Answer:
Chargaff discovered base pairing rules. Franklin took X-ray photographs that revealed that DNA has a spiral structure. This finding helped Watson and Crick create a model of DNA and discover the double-helix.
Explanation:
The ultimate source of energy (for most ecosystems) is the sun<span>. The ultimate fate of energy in ecosystems is for it to be lost as heat. Energy and nutrients are passed from organism to organism through the food chain as one organism eats another.</span>
<span>
are always unicellular
may have evolved from prokaryotes
</span><span>are more primitive than prokaryotes
</span>
