The chemical composition of the gases surrounding the Earth has changed substantially over the past 4 billion years. One notable change was due to the emergence of photosynthetic organisms. The process of photosynthesis increased the amount of what gas in the atmosphere?
A. Carbon dioxide (CO2).
B. Nitrogen (N2).
C. Hydrogen sulfide (H2SO4).
D. Oxygen (O2).
E. Water vapor (H2O).
D. Oxygen (O2).
Biology & Microbiology
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The letter "D" in the accompanying figure represents which teeth?
a. incisors b. molars
c. canines d. premolars e. grinders
Biology & Microbiology
How does RNA differ from DNA?
A) RNA is contained in the nucleus. B) RNA doesn't contain a sugar. C) RNA is single-stranded. D) RNA takes part in transcription.
Biology & Microbiology
Which of the following tissues makes up the majority of the interior of the plant?
A. vascular tissue B. meristem C. ground tissue D. epidermal tissue
Biology & Microbiology
If the slope of the relationship between the phenotype and fitness is positive, natural selection would decrease the phenotype over generations.
a. true b. false
Biology & Microbiology