Structural Morphology
Structural morphology refers to the physical structures of organisms that contribute to their function and development. Structures such as bones, muscles, organs, and tissues can be compared between species to determine their relatedness.
Species that have descended from a common ancestor often share similar structures but may use these structures differently due to varying selective pressures and adaptations to different environments.
By comparing the structural features of species, scientists can infer a common ancestor based on the degree of similarity that it shares with this common ancestor.
Vestigial structures are anatomical features or organs in an organism that have lost their original function due to evolution. While these structures may still exist, they no longer serve their ancestral purpose. Over time, they have been reduced or modified through natural selection . Despite this modification, vestigial structures can provide evidence of an organism's relatedness to a common ancestor.
Use this page to revise the following concepts within structural morphology:
Homologous structures
Related organisms typically exhibit similarities in basic structures, regardless of the different evolutionary pressures they have experienced over time. Such common structures are referred to as homologous. Homologous structures are derived from a common ancestor and share a similar anatomy, although they may serve different functions in different species.
For example, consider the forelimbs of land animals: the wing of a bird, the wing of a bat, the leg of a crocodile, the flipper of a whale and the arm of a human all share a similar structure. While each species has evolved variations in the precise number and length of the bones, due to their unique selective pressures, the underlying structure remains recognisably similar.
Vestigial structures
Organisms related by evolutionary descent typically have similar or identical structures that have been passed down through generations.
However, if these structures are not required for the species’ habitat or behaviours, they may become reduced in size or function over time due to a lack of selective pressure for those structures.
This process results in a special kind of homologous structure, where a species displays functionless or highly reduced organs inherited from a common ancestor. These are known as vestigial structures. Vestigial structures are crucial in understanding evolution, as they provide insights into an organism's relatedness to a common ancestor and its adaptation to the current environment over time.
Some examples of vestigial structures include:
