I believe the last option is the correct one for the illustration of the single celled organism provides and the environment that it is found living in.
Parasitic infection because a<span> </span>parasitic<span> disease, also known as parasitosis, and an</span>infectious<span> disease caused or transmitted by a</span>parasite<span>. Many </span>parasites<span> do not cause diseases.</span>Parasitic<span> diseases can affect practically all living organisms, including plants and mammals.
The study of </span>parasitic<span> diseases is called parasitology.</span>
Fossils could not be found in that layer of rock
Building models doesn't actually help scientists observe phenomena. Scientists build models to describe how nature and systems operate then make observations to see if their models match what they observe. Models which don't match what they observe are either alterated or scrapped. Good models are kept and used by the scientific community.
Here is the answer to this question:
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According to the </span>RNA<span> World </span>Hypothesis<span>, life later evolved to use DNA and proteins due to </span>RNA's<span> relative instability and poorer catalytic properties, and gradually, ribozymes became increasingly phased out. The ribosome, a large molecular machine that drives protein synthesis, is a ribozyme.
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I hope this helps you