Johannes wants to know whether soil, water, or both are needed for plant growth. he chooses to conduct experiments on a willow tree for five years to answer his question. how can his experimental methods be changed to improve his experiment? he needs to ask scientists what they think. he needs to conduct the experiment for a longer period. he needs to use a larger sample size. he needs to test more factors in the environment.

Which of the following describes a negative feedback loop? when the heart rate is too high, the body sends hormones that continually increase the heart rate higher. when a pregnant woman is in labor, the body sends hormones that increase the intensity of contractions, which then increases the secretion of the same hormones. when blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows. when a person is jogging, the body sends hormones that continually decrease the rate of oxygen supply to the legs.