Here is my paper on darwin and his theory of evolution, I will be posting pictures as well as the paper, I hope you guys enjoy reading it.
Natacha Revelus
April 21, 2008
Bio. 1040
Darwin’s Theory of Evolution:
Turtles & Tortoises
April 21, 2008
Bio. 1040
Darwin’s Theory of Evolution:
Turtles & Tortoises
When you think of the phrases: battle of the fittest or only the strongest survive, does evolution come to mind? Well, for me I always think about Darwin and his Theory of Evolution. Darwin’s research on the Galapagos Islands was a major scientific break-through. It helped shaped a lot of ideas and hypothesis about evolution of mankind and animals alike. Although the theory of evolution was not new, Darwin developed the more modern version of the theory. He along with Alfred Russel Wallace proposed the principle of natural selection (Darwin, 2008). Eventually, after conducting all his testes, Darwin published his finding in, The Origin of the Species by Natural Selection.
Darwin’s foundation for his works is the process or theory of Natural Selection. Natural selection according to Darwin is the fact that animals that are better suited or that are more adaptable to their environment have a better chance of survival and ability to breed. If for example a land tortoise has a longer neck than the other and can feed off of the higher plants, that tortoise has more of a chance to outlive the other and breed with the female tortoises to pass on the favorable characteristics to their offspring.
Darwin made very distinctive discoveries about the tortoises and finches of the Galapagos. “A tortoise of finch on one island was not quite like a tortoise or finch on another island. By looking at the shell of a tortoise of the beak of a finch you could tell which island it had come from (Darwin, 2008).
The Galapagos tortoise most closely resembled the South American tortoises; isolated on these remote islands, these tortoises has evolved distinctive forms (Johnson, 1998-2008). “Of course, because of adaptation to localized habitats, island forms are not identical to those on the nearby continents. The turtles have evolved different shell shapes, for example; those living in moist habitats have dome-shaped shells while others living in dry places have low, saddle-backed shells with the front of the shell bent up to expose the head and neck” (Johnson, 1998-2008).
This example is relevant to the exercise that we conducted in class. The 8 turtles and tortoises that we introduced to us in class share some of the same characteristics as the ones studied by Darwin. For example, turtles number 1, 4, and 5 are box turtles who all eat plants and insects, with a hinge in the under belly of their shells and although they are called turtles and are supposed to be in water they can also live on land. These shells of these turtles distinguish their genders. Colorful shells belong to the males whereas the plain shells belong to the females. I believe that this adaptive nature of the box turtle allows it to travel and be able to thrive in other environments outside of its natural habitat if Texas.
The Russian tortoise of course is a land animal. It’s a vegetarian. These tortoises have a distinctive shell that’s usually a ruddy brown or black, fading to yellow between the scutes. The male in this species has a long tail that is tucked to the side and females have a short tail. However the females grow slightly larger than the males. Upon observing this animal we noticed that the snout is somewhat beak-shaped and it has very long claws which can be used for digging. According to Wikipedia, they are avid burrowers and can dig large burrows that might be two meters (several feet) long (Wikipedia, 2008). This tortoise was also observed to be agile and fast-paced.
The Red-foot tortoise is a native of South America. It is named from the red or orange scales on its limbs and also on its head and tail. They can live in a variety of habitats including grasslands and but prefer humid forested areas (Wikipedia, 2008). Being primarily a forest dweller, they have evolved a high domed narrow width carapace to facilitate getting between narrow openings of trees and vegetation in the rain forest (Wikipedia, 2008). Males in this species have a concave shaped shell and a much longer pointed tail which makes it easy for them to mate, the females, on the other hand, have a flat shaped shell and a stubby tail. In the case of evolution, red-foot tortoises are very sensitive to environmental changes. When first introduced to a new environment they will go for long periods of time without eating. It is not until they feel comfortable in their new environment, that they will start eating again. We observed that they have a short snout and that is good for eating most vegetables and fruits, especially dark green leafy vegetables (Wikipedia, 2008).
Our colorful friend the Central American Ornate Wood Turtle is another one that is adaptive enough to live both in water and on land. They like to live shallow waters but if in captivity can also live on damped sand and cypress mulch, sheets of bark and piles of hay or leaves which adds secure hiding places for it (Animal-World, 1998-2008). There is quite a variation of color along this species. Those from southern Nicaragua are bland compared to those from northern Costa Rica which are brightly colored. Some of them are covered with swirls of orange and yellow with different degrees of black ocelli (eyespots) on the shell, just like the one we observed in class. This animal had short claws and tail, which we assumed that it was a female also because it had the triangular shaped shell. The shell also has a hinge for when the turtle retreats into its shell. Our turtle had a long neck which is useful in the wild because it can reach up for food and is very agile. Those, ornate wood turtles, kept in captivity then released into the wild wont be able to adapt or survive due to their inability to cope with extreme weather changes and many surely fall prey quickly to the wary predators they may encounter (Animal-World, 1998-2008).
The yellow-foot tortoise is the larger cousin of the red-foot tortoise. This name is derived from its several yellow head scales and its carapace is black with a small, distinct yellow area around the areola on each shell scale (Wikipedia, 2008). The adult males are bigger than the females however they are also much lighter than the females. Like the one we had in class, mature yellow-foots have distinctive incurving on the side of their shells, giving them a well-defined “waist” (Wikipedia, 2008). In addition, the plastron is extremely concave in males which make it easy for him to mate with the female who has a very flat plastron and short stubby tail. These species are found in the drier forest areas, grasslands, and the savanna, or the rainforest belts adjoining more open habitats (Wikipedia, 2008). Because of their considerably short neck and snout, the yellow foot’s diet consist of grasses, fallen fruits, plants, and any slow moving animals like snails, worms, and others that they are able to capture (Wikipedia, 2008); as you’ve probably have already guessed these creatures do not move fats at all compared to the other tortoises that we observed. This species has a very interesting evolutionary trait; it is interesting to note than in almost every tortoise species where male combat occurs, the males are always larger than the females. This is in comparison to aquatic species, where the males are usually smaller than the females and do not engage in male to male combat. It is thought that species with male combat evolved larger males because larger males have a better chance of winning a bout and mating with a female, thus passing on their larger size to their offspring. Species with smaller males evolved because smaller males are more mobile and can mate with a large number of females, thus passing on their genes (Wikipedia, 2008). Now that’s survival for ya!
The last turtle observed was the only true full water turtle: the mudd turtle from North America. This little creature prefers to live in shallow, slow moving bodies of water with muddy bottoms. Also they have a dome shaped carapace (Wikipedia, 2008). Even though they are small they can live up to 50 years old! It’s known for it’s dull shell and has a black under belly which helps it to camoflague well in seaweed, protecting it against predators. Also, this little guy is carnivorious, and will consume almost anything they can catch including small fish, worms, insects, grubs, crustaceans, tadpoles, small berries and even carrion. In this species the females are generally larger than the males but the males have a much longer tail, furthermore they can be black, brown, green or yellowish in color (Wikipedia, 2008).
Each of the turtles observed had their own specific traits and characteristics for survival and battle of the fittest. A lot of them have overcome the natural selection process because they are so adaptive, hence the turtles and tortoises that can live in both water and on land. Shell size, snout size, length of neck and mobility all play a major role in determinig which species can and will outlive the other and has the strongest genes/characteristics to pass on to the next generation.
Works Cited
http://en.wikipedia.org/
http://www.zephyrus.co.uk/charlesdarwin.html
http://txtwriter.com/Backgrounders/Evolution/EVpage15.html
http://animal-world.com/encyclo/reptiles/turtles/OrnateWoodTurtle.php
Darwin’s foundation for his works is the process or theory of Natural Selection. Natural selection according to Darwin is the fact that animals that are better suited or that are more adaptable to their environment have a better chance of survival and ability to breed. If for example a land tortoise has a longer neck than the other and can feed off of the higher plants, that tortoise has more of a chance to outlive the other and breed with the female tortoises to pass on the favorable characteristics to their offspring.
Darwin made very distinctive discoveries about the tortoises and finches of the Galapagos. “A tortoise of finch on one island was not quite like a tortoise or finch on another island. By looking at the shell of a tortoise of the beak of a finch you could tell which island it had come from (Darwin, 2008).
The Galapagos tortoise most closely resembled the South American tortoises; isolated on these remote islands, these tortoises has evolved distinctive forms (Johnson, 1998-2008). “Of course, because of adaptation to localized habitats, island forms are not identical to those on the nearby continents. The turtles have evolved different shell shapes, for example; those living in moist habitats have dome-shaped shells while others living in dry places have low, saddle-backed shells with the front of the shell bent up to expose the head and neck” (Johnson, 1998-2008).
This example is relevant to the exercise that we conducted in class. The 8 turtles and tortoises that we introduced to us in class share some of the same characteristics as the ones studied by Darwin. For example, turtles number 1, 4, and 5 are box turtles who all eat plants and insects, with a hinge in the under belly of their shells and although they are called turtles and are supposed to be in water they can also live on land. These shells of these turtles distinguish their genders. Colorful shells belong to the males whereas the plain shells belong to the females. I believe that this adaptive nature of the box turtle allows it to travel and be able to thrive in other environments outside of its natural habitat if Texas.
The Russian tortoise of course is a land animal. It’s a vegetarian. These tortoises have a distinctive shell that’s usually a ruddy brown or black, fading to yellow between the scutes. The male in this species has a long tail that is tucked to the side and females have a short tail. However the females grow slightly larger than the males. Upon observing this animal we noticed that the snout is somewhat beak-shaped and it has very long claws which can be used for digging. According to Wikipedia, they are avid burrowers and can dig large burrows that might be two meters (several feet) long (Wikipedia, 2008). This tortoise was also observed to be agile and fast-paced.
The Red-foot tortoise is a native of South America. It is named from the red or orange scales on its limbs and also on its head and tail. They can live in a variety of habitats including grasslands and but prefer humid forested areas (Wikipedia, 2008). Being primarily a forest dweller, they have evolved a high domed narrow width carapace to facilitate getting between narrow openings of trees and vegetation in the rain forest (Wikipedia, 2008). Males in this species have a concave shaped shell and a much longer pointed tail which makes it easy for them to mate, the females, on the other hand, have a flat shaped shell and a stubby tail. In the case of evolution, red-foot tortoises are very sensitive to environmental changes. When first introduced to a new environment they will go for long periods of time without eating. It is not until they feel comfortable in their new environment, that they will start eating again. We observed that they have a short snout and that is good for eating most vegetables and fruits, especially dark green leafy vegetables (Wikipedia, 2008).
Our colorful friend the Central American Ornate Wood Turtle is another one that is adaptive enough to live both in water and on land. They like to live shallow waters but if in captivity can also live on damped sand and cypress mulch, sheets of bark and piles of hay or leaves which adds secure hiding places for it (Animal-World, 1998-2008). There is quite a variation of color along this species. Those from southern Nicaragua are bland compared to those from northern Costa Rica which are brightly colored. Some of them are covered with swirls of orange and yellow with different degrees of black ocelli (eyespots) on the shell, just like the one we observed in class. This animal had short claws and tail, which we assumed that it was a female also because it had the triangular shaped shell. The shell also has a hinge for when the turtle retreats into its shell. Our turtle had a long neck which is useful in the wild because it can reach up for food and is very agile. Those, ornate wood turtles, kept in captivity then released into the wild wont be able to adapt or survive due to their inability to cope with extreme weather changes and many surely fall prey quickly to the wary predators they may encounter (Animal-World, 1998-2008).
The yellow-foot tortoise is the larger cousin of the red-foot tortoise. This name is derived from its several yellow head scales and its carapace is black with a small, distinct yellow area around the areola on each shell scale (Wikipedia, 2008). The adult males are bigger than the females however they are also much lighter than the females. Like the one we had in class, mature yellow-foots have distinctive incurving on the side of their shells, giving them a well-defined “waist” (Wikipedia, 2008). In addition, the plastron is extremely concave in males which make it easy for him to mate with the female who has a very flat plastron and short stubby tail. These species are found in the drier forest areas, grasslands, and the savanna, or the rainforest belts adjoining more open habitats (Wikipedia, 2008). Because of their considerably short neck and snout, the yellow foot’s diet consist of grasses, fallen fruits, plants, and any slow moving animals like snails, worms, and others that they are able to capture (Wikipedia, 2008); as you’ve probably have already guessed these creatures do not move fats at all compared to the other tortoises that we observed. This species has a very interesting evolutionary trait; it is interesting to note than in almost every tortoise species where male combat occurs, the males are always larger than the females. This is in comparison to aquatic species, where the males are usually smaller than the females and do not engage in male to male combat. It is thought that species with male combat evolved larger males because larger males have a better chance of winning a bout and mating with a female, thus passing on their larger size to their offspring. Species with smaller males evolved because smaller males are more mobile and can mate with a large number of females, thus passing on their genes (Wikipedia, 2008). Now that’s survival for ya!
The last turtle observed was the only true full water turtle: the mudd turtle from North America. This little creature prefers to live in shallow, slow moving bodies of water with muddy bottoms. Also they have a dome shaped carapace (Wikipedia, 2008). Even though they are small they can live up to 50 years old! It’s known for it’s dull shell and has a black under belly which helps it to camoflague well in seaweed, protecting it against predators. Also, this little guy is carnivorious, and will consume almost anything they can catch including small fish, worms, insects, grubs, crustaceans, tadpoles, small berries and even carrion. In this species the females are generally larger than the males but the males have a much longer tail, furthermore they can be black, brown, green or yellowish in color (Wikipedia, 2008).
Each of the turtles observed had their own specific traits and characteristics for survival and battle of the fittest. A lot of them have overcome the natural selection process because they are so adaptive, hence the turtles and tortoises that can live in both water and on land. Shell size, snout size, length of neck and mobility all play a major role in determinig which species can and will outlive the other and has the strongest genes/characteristics to pass on to the next generation.
Works Cited
http://en.wikipedia.org/
http://www.zephyrus.co.uk/charlesdarwin.html
http://txtwriter.com/Backgrounders/Evolution/EVpage15.html
http://animal-world.com/encyclo/reptiles/turtles/OrnateWoodTurtle.php
No comments:
Post a Comment