# Grouping Species Using DNA

Explain cladistics: organisms are grouped by shared derived characters, not just similarity; how phylogenetic trees are built using molecular data (DNA sequence alignment) and the molecular clock; explain why birds are technically a group within dinosaurs (crown Avemetatarsalia); distinguish convergent evolution (unrelated species evolving similar traits) from parallel evolution; introduce horizontal gene transfer and why the tree of life is more accurately a web; explain why classification systems keep changing as new data emerge

Builds on: The Biodiversity Crisis (hard, https://ai.page/c/the-biodiversity-crisis/en.md), Chromosomes, Genes & DNA (soft, https://ai.page/c/chromosomes-genes-and-dna/en.md), Invasive Species (hard, https://ai.page/c/invasive-species/en.md)

Concept id: grouping-species-using-dna. Subject: science. Licence: CC BY-SA 4.0.

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