Idon't have much time! answer quickly! 2 questions:
1. which system of grouping is in figure 18-2, a or b provides information about the evolution of the three animals
2. according to the cladogram in figure 18-2, what two characteristics do crabs and barnacles share that limpets do not?
you in advance

The correct answer is-

1) Cladogram

2) Molted external skeleton and segmentation.

A cladogram can be described as a diagrammatic representation in a  branching treelike form, which is used to depict phylogenetic relationships among different species.

For every divergence point in a cladogram, the two branching lines show descendance, which indicates divergence of species from a common ancestor. Thus, it is a system of grouping of various organisms.

In the given cladogram, the two characteristics that are shared by crabs and barnacles but not by limpets are Molted external skeleton and segmentation.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.

ans.

dna fingerprinting is defined as a process that determines the dna characteristics of an individual. these dna characteristics are unique among individuals as their fingerprints, so it is known as dna fingerprinting.

steps of dna fingerprinting includes extraction of dna from sample, amplification of dna, restriction digestion of amplified dna, and then analysis of dna by gel electrophoresis, respectively.

thus, the next step performed by the scientist is 'to cut the amplified dna (obtained by polymerase chain reaction) by restriction enzymes that cleave the dna into fragments and their analysis.'