Rise of the Other Kind(s): Part I

Maliha Tanjum Chowdhury

Freshman

School of Life Sciences

Independent University

July 1st, 2017

This is the first in a three-part series that will broadly introduce and describe the study of evolution using microbes as model systems, and specifically focus on a recent study on speciation.

If you’re still one of those people who constantly pick their brains trying to figure out how a small, often seemingly benign creature like the bird could possibly be descended from the titan-like dinosaurs who once ruled the planet, you are not alone. The word evolution is generously and rightly paraded around to explain this phenomenon, but it is difficult for most to visualize. However, speciation, a word – an idea – much less known to the general public, comes much closer to explaining such transitions. Speciation describes the complex and extremely slow-paced chain of events that directly bring about this incredible metamorphosis from one creature to another over the course of millions of years.

Now, the term “species”, from which “speciation” has been derived, can be described as a group of organisms with strongly similar physical and biochemical properties. In more bookish terms, speciation is defined as the divergence of a single species into two (or more) groups of organisms so different from each other (and from the original species) that they can no longer produce viable, fertile young together. Allopatric speciation is when new species emerge due to a geographical rift between factions of the same population thereby exposing them to different selection pressures and thus, different responses to them. On the other hand, sympatric speciation is the emergence of divergent species from a single, original species in the same geographical region. The latter form of speciation is relatively harder to conceive as the incidence of reproductive isolation (wherein members of the same species stop interacting to reproduce) within closely knit communities is a much rarer phenomenon. However, this can be explained by the fact that separation often occurs due to separation into different ecological niches. For instance, individuals of an aquatic species may prefer to live near the surface or at the bottom of a pond, thereby leading to separation into different niches or locales within the same broad geographical location.

It is quite difficult to imagine how small changes in the characteristics of living organisms in response to different selection pressures could lead to the vast amount of biodiversity we see on earth. But a few billion years on the course of speciation, and magic happens – ancient amoeba-like creepy crawlers may transform to graceful sea-creatures, simple algal ancestors may flourish into magnificent flowering plants, and according to some, the ancestors of the apes that you go visit at the zoo may even turn into a person. The odds are as endless as the universe itself, and so, evolution is a beautiful thing – something quite poetic. It has helped and will continue to help scientists trace back to the ancestors of organisms that exist now, thereby creating a bridge between the present and some long-forgotten, illusory time in the past, and just simply help understand the dynamics of the living world better. Just as boundless oceans are formed from the assemblage of billions of droplets, a steady accumulation of mutations, products of recombination and the like generate more and more diversity and the uninterrupted influence of natural selection continually increases the frequency of fitter variants among this generated diversity. At the current moment, we see a snapshot of life on earth that is very far along, according to our sense of time. We see millions of different species that have evolved from a focal common ancestor.

Honestly, who wouldn’t want to play god and observe such enchanting changes under the microscope in their own little petri-dish? Sadly, and quite obviously, speed-racing through billions of years in a lab is NOT feasible, and thus we cannot hope to observe processes like the evolution of humans and birds. It is this powerlessness of humankind that has driven evolutional theorists and biologists to more often try and establish links between larger, multicellular species based on fossils, geological evidence, DNA sequences (when available), and mathematical modeling.

However, there does happen to exist a way of observing evolution in the lab, by using organisms that go through generations much, much faster than us...

To be continued

Maliha is a weirdo who somehow believes she's from a different planet. But she likes Earth just fine, and is fascinated by the science and beauty of life and has made it her purpose to explore it. Besides this, her most burning desires include becoming a synthetic biologist/ genetic engineer and running away with a heavy metal band.