________ is a directional movement in response to a graded chemical stimulus.
Fill in the blank(s) with the appropriate word(s).
Chemotaxis
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Kuru is a degenerative disease of the central nervous system believed to be caused by which type of agent?
A) virus B) bacterium C) prion D) viroid E) protozoan
The macromolecule that can accomplish the widest range of biological functions are
A. carbohydrates. B. proteins. C. nucleic acids. D. lipids. E. glycolipids.
Consider the model for equilibrium number of species in a mainland (continental) region, as illustrated in Figure 20.23. What does this model say about the rate of extinction?
A) The rate of extinction decreases as a linear function of the number of species. B) The rate of extinction increases as a linear function of the number of species. C) The rate of extinction increases as a function of the number of species, but the rate of increase accelerates as the number of species becomes large.
What term describes the ectoderm, mesoderm, and endoderm?
A) Inner cell mass B) Extraembryonic membranes C) Primary germ layers D) Blastomeres