Molluscs and Natural Selection Essay Example for Free

Molluscs and Natural Selection Essay The process of natural selection is one of the most cited reasons for the evolution of a species, and it was made famous by Charles Darwin’s famous observations of finches in the Galapagos Islands. It is believed to work by way of random mutations; random mutations occur, as it indicates, randomly and spontaneously in a population for a multitude of genetic reasons. Mutations help to create variation of different traits within a species, and they can be expressed with different phenotypes. In times where a mutation has no negative effect on the individual organism, this trait could be advantageous in a new habitat or predatory situation, etc. With an advantage in survival, and thus reproduction, these organisms are often selected for over other members of the species, creating a change in variation of a species over generations. Molluscs, although a very large and diverse group of animals, often share certain features: a mantle, radula, shell, and foot. The mantle is a thin and fleshy layer which secretes the hard shell of a mollusc. The radula is a grate-like structure in the mouth used to scrape surfaces and drill holes. The foot is a muscle which assists in locomotion and movement of the molluscs. It is hypothesized that all current-day molluscs share a common ancestor, called the hypothetical ancestral mollusc or HAM, because of the similar characteristics and body plans that have been modified in diverse ways over time to adapt to different environments. Two members of the mollusc family include the clam, of the class bivalvia, and the squid, of the class cephalopoda, and these are an example of variation from the HAM that helped them adapt for their particular environment, feeding behavior, and movement (Sigwart, 2007). The squid species has undergone many adaptations. The squid’s radula resembles a beak-like structure that it uses to devour its food, very different from the chiton-like HAM which probably had a small radula. Over time, the radula’s shape has been mutated and then selected for as the squid changed its eating habits – if it provided quicker eating time, then it would be selected for. The squid lacks an outer shell (it’s internalized), so the mantle of the squid has also been modified into muscular â€Å"flaps† that it uses to propel itself quickly through the water, nd thus capture prey or avoid predators, a necessary function due to the squid’s lack of a hard protective barrier (Sigwart, 2007) A large shell would be unnecessary for the squid since it can propel quickly away from predators, and may even hinder its ability to swim; this would lead one to believe that the squid developed a muscular mantle from HAM and then a mutation for loss of the shell was selected for following the muscular body. Also, the foot of the squid has adapted from the single foot of the HAM to become tentacles and arms, used to quickly capture and bring prey closer to its beak-like radula to eat, which is buried behind its many arms. This modified version of its foot is an extremely effective feeding method that, coupled with the squid’s speed, enables it to catch and hold prey that otherwise might be able to escape (Sutton, 2007). The clam is a sedentary mollusc that uses its foot to burrow into the sand. The clam is a filter feeder, straining food particles from the water. The clam doesn’t have a radula, probably the result of a random mutation that caused some clam ancestors to lack the structure, or it may have been modified into another structure that aided in the filter feeding process. The filter feeding process is environmentally selected for because it enables the animal to take in food particles while buried under the sand. The mantle of the clam is found inside of its hard, hinged shell. The strong shell of the clam was environmentally selected for since it prevents predators from easily eating the clam, allows it to bury safely into the sand without affecting its internal organs, and improves the clams ability to survive and reproduce. The foot of the clam has adapted so that the species can dig into the sand with this muscle which can be moved out of the shell, a very different type of foot than the HAM’s muscular, positioned foot which allows for scavenging (Sutton, 2007). The HAM, very similar to the chiton, served as a good base model for this very diverse phylum of animals. Lots of spontaneous and random mutations must have occurred for such diversity – to have sedentary, burrowing animals and predatory, jet-propelling animals in the same phylum of animals is quite a feat.

A Good Man is Hard to Find, by Flannery OConnor :: Good Man Is Hard to Find Essays

A Good Man is Hard to Find, by Flannery O'Connor In the short story, A Good Man is Hard to Find, by Flannery O'Connor, every object including the characters are symbols. The Grandmother, who is the one and only dynamic character, represents all of us who have repented. The story is, as Flannery O'Connor has suggested a spiritual journey because of the Grandmother's Plight. In the beginning of the story the Grandmother is obsessed with everything worldly and superficial. She cares far too much about how others perceive her, "Her collars and cuffs were white organdy trimmed with lace and at her neckline she had pinned a purple spray of cloth violets containing a sachet. In case of an accident, anyone seeing her dead on the highway would know at once that she was a lady" (O'Conner 138). She gets dressed up for a car trip so that, on the off chance that they would be in a car wreck and that in that wreck she would be thrown from the car and laying on the pavement, she would be happy because the people passing would think that she is a lady. This represents us as humans because daily we choose to be way too self-conscience. Think about females and make-up. Make-up is a perfect example of us caring a great deal about what others think of us. She is also very selfish in her endeavors. Instead of caring about what is best for the family, she wants to go to Tennessee because she has friends there whom she would like to see. There are three phases of thought for the Grandmother. During the first phase, which is in the beginning, she is completely focused on herself in relation to how others think of her. The Second Phase occurs when she is speaking to The Misfit. In the story, The Misfit represents a quasi-final judgment. He does this by acting like a mirror. He lets whatever The Grandmother says bounce right off him. He never really agrees with her or disagrees, and in the end he is the one who kills her. His second to last line, "She would of been a good woman," The Misfit said, "if it had been somebody there to shoot her every minute of her life," (O'Conner 152). might be the way O'Conner felt about most of us alive, or how she felt that God must feel about us.

Environmental Protection Essay

Environmental protection is an increasingly pressing issue all over the world. Ozone depletion, green house effect, global climate changes or global warming, etc, are the main issues in environment. Recent years, many countries and various organizations have paid more attention into environmental protection. A treaty about global environmental protection was discussed by 192 nations in Copenhagen in December 2011. But I fell every individual on this earth should make sacrifices to prevent environment changes. Yes it is the need of the hour. We should protect the world for the future generations. Why? It is because of mans greed he has the once beahtiful earth into a rubbish of Earth. He has increased his numbers to terrible proportions, has caused the death of hundreds of species of animals, has robbed and destroyed the planet in his search for fuels; now he stands, like a violent, spoilt child, delighted at the speed of his rise to power, It is he who is on the edge of the final mass destruction and of killing all the life which exists in the solar system. The Earth is our home but much of it is dirty and dying. Rapid industrial development caused a lot of ecological problems. They are: air pollution, water pollution, growth of population and shortage of mineral resources. Air becomes polluted with Cars, trucks, buses, airplanes, factories and plants send burnt gases into the air. The production of electricity causes not only air pollution but acid rains and global warming. Because of acid rains the Earth losses twenty million acres of tropical rainforests every year. This means the extinction of thousands of species that live there, for example tigers. Only 67 thousand tigers remain. Tigers are hunted and killed for their body parts. Ozone layer is destroyed too and the dangerous rays get through the atmosphere causing skin cancer and other diseases. Most of the air pollutants directly affect the respiratory and cardiovascular systems Nitrogen dioxide and ozone also effect the respiratory system, irritate the eyes, nose and throat and headaches. Carbon monoxide is able to displace oxygen in the blood which in turn can result in cardiovascular and neurological effects. Lead affects bone narrow, impairs liver and kidney function, causes neurological damage and also causes mental retardation in children. Oceans are vital for the life on Earth. We need to protect it. They provide homes for millions of plants and animals, provide people with food and help regulate the climate. But now they are a big dumping ground for tons of toxic waste. Most big cities pour their waste into seas and rivers. Water pollution is due to mixture of dirt, sewage and industrial waste , increased use of fertilizers and insecticides that seep through the earth and pollute the ground water As a result, there are numerous health problems like dysentery, cholera and paratyphoid fever. Noise pollution is yet another problem that the researchers say causes ulcers, abortions, cardiovascular diseases and hypertension besides several mental disorders. Checking of environmental pollution has been absolutely necessary. if it is not checked, the earth will become a graveyard. So we must give due attention to protect it from our own abuses. We must have balanced and planned industrial growth in order to check thin pollution. Towns and cities should be planned very carefully and stress should be given on planting of more trees. I would like to dwell on practical measures which must be taken in order to improve the ecological situation: -the factories must be removed from cities; -have balanced and planned industrial growth -purifying systems for cleaning and trapping harmful substances must be widely used; -green zones must be created by planting more trees. -almost everything is recyclable today – recycling is a great way to reduce waste. We need clean air to breathe and pure water to drink. So we have to prevent disposal of toxic waste and nuclear tests. I feel formal education programmed should be provided and implemented for the environ ­mental protection We need to conserve resources like water by planting rain water harvest in our houses Earth is the only planet endowed with a beautiful environment for man to live We should pass it on to our future generation as their legacy. Protect our earth today for our children tomorrow.

A Report On Second Quarter Data - 1594 Words

Second Quarter Data Assumes Extra Importance Most economic commentators and forecasters are expecting a disappointing headline figure for US Q1 real GDP growth, despite good weather during the first two months of the year. According to the Atlanta Fed’s latest weekly live reading, the US economy will grow only +0.5%, significantly below the Blue Chip Consensus estimate of +1.4%. Inventory liquidation is forecast to be a significant drag, shaving -0.8 percentage points off headline growth. Their GDP estimates have been steadily declining since late-January as more economic data has been released. The apparent failure of the economy to accelerate in reaction to the bounce in business optimism following the Presidential Election may scare†¦show more content†¦During recent years, there has been an almighty game of chicken played out between bond investors and the Fed. The former group have embraced a secular stagnation thesis of slow economic growth and low inflation. Meanwhile, the FOMC has been forced to accept s ome of these conclusions by reducing their estimate of the neutral federal funds rate to 3%. Economic Dynamics: Not Much Has Changed Since November While it is easy to be impressed by the sharp recovery in business optimism since the Presidential Election, the reality is that economic conditions have not really changed that dramatically. Moreover, the failure to replace the Affordable Health Care Act has been a brutal reminder that major legislative changes require bipartisanship. The most crucial component of President Trump’s election agenda is tax reform and failure to deliver could have a significant bearing on risk-taking in the US economy. Thus, should the economic deceleration in Q1 turn out to be more sinister, then the urgency to enact tax cuts will commensurately increase. Treasury Secretary Mnuchin originally targeted August as the most likely point to witness tax reform being passed. 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