A disadvantage of using DNA or RNA sequences to identify species is that
A. it can only be used for sexually reproducing organisms.
B. it cannot be used for extinct species.
C. there are no rules for determining the number of sequence differences needed for a new species.
D. if can be misleading because many species exhibit large variation in phenotype.
C. there are no rules for determining the number of sequence differences needed for a new species.
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A special structure on certain cyanobacteria for nitrogen fixation is called a(n):
a. ammonia cyst. b. homocyst. c. heterocyst. d. nematocyst. e. pneumatocyst.
Which of the following is true concerning the checkpoints in the cell cycle?
A. Mitosis stops if chromosomes are not properly aligned. B. The purpose of the cell cycle checkpoints is to ensure that mitosis results in haploid daughter cells. C. Most cells that undergo mitosis cannot proceed through all the cell cycle checkpoints and end up undergoing apoptosis. D. Mitosis will still occur if the DNA is damaged or not replicated. E. The G1Â checkpoint is located at the tail end of the S phase of interphase.
Plasmodium is likely to destroy
a. sperm cells. b. white blood cells. c. purple blood cells. d. red blood cells. e. egg cells.
Which of the following best explains why many different species can live together within an ecosystem with limited resources?
(A) Each species lives in a slightly different habitat. (B) Each species occupies a different niche. (C) Each species inhabits a different biome. (D) Each species makes up a different population.