A list of 7 model organisms that are commonly used in biological research and testing, along with brief descriptions of why they are used.
Biology is a field that is growing every day. It is so complex and vast that if new research, gene therapy, genetic engineering, drug treatments, etc. need to be tested or created in vivo, they would need to be done cheaply, efficiently, and quickly. In order to do so, biologists have concurred upon several model organisms. These model organisms are used in particular because of their practical and genomic benefits. They are simple enough such that research, treatments, and other such testing will be much easier than performing them in more complex organisms. This approach is also more humane and allows for reproduction of results from other scientists who try the same experiment (as opposed to using rare species).
Some reasons as to why humans are not used (other than for ethical and moral reasons) is because we reproduce too slowly and in too few numbers, our lifespan is too long (we have long maturation periods), we are too large and therefore, it would be inefficient to store in small areas, and we have quite a large genome with twenty-three pairs of chromosomes. Our complex immune system would provide a difficult challenge for drug testing and all in all, it would cost too much money to keep us alive.
Drosophila melanogaster (the common fruit fly that one finds on bananas)—Drosophila is particularly useful in biology because they reproduce particularly quickly for a multicellular organism. A complete life cycle only takes about two weeks, which is much shorter than the lifespan of a laboratory mouse. Their genome is so small (with only four chromosomes) that this keeps most of the genetic “junk” out from testing, which makes experiments much simpler. One of the most interesting things about using Drosophila is that its pupae have bands, and these bands can be correlated with parts of the fly’s body, which, depending on the experiment, may be genetically altered. Additionally, many results found for the Drosophila can be related to humans due to our closeness in evolution and hence striking similarities in parts of our genome.
Mus musculus (laboratory mouse)—Laboratory mice are useful when experiments need to be performed on mammals. As they are mammals, biologists can replace some genes in these mice with human genes to test drugs before human testing or to see what a particular mutated gene may do. Because it is quite inhumane, expensive, and time-consuming with other species of mammals, laboratory mice are perfect for experimentation. They are inbred to be genetically similar, where inbreeding also results in mental retardation, genetic illnesses, and other such handicaps. Their small size allows for storage of many mice at once. Because they reproduce often and in large quantities, biologists have found mice as a very useful tool.
Caenorhabditis elegans (nematode)—C. elegans is a very simple organism with a very simple nervous system. Because it is so simple, it is easier to study neural development. It is also transparent, which allows for biologists to study its internal processes as they occur. It is small with a short lifespan and thus, is easy to breed. In fact, scientists can freeze this organism for a while and thaw it when needed for later use. Genetic manipulation is also somewhat uncomplicated because its genome is quite small.
Danio rerio (zebrafish)—These are very small fish and reproduce relatively quickly (at approximately three months) and are easy to care for. The most important characteristic of the zebrafish is that the embryos are transparent. Therefore, biologists can study it development even before the eggs hatch and can watch certain processes occur in the fish. It is also easier to test drugs on fish because the drugs do not have to be administered via injection, but instead, can just be mixed in the water.
Arabidopsis thaliana (thale cress)—Arabidopsis is a small species of plant that is easy to cultivate and store. Their life cycle is relatively short at approximately six weeks, with a very manageable genome of only five chromosomes. Genetic alteration of this plant is much easier because of the fact that the genome is so small.
Saccharomyces cerevisiae (baker’s yeast)—These fungi are easy to breed and reproduce quickly (approximately two hours). Because they are eukaryotes, they are similar to humans in that they can perform meiosis (in fact, biologists studied yeasts to learn about meiosis) and that they have structures that our cells have (nucleus, mitochondria, etc.). Their genomes are also very small, which allow for easier genetic manipulation.
Escherichia coli (E. coli)—E. coli used in a laboratory have much of the properties of E. coli found in intestines, except that they have adapted to living in laboratory petri dishes and cannot thrive in intestines any longer. Therefore, they have to ability to translate many of the proteins that “normal” E. coli can without being as hazardous to humans but still give very similar data. This data is more useful than data collected from a rare type of bacterium because it may be applied to bacteria living in our bodies. E. coli have very short lifespans of a couple of hours, so mutations and such occur at a much faster rate.