An ecologist conducts a greenhouse experiment to study the effect of nitrogen concentration on the productivity of sunflower seedlings. What is the independent variable in this experiment?
A) productivity of sunflowers
B) concentration of nitrogen
C) the number of sunflower seeds planted
D) the daily amount of water given to each sunflower seed
B
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Clay in soils represents a trade-off in nutrient availability, such that _____
A) anions are less likely to leach out of soil and are difficult for plants to extract B) cations are less likely to leach out of soil and are difficult for plants to extract C) nitrogen levels are exceptionally high, but much of the nitrogen leaches away D) oxygen levels are exceptionally high, but much of the nitrogen leaches away
Most fluid that enters the digestive system is absorbed through the ____
a. stomach b. pancreas c. small intestine d. lymph vascular system e. large intestine
What is the volume of air moved into and out of the lungs in a single breath during unforced breathing called?
A) tidal volume B) total lung capacity C) minute ventilation D) functional residual capacity E) vital capacity
In contrast to a eukaryotic chromosome, a prokaryotic chromosome
(a) is shorter and fatter (b) has a single loop of DNA (c) never replicates (d) contains many histones (e) all of these are correct