500 Million Years of Fish Evolution

Compared to dinosaurs, mammoths and saber-toothed cats, fish evolution may not seem all that interesting — until you realize that if it werent for prehistoric fish, dinosaurs, mammoths, and saber-toothed cats would never have existed. The first vertebrates on the planet, fish provided the basic body plan subsequently elaborated on by hundreds of millions of years of evolution: in other words, your great-great-great (multiply by a billion) grandmother was a small, meek fish of the Devonian period. (Here are a gallery of prehistoric fish pictures and profiles and a list of ten recently extinct fish.) The Earliest Vertebrates: Pikaia and Pals Although most paleontologists wouldnt recognize them as true fish, the first fish-like creatures to leave an impression on the fossil record appeared during the middle Cambrian period, about 530 million years ago. The most famous of these, Pikaia, looked more like a worm than a fish, but it had four features crucial to later fish (and vertebrate) evolution: a head distinct from its tail, bilateral symmetry (the left side of its body looked like the right side), V-shaped muscles, and most importantly, a nerve cord running down the length of its body. Because this cord wasnt protected by a tube of bone or cartilage, Pikaia was technically a chordate rather than a vertebrate, but it still lay at the root of the vertebrate family tree. Two other Cambrian proto-fish were a bit more robust than Pikaia. Haikouichthys is considered by some experts--at least those not overly concerned by its lack of a calcified backbone — to be the earliest jawless fish, and this inch-long creature had rudimentary fins running along the top and bottom of its body. The similar Myllokunmingia was slightly less elongated than either Pikaia or Haikouichthys, and it also had pouched gills and (possibly) a skull made of cartilage. (Other fish-like creatures may have predated these three genera by tens of millions of years; unfortunately, they havent left any fossil remains.) The Evolution of Jawless Fish During the Ordovician and Silurian periods — from 490 to 410 million years ago — the worlds oceans, lakes, and rivers were dominated by jawless fish, so named because they lacked lower jaws (and thus the ability to consume large prey). You can recognize most of these prehistoric fish by the -aspis (the Greek word for shield) in the second part of their names, which hints at the second main characteristic of these early vertebrates: their heads were covered by tough plates of bony armor. The most notable jawless fish of the Ordovician period were Astraspis and Arandaspis, six-inch-long, big-headed, finless fish that resembled giant tadpoles. Both of these species made their living by bottom-feeding in shallow waters, wriggling slowly above the surface and sucking up tiny animals and the waste of other marine creatures. Their Silurian descendants shared the same body plan, with the important addition of forked tail fins, which gave them more maneuverability. If the -aspis fish were the most advanced vertebrates of their time, why were their heads covered in bulky, un-hydrodynamic armor? The answer is that hundreds of millions of years ago, vertebrates were far from the dominant life forms in the earths oceans, and these early fish needed a means of defense against giant sea scorpions and other large arthropods. The Big Split: Lobe-Finned Fish, Ray-Finned Fish, and Placoderms By the start of the Devonian period--about 420 million years ago--the evolution of prehistoric fish veered off in two (or three, depending on how you count them) directions. One development, which wound up going nowhere, was the appearance of the jawed fishes known as placoderms (plated skin), the earliest identified example of which is Entelognathus. These were essentially larger, more varied -aspis fish with true jaws and the most famous genus by far was the 30-foot-long Dunkleosteus, one of the biggest fish that ever lived. Perhaps because they were so slow and awkward, placoderms vanished by the end of the Devonian period, outclassed by two other newly evolved families of jawed fish: the chondrichthyans (fish with cartilaginous skeletons) and osteichthyans (fish with bony skeletons). The chondrichthyans included prehistoric sharks, which went on to tear their own bloody path through evolutionary history. The osteichthyans, meanwhile, split into two further groups: the actinopterygians (ray-finned fish) and sarcopterygians (lobe-finned fish). Ray-finned fish, lobe-finned fish, who cares? Well, you do: the lobe-finned fishes of the Devonian period, such as Panderichthys and Eusthenopteron, had a characteristic fin structure that enabled them to evolve into the first tetrapods — the proverbial fish out of water ancestral to all land-living vertebrates, including humans. The ray-finned fish stayed in the water, but went on to become the most successful vertebrates of all: today, there are tens of thousands of species of ray-finned fish, making them the most diverse and numerous vertebrates on the planet (among the earliest ray-finned fish were Saurichthys and Cheirolepis). The Giant Fish of the Mesozoic Era No history of fish would be complete without mentioning the giant dino-fish of the Triassic, Jurassic and Cretaceous periods (though these fish werent as numerous as their oversized dinosaur cousins). The most famous of these giants were the Jurassic Leedsichthys, which some reconstructions put at a whopping 70 feet long, and the Cretaceous Xiphactinus, which was only about 20 feet long but at least had a more robust diet (other fish, compared to Leedsichthys diet of plankton and krill). A new addition is Bonnerichthys, yet another large, Cretaceous fish with a tiny, protozoan diet. Bear in mind, though, that for every dino-fish like Leedsichthys there are a dozen smaller prehistoric fish of equal interest to paleontologists. The list is nearly endless, but examples include Dipterus (an ancient lungfish), Enchodus (also known as the saber-toothed herring), the prehistoric rabbitfish Ischyodus, and the small but prolific Knightia, which has yielded so many fossils that you can buy your own for less than a hundred bucks.

Current Freshman At California State University - 939 Words

My name is Moises Alberto Albayero, and I’m a current freshman at California State University, Northridge (CSUN). I was born on July 26, 1997, in Los Angeles, CA at California Hospital Medical Center at 6:32 am on a Saturday morning. I have spent my whole life in Los Angeles, where in my opinion is the entertainment capital of the world and has outstanding weather. I can truly call Los Angeles my home; it’s a huge city where the current population is about 3.96 million and has wonderful beaches such as Venice Beach. Today, I live in a small apartment in the West Adams District of Los Angeles, where I have lived for the past five years with my mother, step-father, and my three brothers; Alexander (3), Joshua (15), and Jario (24). My mother is the greatest mother anybody can ask for; she brings unity and structure to the family and is a great cook. My mother is the reason why I work hard every single day, she my motivation to be successful in life. She would always tell me, â€Å"Shoot for the moon. Even if you miss, you’ll land among the stars.†, and my interpretation of it was to pursue ambitious goals in life and for some reason, if I fail to achieve them, I might still accomplish other great thing in the process. I have taken this quote and applied to many situations in my life; such as graduating both middle and high school with high honors and receiving the gold cord. I attended James A. Foshay Learning Center (Home of the Wolverines) for middle school (class of 2011), whereShow MoreRelatedBackground And Qualifications : Application And Evaluation Of Culturally Responsive Public Health Level At The George Washington University Milken1022 Words   |  5 Pagesapplying to a Master of Public Health degree in Health Promotion at the George Washington University Milken Institute School of Public Health. 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Personality And Personality Development Freud S...

PERSONALITY Personality can be defined as the stable pattern of behavior, thoughts, motive and emotions that characterizes an individual. (Wade, Tavris, Gary, 2014). This means personality deals not only with the way we behave but deals with our emotions i.e. our feelings; it deals with our thoughts the way we think about some certain things that defines us as individuals. Personality is also the habitual way of behaving, thinking and feeling. (Class note). Personality is also the combination of characteristics or qualities that form an individual s distinctive character. FREUD’S PSYCHOSEXUAL STAGES/STRUCTURE OF PERSONALITY Freud believed that life was built round tension and pleasure. Freud also believed that all tension was due to the buildup of libido (sexual energy) and that all pleasure came from its discharge. (Wade et al., 2014). In describing human personality development as psychosexual Freud meant to convey that what develops is the way in which sexual energy accumulates and is discharged as we mature biologically. Freud argued that people have three levels of awareness: conscious (what we are aware of), preconscious (what we can be aware of if we attend to is carefully) and unconscious (that about which we cannot be aware except under exceptional circumstances). (Wade et al., 2014). Therapies often aimed precisely at bringing the unconscious into the conscious. He also maintained that personality has a structure. It is the result of threeShow MoreRelatedEssay about Jennys Personality; Interpretation of Forrest Gump1419 Words   |  6 PagesForrest Gump: Jenny’s Personality Monday, August 22, 2011 PSY202 – Principles of Psychology In this character analysis paper the character of Jenny Curran from the award winning movie Forrest Gump will be the subject of discussion. 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The Stem Cell Dilemma Essay Example For Students

The Stem Cell Dilemma Essay The Stem Cell Dilemma Essay Every day, nearly 3,000 people die while waiting for an organ transplant (DAgnese). Moreover, 66,000 people are still on an organ donor list in the United States, few of which will ever see their name come up on that list (Improving). Many people believe nothing can be done about this sad fact. However, this is not the case. Studies on stem-cell research point toward a solution to this deadly problem. With efficient use of stem cells, many diseases and medical problems could be solved. Stem-cells are very young, specialized cells. Usually coming from a human embryo, they have the ability to develop into more specialized groups of cells or tissues (Stem Cells: A Primer). As of 2001, scientists could develop stem-cells into more than 110 different types of tissues, such as blood, brain or heart tissue (Robinson). If these cells could be so useful in the medical field, why are they not being used now? First of all, the research on stem-cells is still ongoing, though if given funding this research may have already been accomplished. According to Gary Stix, a writer for Scientific American, on November 5th, 2001, a company called Advanced Cell Technology (ACT) was the first to actually clone embryonic cells. This is not cloning in the most common sense, though. Stem-cells have previously been obtained from tissues of early stage embryos. With this experiment, scientists tried to use a new technique in making stem-cells so that real embryos need not be used. The scientists injected cells into eggs which had their nuclei removed, rather than making an actual copy of the cell. These cells developed, though the furthest development was from the one cell to eight cells, which is not enough to provide stem-cells (Lauritzen). This may not seem like much, but it is seen as a small step on the path to greater and more efficient use of these cells. So, one factor in the question of why do we not use stem-cells is that certain people do not approve of the use of embryonic tissue in research. There are many reasons, however, in which it could be seen as feasible to use embryonic stem-cells in the sake of medicine. For example people with heart disease or kidney failure could be cured with a relatively cheap operation. Today organ transplants are quite expensive and sometimes a matching donor can not even be found if a patient had the money to pay for it. However if stem-cells could be used, organs would be easily accessible, and many of those who would not have been able to get a transplant would have new hope. Not only would stem-cells help with organ transplants, but they have also been shown to treat other diseases such as multiple sclerosis (Lee). Despite these facts, some may still think it is morally wrong to use stem-cells. There are many reasons that help prove the fact that the use of stem-cells does not equal the destruction of a life. Supporters of stem-cell research believe that embryos composed of only a few cells that are being stored in a lab are not alive, because they are frozen. They may have once had the potential to live, and though this potential was lost, it was not lost because of stem-cell research. Many of the cells that are being used come from ended pregnancies when a life would not develop anyway. If an embryo were to go unused, why not use it instead to save another life? There are actually over 110,000 embryos being stored in the United States alone, with no life in sight for them (Robinson). .u2225ada7c59244da99ebfbb82ca4dc3a , .u2225ada7c59244da99ebfbb82ca4dc3a .postImageUrl , .u2225ada7c59244da99ebfbb82ca4dc3a .centered-text-area { min-height: 80px; position: relative; } .u2225ada7c59244da99ebfbb82ca4dc3a , .u2225ada7c59244da99ebfbb82ca4dc3a:hover , .u2225ada7c59244da99ebfbb82ca4dc3a:visited , .u2225ada7c59244da99ebfbb82ca4dc3a:active { border:0!important; } .u2225ada7c59244da99ebfbb82ca4dc3a .clearfix:after { content: ""; display: table; clear: both; } .u2225ada7c59244da99ebfbb82ca4dc3a { display: block; transition: background-color 250ms; webkit-transition: background-color 250ms; width: 100%; opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #95A5A6; } .u2225ada7c59244da99ebfbb82ca4dc3a:active , .u2225ada7c59244da99ebfbb82ca4dc3a:hover { opacity: 1; transition: opacity 250ms; webkit-transition: opacity 250ms; background-color: #2C3E50; } .u2225ada7c59244da99ebfbb82ca4dc3a .centered-text-area { width: 100%; position: relative ; } .u2225ada7c59244da99ebfbb82ca4dc3a .ctaText { border-bottom: 0 solid #fff; color: #2980B9; font-size: 16px; font-weight: bold; margin: 0; padding: 0; text-decoration: underline; } .u2225ada7c59244da99ebfbb82ca4dc3a .postTitle { color: #FFFFFF; font-size: 16px; font-weight: 600; margin: 0; padding: 0; width: 100%; } .u2225ada7c59244da99ebfbb82ca4dc3a .ctaButton { background-color: #7F8C8D!important; color: #2980B9; border: none; border-radius: 3px; box-shadow: none; font-size: 14px; font-weight: bold; line-height: 26px; moz-border-radius: 3px; text-align: center; text-decoration: none; text-shadow: none; width: 80px; min-height: 80px; background: url(https://artscolumbia.org/wp-content/plugins/intelly-related-posts/assets/images/simple-arrow.png)no-repeat; position: absolute; right: 0; top: 0; } .u2225ada7c59244da99ebfbb82ca4dc3a:hover .ctaButton { background-color: #34495E!important; } .u2225ada7c59244da99ebfbb82ca4dc3a .centered-text { display: table; height: 80px; padding-left : 18px; top: 0; } .u2225ada7c59244da99ebfbb82ca4dc3a .u2225ada7c59244da99ebfbb82ca4dc3a-content { display: table-cell; margin: 0; padding: 0; padding-right: 108px; position: relative; vertical-align: middle; width: 100%; } .u2225ada7c59244da99ebfbb82ca4dc3a:after { content: ""; display: block; clear: both; } READ: The thin air held a frigid tone this evening, and a slight breeze brought a sudden rush of coldness to my fac Essay These embryos are not alive, and should be used instead of discarded. To make this debate even easier, stem cells may in the near future come from, for example, the ACT developed embryos. With the ACTs embryos, the scientists started with human eggs, though they were not fertilized with sperm; these eggs were then coaxed into fertilization. The eggs were kept in a culture and seemed to develop like normal embryos, though they could probably never be able to develop fully into a child (Lauritzen). Writer Paul Lauritzen asks about the pro-life statements that s ay .