Arthritis always involves damage to the cartilages, but the specific cause can vary.

We want most cells to be even in and out which is called

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.

How does natural selection change thephenotypes within a population over time?