Which of the following is not a feature of echinoderms?

In sexual reproducing animals once fertilization of the egg takes place, the exists as a single cell until cell division begins. a) egg b) larva c) sperm d) zygote

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.

In which of the following relationships is one organism always benefited while the other organism is always harmed