If you were to travel to a region where rice is grown in paddies, you would see lots of the water fern Azolla growing in the water. A farmer would tell you this is done because Azolla is considered a “natural fertilizer. Explain why this is the case.
What will be an ideal response?
Because Azolla contains the nitrogen-fixing cyanobacterium, Anabaena, it accumulates nitrogen-containing compounds. When the Azolla dies, it degrades and the large amount of nitrogen it has accumulated is released to the rice paddy and thus to the rice plants.
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People homozygous for the sickle-cell anemia allele develop a life threatening disease, while those homozygous for the normal allele are at the highest risk of dying from malaria. Carriers have some resistance to malaria, but do not develop sickle cell anemia. This is an example of ____
A. founder effect. B. genetic bottleneck. C. heterozygosity. D. heterozygote advantage. E. point mutation.
Oxygen (O2) makes up about 21% of the Earth's atmosphere. The graph below depicts changes in atmospheric O2 levels measured between the years 1990 and 2008. Which biological process accounts for the oscillating pattern observed in this dataset?
A. photosynthesis B. respiration C. More information would be needed to answer this question.
As part of the previous experiment, you monitor the growth of tree A (ants blocked from the canopy) and tree B (ants are not blocked from the canopy) over the three-year period. You expect __________ because _________
A. higher growth in tree A; the number of aphids will fall because ants are absent, and aphids are parasites of the tree B. higher growth in tree B; the natural environment is always optimized so any change (e.g., blocking the ants from tree A) will reduce the performance of all members of the network C. no change in growth; due to the size difference between the trees and the insects, the presence or absence of insects will not have an effect on tree growth
Leptospirosis has all the following characteristics except
A) It infects kidneys, liver, brain, and eyes. B) It can be transmitted by animal bites. C) Humans acquire it by contact with abraded skin or mucous membranes. D) It most common in cattle, horses, pigs, and dogs. E) The pathogen is a spirochete.