Part 1: Evaluating proxy data to understand Earth's past climate

Foraminiferids ("Forams") are single-celled organisms, more officially referred to as "protists". They are mostly planktonic, meaning that they float in the upper (sunlit) portions of the ocean. They are heterotrophic, that is, they need to eat, and their food consists of phytoplankton they snag out of the water with leg-like "pseudopods". Forams have hard external skeletal material called a test, similar to how a snail has a shell. These skeletons are made of calcite (CaCO3). Forams grow by adding new chambers to their test , like we might add newer, bigger rooms to a house or a tree grows in rings each year. Each chamber looks a bit like a bulb or a globe. Interestingly, when ocean water temperatures are cooler than 8 to 10C, forams add these new chambers in a counterclockwise spiral ("left-coiling"). When temperatures are warmer than 8 to 10C, they add their new chambers in a clockwise spiral ("right-coiling"). The coiling direction of fossil forams can therefore serve as an indication of ancient temperatures. We call this sort of evidence a proxy of paleotemperature. Proxies are not a direct measurement of temperature, but they are evidence of ancient temperatures.

In this activity, you will calculate the proportions of lef and right- coiling individuals of one of the most common foram species, Neogloboquadrina pachyderm,seen in Fig 1. The specimens were collected from sea floor sediment samples from different periods of time over the last 160,000 years. Then you will interpret that graph to arrive at an interpretation of what Earth's climate was doing during this interval of time.

C a b 19 20280 8236 18% 295 75%% 25% 300 23% 77%% 345 13% 87% 352 86%% 454 14% 869% 160 13% 343 16% 330 19% 268 79%% 2196 143 84% 16% 132 66% 34% 269 75%% 259% 261 2196 79%% 377 12% 88% 224 409% 60%% 289 43%%\f\f\f\f