The major purpose for stems appears to be
A. to serve as a framework for the positioning of leaves.
B. to provide food for animals.
C. to provide shelter for animals in a coevolutionary relationship.
D. to provide protection for inner vascular tissue.
Answer: A
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What will be an ideal response?
In skeletal muscle contraction, which of the following undergoes a conformational change when it
binds to a specific ion and then uncovers the crossbridge binding site by causing another factor to be moved to the grooves in the actin double helix?
a. troponin b. Ca2+ c. tropomyosin d. ATP e. acetylcholine
Two or more alleles of a gene are circulating at relatively high frequency in a population's gene pool. What term describes this state?
a. frequency-dependent selection b. polyploidy c. multiple allele systems d. balanced polymorphisms e. prominent alleles
What is needed to estimate species relatedness with a molecular clock?
A. DNA accumulates mutations at a regular rate B. known mutation rate for a gene C. the number of differences in DNA sequences for a gene in two species D. the same gene identified in two species E. All answers are correct.