Blood is classified into different types based on the presence or absence of certain ________ on the surface of a person's red blood cells.
A) MHC molecules
B) HLA molecules
C) antibodies
D) antigens
E) IL-2 molecules
Ans: D) antigens
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Chlorophyll a and chlorophyll b as well as the accessory pigments are arranged in an antenna array with a reaction center chlorophyll. These antenna arrays with the reaction center chlorophyll are known as
A. reaction center systems. B. photosystems. C. photomembrane systems. D. Calvin systems.
All of the following are features of capillaries that promote exchange between blood and interstitial fluid EXCEPT which one?
A) Capillaries lack connective tissue in their walls. B) Capillary walls consist of a single layer of squamous epithelial cells. C) Capillary walls have pores within the cells and slits between the cells, making them "leaky." D) Capillary walls lack smooth muscle. E) Capillaries have tiny valves that keep the blood flowing in one direction.
Food webs model the relationships among species that live in the same environment. Which of the following best illustrates a producer-decomposer relationship in an ecosystem?
A) a ladybug eating aphids B) a vulture eating from a rabbit carcass C) a squirrel eating walnuts D) mushrooms on a tree stump
All of the following are plant cellular levels of communication except:
A. alarm signaling B. perception C. transduction D. response E. all are plant levels of communication