Why is there a wide variation in skin color in humans?
A. Crossing-over increases the rate of color variation.
B. Skin color is a polygenic trait.
C. Environmental changes like improvements in diet change the color of the skin over time.
D. Artificial selection causes variation in skin color.
E. Genetic drift selects for genes that blend skin colors.
B. Skin color is a polygenic trait.
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Examine Figure 44.1 in your text. According to this phylogeny, which of the following correctly lists the sequence in which multicellularity, tissues, and bilateral symmetry arose, from the oldest character to the most recent character?
A. multicellularity, tissues, bilateral symmetry B. multicellularity, bilateral symmetry, tissues C. tissues, bilateral symmetry, multicellularity D. tissues, multicellularity, bilateral symmetry E. That information cannot be determined from the phylogeny.
The binding of a neurotransmitter to ligand-gated K+ channels will cause ____ in the postsynaptic
membrane.
a. depolarization b. hyperpolarization c. repolarization d. apolarization e. depolarization and repolarization
Some of the functions of the eukaryotic organelles are performed in bacteria by the:
A. capsule. B. cell wall. C. flagella/cilia. D. plasma membrane. E. nucleoid area.
Which unit of measurement is most commonly used for expressing cell size?
a. centimetre (cm) b. decimetre (dm) c. micrometre (µm) d. millimetre (mm)