What two organ systems are involved in the transfer of oxygen to the cells from outside the body? A. skeletal and digestive
B. skeletal and respiratory
C. circulatory and digestive
D. circulatory and respiratory

Which element is used in photosynthesis found in atmosphere and fixed by bacteria?

Suppose you are estimating the size of a blue crab population. what is the population size if the number marked in the first catch is 40, the total number in the second catch is 200, and the number marked in the second catch is 50?

What is the "great pacific garbage patch"? a large area of marine debris concentrated by rotating ocean currents a large area around the pacific rim where debris collects from natural disasters such as tsunamis an area in the pacific ocean where trash is intentionally dumped due to lack of landfill availability a large trash dump located in hawaii