Help

Which kind of worm has a closed circulatory system? a planarian b fluke c pinworm d an earthworm

Parthenogenesis is a type of reproduction that does not require a mate. it’s rarely seen in birds and higher vertebrates. parthenogenesis involves the formation of a zygote. but this zygote is formed without fertilization. in parthenogenesis, in the absence of a male gamete, the ovum develops directly in the zygote.

What happens when two nitrogen atoms share electrons