Why is nitrogen fixation an essential process?
A) Nitrogen fixation can only be done by certain prokaryotes.
B) Fixed nitrogen is often the limiting factor in plant growth.
C) Nitrogen fixation is very expensive in terms of metabolic energy.
D) Nitrogen fixers are sometimes symbiotic with legumes.
B
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The beach flea Talitrus is a member of the order:
a. Stomatopoda. b. Decapoda. c. Euphausiacea. d. Amphipoda. e. Isopoda.
Compare feeding in a sponge, a cnidarian, and an annelid
What will be an ideal response?
A group of people whose ancestors immigrated to North America 200 years ago have certain allele frequencies that differ significantly from those in surrounding populations in the United States. Which of the following is the most likely explanation for the difference in allele frequencies?
(A) Mutation (B) Independent assortment (C) Reproductive isolation (D) Sex linkage
Plant species regularly hybridize in nature, but only some crosses result in new polyploid species. Of the crosses below, if each one occurred, which would be most likely to result in a new stable polyploid species?
A. A cross between a species with a CC genome and a species with a DD genome, forming a hybrid with a CD genome. B. A cross between a species with a BB genome and a species with a DD genome, followed by a doubling of chromosomes, forming a hybrid with a BBDD genome. C. A cross between a 4n gamete and a 1n gamete, forming a 5n hybrid. D. A cross between a 2n gamete and a 1n gamete, forming a 3n hybrid.