Coral reefs are built by coral polyps as they secrete layers of calcium carbonate beneath their bodies. And inside each coral poly lives single-celled algae called zooxanthellae. So basically in simplistic terms, coral polys create coral reefs and algae is in coral polys which also goes into coral reefs when they are made.
A movement in response to gravity is called tropism.
Muscular movement is the correct answer
An alligator can have up to 74 to 80 teeth.