Why was Earth's early atmosphere devoid of oxygen?
What will be an ideal response?
Because oxygen is a strong oxidizer of other elements, it tends to form oxides with them, which binds any free oxygen.
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Who first demonstrated transformation using mice and two strains of Streptococcus pneumoniae?
A. Hershey and Chase B. Watson and Crick C. Jacob and Monod D. Avery, McCarty, and MacLeod E. Griffith
A ________ epidemic is characterized by a sharp rise to a peak then a rapid, but not as pronounced, decline in the number of individuals infected.
A. common-source B. sporadic C. herd D. propagated
The term "plankton" ____
a. refers to a taxonomic division of algae b. is a common term for microscopic organisms that drift or swim weakly in water c. includes only multicellular forms d. refers to small aquatic plants e. would apply to large brown algae
Genes that normally block cell division are called:a
growth factor genes. b. oncogenes. c. tumor suppressor genes. d. proto-oncogenes. e. growth inhibiting genes.