Which of the following describes a trophoblast?
a. the outer layer of blastocyst cells
b. a combination of Z and W chromosomes
c. the inner layer of blastocyst cells
d. a fertilized egg retained in the female
a. the outer layer of blastocyst cells
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What large molecules are essential in determining the structure and function of cells and tissues?
a. RNA b. genes c. proteins d. hormones e. nucleotides
The breast muscle of turkeys and chickens is usually referred to as light meat, whereas that of wild ducks and geese is described as dark meat. Which of the following is consistent with this observation?
A. Turkeys and chickens are not closely related to ducks and geese. B. Turkeys and chickens do not use their breast muscle, ducks and geese do. C. Turkeys and chickens do not fly for sustained periods, whereas wild ducks and geese do. D. The muscles of ducks and geese do not contain myosins. E. The darker body color of ducks and geese provides protective camouflage against predators.
. Four of the five answers listed below are
grasses. Select the EXCEPTION.
a. rye b. wheat c. rice d. lilies e. corn
Competition shapes communities because there are usually limited
A. species. B. resources. C. interactions. D. nutrients.