In sea urchins, the primary mesenchyme cells eventually become the ____
a. ectoderm
b. endoderm
c. mesoderm
d. endoderm and mesoderm
e. ectoderm and endoderm
ANSWER: c
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Which of the following statements about marine bony fish is false?
A. Chloride cells in the gills actively pump chloride ions into the body. B. They maintain a body fluid solute concentration that is lower than that of the surrounding seawater. C. They drink water to replenish water supplies. D. They are osmoregulators. E. They tend to lose water through osmosis.
Which of these stages were a focus of study for Miller and Urey in their FIRST experiment?
Study of the origin of life has resulted in the breakdown of cellular development into overlapping stages, beginning with the synthesis of precursor molecules for the synthesis of nucleotides and amino acids and ending in polymers enclosed in membranes acquiring cellular properties. A. Stage 1: Nucleotides and amino acids were produced prior to the existence of cells. B. Stage 2: Nucleotides became polymerized to form RNA and/or DNA, and amino acids became polymerized to form proteins. C. Stage 3: Polymers became enclosed in membranes. D. Stage 4: Polymers enclosed in membranes acquired cellular properties. E. Stage 5: Ribosomes were developed inside the membrane.
Plants having the ability to take up organic nitrogen are most likely in which of the following
environments?
a. arctic tundra d. grassland b. salt marsh e. temperate forest c. tropical forest
The cell membrane is selectively permeable and regulates transport. It is also involved in
A) secretion. B) storage of wastes. C) storage of DNA. D) Gram stain reactions.