Each hereditary trait corresponds to O a sequence of nitrogen bases
O a step on the ladder
an arrangement of nucleotides
O an enzyme

The kind of fertilization found in the majority of aquatic animals is (internal or external) fertilization.

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.

Several billion years ago which gas was the least prevailant in the atmosphere