The location and/or metabolism of a substance such as a hormone or drug can be followed in the body by labeling the
substance with a(n):
a. acid
b. isotope
c. element
d. radioisotope
e. DNA molecule
d
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Which of the following statements about the evolution of complex multicellularity is true?
A. Complex multicellularity evolved independently at least six times in different groups of organisms. B. Complex multicellularity evolved twice: once in the common ancestor of plants and fungi and once in animals. C. Complex multicellularity evolved once in the common ancestor of all eukaryotic organisms. D. Complex multicellularity evolved independently in prokaryotes and eukaryotes. E. Simple multicellular organisms evolved from complex multicellular ancestors.
The binding of a plant hormone to its receptor
typically induces
a. an increase in membrane permeability. b. an enzyme-substrate cascade. c. an inhibition of protein synthesis. d. a change in gene expression. e. increased DNA replication activity
Cystic fibrosis is a pleiotropic disease
Indicate whether the statement is true or false
In its youth, a pet parrot was owned by someone who kept the wings clipped and never allowed it to fly. Later in life, the new owner let the feathers grow and let the parrot fly around the house. But the parrot kept knocking over lamps and crashing into walls. "Wow," said the owner, "I guess parrots are just too clumsy to fly around a house without destroying everything." What is an alternative explanation?
A. Since the parrot was not able to practice flying during the critical period for flight development, the brain circuits for accurate flying were not able to develop. B. The critical period for flying development in the brain has just now begun with the bird's first attempt. In a few weeks the critical period will end, so it must practice during this time. C. The parrot just needs more practice flying -- although it did not get to fly when young, this should not affect later ability. D. In nature, parrots have much more room to fly, and do not have to navigate around delicate home decor.