Geologic Time Scale Time Period Duration (Millions of Years ago)

Cenozoic 66-0

Mesozoic 252-66

Paleozoic 541-252

Trilobites appeared approximately 521 years ago and disappeared approximately 250 million years ago. During which era did the trilobites live?

a
Cenozoic
b
Mesozoic
c
Paleozoic
d
None of These

C. Paleozoic

Explanation:

Trilobites are a group of extinct marine arthropods. Just like many animals from today, including crustaceans, spiders, and insects, they belonged to the phylum Arthropoda. They lived in the Paleozoic era.

We can make this conclusion based on the fact that the period they existed in (from 521 to 250 million years ago) mostly fits the period described as Paleozoic (from 541 to 252 million years ago). However, we can see that they went extinct in the Mesozoic (250 million years ago is more than 252 million years ago). Compared to the entire time they existed, 2 million years is a relatively small amount of time, which makes Paleozoic the correct option.

dna is made up of six smaller molecules -- a five carbon sugar called deoxyribose, a phosphate molecule and four different nitrogenous bases (adenine, thymine, cytosine and guanine).

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