Upon vigorous exercise, your heart rate increases to 200 beats per minute to supply sufficient oxygen to muscles. which is responsible for this regulation of the heart rate? a. semilunar valves
b. sinoatrial node
c. aorta

*will mark brainliest for first correct answer* which of the following is most likely to affect the biodiversity of a park ecosystem? a. less rain than usual for several months b. ongoing pollution from a nearby factory c. park rangers plant a new type of tree d. disease wipes out an entire population

The process by which natural forces move weathered rock and soil brim one place to another is called

What was the land like over 500 million years ago? what was under the sea?