The mammalian is a fascinating creature, not least because we humans belong to this group, too. All mammalians are closely related but still looking very different. This article will give a general definition of what constitutes a mammalian, highlight examples of how diverse the group of mammals really is and the role that CHO cells, for instance, have in recombinant antibody expression. Be prepared for fascinating surprises!
A mammalian is a member of the phylogenetic group of mammals. The word “mammalian” may also be used as an adjective, in the sense of pertaining to mammals.
In biology, mammals are defined as vertebrate animals with the following features: mammary glands and lactation, hair or fur, presence of a brain region termed neocortex, and three middle ear bones.
Even though this definition seems very restrictive, the phylogeny and systematics of mammalian lineages is extremely rich. Mammals show a huge variability in morphology, from very large cetaceans weighing hundreds of metric tons, over ungulates, to small rodents and shrews. Moreover, mammalian modes of reproduction are quite variable among marsupials like kangaroos (carry their young in a pouch), monotremes like platypus and echidna (lay eggs) and the well-known placental mammals.
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Here are some classification and example of mammalian. It is noteworthy that mammal species exhibit a strikingly large biodiversity:
As you can see, mammals populate very different habitats and exhibit diverse but highly specialized lifestyles that overlap with other animals like birds, fish, or reptiles. This is a prime example of convergent mammalian evolution.
After an event of mass extinction 66 million years ago, evolutionary history and fossil records indicate that mammals took over large ecosystems and diversified exponentially to specialize into now vacant niches of ecology.1
The mammalian capability to specialize correlates with their diverse habitats: oceans, the plains of North America, streets of New York, Russian tundra and taiga. Practically every habitat and climate zone is populated with mammals. Major reasons are the exceptional thermoregulatory capabilities and them being warm-blooded. Consider reptiles which depend on warm climates and can’t compete with mammals in colder climates.2
After this high-level macroscopic take on mammals, let’s dive in deeper and consider the peculiarities of mammals at the cell level.
Mammalian cells share many traits with other animals and eukaryotes in general. With a cell nucleus, Golgi Apparatus, and endoplasmic reticulum, they are distinct from prokaryotic cells. These cell structures allow them to significantly alter their proteins after expression (production of proteins from amino acid building blocks) in processes termed post-translational modifications.
The biopharmaceutical industry thus relies on mammalian cell cultures such as HEK293 cells or CHO cells to produce protein products for medical applications such as therapeutic monoclonal antibodies (while CHO cells are often preferred), and thanks to the laboratory technique of mammalian cell culture, no actual mammals have to be harmed in the process today.
More about this topic:
How to grow mammalian cell culture
1.Testing the roles of competition and expansion in tetrapod evolution. Proc R Soc B. Published online May 22, 1996:641-646. doi:10.1098/rspb.1996.0096
2.What Habitats Do Mammals Live In? North American Nature. Accessed November 2022. https://northamericannature.com/what-kind-of-habitats-do-mammals-live-in/