Mass extinctions
A. have occurred at least 5 times throughout Earth's history.
B. may have been due to climatic changes after a metorite collision.
C. may have followed continental drift.
D. All of the choices are correct.
Ans: D. All of the choices are correct.
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Who discovered that DNA was the genetic material or transforming factor that could convert nonvirulent R-type Streptococcus pneumoniae bacterium to the virulent S-type?
A. Weismann and Nageli B. Griffith C. Avery, MacLeod, and McCarty D. Hershey and Chase E. Watson, Crick, Wilkins, and Franklin
The most economically useful unicellular fungi are
A. basidiomycetes. B. actinomycetes. C. yeasts. D. mushrooms.
Why did scientists turn to genetic engineering for rice to create resistance to blight?
a. The bacteria causing blight cannot be identified. b. Efforts to cross-breed crop rice with blight-resistant rice produced rice unsuitable as a food source. c. It is the cheapest and easiest way to produce blight-resistant rice. d. Almost of the crop rice planted is lost each year to blight. e. It provided the funding necessary to sequence the rice genome.
How long ago did Neanderthals go extinct?
a. 30,000 years ago. b. 100,000 years ago. c. 500,000 years ago. d. 1 000,000 years ago. e. 2,000,000 years ago.