Its common. In the last 10 million years, there have been 4 or 5 reversals per million years
Answer:
Answer is D - cAMP.
Explanation:
cAMP is a small molecule that functions as an intracellular signaling molecule - a second messenger. The first messenger would be the thing that activated the GPCR (e.g. a hormone). The GPCR is a signal transducer (converts extracellular signal to intracellular signal). Once activated, the GPCR activates adenylate cyclase which can be called a signal effector - it is an enzyme that produces cAMP.
You didn't give any answer choices (i'm answering this through research and what i already know)
the first is fossilized dung, and that's not generally gastropod shells. A carbon film would be something thin, seeing as it's a film, and gastropods aren't that. A gastrolith is a stone swallowed by an animal to help with digestion, and that's also not a gastropod.
<span>Gastropod fossils may be molds, but usually aren't. Still, they can be. It's a better answer than; film or stomach stones.</span>
