Answer to Question 1
Because certain organisms that once lived near the surface of water can only live within a narrow range of temperatures, the distribution and type of organisms within the sediment indicate the temperature of the surface water. Most of the oxygen in seawater is composed of 8 protons and 8 neutrons in its nucleus, giving it an atomic weight of 16. However, about one out of every thousand oxygen atoms contains an extra 2 neutrons, giving it an atomic weight of 18. When ocean water evaporates, the oxygen-18 tends to be left behind. Consequently, during periods of glacier advance, the oceans, which contain less water, have a higher concentration of oxygen-18. The shells of marine organisms are constructed from the oxygen atoms exiting in ocean water, so determining the ratio of oxygen-18 to oxygen-16 within these shells yield information about how the climate may have varied in the past. A higher ratio of oxygen-18 to oxygen-16 in the sediment suggests a colder climate, whereas a lower ratio suggests a warmer climate.
Answer to Question 2
B
Antifreeze in living organisms
Measures of ocean chlorophyll-a concentrations from part of Atlantic Canada in (a) January 2006, and
Some organisms used as models in genetic research
Adult blue whale from the eastern Pacific Ocean
Skeletal remains from the Sima de los Huesos, Sierra de Atapuerca, Spain.
Shapes of cells found in the brain.