Final answer:
Zebrafish is the frequently studied model vertebrate, as they are vertebrates like humans and have many genetic similarities. They are also transparent during embryo development, aiding in research observations.
Step-by-step explanation:
The model vertebrate that is frequently studied is Zebrafish. Zebrafish have become a popular model organism in biology for various reasons. They are vertebrates, which means they have a backbone, similar to humans, and they share a significant number of genes with humans, making them a relevant model for human biology. Additionally, zebrafish embryos are transparent, which allows researchers to easily observe their development. Other model organisms mentioned, such as Arabidopsis thaliana, the fruit fly Drosophila melanogaster, and the nematode Caenorhabditis elegans, are also important for biological research but are not vertebrates, with Arabidopsis being a plant, Drosophila an invertebrate, and C. elegans a roundworm.