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?

Question

A.  Lungs clogged with dust.
B.  Highly skewed sex ratios.
C.  Hormonal disruptions due to contaminated water.
D.  Weak eggshells due to radiation.
E.  Inability to recognize mates due to diminished sunlight.


Clarify Question
What is the key concept addressed by the question?

What type of thinking is required?


Gather Content
What do you already know about dinosaurs? What other information is related to the question?


Choose Answer
Given what you now know, what information is most likely to produce the correct answer?


Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  Highly skewed sex ratios.

Clarify Question
What is the key concept addressed by the question?
     · The concept addressed here is a possible cause of dinosaurian, and not mammalian, extinction based on differences between the two groups.

What type of thinking is required?
     · Evaluate level:
       o This question is asking you to weigh and judge, or evaluate, differences between mammals and dinosaurs as they relate to the long term survival of each group.


Gather Content
What do you already know about dinosaurs? What other information is related to the question?
     · Dinosaurs are grouped with reptiles.
     · Some reptiles have temperature-dependent sex determination.
     · Mammals have chromosomally-determined sex determination.
     · The impact of a meteor creates particulate matter that is cast into the atmosphere. This can impact air quality and as a result of impeded sunlight penetration, temperature.


Choose Answer
Given what you now know, what information is most likely to produce the correct answer?
     · Both mammals and reptiles require oxygen for cellular respiration, but as warm-blooded creatures, mammals have higher physiological demands overall, and impaired lung function would negatively impact mammals before reptiles.
     · Effects on hormones and mate recognition would not differ for mammals and reptiles in this instance.
     · The impact of  radiation from a meteor impact would likely have more significant and rapid impacts on both dinosaurs and mammals before it would have an impact on leathery reptilian egg covering.
     · Like many other reptiles, dinosaurs may have used temperature-dependent sex determination. This would have made them quite vulnerable to temperature changes following the meteor impact, and could have resulted in the rarity of one of the sexes of dinosaurs.


Reflect on Process
Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
     · Evaluate level:
       o Answering this question correctly depended on your ability to weigh and judge, or evaluate, the impacts of a meteor impact on the environment of dinosaurs and mammals. If you got an incorrect answer, did you remember that some reptiles, with the possible inclusion of dinosaurs, have temperature-dependent sex determination, or the criteria to compare reptiles and mammals includes the meteor’s influence on environmental temperature? Did you have trouble weighing the merits of mammals vs. dinsoaurs to determine the correct answer?