Worms, Wings and Spinal Columns -

Sue the T. rex.

By ScottRobertAnselmo (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

December 30th, 2014:

It the world of developmental biology there has long been a sense that as we understand common features of how creatures develop we will learn something about how they arose. That is the mechanics, morphology and genetics of the process that the organism goes through to become an adult shows common features among organisms that are related.

Scientists believe that around 65 million years ago our planet was violently disrupted by a collision with a large asteroid, a life ending event that helped push the dinosaurs over the edge leading to their eventual extinction, with some exceptions like crocodiles and cassowaries [that I imagine could survive anything].

Cassowary: dinosaurs survive in Australia?

Following that mass extinction, the surviving creatures divided up the available territories and began to specialize to succeed in whatever niches they found themselves in. That resulted in a huge expansion of variations between the various surviving organisms in a process called evolutionary radiation. The expansion of these various species, though, maintained those strategies, genes and processes that were most important to their survival. Thus commonality in aspects of life such as early development can show us the fundamental biology that is central to many organisms as well as what organisms are more or less closely related to each other. It is one tool in the work-bag of evolutionary biologists.

George Romanes’s 1892 copy of Haeckel’s concept that stages of early development “reveal” evolutionary ancestors, that there is a commonality seen in developmental stages. That is, “ontogeny recapitulates phylogeny”, a concept largely discredited now, although clearly there are relationships between how we develop and where we came from.

For developmental biologists the approach allows experimentation and the seeking of new knowledge with one animal (because it is cheap or convenient or ethical or all of those) and gain knowledge that is relevant to other animals like us. Modern genetics has greatly expanded our ability to do this.

Over many decades of scholarship biologists seem to have sorted out into broad categories of study with respect to what animals they use to peel back the layers of mystery surrounding the way one generation of animal produces the next. This is a right and proper endeavor as that ability goes a long way to defining what life is. Some have taken the role of vermiformist using the lowly worm as the subject of their investigations, in the sure knowledge that we will be serving them soon enough.

Others have studied the fly [specifically the fruit fly, D. melanogaster], an animal cheap and easy to maintain and manipulate and one that fails to provoke emotion in even the most ideologue minded animal activists. The remainder prefers to look at vertebrate animals that have a spinal column, because they are most like us. A famous developmental biology once referred to the groups as vermiformists, celestialists and analogists. More useful I suppose would be to distinguish model systems (worm, fly, frogs, sea urchins, and others) from analogous systems (mouse, rat, primates). The fact is that these distinctions are not so meaningful now as they once were; we now know that there is an awful lot that all of these members of the zoo have in common.

Indeed the most shocking revelation in the last 30 years of research has been how much of development is conserved [remains the same] throughout evolutionary time. Not only is the structure (linear DNA sequence) of key genes remarkably alike between these animals, but also how these genes interact with each other, and what the proteins they code for actually do for the animal are amazingly similar.

Of course we do not have wings or fins, although we have structures that are very similar, and we are much bigger than some and much smaller than others of our buddies and so the similarities are not sufficient to allow a complete model of our biology to be drawn from studies of other animals. Nevertheless, completely apart from the inherent interest in understanding how they put themselves together we learn where to look and what to look for in a quest to determine how we put ourselves together.

In aid of that understanding we should look more deeply at what happens from one generation to the next in some of the more popular animals that we study.

Next time we will examine this in the lowly round worm, nematode:

The nematode C. elegans.

By Bob Goldstein, UNC Chapel Hill (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License.

Originally published at lcresearchcenter.tumblr.com.