Evolutionary Essay

Evolutionary Essay

Caryn Bradshaw

3^rd hour

The fact of evolution is the backbone of biology, and biology is thus in the peculiar position of being a science founded on an improved theory, is it then a science or faith?"

                                                -Charles Darwin

            Everyday plants and animals are growing in size and population, each living organism looks so different from another. But are they really that different? In this paper I will explore the people who have discovered and researched the theory of evolution and how they have changed the way we look at science.

           

            Evolution has been a popular subject in Biology for many years, but who really sparked the idea? Jean Baptiste De Lamarck was the first to describe a mechanism by which he concluded that evolution could not occur. This proposition was known as: ‘the inheritance of acquired characteristics”. His theory was based off of creatures that inherit different features from other creatures that are like them. For example, salamanders have short legs; therefore they cannot walk across tall grass. So suppose these salamanders started to slither on their bellies to get from place to place and since they didn’t use their legs their leg muscles wasted away and the salamanders became legless. Lamarck’s theory states that this trait was then passed on to the salamander’s off spring. Lamarck then argues that the legless salamander evolved from the salamander by inheriting the characteristic of having no legs.

           

            Charles Darwin then left off where Lamarck left off. Darwin was always fascinated by plants and animals ever since he was a young boy. He traveled around the world to observe different species of animals and started a notebook of each one he found. On his travel to the Galapagos Islands he was surprised to find that the birds their were slightly different from one another. He realized that each bird particularly the Finch was different according to the different kinds of environments. Returning from his travels he had identified thirteen species of finches that had different features in the Galapagos Islands. Each bird although they were the same species, had different beak shapes and sizes. The beak varieties were also associated with the way the diet was with certain types of foods and the different environments. He came to the conclusion that the original South American finches reached the Island then separated to different areas where each bird had to adapt to that environment and its conditions. Over many years they would change to allow them to get food, shelter, and to be able to reproduce. Darwin then came to the understanding that each organism is slightly different from one another. Each organism would need to successfully reproduce and pass on their traits to the next generation so that those traits would become more common and the population would evolve.

           

            Thomas Malthus, an English clergyman published “Essay on the Principals of Population” which spoke of human populations. Thomas Malthus stated that the human population would double every twenty-five years unless they are limited in food supply. This essay was read by Darwin and it sparked an idea that plants and animals are the same way.  These organisms’ populations could increase rapidly unless they are constantly affected by predators, diseases, or limited with food, water, or other resources. He realized that the plant or animal that is fit for survive against these things would be the species that would survive and pass on their traits to the next generation. For example, suppose you are observing brown and green beetles. You see that there is a decrease in population for the green beetles and an increase of population in the brown beetles.  You may wonder why there is such a different number of each beetle, and that is when the first mechanism of microevolution I will talk about comes into the picture.  Since the brown beetles can blend in with the dirt or the bark of a tree, they are easily hidden from birds or other predators. On the other hand the green beetles can not be hidden therefore they are eaten and are not able to pass on their traits to the next generation. The brown beetles will proceed to reproducing, as a result increasing their population and carrying on their “brown genes” this is called “natural selection”. There are times though when some of the green genes from the green beetle are randomly mutated into brown genes. This type of mechanism is very rare and can not have a big change in the frequency over one generation but it can happen in any organism therefore playing the part of “mutation” in microevolution’s mechanisms. Another reason for the decease in green beetles and the increase of brown beetles would because of where the beetles are located. If there are many trees and a lot of areas with dirt or mud you are most likely to find many brown beetles. This is where they blend in and are protected from predators. But if there are a lot of bushes, grass, and green areas you are most likely to find the green beetles for the same reason that the brown beetles are where there are matching surroundings. Over time the green beetles in your area will want to move to a place where there are more places to blend in with their surroundings. This means that “migration” will take place. Many of the green beetles could not survive in your area in which the brown beetles could so they have migrated to a place where they can blend in more to their surroundings. This could be a reason why the there has been a decrease in the population of the green beetle. Not everything in the population changes in the two types of beetles has to do with their surroundings and colors of the environment they are in. When the beetles reproduce, by some way more brown genes than green genes could end up in the off spring. Brown genes could occur slightly more frequently in the offspring therefore increasing the population of the brown beetle in your area. This process is call “genetic drift”.

            After all of this talk of what Darwin found and how species are all alike in some kind of way you may ask, where is the evidence in all of this research? Well, there is much evidence that has been researched and found throughout history. This includes similarities in DNA, embryology, and fossils. Similarities in humans and primates show that DNA plays a role in the evidence of evolution. Research shows that the jaw of an ape and a human show similar traits from the teeth and the bone structure of the jaw. Fossils also show evidence in evolution, many fossils were found in the ocean from pre-historic times to present day of many different fish. In the fossils from pre-historic times the fish are much bigger, but compared to present day fossils the fish are basically the same except for the size. The way both fishes are formed by the way it looks in the skeleton it left behind you can see that both fish have the same form of skeleton and the same shape. Embryology plays a big role when it comes to evidence in evolution. Comparing a chicken embryo and a human embryo is a great example when finding evidence for evolution. When you put a picture of a chicken embryo next to a human embryo you can see that each one has the same shape and form of one another’s. Both the chicken and the human have Pharyngeal pouches and they both also have a post-anal tail located in the exact same spot.

            In my opinion, Darwin’s evidence about species changing over time is the most convincing for me. Although some people do not agree with some of the ideas he has sparked, I feel that with his research he has concluded some of the most changes in animals and plants. His “Survival of the fittest” theory states that the animal and plant that is best fitted to survive in the environment it is put in is the specie that is most likely to survive and be able to pass on their traits to the next generation. His research on the finches he had found in different areas in the Galapagos Islands prove that animals can change either over time to either survive in their environment or traits from the generation before them had changed. Fossils are also great evidence that species have changed over time because we still have that evidence today. Looking at the fish fossils and comparing them to present day ones you can see the similarities but also the differences that they have changed over time. Looking at the bone structure and how it is formed you could see that it is the same. The differences in these fish were the size in teeth and the fish’s size in general. In the pre-historic days there were many different predators in the sea at that time. So the fish needed to be bigger in size as well as teeth to defend itself from these predators. Today, there are still predators in the sea after fish but there aren’t as many. Therefore the size of teeth and the general size are much smaller. From looking at fossils all of these observations are enough evidence that species have changed over time.

            The fact of evolution is the backbone of biology, and biology is thus in the peculiar position of being a science founded on an improved theory, is it then a science or faith?"

                                                -Charles Darwin

            I use this quote again to conclude my paper because Darwin asks a very complex question that can’t be answered in a day. Is evolution in fact a science or a faith? Well Darwin did get a lot of criticism for his theories and his research in science. Some people took it as though Darwin was trying to replace God, but in all reality he was only doing something he loved to do and that he was good at. It just happened that he had stirred up a whole whir wind of mind boggling questions and intelligent research as well as theories. So, it depends on what you think of Mr. Darwin, and how you perceive the world and the organisms that happen to live on this planet. Is evolution science or is it a faith?

                                                            Bibliography

     

Title: Charles Darwin quotes

Site: http://www.darwin-literature.com/l_quotes.html

Evolutionary Essay

Caryn Bradshaw

 Biology

3^rd hour

Evolution Essay

“Change is at the very core of evolution and without it, all creatures would look alike and behave the same way.” -Martin Dansky-

          Things are growing and changing around us everyday. Creatures big and small all over the world posses their own unique characteristics, but when you get to the bottom of things, every living, breathing, organism is made up in the same way.  So you would ask, if we are all made up the same way, then how are we so diverse?  There is no simple answer, but there is a theory.  This theory has grown over the years and is still studied today; it is the Theory of Evolution.  The definition of evolution is a change in the lines of decent of living creatures over time.  This means that it is believed new species develop from earlier species as a result of molecular changes.  Now, this theory is commonly perceived as scientists trying to explain the origin of life.  However, it is simply an explanation as to how organisms formed after life was created.  In addition, evolution is not something that just occurred in the past.  It is happening right at this moment and will continue to happen for eternity!  Included in this paper is information on the early theories of evolution, examples of microevolution occurring, and evidence of the theory of macroevolution.  Also included will be my personal opinion on the most convincing evidence of evolution.

            In the 18^th century, comparative morphology became a study among scientists.  Comparative morphology is the systematic study of similarities and differences in body plans between major groups.  Studying this requires taking a closer look at bone structures and physical appearances of life forms.  This study brought about a question in scientists minds.  How can animals appear different in bodily features, but so much alike in others?  An example of a study performed to look at comparative morphology would be to compare the pelvic structure of a manatee.  Now, for a sea manatee, there would be no need for a pelvic structure because they don’t walk.  However, scientists have found that sea manatees do in fact have a ghost socket where a pelvic structure would be found.  Why is this?  There were intermediate fossils found that gave evidence to there being such a thing as a “land manatee.”  These fossils contained many of the same characteristics of sea manatees, but included pelvic structure meaning they were able to walk.  How is this possible?

            A well-respected anatomist, Georges Cuvier, was first to come up with the theory of Catastrophism.  This theory suggested that at one point in time, there was a universal catastrophe that destroyed many of the life forms on the planet.  Then the survivors repopulated the world.  Cuvier stated that the offspring of those species were not new, but were just ones that scientists had not found fossils of yet dating clear back to the time of creation. 

            Some people were able to accept Cuvier’s theory, but others, like a man named Jean Lamarck, set out to prove the theory wrong.  He knew that inheritance of characteristics had something to do with the way species grew and changed.  So he hypothesized that environmental pressures and needs bring about permanent changes in animals and their offspring.  For example, if a species of giraffes have a short neck and are unable to reach high branches for food, they simply stretch out their necks to reach it.  By stretching out their necks day after day for food, the giraffe develops a long neck.  Once the long neck is developed, the giraffe passes the characteristic on to its offspring.  Although Lamarck’s theory is not necessarily reasonable, he was right with the fact that the environment plays a role in evolution.

            In the 1800’s, a geologist by the name of Charles Lyell began contradicting Lamarck’s theories.  He spent his time examining sedimentary rock layers and their age.  While many scientists suggested the earth was about 6,000 years old, Lyell came to the conclusion that the earth had to be millions of years old.  He came about this conclusion because there were so many rock layers that is was impossible for them to all form in the short period of time of 6,000 years.  This became known as the Theory of Uniformity.  After taking an even closer look at the rock layers, it was also understood that the possibility that a catastrophe occurred was nearly impossible. 

            In the middle of all of these forming theories about evolution came a man who would truly influence the way everyone viewed evolution.  In 1831, Charles Darwin embarked on a voyage across the sea to South America where he studied the diverse life on all the different islands.  Marine life was also part of his collection. 

            When Darwin returned to England, he began to review his notes and drawings of his findings.  He noticed that he had discovered some fossils of extinct animals, but then saw that some of the new species he examined resembled the extinct animals!  As he looked through his drawings and notes, he observed that not all of the species were alike, but they did show variation in size, color, and many other traits.  By reviewing all of his findings, Darwin was able to combine his new theories with those of Lyell and other scientists.  He was then able to formulate a theory that included all of the evidence found.  Variation became a huge part of Darwin’s conclusion because variation would enable the species to survive and reproduce in certain environments.  In other words, he proposed that an environment would “select” specific characteristics for a species to possess.  This is now called natural selection.  For example, if a finch lives on an island where their only food source is hard-shelled seeds, they must have a strong beak to crack the seeds open.  However, there are a few finches that lack a strong beak and have a lesser chance of survival.  Therefore, the strong beaked finches have a better chance of surviving and reproducing.  Over time, the strong beaked finches become abundant and the population of finches will be mostly strong beaked finches.  With that information you can conclude that a population is evolving if inheritable traits continue to change over time.

            Since Darwin’s theory emerged, variations in traits have been shown to be controlled by genes in DNA.  Microevolution occurs when little changes in allele frequencies are brought about by mutation of genes, genetic drift, migration, and natural selection.  When mutation in genes occurs, the result is a change in the DNA structure, which is heritable.  This occurrence is the source for diversity in species and organisms.  Gene flow and genetic drift is also a contribution to the diversity of things, but is can only cause a change in existing allele frequencies.  When alleles leave or enter a population, as a result of immigration or emigration, it is called gene flow.  This idea is much like genetic drift, however, genetic drift is brought about by chance only.  This size of a population affects the diversity of genetic drift because of the fact that small populations are more likely to loose alleles completely.

            An example of microevolution could be the guppy computer activity we did in class.  Imagine that there are all kinds of different colored guppies; some bright, some semi-bright, and some dull.  They all live in the same pond and share the same predators.  Because the brightly colored guppies attract the predators, they are eaten and unable to reproduce further.  However, the dull colored fish and even a few semi-bright guppies are less attractive and don’t get eaten as much, so they go on to survive and the population of them increases.  Now in another pond, the guppies share their habitat with fewer predators.  Since female guppies prefer to mate with brightly colored guppies, the dull colored ones are unable to mate enough to keep their population up.  So in the second pond, unlike the first pond, the brightly colored guppies make up most of the population.  As a conclusion, you can see how microevolution plays into the survival of different species.  The simplest factor in a population can play the biggest role in how an environment thrives. 

             Macroevolution is large-scale patterns, trends, and rates at a broader view.  Some examples of this broader study are fossil records, comparative morphology, and biochemistry.  However, most would say the most recognizable forms of evidence of macroevolution would be fossils.  Scientists use sedimentary rock sequences as geological time scales to define eras and eons.  Comparative morphology uses fossils as well as existing life to form similarities that show evolutionary relationships among groups.  Taking it a step further would be the use of biochemistry.  This is where scientists identify differences and similarities between species on a molecular level.  They can look at how one strand of DNA pairs with another strand from a different species and form an idea of the evolutionary distance between the two tested. 

            Out of everything I have discussed, I feel that the most convincing evidence is the study of macroevolution.  Those scientists are able to look at geological evidence, morphology, and DNA structures.  All of these things put together in my opinion are the keys to life and evolution.  You are able to look at time and age first, then you can see different structures of species and compare them to modern day species, and to take it a step further, you are able to look at DNA structures between species.  As Martin Dansky stated, “Change is at the very core of evolution and without it, all creatures would look alike and behave the same way.”  I feel this quote sums up my discussion on evolution.  We are all basically the same, and therefore we must have come from one common ancestor.  Everything in life has a cause; it’s just a matter of finding that definite reason for existence. 

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