Study this image of a geologic time scale.

\begin{tabular}{|c|c|c|c|}
\hline ERA & PERIOD & \begin{tabular}{l}
MILLIONS OF \\
YEARS AGO
\end{tabular} & KEY EVENTS \\
\hline \multirow{2}{}{ Cenozoic } & Quaternary & & \multirow{2}{}{\begin{tabular}{l}
Humans evolve \\
Extinction of \\
Dinosaurs
\end{tabular}} \\
\hline & Tertiary & & \\
\hline \multirow{2}{}{ Mesozoic } & Cretaceous & 138 & \\
\hline & Jurassic & & \\
\hline \multirow{6}{
}{ Paleozoic } & Permian & 240 & \multirow{6}{}{\begin{tabular}{l}
Permian mass \\
extinction \\
Invertebrates \\
become common
\end{tabular}} \\
\hline & Carboniferous & 330 & \\
\hline & Devonian & 410 & \\
\hline & Silurian & & \\
\hline & Ordovician & & \\
\hline & Cambrian & & \\
\hline \begin{tabular}{l}
Proterozoic \\
Archean
\end{tabular} & \multirow{2}{
}{\begin{tabular}{l}
Also known \\
as \\
Precambrian
\end{tabular}} & 3500 & \\
\hline & Hadean & & \\
\hline
\end{tabular}

How long ago did invertebrates become common on Earth?

A. 1.6 million years ago
B. 132 million years ago
C. 410 million years ago
D. 520 million years ago



Answer :

To determine when invertebrates became common on Earth, let's refer to the Paleozoic era on the geologic time scale.

In the Paleozoic era, there's a listing for the Devonian period with a note "Invertebrates become common" marked at "410 million years ago".

Based on this information:

- Era: Paleozoic
- Period: Devonian
- Years Ago: 410 million (when invertebrates became common)

Thus, the correct answer to the question "How long ago did invertebrates become common on Earth?" is:

410 million years ago.

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