What are porous marine invertebrates who pull water through their soft bodies in order to obtain oxygen and nutrition?

Which of the following explains why a tree is often used as a model to represent the principle of common descent

As kate is moving down the hill, what type of energy does she have? a. sound energy b. electrical energy c. light energy d. mechanical energy

American scientist, linus pauling, was one of many scientists racing to discover the molecular structure of dna. pauling initially thought that the molecule was a triple helix. later, james watson and francis crick unveiled their double helix model, which turned out to be an accurate description of the molecule's shape. why did watson and crick succeed when pauling failed?