Diffusion occurs because
A. Molecules constantly move and collide with each other
B. Cellular energy forces molecules to collide with each other
C. Molecules are attracted to one another
D. Cellular energy pumps molecules across the cell membrane
Answer: A. Molecules constantly move and collide with each other
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Although extinction is a natural process, current extinctions are of concern to environmentalists because _____
A) more animals than ever before are going extinct B) most current extinctions are caused by introduced species C) the rate of extinction is higher than background extinction rates D) current extinction is primarily affecting plant diversity
Huntington's disease is caused by a single dominant allele. It is a lethal disease, yet it persists in the human population. Which of the following statements best describes why?
A. Huntington's disease is sex-linked and every human has at least one X chromosome; thus, the chances are extremely high for this allele to be maintained in the human population. B. Huntington's disease can present symptoms so mild that they appear to lack dominant expression of the allele in some individuals; in those cases, the allele is passed on to the offspring. C. While lethal to a parent, Huntington's disease will not be lethal to the offspring since it can skip a generation. D. Huntington's disease presents symptoms in mid-life, after most people have already had offspring. E. Even though Huntington's disease is lethal, it improves chances for reproduction before the person dies.
Ectotherms have a higher metabolic rate than endotherms of the same size
A. true B. false
Cellulose is a major component of plants and is only directly digested by
A. herbivores. B. carnivores. C. termites. D. microorganisms