ANATOMY

Detailed explanation-1: -Organisms that share similar physical features and genetic sequences tend to be more closely related than those that do not. Features that overlap both morphologically and genetically are referred to as homologous structures; the similarities stem from common evolutionary paths. For example, as shown in Figure 12.2.

Detailed explanation-2: -But for a clear understanding of how closely they are related, scientists compare their DNA, an essential molecule that’s the instruction manual for building each species. Humans and chimps share a surprising 98.8 percent of their DNA.

Detailed explanation-3: -The basic idea behind this approach is that two species have the “same” gene because they inherited it from a common ancestor. For instance, humans, cows, chickens, and chimpanzees all have a gene that encodes the hormone insulin, because this gene was already present in their last common ancestor.

Detailed explanation-4: -Biologists often compare the sequences of related (or homologous) genes. If two species have the “same” gene, it is because they inherited it from a common ancestor.

Detailed explanation-5: -When two organisms are related, it means that they share a common ancestor. The more recent the ancestor, the more closely related the organisms are.