Which part of an amino acid is the only one that varies and is what defines its properties?

Amale bird-of-paradise uses a dance to attract mates in which it flaps its tail feathers on the ground and jumps around a potential female mate. a different male bird-of-paradise does a similar dance but it jumps around the female in the opposite direction. the female bird is only attracted to one style of dance, in one direction. this is an example of speciation.

What element does susan b. anthony include in this passage to strengthen her argument?

In the diagram below, the northern hemisphere would be in what season at position a a.fall b. winter c.summer d.spring