Key physical features. All three species share similar physical characteristics - a relatively small body and a 'robust' or strongly built skull including large lower jaws with extremely large molar teeth.
The answer is <span>provide basis of food chains.
</span><span>Plankton includes a diverse group
of organisms that live in the water, but are not capable of active
swimming against the current. They are usually present in the upper part of the ocean, where is enough sunlight.
They are the basis of food chains in water ecosystems. They provide food for different animals, such as jellyfish, shrimps, whales, etc. </span>
The substance is called DNA.
I believe the answer is Genes??If that is the answer. Hope this helps
