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The example of the streamlined body shape of fish and squid provides ease of swimming. The analogous structures could be a result of convergent evolution. However, the structures are not homologous, so they more likely adapt organisms for the same role, like flight. The analogous structure evolves separately in each organism to serve the same or similar purpose present in some different animals as well. So, a phylogenetic tree is not monophyletic. The organisms with analogous structures are not commonly closely related and do not thus share a common ancestor. Hence, they may appear on the surface to have a similar structure, but this varies from one organism to another. The analogous structures evolved independently to have similar or the same functions. In some of the plants, the leaves appear from the same basic pattern and ancestor, but while some altered to store water like cactus, others were altered to trap insects, for example, Venus flytrap and pitcher plant. In some types of plants, the leaves are examples of homologous structures. For example, although a bat and a bird have wings while a human does not, the bones are modified for flight in some vertebrate animals, while in others they are used for simple movements like walking and running. The same bones, namely the radius, humour, and ulna, can be seen in the arms of bats, birds, and humans.

A common pattern is the same between all representatives, but that has become converted and adapted for different functions. The most common examples are the limbs of animals. There are various examples of animals that have homologous structures. For example, the embryo formed from all vertebrate animals resembles appearance. This close relationship is often seen because development patterns during embryology are similar among organisms with homologous structures. Organisms that share a common ancestor form this, which is called a monophyletic group, when they are classified based on phylogenetic relationships. This means that closely related species share homologous traits of a similar structure but may or may not have the same or different functions.

Homologous structures are the morphological features of organisms that evolved from a common ancestor.