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Part 1Human Evolution- Skulls Trend
Trends as you go from the ancestral primates to modern Human
The braincase becomes larger as the brow ridges become smaller and smaller. Additionally, the cranial ridge continues to fade as the time goes. This is due to the fact that, early humans pass through new business environmental challenges which made them evolve into bigger bodies with more complex brains(Craze, 2013). This is evidenced by the Australopithecus brain case was small which measured 4.5to transitional homoerectus and homosapiens who had a brain case of 11 inches. However other modern primates have extremely evolved showing larger forms of intelligence(Martínez-Abadías et al., 2012). For instance, a chimpanzee male has a brain case of 6.5 inches and a male gorilla has a larger braincase of 8.5 inches.
The trends of the teeth in human has been changing from large to smaller as canines get smaller and less sharp over the time. This is because human developed larger brain capacities which made them invent advanced tools thus chewing was made easier(Martínez-Abadías et al., 2011). This is evidenced by the modern apes like a male gorilla has very large and sharp canines followed by a chimpanzee. The Australopithecus had no defined incisors but big molars, homoeructus, and homo sapiens teeth are similar with equal size of incisors and small canines.
The palate has changed from a U shape to V shape. This is because the ancestral primates had no leveled teeth as compared to homo sapiens. The property leveled teeth of homelectus and homosapiens from the back of the mouth assist each other in lower and upper jaws which have developed multiple purposes(Craze, 2013).
Forehead in relation to the Face
The forehead of modern human have progressed to being parallel to the eyes as compared to Australopithecus which had a pushback forehead
Comparing with the Australopithecus which had very deep eye socket, the eyes socket of homosapiens have grown close together.Additionally, the homoerectus, and transitional homosapiens had also deep eyes sockets. The ancestral primates had a field visual that was not equally from both eyes as compared to the modern human where both right and left eyes have an equal field visual.
The ancestral primates had a snout that was pushed forward as compared to Homosapien whose snout is pushed inward(Martínez-Abadías et al., 2012). The Australopithecus had a long and wider nose as compared to a modern human whose nose is proportional to the size of the face(Craze, 2013).
The ancestral primate had a foramen magnum that was in the back of the skull which has progressed to the center of the skull(Martínez-Abadías et al., 2012). The homo erectus and homosapiens have a foramen magnum that in the middle of the skull.
Homo erectus was the first stage in human evolution where the hominids were able to walk upright. This is because, by observing all the species of hominids, the only homoerectus have a high similar characteristic with the modern man and homosapiens. In additional, Homoerectus have distinguished features that could have made them be the first hominids to walk upright. These include short zygomatic bones and foramen magnum located at the center.
Part 2 Comparative Study of Terrestrial Mammals (Herbivorous, Omnivores and Carnivorous)
Trends – Carnivorous, Omnivorous and herbivorous
The carnivorous have sharp-pointed canine teeth. Omnivorous teeth are at the same level as other teeth while herbivorous lack canine teeth(Kim et al., 2016)
Carnivorous mammals need canine teeth for tearing of fresh meat and hunting other animals. On the other hand, herbivorous lack canine teeth since they are just plant eaters(Prevosti, Turazzini, Ercoli, & Hingst-Zaher, 2012)
Carnivorous have intence molars as compared to herbivorous which have flat molars(Kim et al., 2016)
Since the herbivorous need to glide their food, their molars are flat. Carnivorous molars are spikey as they are used to break bones
The masseter muscles become enlarged from carnivorous to herbivorous
Carnivorous shred up food that they do not need larger masseter muscles. On the other hand, Herbivorous larger masseter muscles are used to assist in gridding food(Kim et al., 2016).
Carnivorous and herbivorous mammals have had eye sockets located on the sides but those of carnivorous are more intersecting. Omnivorous mammals’ eyes sockets are just below the forehead.
Carnivorous eye sockets are used to assist in hunting and locating the prey. Herbivorous eyes sockets are used to provide a good visual of the surrounding as a defense mechanism from the carnivorous(Prevosti et al., 2012).
The temporalis muscles decrease from carnivorous to herbivorous
The large temporalis muscles obtained from carnivorous are used for prey gripping. Due to the fact that herbivorous are plant eater, they do not require temporal muscles for hunting the prey.
The number of teeth decreases from carnivorous to herbivorous as the number of molars increases. Incisors and molars are present to all groups but the herbivorous lack canines(Nelson, Rogers, & Brown, 2013).
Herbivorous lack canine teeth thus they have less number of teeth as compared to carnivorous and omnivorous(Clauss, Kleffner, & Kienzle, 2010). In addition, the number of molars increases due to the fact that herbivorous need more molars for grinding of food. The difference in dental formula is because all the three groups have different nutrition thus their teeth evolve differently.
The blowhole of a dolphin corresponds to nasal passages the terrestrial mammal's skull have. The terrestrial mammals are able to breathe through the use of snout and thus the dolphin blowhole operates in the same way. The dolphin's zygomatic bones are different as compared to carnivores since dolphins swallow fish as a whole but do not grip them but carnivorous always chew their food.
Considering that dolphins have many canines and incisors with pegged teeth, they are likely to swallow their prey as a whole. in addition, dolphins lack molars thus they are not likely to grid their food.
Part 3 Marine Mammals
Masseter and temporalis muscles
Dolphin have Pegged teeth
The dolphin have eye sockets located on the sides of the skull making them have an overlapping visual(Perrin, Wursig, & Thewissen, 2009)
Dolphins have very small masseter muscles nearer to based but their temporalis muscle are basically large(Perrin et al., 2009)
River otters have very large canine teeth and sharp molars
The eyes of river otters are located toward the sides of the skull
The River Otters have large masseter muscles but temporalis muscles are diminutive(Berta, Sumich, & Kovacs, 2005)
Sea otters have levelled molars and spikey and larger canine teeth
The eye sockets of a Sea Otter are located toward the sides of the skull
Sea Otters have large Tempolais and Masseter Muscles
The harp seal have small canine teeth and the molars are absent(Perrin et al., 2009)
The harp Seal eyes Sockets are located anonymously and nearby
Both the masseter and Temporalis muscles are very small near to absent(Perrin et al., 2009)
Gray seals have large canine but molars are absent
Gray Seals Eyes are located distantly toward the sides of the skull
Gray seals have regular sized masseter and temporalis muscles
The above marine animals can be grouped into three major categories. This includes the dolphins in one group, the Gray Seal and Harp Seal in another group and the final group could consist of River Otters and Sea Otters. The Dolphin, Harp Seal, and Gray seals have no molars but temporaries muscles. This means they can be able to tear food but cannot grid. However, the dolphins have pegged teeth as compared tp Harp Seal and Gray seal which has Canines thus differentiating them into two groups. In addition, the River Otters and sea otters have both masseter muscles and all type of teeth thus differentiating them to a very different group(Berta et al., 2005).
Comparative of Terrestrial and Harp Seal
Masseter and temporaries muscles
Eyes are located sideways to provide an extensive view
Have incisors and molars only but lack canines
Have large masseter muscles but lack temporalis muscles
Have sharp and spikey canine teeth. Molars are present
Have both masseter and temporalis muscles
Raccoon have both canines and flat molars
Have masseter but lack temporalis muscles
Leopards canine are sharp and spiky.
Have tempralis muscles but lack masseter muscles
Human have both flat canine and molars
Have both masseter and temporalis muscles
Harp seal have canines but lack molars
Lack both masseter and temporalis muscles
(Perrin et al., 2009)
Comparing all the above mammals with Harp Seal, the leopard has many mutual characteristics although the two mammals have differences when it comes to large temporalis muscles and molars.
1. Berta, A., Sumich, J. L., & Kovacs, K. M. (2005). Marine mammals: Evolutionary biology. Second Edition. Academic Press San Diego CA 494pp 1999 (Vol. 406). Retrieved from http://books.google.com/books?id=4sWbuL0hM1kC&pgis=1
2. Clauss, M., Kleffner, H., & Kienzle, E. (2010). Carnivorous mammals: Nutrient digestibility and energy evaluation. Zoo Biology, 29(6), 687–704.
3. Craze, P. (2013). Early human evolution and the skulls of Dmanisi. Significance, 10(6), 6–11.
4. Kim, S., Cho, Y. S., Kim, H. M., Chung, O., Kim, H., Jho, S., … Yeo, J. H. (2016). Comparison of carnivore, omnivore, and herbivore mammalian genomes with a new leopard assembly. Genome Biology, 17(1).
5. Martínez-Abadías, N., Esparza, M., Sjøvold, T., González-José, R., Santos, M., Hernández, M., & Klingenberg, C. P. (2012). Pervasive genetic integration directs the evolution of human skull shape. Evolution, 66(4), 1010–1023.
6. Martínez-Abadías, N., Mireia, E., Sjøvold, T., González-José, R., Santos, M., Hernández, M., & Klingenberg, C. P. (2011). Pervarsive genetic integration directs the evolution of human skull shape. Evolution, 1–14.
7. Nelson, T. M., Rogers, T. L., & Brown, M. V. (2013). The gut bacterial community of mammals from marine and terrestrial habitats. PLoS ONE, 8(12).
8. Perrin, W. F., Wursig, B., & Thewissen, J. G. M. (2009). Encyclopedia of Marine Mammals. Encyclopedia of Marine Mammals.
9. Prevosti, F. J., Turazzini, G. F., Ercoli, M. D., & Hingst-Zaher, E. (2012). Mandible shape in marsupial and placental carnivorous mammals: A morphological comparative business study using geometric morphometrics. Zoological Journal of the Linnean Society, 164(4), 836–855.