Model organisms are species that have been specifically chosen and used by scientists to study biological phenomena because they exhibit certain characteristics or traits that make them ideal for research purposes. These animals or plants often have relatively simple anatomy, short life cycles, and well-understood genetics, which makes it easier to conduct experiments on them and draw conclusions about other organisms, including humans. Some common model organisms include the fruit fly (Drosophila melanogaster), the zebrafish (Danio rerio), the nematode worm (Caenorhabditis elegans) and the Arabidopsis thaliana plant. By studying these species, scientists can gain valuable insights into genetics, development, behavior, and other aspects of biology that are applicable to a wide range of organisms.