A fetus is especially at risk because they are under developed and easily susceptible to sicknesses or radiation
Answer:
A census is a count of the population in particular areas.
Explanation:
Vertebrates developed about 550 million years ago. The oldest vertebrate fossils are those of FISH with no jaws. These e<span>arly jawless fish did not have paired fins and their bodies were covered with heavy, bony scaled, but their skeletons were made of cartilage. For the next 50 million years, they were the only vertebrates.</span>
Answer:
The characteristic features of the phylum Chordata are a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a tailgut.
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