52- Great American Interchange

Back in episode 49, I mentioned the Great American Interchange, which took place three million years ago when North America and South America collided and were connected by the isthmus of Panama. However, I largely glossed over it as it was only of tangential relevance to the topic of the Wallace Line. So, today, let’s correct that oversight and explore the Great American Interchange…

Sources for this episode: 1) Domingo, L., Tomassini, R. L., Montalvo, C. I., Sanz-Pérez, D. and Alberdi, M. T. (2020), The Great American Biotic Interchange revisited: a new perspective from the stable isotope record of Argentine Pampas fossil mammals, Scientific Reports 10(1): 1608. 2) Marshall, L. G., Webb, S. D., Sepkoski, J. J. and Raup, D. M. (1982), Mammalian Evolution and the Great American Interchange, Science 215(4538): 1351-1357. 3) Weir, J. T., Bermingham, E. and Schluter, D. (2009), The Great American Biotic Interchange in birds, Proceedings of the National Academy of Sciences 106(51): 21737-21742. 4) Author unknown, Wikipedia (date unknown), Great American Interchange (online) [Accessed 15/06/2021 and 13/08/2021]. 5) Author unknown, Wikipedia (date unknown), δ13C (online) [Accessed 10/08/2021]. 6) Author unknown, Wikipedia (date unknown), δ18O (online) [Accessed 10/08/2021].

51- RuBisCO, C4 and CAM

Photosynthesis has proven a useful tool in life’s arsenal, but it isn’t perfect. This is because one of its enzymes- RuBisCo for short- is not equipped to deal with our oxygenated world and as such sometimes creates toxic by-products which the organism then has to expend energy to deal with. However, some plants have evolved strategies to deal with this issue. Instead of simply working with vanilla-flavoured C3 photosynthesis, they have switched to alternative strategies known as C4 or CAM photosynthesis…

Sources for this episode: 1) Cain, M. L., Bowman, W. D. and Hacker, S. D. (2011), Ecology (Second Edition). Sunderland, Massachusetts, Sinauer Associated Ltd. 2) Campbell, N. A., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Reece, J. B. (2018), Biology: a global approach, 11th edition (Global Edition), Harlow, Pearson Education Limited. 3) Hirst, K. K., ThoughtCo (Updated 13/11/2019), Adaptations to Climate Change in C3, C4 and CAM Plants (online) [Accessed 27/07/2021]. 4) Thain, M. and Hickman, M. (2014), Dictionary of Biology (Eleventh Edition). London: Penguin Books Ltd.

50- Kin Selection and Hamilton’s Rule

Altruism- or actions by organisms which ultimately provide a benefit to other organisms- have been puzzling evolutionary scientists since Darwin’s time. As such, attempts have been made to explain how this phenomenon comes about. One of these explanations is the subject of today’s episode- kin selection and Hamilton’s rule. Now, I am not going to go into the arguments and evidence for and against it, which is probably a topic for future episodes. For now, it’s probably best to say that my previous studies on the topic have taught me that there is a tangible divide within biology on this topic…

Sources for this episode: 1) Campbell, N. A., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Reece, J. B. (2018), Biology: a global approach, 11th edition (Global Edition), Harlow, Pearson Education Limited. 2) Dugatkin, L. A. (2007), Inclusive Fitness Theory from Darwin to Hamilton, Genetics 176(3): 1375- 1380. 3) The Editors, Encyclopaedia Britannica (2018), Kin selection (online) [Accessed 18/06/2021]. 4) Herron, J. C. and Freeman, S. (2015), Evolutionary Analysis (Fifth Edition, Global Edition). Harlow: Pearson Education Limited. 5) Oshaka, S., OUPblog (Oxford University Press, 2015), Kin selection, group selection and altruism: a controversy without end? (online) [Accessed 17/06/2021]. 6) Thain, M. and Hickman, M. (2014), Dictionary of Biology (Eleventh Edition). London: Penguin Books Ltd.

49- The Wallace Line

If Alfred Russell Wallace (1823- 1913) is thought of at all, he is an after-thought to his far more famous counterpart Charles Darwin and the theory of natural selection. However,he has also had an impact in other fields. Today, we’ll be exploring the Wallace Line and Wallace’s contribution to zoogeography.

Sources for this episode: 1) Cain, M. L., Bowman, W. D. and Hacker, S. D. (2011), Ecology (Second Edition). Sunderland, Massachusetts, Sinauer Associated Ltd. 2) Camerini, J. R., Encyclopaedia Britannica (2021), Alfred Russell Wallace (online) [Accessed 10/06/2021]. 3) The Editors, Encyclopaedia Britannica (2019), Wallace Line (online) [Accessed 10/06/2021]. 4) Marshall, M., New Scientist (2021), The other humans: The emerging story of the mysterious Denisovans (online) [Accessed 11/06/2021]. 5) Scoville, H., ThoughtCo (2020), What Is the Wallace Line? (online) [Accessed 10/06/2021]. 6) Smithsonian Tropical Research Institute, Phys (2016), Recent connection between North and South America reaffirmed (online) [Accessed 10/06/2021]. 7) Tang, C. M., Encyclopaedia Britannica (2018), Tethys Sea (online) [Accessed 11/06/2021]. 8) Thain, M. and Hickman, M. (2014), Dictionary of Biology (Eleventh Edition). London: Penguin Books Ltd. 9) University of Adelaide, Phys (2013), Mysterious ancient human crossed Wallace’s Line (online) [Accessed 10/06/2021]. 10) Author unknown, Understanding Evolution (Berkeley, date unknown), Biogeography: Wallace and Wegener (online) [Accessed 11/06/2021]. 11) Author unknown, Wikipedia (date unknown), Wallacea (online) [Accessed 11/06/2021].

48- The Creation of Chromosome 2

It’s a well-known fact that humans have 23 pairs of chromosomes- 46 chromosomes in total. However, chimpanzees have 48 chromosomes, as do the other ‘great apes’. Why is this? Well, it centres around human chromosome 2.

Sources for this episode: 1) Fullick A., Locke, J. and Bircher, P. (2015), A Level Biology for OCR A. Oxford: Oxford University Press. This is where I originally learned the chromosome numbers of horses and donkeys; however, I don’t have access to this book at the moment due to COVID. For an alternative source, see: Rodriguez, M., Understanding Genetics, The Tech Interactive (2007), Chimeras, Mosaics, and Other Fun Stuff: Why can’t mules breed? I understand that a horse and a donkey make a mule but why can’t 2 mules have a baby mule? (online) [Accessed 06/06/2021]. 2) IJdo, J.W., Baldini, A., Ward, D. C., Reeders S. T. and Wells, R. A. (1991) Origin of human chromosome 2: an ancestral telomere-telomere fusion, Proceedings of the National Academy of Sciences of the United States of America 88(20): 9051-9055. 3) Willey, J. M., Sherwood, L. M. And Woolverton, C. J. (2017), Prescott’s Microbiology, 10th edition (International Edition). New York, McGraw-Hill Education. 4) Young, W. J., Merz, T., Ferguson-Smith, M. A. and Johnston, A. W. (1960), Chromosome Number of the Chimpanzee, Pan troglodytes, Science 131(3414): 1672-1673. 5) Author unknown, Wikipedia (date unknown), Chimpanzee genome project (online) [Accessed 02/06/2021]. 6) Author unknown, WWF (date unknown) Great apes (online) [Accessed 06/06/2021].

47- Sibling Species

Moving away from previous topics somewhat, we’re going to dive back into ecological theory and discuss the concept of sibling species. What is a sibling species? Well, they’re species which appear broadly very similar, but do have some differences when you get up close. As we’ll see in today’s episode, sibling species are essentially part of the process of speciation..

Sources for this episode: 1) Eisenmann, E., Amadon, D., Banks, R. C., Blake, E. R., Howell, T. R., Johnson, N. K., Lowery, G. H., Parkes, K. C. and Storer, R. W. (1973), Thirty-Second Supplement to the American Ornithologists’ Union Check-List of North American Birds, Auk 90(2): 411-419. 2) Gittleman, J. L., Encyclopaedia Britannica (2019), Species (online) [Accessed 29/05/2021]. 3) Nelson, D., OSU Bio Museum (2015), Examples of sibling species (online) [Accessed 02/06/2021]. 4) Thain, M. and Hickman, M. (2014), Dictionary of Biology (Eleventh Edition). London: Penguin Books Ltd. 5) Author unknown, Wikipedia (date unknown), Alder flycatcher (online) [Accessed 02/06/2021].

46- Ediacaran Biota

Today, we’re going to be discussing the Ediacaran fauna. This is a faunal assemblage that came before the Cambrian Explosion (535-525 Mya) but is less well known. Unlike the Cambrian Explosion- which saw the creation of most of the phyla we know today- the Ediacaran biota is much less familiar. It also appears to be quite confusing in terms of what category its constituent organisms fall under…

Sources for this episode: 1) Campbell, N. A., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Reece, J. B. (2018), Biology: a global approach, 11th edition (Global Edition), Harlow, Pearson Education Limited. 2) Ebling, F. J. G., Encyclopaedia Britannica (2017), Integument (online) [Accessed 29/05/2021]. 3) Flannery, T. F., Encyclopaedia Britannica (2019), Cambrian explosion (online) [Accessed 27/05/2021]. 4) Grazhdankin, D. (2011), Ediacaran Biota. In: Reitner J. and Thiel, V. (eds) Encyclopedia of Geobiology. Encyclopedia of Earth Sciences Series. Springer, Dordrecht. 5) Herron, J. C. and Freeman, S. (2015), Evolutionary Analysis (Fifth Edition, Global Edition). Harlow: Pearson Education Limited. 6) Rafferty, J. P., Encyclopaedia Britannica (2018), Ediacaran Period (online) [Accessed 28/05/2021]. 7) Shen, B., Dong, L., Xiao, S. and Kowalewski, M. (2008), The Avalon Explosion: Evolution of Ediacara Morphospace, Science 319(5859): 81-84. 8) Thain, M. and Hickman, M. (2014), Dictionary of Biology (Eleventh Edition). London: Penguin Books Ltd. 9) Virginia Tech, ScienceDaily (2008), Two Explosive Evolutionary Events Shaped Early History Of Multicellular Life (online) [Accessed 28/05/2021]. 10) Windley, B. F., Encyclopaedia Britannica (2019), Ediacara fauna (online) [Accessed 28/05/2021]. 11) Author unknown, Wikipedia (date unknown), Ediacaran biota (online) [Accessed 28/05/2021]. 12) Author unknown, Wikipedia (date unknown), Marinoan glaciation (online) [Accessed 28/05/2021].

45- The DNA of Louis XVI

Almost no French king is more famous than Louis XVI, reigning during the turbulent times of the French Revolution at the tail-end of the eighteenth century. Previous studies have attempted to characterise his Y-chromosomal single tandem repeat (STR) profile, but were ultimately unsuccessful due to contradictions. So, today, let’s explore a 2016 study which analysed a loyalist-owned lock of hair and compared it to three living male-line relatives.
Sources for this episode: 1) Wikipedia articles were used to determine the number of generations between Louis XVI and Hugh Capet mentioned [Accessed 16/05/2021]. 2) Popkin, J. D. and Goodwin, A., Encyclopaedia Britannica (2021), Louis XVI (online) [Accessed 16/05/2021]. 3) Lucotte, G., Thomasset, T. and Wen, S. (2016), The DNA Y-STRs Profile of Louis XVI (1754-1793). International Journal of Sciences 5(4): 68-93. 4) Author unknown, Wikipedia (date unknown), Karl Wilhelm Naundorff (online) [Accessed 16/05/2021].

44- Point Mutations and Almonds

Point mutations can have a huge impact on the genome depending on where in the genetic code they occur. To illustrate this, we’re going to be looking at a case study in the form of almonds- formerly poisonous nuts which had their metaphorical fangs taken out by a single base change…
Sources for this episode: 1) Hardy, E. R., Encyclopaedia Britannica (2021), Saint Basil the Great (online) [Accessed 22/05/2021]. 2) Herron, J. C. and Freeman, S. (2015), Evolutionary Analysis (Fifth Edition, Global Edition). Harlow: Pearson Education Limited. 3) Leman, J., Scientific American (2019), The Bitter Truth: Scientists Sequence the Almond Genome (online) [Accessed 18/05/2021]. 4) Petruzzello, M., Encyclopaedia Britannica (2021), almond (online) [Accessed 18/05/2021]. 5) Sánchez-Pérez, R., Pavan, S., Mazzeo, R., Molodovan, C., Cigliano, R. A., Del Cueto, J., Ricciardi, F., Lotti, C., Ricciardi, L., Dicenta, F., López-Marquéz, R. L. and Møller, B. L. (2019), Mutation of a bHLH transcription factor allowed almond domestication, Science 364(6445): 1095-1098. 6) Author unknown, Wikipedia (date unknown), Almond (online) [Accessed 18/05/2021].

43- Two-Component Systems

Bacteria are far simpler in molecular terms than eukaryotes. However, they still need to be able to sense and respond to their environment. How do they do this? Enter the two-component system; a two-protein system which allows stimuli to be detected and gene expression altered using phosphate transfer.
Sources for this episode: 1) Madigan, M. T., Martinko, J. M., Dunlap, P. V. and Clark, D. P. (2009), Brock Biology of Microorganisms (12th Edition, International Edition), San Francisco: Pearson Benjamin Cummings Ltd. 2) Thain, M. and Hickman, M. (2014), Dictionary of Biology (Eleventh Edition). London: Penguin Books Ltd. 3) Willey, J. M., Sherwood, L. M. and Woolverton, C. J. (2017), Prescott’s Microbiology (10th Edition, International Edition), Singapore: McGraw Hill Education Ltd. 4) Author unknown, Wikipedia (date unknown), Osmotic concentration (online) [Accessed 27/05/2021].