ANATOMY

Detailed explanation-1: -If two or more species share a unique physical trait they may all have inherited this trait from a common ancestor. Traits that are shared due to common ancestry are homologous structures. The similar bone arrangement of the human, bird, and whale forelimb is a structural homology.

Detailed explanation-2: -Similarities between organisms which do share a common ancestor are called homologous characters. Relative to groups not possessing these characters they are also shared derived characters uniting the group which have them.

Detailed explanation-3: -Homologous structures provide evidence for common ancestry, while analogous structures show that similar selective pressures can produce similar adaptations (beneficial features). Similarities and differences among biological molecules (e.g., in the DNA sequence of genes) can be used to determine species’ relatedness.

Detailed explanation-4: -If different species share common ancestors, we would expect organisms to share similarities inherited from those ancestors. Features inherited from common ancestors-even if their appearance is quite different in close relatives-are known as homologies.

Detailed explanation-5: -In general, organisms that share similar physical features and genomes tend to be more closely related than those that do not. Such features that overlap both morphologically (in form) and genetically are referred to as homologous structures; they stem from developmental similarities that are based on evolution.