4. From the perspective of the causes of extinction, a reduction in the population of a species is... a) A biological factor b) An environmental change c) A discrete event d) None of the above 5. What is one reason that times of climatic warming are often associated with decreased oxygenation of the seafloor? a) Climatic warming is always associated with asteroid impacts, which results in obliteration of the asteroid into fine particles that absorb oxygen in the ocean b) Because warm water can hold less dissolved oxygen than cool water c) All times of rapid climatic warming are associated with a total loss of photosynthetic organisms d) None of the above.