Some bird species have not adapted to the tundra’s harsh environment, so they . A leave for the summer and come back in fall
B leave for the winter and come back in spring
C burrow under the soil during the winter
D never fly above the Arctic Circle or below the Antarctic Circle

Cattle with brown fur and cattle with white fur will produce a reddish roan calf . when examined closely, the calf show about an even number of brown hairs and white hairs that give a reddish appearance when viewed from far away. the fact that both the brown fur allele and the white fur allele are expressed equally in the offspring is an example of