What is the main organ for gas exchange in fish?

a. Lungs
b. Respiratory system
c. Gills
d. Heart


Ans: c. Gills

Biology & Microbiology

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Explain why HIV becomes resistant so quickly when a single drug is used therapeutically

A. The virus is an RNA genome virus-by using host RNA polymerase to directly copy the genome to make more virus particles, there's no proofreading capability. This leads to a high rate of mutation of the viral genome and increased chance for drug resistance. B. HIV utilizes reverse transcriptase to make a cDNA version of its RNA genome. This polymerase is "'sloppy," with a high rate of error and lack of a proofreading capability. This leads to a high rate of mutation of the viral genome and increased chance for drug resistance. C. HIV synthesizes a protein enzyme that directly cleaves anti-HIV drugs, giving it a characteristically high rate of resistance to a single drug type. D. HIV is constantly changing its genetic structure by swapping genetic elements with other virus strains. This leads to a high rate of mutation of the viral genome and increased chance for drug resistance.

Biology & Microbiology

The cellular fragments in the blood that function in blood clotting are

a. erythrocytes. b. leukocytes. c. platelets. d. none of the above.

Biology & Microbiology

Transformation in a cloning experiment is ________

A) ligating pieces of foreign DNA together B) inserting DNA into bacteria cells C) cutting DNA with restriction enzymes D) using PCR to clone a gene E) a technique for determining gene copy number in a genome

Biology & Microbiology

Chalk deposits are formed from the ancient remains of apicomplexans

Indicate whether the statement is true or false

Biology & Microbiology