Plants and fungi first became established on land during the
A) Archaean.
B) Proterozoic.
C) Paleozoic.
D) Cenozoic.
Answer: C
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The type of Escherichia coli that produces a verotoxin similar to the one produced by Shigella dysenteriae is ________ E. coli
A) enterohemorrhagic B) enterotoxigenic C) enteropathogenic D) enteroimmunogenic
How does an insect "hold its breath"?
A. by closing its tracheae B. by closing its mouth C. by closing its spiracles D. by closing its gills E. by closing its nostrils
Generally, vaccines are used to stimulate the immune system by providing antigens of potential pathogens. What is the typical composition of a vaccine?
What will be an ideal response?
Which of the following four statements, if any, is true regarding essential elements and living organisms?
a. All organisms require 25 of the 92 naturally occurring elements to survive. b. The elements carbon, hydrogen, nitrogen, and oxygen make up 20-25% of living mass. c. Although all forms of life require iron, other elements are required only by certain species. d. Given their low concentrations in nature, the toxicity of some elements is generally not a factor in the evolution of biological communities. e. All of the listed responses are correct.