For a span of 248 mya to 65 mya, the Mesozoic era, in which dinosaurs appeared, dominated, and became extinct, lasted approximately ___ of the geologic timescale.
A. 4%
B. 50%
C. 7%
D. 20%
E. 15%
A. 4%
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The first haploid cell in the life cycle of a plant that begins the gametophyte generation is a
a. zygote. b. gamete. c. male gametophyte. d. female gametophyte. e. spore.
An advantage of chorionic villus sampling (compared with amniocentesis) is that:a
chorionic villus sampling detects a much wider range of genetic defects than does amniocentesis. b. chorionic villus sampling is much less expensive than is amniocentesis. c. chorionic villus sampling is much less invasive than amniocentesis. d. chorionic villus sampling is much easier to perform than amniocentesis. e. chorionic villus sampling can be performed much earlier than can amniocentesis.
The responses observed in type IV hypersensitivities result from the action of
A) IgE antibodies and mast cells. B) T cells and phagocytes. C) IgG and complement. D) autoantibodies. E) inflammatory chemicals.
Enzymes increase the rate of a reaction by increasing molecular motion, thereby providing kinetic energy to drive the reaction.
Answer the following statement true (T) or false (F)