Major extinctions of dinosaurs are associated with large meteor impacts, including the final extinction that wiped them out at the Cretaceous-Tertiary boundary. The particulate matter that would have arisen as a result of impact would have entered the atmosphere and had secondary impacts. Some scientists believe that a fundamental difference between mammals and dinosaurs allowed mammals to survive this event, but doomed the dinosaurs. What may have characterized the last generation of dinosaurs as they went extinct?
A. Highly skewed sex ratios
B. Hormonal disruptions due to contaminated water
C. Inability to recognize mates due to diminished sunlight
D. Lungs clogged with dust
E. Weak eggshells due to radiation
Answer: A
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The male pine cone
(a) produces pollen. (b) contains a female gametophyte. (c) bears a megasporangium containing a megaspore mother cell. (d) gives rise to a seed.
Which of the following relationships between groups is correct? Select all that apply
A. cephalopod are a group of annelid B. crustaceans are a group of arthropods C. insects are a group of hemichordates D. sea stars are a group of echinoderms E. tunicates are a group of chordates
Which of the following is a product of the citric acid cycle?
a. ADP b. NADPH c. carbon dioxide d. water
Which of the following groups can be distinguished
from other arthropods by its two pairs of antennae? a. insects b. millipedes c. chelicerates d. crustaceans e. trilobites