Hi everyone, just a quick plug for my other show- After Alexander. This is a history podcast where we examine what happened between Alexander the Great’s death in 323 and the destruction of the last of the Hellenistic kingdoms by the Romans and Parthians. Specifically, it focuses on the Seleucid dynasty, descended from Seleucus I Nicator and eventually rulers over most of Alexander’s old empire in their glory days. If that sounds like it might be for you, feel free to head over and join us! Regular content resumes next week.
22- The Central Indo-Pacific
The Central Indo-Pacific (or CIP if you’re stuck for time) is a highly diverse region of the ocean. But how did it get to be this way? That’s what I’m going to be discussing, based on facts collated from the primary literature.
Sources for this episode: 1) Author unknown, Wikipedia (date unknown), Eocene (online) [Accessed 17/01/2021]. 2) Siqueira, A. C., Bellwood, D. R. and Cowman, P. F. (2019), Historical biogeography of herbivorous coral reef fishes: The formation of an Atlantic fauna. Journal of Biogeography: DOI: 10.25903/5cd265eb0a405. 3) Renema, W., Bellwood, D. R., Braga, J. C., Bromfield, K., Hall, R., Johnson, K. G., Lunt, P., Meyer, C. P., McMonagle, L. B., Morley, R. J., O’Dea, A., Todd, J. A., Wesselingh, F. P., Wilson, M. E. J. and Pandolfi, J. M. (2008), Hopping Hotspots: Global Shifts in Marine Biodiversity. Science (321): 654- 657. 4) Ivany, L. C., Patterson, W. P. and Lohmann, K. C. (2000), Cooler winters as a possible cause of mass extinctions at the Eocene/Oligocene boundary. Nature 407: 887- 890. 5) Author unknown, Wikipedia (date unknown), Coral (online) [Accessed 17/01/2021]. 6) Miller, E.C., Hayashi, K. T., Song, D., Wiens, J. J., (2018) Explaining the ocean’s richest biodiversity hotspot and global patterns of fish diversity. Proceedings of the Royal Society B 285: 20181314. 7) Jones, K. R., Klein, C. J., Halpern, B. S., Venter, O., Grantham, H., Kuempel, C. D., Shumway, N., Friedlander, A. M., Possingham, H. P. and Watson, J. E. M. (2018), The Location and Protection Status of Earth’s Diminishing Marine Wilderness. Current Biology 28: 2506- 2512.
As far as I am aware, the separate elements and studies that I mention have not been collated into one paper. So, although our discussion is based off scientific literature, it might potentially be best to view it as just that- a discussion. I mention this note of caution simply because I am not an expert in this field.
21- The Black Queen Hypothesis
Building on our discussion of the Red Queen hypothesis last week, we’re going to go through a theorem which is similarly chess-themed but goes against our hypothesis from episode 20. This theory holds that, rather than continual evolution being necessary for a species to survive, natural selection can sometimes allow genes to be lost from the gene pool.
Sources for this episode: 1) Author unknown, Wikipedia (date unknown), Black Queen hypothesis (online) [Accessed 15/01/2021]. 2) Morris, J. J., Lenski, R. E. and Zinser, E. R. (2012), The Black Queen Hypothesis: Evolution of Dependencies through Adaptive Gene Loss. mBio 3(2): e00036-12. 3) Willey, J. M., Sherwood, L. M. and Woolverton, C. J. (2017), Prescott’s Microbiology (Tenth Edition, International Edition). New York: McGraw Hill Education. 4) Allen, R. C., Popat, R., Diggle, S. P. and Brown, S. P. (2014), Targeting virulence: can we make evolution-proof drugs? Nature Reviews Microbiology 12(4): 300- 308.
20- The Red Queen Hypothesis
This week, I’m going to discuss the Red Queen Hypothesis, which sounds intimidating but is actually rather straightforward. Not only is it an evolutionary theory, but it’s also a reminder that biologists really like finding obscure reasons to name things…
Sources for this episode: 1) Author unknown, Wikipedia (date unknown), Red Queen Hypothesis (online) [Accessed 14/01/2021]. 2) Thain, M. and Hickman, M. (2004), The Penguin Dictionary of Biology (11th edition). London: Penguin Books Ltd. 3) Scoville, H., ThoughtCo (updated 2019), What Is the Red Queen Hypothesis? (online) [Accessed 14/01/2021].
Darwin’s Day 2021
Happy Darwin’s Day! On the anniversary of Darwin’s birthday on 12th February 1809, I thought it would be fun to release a special episode covering some aspect of Darwin’s life or theories. Today, we’re going to discuss the health of Darwin’s children and of Darwin’s immediate family, using a 2017 paper by Hayman et al.
Sources for this episode: 1) Hayman, J., Álvarez, G., Ceballos, F. C. and Berra, T. M. (2017), The illnesses of Charles Darwin and his children: a lesson in consanguinity. Biological Journal of the Linnean Society 121: 458- 468. Information on the immediate family of Charles Darwin can also be found on Wikipedia, whether his article or the article on the Darwin-Wedgewood family.
19- How Evolution Works
This week, I’m going to do something a little different and talk through a process we hear a lot about, but which isn’t often discussed as a process outside biology classrooms very much- evolution. This episode will be a little different from my usual, as it’s mainly going to be me talking rather than drawing on sources. Instead, this discussion is going to be based on my biological education so far.
Update on the ‘conditions explained’ series
Hi everyone, Vince here with a quick update.
I’ve been thinking of explaining the cause of some more illnesses and/or conditions, as I have already done with porphyria and leprosy. Where applicable, I might also use some real-life historical examples of sufferers, such as with George III and Baldwin IV of Jerusalem for the two cases mentioned above.
I don’t know exactly what this would include, but I might, for example, a post about heterochromia or arthritis. Alternatively, I might expand the idea to include phenomena such as the cause of tabby/calico patterns in cats.
However, I thought it would be interesting to see what you think. If I were to make this into a series of posts, which condition should I cover next? Let me know what you think in the comments!
- Image Credit:
- Image: Pixabay
- User: vjohns1580
- Featured image: Medical Record Health – Free photo on Pixabay
- Image labelled for reuse
- No changes have been made
18- Apoptosis
Apoptosis is the phenomenon by which cells commit suicide in an orderly and programmed fashion. But why is it important? And what happens if it goes wrong? Today, we’re just going to introduce the topic briefly and give some examples of why it is biologically useful.
Sources for this episode: 1) Alberts, Johnson, Lewis, Raff, Roberts, and Walter (2008), Molecular Biology of the Cell, Fifth Edition. Abingdon: Garland Science, ‘Taylor and Francis Group LLC’. 2) Thain, M., and Hickman, M. (2014), The Penguin Dictionary of Biology, 11th edition. London: Penguin Publishing Group.
17- How To Make An Eye Colour
Eye colour is one of the first examples of genetic inheritance talked about in schools across the country. But what is it that these genes really do? What causes eye colour from a functional perspective? As we’ll see on the podcast today, it’s all to do with the pigment melanin…
Sources for this episode: 1) Sturm, R. A. and Frudakis, T. N. (2004), Eye colour: portals into pigmentation genes and ancestry. Trends in Genetics 20(8): 327- 332. 2) Alberts, Johnson, Lewis Raff, Roberts, and Walter (2008), Molecular Biology of the Cell, Fifth Edition, p.786. Abingdon: Garland Science, Taylor and Francis Group LLC.
Making a phylogenetic tree
I thought I’d take a moment to discuss how exactly biologists create phylogenetic trees. Our discussion will not include factors such as morphological comparisons etc.- which was more widely used before genetics came along- but rather the molecular methods used today. I thought this would be better served as a blog post rather than a podcast episode, as in blog format I can use images to illustrate what I’m saying (which is predictably rather difficult in audio format!).
So, let’s say that you’re an ecologist who’s just discovered an uninhabited island far out to sea. There’s three species of snake on this island (hence the picture at the top) and you want to know how long ago these species diverged from their common ancestor. You find a fossil which tells you that species A and species C must have diverged 15 million years ago, but you can’t find anything for the other species. So, instead, you sequence a protein common to all species (let’s say haemoglobin for the sake of argument) which gives you the results in Table 1. How does this help you?
Looking at our table, you can see that, in 15 million years, there have been thirty amino acid sequence changes between species A and species C. However, this doesn’t quite give us our rate of mutation yet. To know why this is the case, you’ve got to consider that both species have been evolving away from their common origin. This means that we’ve effectively got to double the time between them to 30 million years. After all, species A has been evolving for 15 million years and species C has been.
This means that, if we assume a constant mutation rate, we end up with a rate of 1 mutation per million years. What we’ve done is calibrate our molecular clock- we now know the rate of mutation for the protein we’re using to build our tree.
So, let’s now look at the difference between species B and species C, which is also 30 mutations. This means that these two species also had a total evolution time of thirty million years. Dividing by two, we get a divergence time of 15 million years, as with species A. By contrast, species A and species B have eleven amino acid differences, meaning that they must have diverged 5.5 million years ago.
How does all of this fit together? Well, A and B must have diverged after both the A-C divergence or the B-C divergence. This means that C must have split off from the common ancestor first, and then A and B diverged, as shown below:
Of course, there are some assumptions we’ve made while constructing our tree, such as a constant rate of mutation. Added to this, most phylogenies will be a lot more complicated than just three species. However, it serves well as an example of the process by which such tree are constructed. A more in-depth discussion of these assumptions, as well as the process of speciation itself, is a story for another time.
- Image Credit:
- Image: Pixabay
- User: Syaibatulhamdi
- Featured image: Mountains Photographer Man – Free image on Pixabay
- Image labelled for reuse
- No changes have been made