HOW LIVE ALL STARTED...
EVOLUTION
Have you ever wondered why we have opposable thumbs like gorillas and monkeys and other organisms do not? If we are related then why are we not hairy and live in the jungle. Well, the answer to that question is evolution. Evolution is a change in allele frequency. An allele is found on a chromosome and is a version of a trait, like brown or white fur. Here is how the change over time occurred: Life started a very, very, very long time ago. The Earth is said to be 4.6 billion years old. Our ape ancestors are said to be 1.2 old, while humans, the youngest living thing on Earth is said to be 10,000 years old. Sorry I got distracted, now back to the story. A long time ago, a single celled organism developed. Years later, multicellular organisms, such as sponges and jellyfish. These multicellular organisms developed organs! Then, they were able to move to land. When on land they developed legs and lungs. Amphibians] were first born with gills in order to breathe. With the 3 L's: land, legs, and lungs, reptiles were developed. They had scales that did not need water and shelled eggs. Then, a long time passed, history and life. After a long time, mammals were developed. They were warm blooded and were able to live in different environments. Then, there was primates, and now there's us! Humans! and all other creatures of life known and still being discovered.
How it began....
There was a case on The Peppered Moth where there were two versions: black and white. In the early 1800s there were more peppered white moth then black because the black ones were seen by birds easily. Then as time went on it was a different case. In the 1880's, during the Industrial Revolution, there was more black peppered moth then white ones because the white ones stood out more on the black soot caused by the burning coal. The environment changed, causing a change in allele frequency, and animals needing a way to survive. That's called adaptations, an allele(and traits) that help species survive and help an organism evolve. There are 4 factors that drive a change in allele frequency: mutation, genetic drift, migration, and natural selection. Mutation is a change in the DNA sequence, which next results in a change in amino acid sequence, then a change in protein, followed by a change in alleles and traits. Mutation results in new alleles, can be harmful or helpful, must be heritable( mutation has to be in the gametes.) and it may or may not affect reproductive success. Them, there is genetic drift(The Luck Factor), which is a random change in allele frequency. There are two types the Founder Effect and the Population Bottleneck. When you hear Founder Effect, think of the Amish people(6 fingers), who moved to a new area. If a founder has some mutation, the rest of the population will get it. In Population Bottleneck(Random), there is a disaster of some kind. Take a bottle and imagine having all the alleles in it, then a disaster causes an allele to disappear. Then, there's migration aka Gene Flow, where a group of individuals moves from one population to another. Then, finally there is Natural Selection(Survival of the Fittest) where those that are best suited to the environment, survive and reproduce and it was first described by Charles Darwin in 1830's.
Who's Charles Darwin??
Before Darwin, people believed that life has not changed, Earth was 6,000 years old, and the Bible. However, Darwin was influenced by Georges Buffon who said the Earth was old, Georges Cuvier who found fossils, Jean-Baptiste Lamarck who said organisms do change, and Charles Lyell who argued that geological forces had gradually changed because the earth moves slow. Darwin traveled around the world as a naturalist collecting information and taking it back to England. When he reached South America, he found one type of species on Finch on the mainland. However, as he started traveling through the Galapagos Islands, The breaks were different each island. This is because the food sources were different on each island. The birds that had the most successful beaks lived, reproduced, and passed on their genes. He called this Natural Selection. This is called Adaptive Radiation, which is where a common ancestor gives rise to various species due to the different environment. In Natural Selection, there are 3 conditions needed for Natural Selection to occur: 1.Variation in a trait. 2. The trait must be heritable. For example, in humans, eye color, height, hair color are heritable, but preferences for food and personality are not. and 3. Differential Reproductive Success. In Reproductive Success: there's overproduction, struggle, and survivors. In overproduction, all species overproduce, and organisms make more offspring than can survive. In struggle, there are limiting factors, like food, space, water and then the Survivors with beneficial traits make babies.
How Did the Atlantic Guitarfish come to be??
The Atlantic Guitarfish has special adaptations, as do other animals, to help it survive. The adaptations include:
- a flattened elongated body with a triangular or "shovel-shaped" heads and small ray-like wings instead of pectoral fins and two dorsal fins.
- They are ashy gray to olive brown or even a chocolate brown(are found to inhabitant sandy and weedy bottoms or buried in sand or mud) allowing them to blend in with there surroundings.
- They swim by moving their from side-to-side with their heads slightly higher than their tails.
- They are made of all cartilage.
- They have 56-80 blunt teeth (in 8-10 rows) in their upper jaws and 51-82 teeth (in 7-9 rows) in their lower jaws. Their teeth are rectangular at their base with rounded corners and are fit closely together.
Since appearing on earth some 450 million years ago, some members of class Chondrichthyes, notable the sharks, have been and remain among the fiercest and successful of predators. Their success that has not only assured their survival, but has required their minimal evolutionary adaptation over the eons to assure survival. Sharks have a good sense of smell but poor eyesight. To compensate for the poor eye site, they have a lateral line system of sensory organs running down the side of the body that can detect very small changes in water pressure as would be made by a fish swimming nearby. Skates and rays are other examples of cartilaginous fish that consists of about 1,000 extant.
Structural Adaptation - Type of Body
The guitarfishes body has evolved from the first sharks were round, and shaped as sharks are today, but overtime the bottom of the belly area has become flatter to assist them with swimming along the ocean floor, and hiding in the sand. The tail has also become slightly longer and thinner, and the dorsal fin has become smaller. The thinner tail disturbs the sand less, and it does not need to be as wide as the body is no longer as heavy to push through the water. The compression which has occurred from belly to back has allowed them to hide more easily in the sand, and also hunt more easily, as their mouths are on the bottom of their bodies which comes in contact with the ocean floor. If the body had not compressed from belly to back then it would be very hard for them to hunt effectively as they could not camouflage and bury themselves in the sand as they were known to do. Also as the mouth is on the bottom of the guitarfish, the body being flat means that it is closer to the ocean floor and therefore closer to their prey, being able to simply graze along at the same level, not having to make sudden movements down to reach their prey.
Structural Adaptation - "Shark" Tail
The guitarfish did not swim using their pectoral fins to swim as most rays do, but use their shark like tail instead. This is because they had not yet evolved to become the rays of today and their pectoral fins were not yet large enough or strong enough to be used for swimming. The tails which they had were still very similar to the tails which sharks today have, being very strong and able to move from side to side very fast to propel them through the water. One of the main advantages of having the 'sharks' tail is that they could move through the water faster, and control their movements better, as the tail, which has a small dorsal fin on top of it, could be used as a rudder for changing direction, and also had a larger range of movement than the pectoral fins.
Physiological Adaptation - Breathing
The guitarfish pumps water through two small holes called spiracles, on the top of its head, the water then travels through the gills and out through the gill openings on the bottom of its body. Guitarfish can not take in water to breath through their mouths as this would damage their very delicate gills. The presence of the Spiracles helps the Guitarfish enormously as the water above them is much clearer and has less silt and sand in it, than the water beneath them. Guitarfish always swim with spiracles pointing away from the sea floor which makes it very hard for sand to get in, but if they used their mouths to breath then sand would damage their breathing system, and it would need to be much more complex to ensure that food does not enter their breathing system and their digestive system does not become full with water.
The guitarfishes body has evolved from the first sharks were round, and shaped as sharks are today, but overtime the bottom of the belly area has become flatter to assist them with swimming along the ocean floor, and hiding in the sand. The tail has also become slightly longer and thinner, and the dorsal fin has become smaller. The thinner tail disturbs the sand less, and it does not need to be as wide as the body is no longer as heavy to push through the water. The compression which has occurred from belly to back has allowed them to hide more easily in the sand, and also hunt more easily, as their mouths are on the bottom of their bodies which comes in contact with the ocean floor. If the body had not compressed from belly to back then it would be very hard for them to hunt effectively as they could not camouflage and bury themselves in the sand as they were known to do. Also as the mouth is on the bottom of the guitarfish, the body being flat means that it is closer to the ocean floor and therefore closer to their prey, being able to simply graze along at the same level, not having to make sudden movements down to reach their prey.
Structural Adaptation - "Shark" Tail
The guitarfish did not swim using their pectoral fins to swim as most rays do, but use their shark like tail instead. This is because they had not yet evolved to become the rays of today and their pectoral fins were not yet large enough or strong enough to be used for swimming. The tails which they had were still very similar to the tails which sharks today have, being very strong and able to move from side to side very fast to propel them through the water. One of the main advantages of having the 'sharks' tail is that they could move through the water faster, and control their movements better, as the tail, which has a small dorsal fin on top of it, could be used as a rudder for changing direction, and also had a larger range of movement than the pectoral fins.
Physiological Adaptation - Breathing
The guitarfish pumps water through two small holes called spiracles, on the top of its head, the water then travels through the gills and out through the gill openings on the bottom of its body. Guitarfish can not take in water to breath through their mouths as this would damage their very delicate gills. The presence of the Spiracles helps the Guitarfish enormously as the water above them is much clearer and has less silt and sand in it, than the water beneath them. Guitarfish always swim with spiracles pointing away from the sea floor which makes it very hard for sand to get in, but if they used their mouths to breath then sand would damage their breathing system, and it would need to be much more complex to ensure that food does not enter their breathing system and their digestive system does not become full with water.