Coarse sediment bottoms primarily support
a. infauna.
b. interstitial animals.
c. epifauna.
d. pelagic organisms.
e. seaweeds.
C
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If it were found that all animals except the Parazoa had a particular set of genes, one could conclude
A. that those genes are not useful in interpreting phylogeny. B. that Darwin was incorrect in his idea about descent with modification. C. that the Parazoa are not animals. D. that those genes probably are related to the embryonic formation of tissues. E. that those genes are related to cell wall formation.
The cells that function with the sieve tubes are the
a. vessel members. b. companion cells. c. adjunct cells. d. sclereids. e. periderm.
Many receptor tyrosine kinase (RTK) pathways lead to the activation of Ras. To activate Ras, it is necessary to recruit a guanine nucleotide exchange factor to the plasma membrane, because Ras is a membrane associated protein. Guanine nucleotide exchange factors, such as SOS, stimulate the exchange of GDP for GTP. However, SOS cannot bind directly to most RTKs. The protein Grb2 has a domain that can bind to phosphorylated tyrosines, and another domain that can bind to SOS. Therefore, Grb2 can bind to active RTKs and recruit SOS to the plasma membrane. Grb2 is an example of what kind of signaling molecule?
A. Scaffold B. Adapter protein C. Enzyme D. Second messenger
In a fungus, aggregated hyphae form specialized spore-producing organs called
A. mycelia. B. fruiting bodies. C. sporophytes. D. hyphae. E. gills.