The maternal effect in Lymnaea is such that the genotype of the egg determines the direction of shell coiling regardless of the genotype of the offspring. Apparently, the cause of this spectacular maternal effect results from ________
A) orientation of the spindle apparatus in early cleavage
B) allelic substitution as demonstrated from RNA injection experiments
C) colicins "poisoning" one of the cleavage centers
D) the F factor exerting its influence on the centrosome
E) genophores present in the egg cytoplasm
Answer: A
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Answer the question using the accompanying figure. A species with a relatively constant rate of mortality in all age
classes would most likely exhibit which survivorship curve?
a. Type I, which is graph A b. Type II, which is graph B c. Type I, which is graph C d. Type III, which is graph C e. Type III, which is graph A
Which is an example of a specific line of defense against an infectious agent?
A) The skin acts as a barrier to infection by the agent. B) Macrophages engulf the invading agent in the affected tissue. C) Mucus membranes in the lungs trap the invading pathogens. D) B cells stick to the invading pathogen's surface.
Cyclodextrins are a group of compounds capable of removing cholesterol from membranes. The effect most likely to have a large impact on cells as a result of cyclodextrin treatment would be
A. increased membrane fluidity at higher temperatures. B. increased membrane fluidity at lower temperatures. C. disruption of transmembrane protein structure. D. increased permeability of the membrane. E. increased concentration of transmembrane proteins.
Which of the following is/are used for osmoregulation and excretion in all but the simplest animals?
a. modifications of the respiratory and digestive systems b. the lining of the digestive tract c. the transport epithelium d. specialized blood vessels