Why might a scientist repeat an experiment if she did not make a mistake in the first food

What type of appendages do sponges cnidarians roundworms annelids mollusks arthropods echinoderms and vertebrate have? jointed, not jointed, absent  

Can ground tissue do photosynthesis

Match each description with the correct form of energy. 1. energy of an object's position above the ground. 2. stored in the bonds of atoms and molecules 3. stored in the nucleus of an atom 4. energy of vibrating molecules 5. movement of objects used to do work 6. created by vibrations in electric and magnetic fields chemical energy mechanical energy heat gravitational energy light nuclear energy