Most animal phyla originated in a relatively brief span of geological time, however the diversity among them is extraordinary. Every organism is very unique a detailed in certain ways, comparisons of certain types of organisms can be very difficult. The class in which will be compared is that of the invertebrates.
The main difference between coelomate and acoelomate body plans are that coelomates have a true coelom, which is a fluid-filled body cavity completely lined by tissue which is derived from mesoderm. The purpose of this cavity is to cushion the suspended organs to help them prevent injury, enables internal organs to grow and move independently from the outer body wall. Acoelomates, though, lack a cavity between the digestive tract and the outer body wall. An example of an acoelomate would be a flatworm, or planarian, While an example of a coelomate would be a rotifer.
The differences between protostome and deuterostome development are the characteristics in their cleavage, their coelom formation, and the fate of their blastopore. Many protostomes undergo spiral cleavage. In spiral cleavage, planes of cell division occur diagonal to the vertical axis of the embryo. The cleavage also determinates, which casts the developmental fate of each embryonic cell very early. In deuterostomes, they undergo radial cleavage, where the cleavage planes are either parallel or perpendicular to the vertical axis of the egg. Deuterostomes are further characterized by indeterminate cleavage, which means that each cell produced by early cleavage divisions retains the capacity to develop into a complete embryo. Indeterminate cleavage of the human zygote allows identical twins to be possible. In a protostome, as the archenteron forms, solid masses of mesoderm split to form the coelomic cavities, or schizocoelous development. In deuterostomes, the development of body cavities, or enterocoelous, happens when the mesoderm buds from the wall of the archenteron and hollows to become the coelomic cavities. The mouth of many protostomes develops from the first opening, the blastopore. The mouth of a deuterostome is derived from the secondary opening, and the blastopore usually forms the anus.
The differences between radial and bilateral symmetry is that an animal with radial symmetry has parts that are arranged like the spokes of a wheel and a cut down the central axis, it would divide the animal into mirror images. Radial animals include hydra, jellyfishes, and their relatives. An animal with bilateral symmetry has a left and right side, and a cut down its central axis would divide the animal into mirror-image halves.
There is common plan for all limbs: one bone, followed by two bones, then a bunch of little bones, and finally digits. This array of bones is seen in many species including, but not restricted to bats, whales, and lizards. But how do these limbs develop and why do they all look similar? Shubin explains it by conveying that there are certain genetic switches that help assemble who we are. When scientists went looking for this genetic switch in limbs, they found a couple tissue areas in the limbs that allow this body plan to occur. “A strip of tissue at the extreme end of the limb bud is essential for all limb development…This patch of tissue was named the zone of polarizing activity (ZPA).” ZPA allows humans to have opposable thumbs and pinkies. In other organisms, it differentiates the “thumb” side from the “pinky” side. Scientists then wanted to discover the molecule that allowed this changen in the ZPA, the answer is Sonic hedgehog. Shubin points out that every limbed animal h...
Each cell contains the same genetic code as the parent cell, it is able to do this because it has copied it’s own chromosomes prior to cell death. division. The. Meiosis consists of two divisions whilst mitosis is followed. in one division; both these processes involve the stages of interphase, prophase, metaphase, anaphase, and telophase.
The formation and breakup of continents, mountains, volcanic activity, changes in climate and sea level affected the course of evolution.. Paleozoic Era was restricted to the oceans. Organisms evolved a lot crating the “Cambrian Explosion”.
The skeleton is divided into two major parts: the axial skeleton and the appendicular skeleton. The axial skeleton forms the central axis of the body and includes skull, spine, ribs, and sternum. The appendicular skeleton includes the appendages, which are the shoulders, arms, hips, and legs.
The concept of transitional species is an important and complex notion in evolutionary biology. To begin with, there is no such thing as transitional species since all living things were always evolving in the past, not stopping at one stage or another, and they will continue to evolve in the future. In terms of evolutionary biology, we use the concept of transitional species as a way to dim ambiguity. Much like the use of the Linnean taxonomic system of species, we come up with concepts like transitional species to organize and classify species in order to understand their evolutionary roots and how those species changed through life’s history to become what they are today. “In the same way that the concept of species can be provisionally meaningful to describe organisms at a single point in time, the concept of transitional species can be provisionally meaningful to describe organisms over a length of time, usually quite a long time, such as hundreds of thousands or millions of years” (111). Though it can be difficult to distinguish what can be considered an ancestral species from another, the fossil record can show us how species change through time as they develop ways to adapt to stresses found in their environments. “In the modern sense, organisms or fossils that show intermediate stages between ancestral and that of the current state are referred to as transitional species” (222). The concept of transitional species is, in essence, fairly straight forward. This paper will outline the concept of transitional (or sometimes termed intermediate) species and the latter’s role in evolutionary biology, as well as go in depth about several common transitional species: Tiktaalik, an animal at the cusp between life in the water and ...
Much of the debate over whether species should be separated into different groups arises from the morphological differences between individuals of the same species. For example, Australopithecus Afarensis fossils express high sexual dimorphism, which proposes two individual species (Reno et al., 2003). While Australopithecus Africanus, in comparison, shows more realistic size ratios between males and females suggesting one species (Lockwood, 1999). A study performed by Richmond and Jungers looked at the size variation in Australopithecus Afarensis compared to living hominoids to answer the following question: whether it is possible to see such high differences in size between genders of the same species or whether it makes more sense to divide the species into two (1995). In this study, a conclusion of two separate species for the Australopithecus Afarensis was made based on comparisons of fossils such as the humorous and femur with modern gorillas (Richmond & Jungers, 1995). This study compared the size of postcranial fossils. While most of the research has focused on making interpretations based on only cranial fossils, research by Harmon agrees that by looking at postcranial evidence we can gain better insight into the real variations between and within species (2009). Most research assumes high dimorphism wi...
A whole lot of hypotheses have been used to explain the quick expansion of animal species in the early Cambrian period about from about 541.0 million to about 485.4 million years ago. The most modern explanations for the Cambrian explosion takes pieces of a lot of these hypotheses and melds them together; incorporating genetic, ecologic, abiotic conditions that set the evolutionary wheel in motion. The current state of understanding the Cambrian explosion still remains a topic of open and exciting debate. The processes in the hypotheses can be stand-alone or very tightly interconnected and mutually supporting of another. One can say the complexity of modern Animalia can be attributed to the complexity of the processes that happened during the rapid diversification attributed from an interaction of biotic and abiotic processes in the Cambrian period.
An embryos skeleton is made up mostly of cartilage; cartilage is later replaced by bone over the years, through a process called ossification. The two types of ossification are intramembranous ossification that develop membranous bone and endochondral ossification that develops cartilaginous bone. Cartilage is located in places like your ears and nose, cartilage is also found near the ribs in order to expand whenever you breathe.
The initial product of the union of ovum and sperm; a fertilized ovum, is called the zygote. It begins as a single cell and rapidly divides to become a blastocyst or the development stage of the zygote when it is about 5 days old and ready for implantation; the embedding of the blastocyst in the inner uterine wall. Cell
The embryos are usually extras that have been created in IVF (in vitro fertilization) clinics where several eggs are fertilized in a test tube, but only one is implanted into a woman (Crosta, Paragraph 3). The blastocyst consists of an inner cell mass (embryoblast) and an outer cell mass (trophoblast). The outer cell mass becomes part of the placenta, and the inner cell mass is the group of cells that will differentiate to become all the structures of an adult organism(Crosta, Paragraph 4). In a healthy pregnancy, the blastocyst stage continues until implantation of the embryo in the uterus, at which point the embryo is referred to as a fetus. This usually occurs by the end of the 10th week of gestation after all the primary organs of the body have been created (Crosta, Paragraph 5). Human embryonic stem cells are the cells from which all 200+ kinds of tissue in the human body originate. When stem cells are obtained from living human embryos, the harvesting of such cells necessitates the destruction of the
The zygote is the result of a female egg being fertilized by a sperm cell. For two consecutive weeks rapid cell division in effect, but it only takes 5 days for Blastocyst to occur. Blastocyst is a thin hollow structure that marks the beginning of the embryo. The outermost layer supports growth to placenta (umbilical cord) and surrounding tissue within the uterus.
For years studies and observations have been made on the relationship between body size and physical orientation of an animal. In 1847 Carl Bergmann was one of the first to do observations with this phenomenon (Dictionary of Theories 2002). Bergmann noticed that warm-blooded animals living at climates high in latitude are bigger in size than those living in climates of lower latitudes (Dictionary of Theories 2002). Research has shown there is a correlation of surface area to volume in animals that are located in different parts of the globe. Animals living in a cooler climate have a larger volume, but decreased surface area to retain as much body heat as possible. The inverse is true for animals living in warmer regions; these animals have a smaller volume and larger surface area to allow the body to cool efficiently (McNab 1971). Bergmann’s rule has brought valuable insight into the study of character traits and how we identify where animals originated. One example that I came across is with the Andean passerine bird, a study was done in 1991 by G. R. Graves. He noticed the size of ...
The first step was to obtain the White Rat and to tie it in the supine position, anterior surface facing up in side the dissection pan. To tie the animal, we used butcher’s twine and secured the front and hinds legs using a “lasso” technique, careful not touch the sharp claws. To make the first insicion I had to locate the Xifoid Process of the rat (distal aspect of the sternum). Once I had located the Xifoid Process, I had to use forceps to pull the skin of the animal’s abdomen up and use the scissors to cut. The first incision is made from stem to sternum, cutting through the errectos abdomen muscle down to the groin. The second incision ion is perpendicular to the first below the diaphragm. Because of this technique we were able to open the abdominal cavity first. The third and forth incisions were made bilaterally above the legs. The last two incisions were made in upside down “V” shape on the collarbone, to expose the thoracic cavity. This dissection was both sharp, because of the use of the scissors and scapel and blunt because of the use of the probe and forceps to move organs and skin to expose other organs not yet identified.
"Embryonic stem cells are derived from a four- or five-day-old human embryo that is in the blastocyst phase of development."(source). Before the embryonic stem is produced, the fertilized egg, a zygote, starts to multiply it's cells. Once the group of cells is set in the uterus, it becomes a blastocyst. The blastocyst consists of an inner and outer mass. The outer mass, the
The history of taxonomy dates all the way back to the 4th century, where organisms were divided into 2 groups, plants and animals by a Greek philosopher, Aristotle. Early naturalists did not acknowledge that the similarities and differences between the two organisms were results of evolutionary means. So as the years went on, classification gradually changed and slowly became more and more sophisticated.