The endocrine system is comprised of endocrine glands that secrete hormones directly into the blood rather than through ducts. Glands are organs in the bodies of humans or animals that secrete chemicals for bodily use or to go into the environment. Ducts are tubular canals in the body that carry secretions from glands.
The fraction will be positive . because negative and negative cancels
Im guessing it is due to gene shuffling
They all develop gills, slits and tails
