Why do plants containing nitrogen-fixing bacteria in their roots need less nitrogen-based fertilizer than others?
A) The plants break down the bacteria as a source of nitrogen-rich nutrients.
B) The bacteria convert nitrogen in the air into a form that can be taken up by the plants.
C) The plants and bacteria work together to attract birds, which deposit nitrogen-rich droppings near the plant.
D) The bacteria kill and digest earthworms and other animals in the soil, providing excess nitrogen to the plants.
B
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Why would the Sabin oral polio vaccine need to be eliminated as we get closer and closer to eradication of the polio virus?
A. Since it is a live, attenuated viral vaccine, there's always the chance it could revert back into a pathogenic state by mutation. This would introduce new strains still capable of causing the illness into human populations, thwarting elimination. B. The Sabin vaccine is cheaper than the Salk (killed virus) vaccine, but it isn't as effective at producing a protective response. We'll need to shift to the more effective Salk vaccine worldwide eventually to complete the eradication process. C. The Salk vaccine is far cheaper than the Sabin vaccine. To effectively eradicate polio, we'll need to shift all of our resources into the cheapest and easiest to deliver vaccine possible. That is the Salk vaccine. D. The Sabin vaccine can only be administered to human beings. We need to vaccinate bird populations as well to effectively control the spread of polio. Birds are a natural reservoir for the virus.
The spores that are released when the zygospore splits open are________.
A. sterile B. haploid C. motile D. diploid E. triploid
Sunlight resets biological clocks in plants by activating and inactivating photoreceptors called ________
a. statoliths b. jasmonates c. phytochromes d. phototropin
What is the final step in prokaryotic DNA replication?
a. helicase opens the fork b. elongation c. ligase seals the gaps d. RNA primers are removed