Single or multi-celled structure, membrane-bound organelles, cell(s) larger than prokaryotes
The right answer is B.
Nitrogen fixation is done by decomposers that are prokaryotes (bacteria).
<u>Take the example of legumes.
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The different species of rhizobia bacteria, which are able to infect the roots of legumes (Fabaceae family), are specific to certain host plants. Rhizobium phaseoli infects beans (Phaseolus sp).
Bacteria cause the formation of nodules on the roots by penetrating the root hairs, and transform into larger "bacteroids". The nodules are the seat of a symbiotic activity in which the plant provides the sugars and energy from photosynthesis, and in return benefits from the amino acids that are produced there.
The answer is B.) Insecta.
The nucleotide triplet that encodes an amino acid is called a codon. Each group of three nucleotides encodes one amino acid. Since there are 64 combinations of 4 nucleotides taken three at a time and only 20 amino acids, the code is degenerate (more than one codon per amino acid, in most cases).
