things happened only in the theatre. (DW: Silver Nemesis)

In the year 5000, Jamie and Elric Penley were attacked by a bear. Penley tranquillised it, but was badly injured while doing so. (DW: The Ice Warriors)

"Lynda with a y" Moss told the Ninth Doctor about a popular television series called Bear With Me, a show about three people living with a bear. (DW: Bad Wolf)

These incidents combined, ranging from the 2nd century AD to the year 200,100 indicated that bears, in general, were a hardy species, not threatened by extinction across many millennia.

Breeds
On Earth several specific breeds of bear were known, including the cave bear and the polar bear.

Products related to bears
The First Doctor, Ian, Barbara and Susan encountered evidence of bears in about 100,000 BC. There, they saw that the Tribe of Gum hunted bears for their warm skins. (DW: An Unearthly Child)

Bears were often taxidermal subjects. Hex once came across a seven-foot stuffed bear. The Seventh Doctor said it was used by a university for anatomical demonstration. (BFA: Night Thoughts)

Toy stuffed bears — in the form of anatomically incorrect teddy bears — were also popular on Earth, from around the start of the 20th century. (NA: Toy Soldiers and others)

Extraterrestrial bears
Horned bears were among the native lifeforms of Tiermann's World. (NSA: Sick Building)

On Hyspero, Angela ruled over the bears of Kestheven, who shaved their golden fur and went about hairless. (EDA: The Scarlet Empress)