Summary Sheet

What is Homology?

Similarity due to inheritance from a common ancestor

What is Homoplasy?

Similarity not due to common ancestry, often caused by convergent evolution

What is Analogy?

Similarity in function but different evolutionary origin, type of homoplasy

What is convergent evolution?

Independent evolution of similar traits in different lineages due to similar selective pressures

What is molecular homology

Similarity in DNA or protein sequences due to shared ancestry

What is a Morphogen?

A signalling molecule that controls cell fate depending on its concentration

What are Hox Genes?

Regulatory (homeotic) genes that control body plans along the anterior–posterior (head–tail) axis.

What is Conservation?

The phenomenon whereby genes remain highly similar across species over evolutionary time due to strong functional constraints

What is Evo-Devo?

The study of how changes in development contribute to evolutionary change

What is an example of Morphological Homology?

Vertebrate forelimbs (human, bat, whale → same bones, different functions)

What is an example of Molecular Homology?

Basic - Similar sequences in any related species

Non-Repetitive DNA

• Alu insertions in primates

• Random, non-functional insertions in the same genomic positions

• Unlikely to evolve independently

What is an example of mutations in Developmental Genes?

Antennapedia (Drosophila) Hox gene mutation → legs instead of antennae

What is an example of Developmental Regulation?

Morphogen gradients

Different concentrations → different gene expression → tissue patterning.

Conservation and Ancestry Link

Conserved genes are unlikely to evolve independently because complex gene networks require multiple coordinated changes.

Regulation and Diversity link

Differences in body form usually arise from changes in gene regulation rather than entirely new genes.

Homology and Homoplasy Comparison

Only homologous traits reflect shared ancestry, while homoplastic traits can mislead phylogenetic analysis.

Homology and Phylogeny Link

Combining molecular and morphological data produces more accurate phylogenetic trees.