 Organisms were chosen , in part , for convenience — short generation times and easy genetic manipulation made some organisms popular genetics research tools . Widely used model organisms include the gut bacterium Escherichia coli , the plant Arabidopsis thaliana , baker 's yeast ( Saccharomyces cerevisiae ) , the nematode Caenorhabditis elegans , the common fruit fly ( Drosophila melanogaster ) , and the common house mouse ( Mus musculus ) . 
