What would be the consequence for the plant if it lacked Casparian strips? What will be an ideal response?
Casparian strips in the endodermis block the flow of dissolved substances through the
apoplast. Consequently, in order to minerals and dissolved organic substances to cross the
endodermis into the stele, they must cross the endodermal plasma membrane by carriermediated
transport. If a carrier protein for a particular substance is not present, that substance
will be “stalled” in the apoplast outside the stele forever. This is beneficial to the plant
because the Casparian strips thus prevent potentially damaging molecules (e.g., certain heavy
metals and toxins) from entering the xylem and transported upward to the rest of the plant. If
a plant lacked Casparian strips, no such regulation of transport would occur, and ALL
molecules and ions entering the plant through the apoplast could theoretically be transported
to all parts of the plant.
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In the experiment by Davis et al., only fibroblast cells that took up the cloned myoD gene differentiated into muscle cells. This is because
A. only those cells contained muscle-cell-specific enhancer sequences. B. MyoD is a transcription factor that turned on muscle-specific genes such as myosin C. MyoD is a transcription factor that shut off fibroblast specific genes, allowing the muscle cell characteristics to show up D. MyoA and MyoH are transcription factors that shut off muscle-specific genes E. myoD is the gene for myosin and the presence of myosin converts the fibroblast into a muscle cell
Which of the following are the largest
projections of the small intestine surface? a. microvilli b. cilia c. villi d. brush borders. e. duodena
A number of populations of different species interacting with one another in a natural environment, such as a rotten log, is called
Select one: a. competition. b. a community. c. a biome. d. predation. e. symbiosis.