During which stage of development do cells arrange themselves into three layers?
A) organogenesis B) morula C) cleavage D) gastrulation
Answer: D
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You are trying to determine if honeybees have social immunity to nosema, an economically devastating parasite that attacks adult honeybees. You mark some honeybees with a spot of red dye and expose them to a solution containing a sublethal dose of the parasites. Another set of honeybees is exposed to the same solution without parasites. After this exposure, you mix some of the unmarked bees with
the marked bees (Mixed Group). The rest of the unmarked bees are not mixed with other bees (Unmixed Group). When you expose both the Mixed and Unmixed groups of bees to a lethal dose of the parasite, all the bees die. What might you conclude from this experiment? A. The marked honeybees exposed the unmarked bees to a lethal dose of the parasite. B. There is no social immunity for nosema in honeybees. C. There is social immunity, but only at a sublethal dose. D. There is no social immunity, but there is humoral immunity. E. There is both social and nonspecific immunity for nosema in honeybees.
Which of the following areas of the respiratory tract is lined with a single layer of epithelial cells?
a. nasal cavity b. larynx c. trachea d. bronchi e. alveoli
In batch fermentation, substrate is added continuously, and the product is siphoned off throughout the run.
Answer the following statement true (T) or false (F)
What do seeds contain?
A. embryo and nutritive tissue B. male gametophyte and nutritive tissue C. female gametophyte and nutritive tissue D. mature sporophyte and nutritive tissue