User:Toddy.6osu/sandbox

Hunter's Sandbox Annotated Bibliography

Marx, F.G. (2011). The More the Merrier? A Large Cladistic Analysis of Mysticetes, and Comments on the Transition from   Teeth to Baleen. Journal of Mammalian Evolution, 18(2), 77-100. This paper creates a phylogenetic analysis of whales, grouping them into their most parsimonious relations. This will be helpful in writing about whale teeth because it makes it easier to define the groups of whales which I will be speaking about and possibly draw conclusions about where these adaptations sprouted from.

Cheng, J. Gatesy, J. Meredith, R.W. Springer, M.S. (2011). Pseudogenization of the tooth gene enamelysin (MMP20) in the common ancestor of extant baleen whales. Proceedings of the Royal Society B-Biological Sciences, 278(1708), 993-1102.

This paper suggests precisely where common teeth were lost within baleen whales' evolutionary history. Studies were done analyzing genes and their loss within certain species which could have lead to the adaptation that we now see in baleen whales.

Davit-Beal, T. Sire, J.Y. (2009). Tucker A.S. Loss of teeth and enamel in tetrapods: fossil record, genetic data and morphological adaptations. Journal of Anatomy, 214(4), 477-501.

Researchers for this paper suggest that “functional teeth” were only allowed to be lost through natural selection because secondary adaptations made selection upon these functional teeth weaker. Thus it suggests that the evolutionary history of these secondary adaptations predates that of tooth loss.

Reidenerg, J.S. (2007). Anatomical adaptations of aquatic mammals. Anatomical Record-Advances in Integrative Anatomy and Evolutionary Biology, 290(6), 507-513.

This paper covers the topic of many different adaptations which aquatic mammals have acquired in order to thrive in water environments. The baleen whale and its adaptations are covered within this article as well which makes it useful for my paper to come.

Fitzgerald, E.M.G. (2006). A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales. Proceedings of the Royal Society B-Biological Sciences, 273(1604), 2955-2963.

This paper disputes common thought of baleen adaptations originating in distant ancestors of these animals. Instead it proposes the idea that filter feeding as seein in baleen whales has been a slow process.

Oct 1st: Wiki Assignment 2

https://en.wikipedia.org/wiki/Baleen_whale The evolution of Mysticeti as evidenced by the fossil record, was a gradual one that involved the transition from toothed, to teeth along with baleen, and finally to strictly baleen.

I think it might be useful to include something on fetal development within the "life history" section. Specifically that of tooth formation/resorption. Particularly since the baleen dental structure is one of the most interesting adaptations of this organism. It's definitely eluded to within the first paragraph but not elaborated upon. Furthermore, the sections on certain physical structures (ie jaw) don't seem to be fully fleshed out. Finally, I feel as though this article could benefit from a more in depth Evolutionary history section.

FINAL DRAFT

Mysticeti, or more commonly known as baleen whales, include some of the largest known species of animals on the planet today. What is so unique about this group of animals is their unique mode of feeding. Their feeding style allows for the species to grow to gargantuan sizes without over-stressing their prey source (Potvin, Goldbogen and Shadwick 2012). This mode of feeding is called “filter feeding” and is seen in two different forms within the species (Reidenberg 2007). These two forms are continuous and intermittent, and distinguishing amongst the two is done by observing the duration of the animal's open mouth when feeding. The process involves the animal swimming through a large group of prey (for example zooplankton) with its mouth open in order to catch them within its unique dental structure. The prey becomes stuck in the whale's teeth and then the water is forcefully flushed back out of its mouth. This incredible style of feeding would be impossible without several adaptations (including a powerful tongue, and unique jaw structure), but the most notable is their incredible dental structure, known as baleen. The baleen allows the animal to catch and then filter organisms down into its mouth with its distinct shape and structure (similar in appearance to a rake). The evolution of this novel adaptation has had much study surrounding it, from its gradual appearance in ancestors, to other adaptations which relaxed evolutionary constraints on the baleen itself, and finally the genetic basis for the appearance of baleen. This extensive study is in order to more fully understand the creatures possessing this novel adaptation, as the topic is incredibly relevant to the study of evolutionary biology for many reasons which will be discussed later. Interest in the evolutionary history of baleen whales has become more prevalent in recent years, yet the debate about evolutionary relationship is still unsolved (Marx 2011). Properly classifying these animals may help to spot the exact evolutionary origins of the baleen within the common ancestor of present day baleen whales. All who work on this subject agree that the phylogeny of these animals is complex, with many different traits which must be considered in order to best determine the relationship amongst these animals. Generally, Marx's classification of baleen whales is characterized by a transition from toothed whales, to whales who posses both teeth and baleen, to fully baleen whales (Marx 2011). This indicates that the evolutionary processes involved with this adaptation worked very slowly. These processes most likely include a mutation which caused the trait to arise, natural selection which then enforced the prevalence of the new trait and finally fixation of the trait within baleen populations. However, the advantage that an individual gained by possessing baleen in place of typical teeth must have been very small. Or more specifically, the fitness of individuals possessing baleen would not have greatly outweighed the fitness of those without. This can be speculated because if individuals possessing baleen had a much greater fitness than those without, we would expect to see their genes (and thus baleen) passed along to later generations at a faster rate. This would ultimately lead to the fixation (the sole prevalence of the trait within baleen whale populations) of the trait within the species rapidly. Furthermore, the discovery of ancestral species of baleen whales constantly challenges old theories and adds new characteristics that we can classify mysticeti by (Gol'din and Startsev 2014). These other evolved traits, such as large body size and visual acuity, are also very important in classifying these animals properly (Fitzgerald 2006). This is partially why developing a proper phylogeny of common day mysticetes and their ancestors has proven to be very difficult, and thus the exact evolutionary origin of baleen remains elusive. Although the adaptation of interest within this paper is baleen, it is useful to track other traits which arose within mysticeti which allowed the baleen to persist and eventually thrive. Researchers suggest that filter feeding as a behavior arose prior to the evolution of modern baleen (Davit-Beal and Sire 2009). Instead, individuals who invested in this behavior possessed a primitive form of baleen along with common teeth (Davit-Beal and Sire 2009). Furthermore, an incredibly powerful tongue is necessary for this behavior to be successful, as it helps to move organisms that are caught within the baleen farther into the whale's mouth (Reidenberg 2007). Due to the success of filter feeding as a mode of prey acquisition, it is assumed that the selectional pressures on common teeth were lessened and thus baleen was positively selected for because it increased the fitness of individuals possessing it (Davit-Beal and Sire 2009). Therefore, baleen “facilitated the exploitation of an unexploited ecological niche, bulk filter-feeding and laid the foundation for the evolution of the largest animals on the Earth” (Cheng, Gatesy and Springer 2011). As evidenced by these researchers, the behavior of filter feeding was the first novel trait which then allowed for the evolution and later fixation of baleen. This is further evidenced by work done by scientists today on current species of baleen whale, who study diving behavior along with filter feeding behavior (Goldbogen et al 2013). These researchers work has helped to support the idea that filter feeding first developed as a behavior prior to the fixation of baleen in these organisms. Finally, it is useful to study the genetic basis of baleen in order to track its evolutionary origins. Researchers studied many different genetic sequences which were common to the baleen family and coded for tooth structure. These genes included ameloblastin, enamelin, and amelogenin, however none of these were shared by all mysticetes both past and present (Cheng, Gatesy and Springer 2011). Enamelysin is coded for in baleen whales in the gene known as MMP20 (Cheng, Gatesy and Springer 2011). When studying this gene within several species of mysticete, researchers found a very interesting SINE insertion shared by 8 mysticete species, which are representative of all extant mysticete species (Cheng, Gatesy and Springer 2011). This insertion is what caused an end to enamel production in the common ancestor of mysticetes (Cheng, Gatesy and Springer 2011). This is especially interesting because SINE insertions are most often deleterious to species, resulting in a decrease in overall fitness (Cheng, Gatesy and Springer 2011). Thus, researchers argue that this is evidence that there was selection against the deleterious effects typical of a SINE insertion. This is evidenced by the fact that the loss of enamel (and subsequent gain of baleen) is characterized by an uncharacteristic increase in fitness. Therefore, it is unclear whether the MMP20 insertion was actually selected for by natural selection, or if functional constraints (and thus natural selection) were relaxed due to the adaptation of filter feeding (Cheng, Gatesy and Springer 2011). Regardless, it is clear that this mutation in the genome which brought out new diversity within extant mysticete species is the beginning of the evolution of baleen. The study of dental evolution within baleen whales is incredibly important for many reasons. First, it challenges our belief that evolutionary changes must be due to large changes in fitness, and that evolution operates in a clear stepwise format. Instead we see that the fitness differences in baleen whales were very small and thus lead to a very gradual (and often convoluted) evolution of the adaptation. Next, because the transition was so slow, baleen highlights the transition between traits which is often difficult to see in extinct species when relying solely on our fossil record. These other traits include a powerful tongue, and the behavior of filter feeding itself. Many traits which appeared long ago are difficult to track because of their sudden “appearance” in the fossil record. This is primarily due to the inconsistencies associated with relying solely upon the fossil record (differences in species preserved, traits that aren't preserved by the fossil record, etc). Finally, baleen is a trait with a genetic basis (MMP20) which can be directly linked to a particular behavior, filter feeding. This is interesting to the study of animal behavior today as that field seeks to understand both the genetic and environmental causes of behavior. Therefore, the study of the evolution of baleen in mysticeti is an on-going but incredibly relevant topic to many different fields that deserves further attention.

References Marx, F.G. (2011). The More the Merrier? A Large Cladistic Analysis of Mysticetes, and Comments on the Transition from Teeth to Baleen. Journal of Mammalian Evolution, 18(2), 77-100. Cheng, J. Gatesy, J. Meredith, R.W. Springer, M.S. (2011). Pseudogenization of the tooth gene enamelysin (MMP20) in the common ancestor of extant baleen whales. Proceedings of the Royal Society B-Biological Sciences, 278(1708), 993-1102. Davit-Beal, T. Sire, J.Y. (2009). Tucker A.S. Loss of teeth and enamel in tetrapods: fossil record, genetic data and morphological adaptations. Journal of Anatomy, 214(4),477-501. Reidenberg, J.S. (2007). Anatomical adaptations of aquatic mammals. Anatomical Record-Advances in Integrative Anatomy and Evolutionary Biology, 290(6), 507-513 Fitzgerald, E.M.G. (2006). A bizarre new toothed mysticete (Cetacea) from Australia and	the early evolution of baleen whales. Proceedings of the Royal Society B-Biological Sciences, 273(1604), 2955-2963. Gol'din, P. Startsev, D. (2014). Brandocetus, a new genus of baleen whales (cetacea,cetotheridae) from the late Miocene of Crimea, Ukraine. Journal of Vertebrate Paleontology, 34(2), 419-433. Goldbogen, J.A. Friedlaender, A.S. Calambokidis, J. McKenna, M.F. Simon, M. Nowacek, D.P. (2013) Integrative approaches to the study of baleen whale diving behavior, feeding performance, and foraging ecology. Bioscience, 63(2), 90-100. Potvin, J. Goldbogen, J.A. Shadwick, R.E. (2012) Metabolic expenditures of lunge feeding rorquals across scale: Implications for the evolution of filter feeding and the limits to maximum body size. PLOS ONE, 7(9).

FINAL WIKI EDIT

Dentition Mysticeti possess an incredibly unique form of dentition, known as "baleen plates" or simply "baleen". The evolution of this novel adaptation has had much study surrounding it, from its gradual appearance in ancestors, to other adaptations which relaxed evolutionary constraints on the baleen itself, and finally the genetic basis for the appearance of baleen. The evolutionary processes involved with this adaptation operated very slowly. These processes most likely include a mutation which caused the trait to arise, natural selection which then enforced the prevalence of the new trait and finally fixation of the trait within baleen populations. This is evidenced by the fossil record which shows ancestral forms of mysticeti who possess both baleen and regular teeth. Traits which unfortunately cannot be supported by the fossil record include behavioral traits. Researchers suggest that filter feeding as a behavior arose prior to the evolution of modern baleen. Instead, individuals who invested in this behavior possessed a primitive form of baleen along with common teeth. Due to the success of filter feeding as a mode of prey acquisition, it is assumed that the selectional pressures on common teeth were lessened and thus baleen was positively selected for because it increased the fitness of individuals possessing it. Having baleen also allowed for the size of these whales to increase, as they were able to occupy a new niche and expand their food source. Another aspect of studying dental evolution in baleen whales is the genetic mutation which arose to create this novel trait. Enamelysin is coded for in baleen whales in the gene known as MMP20. When studying this gene within several species of mysticete, researchers found a very interesting SINE insertion shared by 8 mysticete species, which are representative of all extant mysticete species. This insertion is what caused an end to enamel production in the common ancestor of mysticetes. Researchers argue that this is evidence that there was selection against the deleterious effects typical of a SINE insertion. It is clear that this mutation in the genome which brought out new diversity within extant mysticete species is the true beginning of the evolution of baleen.

https://en.wikipedia.org/wiki/Baleen_whale