Why can Ursa minor and Ursa major be observed all year round in high latitudes of the northern hemisphere?

Because the high latitudes in the northern hemisphere are close to the North Pole of the earth, and just above the North Pole is the North Celestial Pole. Near the center of the north celestial pole is Polaris.

Polaris, also known as Alpha Ursa minor, is the brightest star in Ursa minor. Ursa major, next to Ursa minor, belongs to the arch constellation and rotates around the north celestial pole. The typical image of this constellation is the Big Dipper. From the earth, the higher the latitude in the northern hemisphere, the higher the height of Ursa Major, and the easier it is to see.

In the high latitudes of the northern hemisphere, Ursa Major and Ursa Minor can be seen at high altitude all year round. At low latitudes, although Polaris can be seen all year round, its height is low. Ursa major may not be seen all year round.

On the equator, Polaris is on the horizon, and you can only see Ursa major for half a year, and the height is very low.