Approximately how many known neurotransmitters are there

How do antiviral drugs work? in your own words.

Legumes, a type of plant, require rhizobia, a type of soil bacteria, to survive since these organisms fix nitrogen during photosynthesis. rhizobia use the legumes for food. what would most likely happen to the legume population if rhizobia suddenly became extinct?

Explain how the number of similarities between the embryos from early stage to late stage is used as evidence of a common ancestry