Tracey was learning about structural organization in animals. What level of structural
organization BEST describes an egg?
A. a cell
B. a tissue
C. a system
D. an organ

Select the correct answer from each drop-down menu. the lac operon in e.coli regulates genes that code for enzymes required for breakdown of lactose. the lac operon is operon that is activated in the presence of .

You are studying a protein that you call protein x. there is an aspartic acid at a key position in protein x which is important in the folding and stabilization of that protein. if this aspartic acid is changed to a different amino acid, which type of amino acid substitutions is most likely to allow the protein to fold normally?

Scientists discovered fossils in several layers of the earth you see here. they found fossils of algae, snails, and clams in layer d. given that information, where do you think they found fossil evidence of simple land plants and amphibians? a. a b. e c. f d. g