Question

The similarity of these structures suggests that the organisms _____.

1) have a common ancestor
2) have evolved independently
3) have the same habitat
4) have different adaptations

Answer 1

The similar structures in different organisms suggest that they have a common ancestor and share homologous structures. These similarities are based on evolutionary development and conserved core processes, distinguishing them from analogous structures resulting from convergent evolution.

Step-by-step explanation:

When structures in different species are similar, it suggests that these organisms have a common ancestor. The similar construction of appendages in certain organisms, such as humans, dogs, birds, and whales, implies the presence of homologous structures that have evolved due to shared ancestry. Such features are based on developmental similarities that are based on evolution, and as described in Figure 18.7, these appendages indicate a common evolutionary origin. Also, according to principle 1.B.1, organisms share many conserved core processes and features that are widely distributed among organisms today due to evolution.

However, it is important to distinguish these homologous features from analogous structures, which look similar not because of common ancestry but because of convergent evolution, where different species independently evolve similar traits as they adapt to similar environments or ecological niches. For example, the wings of insects and birds are analogous structures since they perform a similar function but do not signify a recent common ancestor. In summary, the organisms with similar structures as indicated in the original question most likely share a common ancestor, which is why they have homologous structures.