main idea. A. Aside from the dinosaurs, most of the organisms affected were very small, such as single-celled plankton and insects. B. Herbivores and carnivores were both affected, but the hardest-hit group was the scavengers, including many birds and some mammals. C. Two major food chains were eliminated, one in the oceans based on plankton, and one on land based on leaves. D. Examinations of marine and terrestrial deposits show clearly that ocean extinctions occurred well before those on land. E. In geological samples from around the world, the K/T boundary is marked by a sudden change in plankton and by a spike in fern spores. F. Sudden, high levels of iridium found at the K/T boundary suggest that a meteorite might have caused the extinctions.