Serotonin is derived from the amino acid tryptophan and is an important neurotransmitter. a. true b. false

Diagram of the evolution of land plants?

Iwanna go do something with my ideas? ?

How do the sperm cells get from the stigma to the ovules? a. they slide down the petals to the bottom of the flower. b. they travel through pollen tubes. c. they travel along filaments. d. insects carry the sperm cells from the stigma to the ovules.