Which one of the following structures is not found in all adult and larval tunicates?
A. incurrent siphon
B. excurrent siphon
C. gill slits
D. notochord
E. pharynx
D. notochord
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Cells sometimes use methylation: (Select all correct choices)
A. to prevent the expression of genes in transposable elements. B. to prevent the expression of genes from viruses that have been integrated into the genome. C. to prevent the expression of harmful (mutant) genes such as those responsible for cystic fibrosis.
The buildup of soil on bare rock by the decomposition of early colonizers is characteristic of ________ succession
A) primary B) ecological C) opportunistic D) secondary
In a human population with a high proportion of prereproductive individuals, the population will:a
continue to increase even if the fertility rate is at replacement levels.
b. decline even if the fertility rate is at replacement levels. c. increase only if the fertility rate is above replacement levels. d. decline only if the replacement level fertility rate changes. e. reach ZPG sooner than with a low proportion of prereproductive individuals.
The diffusion of water across a plasma membrane is referred to as
A. osmosis. B. facilitated diffusion. C. bulk flow. D. active transport. E. countercurrent flow.