Carbon-14 is a radioactive isotope of carbon that has a half-life of about 5,730 years. You have discovered a fossil and want to know how old the fossil is. You count
the parent and daughter atoms and calculate that you have about 6.25% of the
parent atom (carbon-14) left. How old is the fossil? (Provide units (years) for your
final answer. You must show your work.
2 points for showing work
1 point for final answer with units

22,920 years

Explanation:

When the fossil first started to decay, it must have had 100% of its parent carbon-14 atoms. Every 5,730 years, that amount gets cut in half. Let's travel back a ways, to the very beginning, 0 years into the decay. We'll keep track of the time elapsed, the number of half-lifes, and the percent of carbon-14 remaining:

That last one represents our situation, so the fossil is 22,920 years old.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.