Homology is a central idea in evolutionary biology: it explains why organisms can share underlying features even when those features look different or perform different jobs. This lesson introduces the meaning of homology, its historical development, and how it differs from similarity caused by independent evolution.
Homology is similarity between anatomical structures, genes, or other biological features in different organisms because the organisms inherited them from a common ancestor. Homologous features may have changed over generations and may now serve different functions.
All flashcards
Homology
Similarity between biological features due to inheritance from a common ancestor, even if the features now differ in form or function.
Richard Owen's contribution to homology
In 1843, Owen introduced the biological use of the term for the same organ in different animals despite differences in form and function.
Serial homology
Correspondence between repeated structures within one organism, such as the legs of a centipede.
Orthologs and paralogs
Orthologs are homologous sequences separated by speciation; paralogs are homologous sequences created by gene duplication.
Deep homology
Ancient shared genetic mechanisms underlying traits that may look very different in different groups.
Quiz questions
In cladistics, what distinguishes secondary homology from primary homology?Answer: Secondary homology is supported by character distributions in phylogenetic analysis.
What is a synapomorphy in cladistics?Answer: A shared derived character that supports a clade.
Some snake embryos form hind-limb buds that later regress. What does this observation support?Answer: The inference that snake ancestors had hind limbs.
What makes two DNA sequences homologous?Answer: They descend from a shared ancestral sequence.
Why can behavioral homology be difficult to establish?Answer: Similar behaviors can arise through different mechanisms or evolutionary histories.
Based on the Wikipedia article Homology (biology), licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.