Macroevolution and Gene Expression - Essay Example

Comparative genomics, developmental, and paleontology, contribute most of the evidence for patterns and processes which can be classified as macroevolution.

Annelida is commonly known as segmented worms which are found in the deepest marine sediments and the city park yards. During the 20th century, Annelida was divided into three main subgroups Oligochaeta, Polychaeta, and Hirudinea (Levinton, 88). Leeches and earthworms are similar to annelids for most people. The Polychaeta comprise an extent of the divergence of the Annelida and is found near the marine habitat. There are even pelagic Polychaeta, which swim, preying on the other plankton and few groups exist in fresh water and moist environments. Around nine thousand species of Polychaeta are recognized, and the overall systematics groups remain unstable. The Oligochaeta and Hirudinea comprise several other species to form a clade which can be referred either clitellata or Oligochaeta. The group may well belong to Polychaeta; this makes Polychaeta similar to Annelida. There is evidence supporting that all annelids have recently been groped as a single group.

The common system used to divide Polychaeta was Errantia; he was essentially a system of convenience with no aim of characterizing evolutionary relationships. Recent analyses of the Annelida and other groups have resulted in a new classification of Polychaeta. The group split into two groups palpate and Scolecida. Scolecida contains species of less than 1000; these worms are all couch from one another. Palpate has the majority of Polychaeta and is also divided into aciculate and canalipalpata. Aciculate are approximately half the polychaete species and largely aggress the old taxonomic group Para podia. Arthropods have taken over almost all the environment on the surface of the earth. Pieces supporting the evidence run that more species of arthropods are multi-celled animals, but that is only true for the expound species and more hobbyists are added to that list for insects.
The phylum arthropod is divided into two subphyla, which are named according to their mouthparts but have several differences.

The chelicerae, named for mouthparts derived from the appearance of the legs and the chelicerae, they do not have antennae found in the subphylum. The chelicerates have six pairs of appendages. One pair of chelicerae is followed by a pair of pedipalps, legs that are adapted for other purposes rather than walking. A horse crab is an old group that has five pairs of legs and no pedipalps; it resembles a shield with two eyes and a tail. They live in sandy zones; have been existing for a long time looking much similar to what they are today. The evolutionary theory, suggests that creatures are suited to an environment that has remained stable for a long time and would change. When exposed to direct radiation chemicals, which mutate animals' DNA, changed molecules.

The process of mesmerization is known in drosophila. The metameric pattern can be extended to arthropods and other related animals. The known diversity of the metameric process should evolutionary interprets the relationship between their developmental and morphological features. We view the aspects of drosophila development that involve Para segmentation and compartmentalization patterns. The regularities are compared with what is known as phenomena in other crustaceans, onychophorans, and millipedes. The Annelida segments and hypothetical soft-bodied cannot be identified with Para segments. The segments do not correspond to any identified developmental body met meres in arthropods. They are not recapitulated during the primary and ontogeny development. The interior most definite segments do not show any traces of being secondarily incorporated in the metasediments as required by the hypothesis of concurrent ontogenetic, and phylogenetic switch from secondary, and primary body segmentation.

Annelida’s body is made up series of sequentially arranged down the length of animals. In addition, the segment organized in tagma which is another notable difference between the two phyla is that the arthropods have paired appendages on their Metameres. The sequence of events tends to assume that the arthropods have the logical, evolutionary steps which followed the annelids (Pontarotti, 79). There is evidence that this may be not the case.

Gene expression is a key determinant in organismal phenotype and evolution. The widespread recognition of the facing this fact occurred long after the synthesis of genetics and evolution. Various studies consistently find that adaptive differences are controlled by a few genetic differences. Most of the studies determine the genetic regions which influence the physical traits differences between species. Changes in genes play a crucial role in modifying evolution, particularly when adapting to a change in environment. Little is known about the molecular mechanism underlying adaptively significant in gene variation. Homologous genes control the same characteristics, but during evolution, the homologous genes mutated making species that originally had the same traits appear different. They represent digital mechanisms, which regulate axial patterning (Pontarotti, 120). By matching and mixing combinations of the expression of the smaller number of the homologous genes, they generate a wide range of morphological possibilities. The subjection of body shape is an effortful process to apprehend, but the hox systems are which researchers are getting closer to comprehending this process.