进化关系

BLAST is a bioinformatics tool that compares DNA sequences to identify similarities between organisms. By analyzing gene sequences from living relatives like chickens, alligators, and zebra finches, students can determine evolutionary relationships and test hypotheses about how organisms are related through common ancestry.

Gene sequences for the chicken, alligator, and zebra finch are available through a GitHub repository at https://github.com/EvolutionGenes/Evolutionary-Relationships-Genes. Students download the ZIP file containing these living relative DNA samples, which serve as reference sequences for comparing against mystery fossil genetic data in the analysis.

Open the BLAST website (https://blast.ncbi.nlm.nih.gov/Blast.cgi) on each computer students will use. Download gene sequence files from the GitHub repository and save them to the desktop for easy access. Print blank cladograms for each student, with extra copies recommended for practice or errors.

Cladograms are branching diagrams that visually represent evolutionary relationships between organisms based on shared characteristics and genetic data. Students use blank cladograms to map how organisms like chickens, alligators, and zebra finches diverged from common ancestors, organizing their BLAST findings into a phylogenetic framework.

By comparing mystery fossil DNA sequences against known gene sequences from living relatives using BLAST, students can determine which modern organism the fossil is most closely related to. Sequence similarity scores reveal evolutionary distance, allowing students to place the fossil accurately on a cladogram.

Using multiple living relatives like chickens, alligators, and zebra finches provides diverse reference sequences for comparison. This approach strengthens evolutionary hypotheses by revealing patterns of genetic similarity across different lineages, making conclusions about fossil relationships more robust and scientifically valid.

After examining the first sequence on the BLAST website, students return to the main page and click the green Clone or download button, then select Download ZIP. This process is repeated on each computer to ensure all students have access to the complete set of gene sequences needed for analysis.