Approximately 3.5 million years ago the Isthmus of Panama formed. This new landmass severed the connection between the Pacific Ocean and the Caribbean Sea. An ancestral fish population (porkfish) was split in two by this event; the two populations no longer interbreed and are two distinct species. This type of speciation is called
A. allopatric speciation.
B. parapatric speciation.
C. hybridization.
D. sympatric speciation.
E. sexual selection due to ecological variation.
A. allopatric speciation.
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Which regulatory mechanism does NOT depend on a conformational change in protein/enzyme structure to change activity?
A) attenuation B) catabolite repression C) feedback inhibition D) negative control
The density of Comet Halley was found to be about 0.2 g/cm3 . This implies that Comet Halley
a. is composed of about 50% rock and 50% frozen water and methane. b. is loosely packed ices with a small amount of rocky material. c. formed in the inner solar system and was ejected by Jupiter to the Kuiper belt. d. is really an S-type asteroid. e. was once a moon of Neptune and was ripped away by a large impact.
Companion cells load most of the carbohydrates into sieve tube members
a. through plasmodesmata. b. by osmosis. c. by antiport. d. through carrier proteins. e. by symport.
Prokaryotes produce the majority of their ATP
A. on the cytoplasmic membrane. B. in the cytosol. C. on the thylakoids. D. on the inner mitochondrial membrane. E. on ribosomes.