Crabs and terrapins have a _____ impact on snail populations while snails have a _____ impact on
cordgrass populations and terrapins have a _____ impact on cordgrass populations.
a. negative; negative; negative
b. negative; negative; positive
c. negative; positive; negative
d. positive; negative; positive
e. positive; positive; positive
B
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A type of horizontal gene transfer in prokaryotes, in which a cell receives DNA from another cell through a sex pilus, is
A. replication. B. fixation. C. transduction. D. transformation. E. conjugation.
Muscles differentiate from which tissue?
a. ectoderm b. endoderm c. mesoderm d. somatoderm e. all of these
Assume that you are studying a trait determined by a number of polygenes. If there are seven phenotypic categories, how many genes are probably involved?
A) 3 B) 7 C) 2 D) 4
The protozoan that causes malaria is an intracellular parasite of red blood cells (RBCs). An adaptive immune response to this parasite is problematic because
A. red blood cells do not produce MHC and, therefore, do not display the fact that they have been infected by presenting antigen. B. the parasite damages leukocytes along with RBCs. C. RBCs normally produce cytokines necessary for adaptive immune response, which this infection prevents. D. complement cannot effectively destroy RBCs. E. RBCs never enter lymphoid tissue.