The SA node initiates the heartbeat by automatically sending out impulses causing the atria to contract.
Answer the following statement true (T) or false (F)
True
It is true that the SA node initiates the heartbeat by sending out impulses that cause the atria to contract.
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The metabolic breakdown of specialized brown fat depots in certain animals is substantially increased during _____
A) acclimatization B) torpor C) evaporative cooling D) nonshivering thermogenesis E) shivering thermogenesis
A plant's ability to absorb carbon dioxide is reduced when:
A. water is plentiful. B. temperatures are cold. C. stomata are closed. D. the epidermis is lacking. E. mesophyll cells lack air spaces.
The functions of antibodies include
A) activating complement, inactivating pathogens, and clumping pathogens. B) activating macrophages, stimulating mast cells, and increasing the white blood cell count. C) creating a warm and swollen area near the site of infection, which harms the pathogens. D) causing B cells to bind to T cells, forming clumps that are visible to the immune system.
Martin Wikelski and L. Michael Romero (Body size, performance and fitness in Galápagos marine iguanas, Integrative and Comparative Biology 43 [2003]:376-86) measured the snout-to-vent (anus) length of Galápagos marine iguanas and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females. Currently the only predators of Galápagos marine iguanas are Galápagos hawks. Iguana body size is not correlated with risk of hawk predation, although small iguanas can sprint faster than large iguanas. If predators (for example, cats) that preferably catch and eat slower iguanas are introduced to the island,
iguana body size is likely to _____ in the absence of other factors; the iguanas would then be under _____ selection. A. increase; disruptive B. decrease; disruptive C. stay the same; stabilizing D. decrease; directional E. increase; directional