Warm Blooded Dinos?

I am not a paleontologist, but I am a big fan of scientific controversy. I love it when two sides argue about how flight originated or how new fossils may be related to our own hominid lineage. That’s why the recent findings that large bi-pedal dinosaurs like the beloved Tyrannosaurus rex may not have the typical large lizards we have long thought really caught my attention.

It’s generally consensus these days that some dinosaurs were birds rather than lizards, and the lineage has been split to include non-avian and avian branches. But there is still controversy among experts as to whether or not these dinos were warm-blooded like their birdy brethren or cold-blooded like their lizardy links. A new study published in the online scientific journal PLoS ONE on Nov. 11th brings to light some new information.

Say the study authors, endothermy, or warm-bloodedness, was widespread “in at least larger non-avian dinosaurs.” The results of their study seem to indicate that the ability to maintain a constant internal temperature may have originated earlier than previously believed.

What this essentially means is that once again we are rethinking how these extinct giants behaved. For the longest time, large dinosaurs like the T-rex were considered unwieldy, hulking and awkward. Now there’s evidence that there was more power and precision behind their lumbering movements.

So why is this such a point of contention? Because being warm-blooded and cold-blooded are very different and require different energy expenditures, different rates of respiration, and different natural histories altogether.

Cold-blooded animals (termed ectothermic), such as amphibians, reptiles and the ilk, rely on the environment to maintain body heat. They generally adapt behaviors to soak up as much heat and sun as possible to run their metabolic processes.

Warm-blooded animals are everything else—including birds (or avian dinosaurs). We can maintain homeostasis (i.e., regulate and maintain a constant body temperature through metabolism). But doing this requires much more energy consumption and output, and requires different anatomical and physical traits. It also means we can live anywhere, hunt for food anytime, and not have to worry about the environment to meet our temperature regulation needs.

So the fact that there is evidence for endothermy among dinosaurs has huge ramifications. We may need to reconsider how we classify them, and even how they became extinct.

Reptiles, a lineage of animals dating back over 300 million years, include organisms such as the extinct dinosaurs and the extant (still living) species of lizards, crocodilians, turtles. It was later expanded to include birds, based on genetic and molecular evidence. These new findings could also lead to more accurate phylogenies, or evolutionary trees.

Your DNA damage looks great, did you get just get back from the beach?

My students in Biology 101 are learning about DNA right now and one asked me how UV radiation causes damage to our genetic material. I know the basics, but was unfamiliar with the process. So I, of course, was intrigued, and had to look it up. Bear with me, I’ve tried to make this as simple and bare-bones as possible, so don’t let your eyes glaze over (like those of some of my students) when you see big scientific words.
DNA structure consists of a backbone molecule made up of sugar (a deoxyribose sugar, what the D in it’s name stands for) paired with phosphate molecules. Attached to each of those sugars is a nitrogenous base: adenine (A), thymine (T), guanine (G) or cytosine (C). It’s the complimentary pairing nature of these bases that allows for such perfect replication of our genetic material; A pairs with T, and G pairs with C, and that is what gives DNA it’s structure, chemical properties, and it’s ability to replicate so faithfully.
DNA replicates, or copies itself, in a process that is nothing short of amazing. The double-helix structure unwinds (with the help of an enzyme) and each parent strand is faithfully copied via complimentary base pairing. Throughout the process are “checkpoints” to prevent errors and proofreaders that won’t allow the DNA to code for protein unless things are correct.
Most DNA damage interferes with the ability to proofread or prevent incorrect proteins from being made, which is the case with UV radiation. UVB light causes one of the nitrogenous bases, thymine, to pair with itself instead of with adenine. These thymine base pairs next to each other in genetic sequences bond together into thymine dimers, an incorrect sequence which disrupts replication in the strand and which enzymes cannot read or copy. This leads to the production of melanin--a tan, or in severe cases, sunburn. Sunburn is the body’s way to get rid of cells damaged by UV radiation.
Direct DNA damage is reduced by sunscreen, which prevents sunburn; it won’t necessarily keep you from getting a tan. On the skin’s surface, sunscreen filters the UV-rays, decreasing their intensity. When sunscreen molecules penetrate the skin, they protect against direct DNA damage because the UV-light is then absorbed by the sunscreen and not by DNA.
So, that beautiful golden color you get when you lay out in the sun, the one you think makes you look so good? Yeah, not so good. That damage accumulates in your DNA, and over time can lead to skin cancer.
We do need some sun, so I’m not advocating staying inside on beautiful afternoons, just be careful and use sunscreen to decrease your risks of skin cancer.