Which of the following components was NOT

a significant part of the earth's early
atmosphere?



a. carbon dioxide
b. water vapor
c. nitrogen gas
d. oxygen gas
e. hydrogen gas


D

Biology & Microbiology

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The cyclic nitrogenous base used in transcription, uracil, is a ________.

A. purine B. porphyrin C. protein D. pyrimidine

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Individuals with ____________________ are extremely sensitive to sunlight and develop skin cancer at a rate 1000 times above normal

Fill in the blank(s) with correct word

Biology & Microbiology

What is a common feature of all organisms?

a. DNA in circular chromosomes c. nucleus b. organelles d. cell structure

Biology & Microbiology

An element has 8 protons, 9 neutrons, and 8 electrons. Its atomic number and atomic mass, respectively, are _________.

Fill in the blank(s) with the appropriate word(s).

Biology & Microbiology