Prehistoric Life During the Ordovician Period

Prehistoric Life During the Ordovician Period One of the lesser-known geologic spans in the earths history, the Ordovician period (448-443 million years ago) didnt witness the same extreme burst of evolutionary activity that characterized the preceding Cambrian period; rather, this was the time when the earliest arthropods and vertebrates expanded their presence in the worlds oceans. The Ordovician is the second period of the Paleozoic Era (542-250 million years ago), preceded by the Cambrian and succeeded by the Silurian, Devonian, Carboniferous and Permian periods. Climate and geography. For most of the Ordovician period, global conditions were as stifling as during the preceding Cambrian; air temperatures averaged about 120 degrees Fahrenheit worldwide, and sea temperatures may have reached as high as 110 degrees at the equator. By the end of the Ordovician, however, the climate was much cooler, as an ice cap formed on the south pole and glaciers covered adjacent landmasses. Plate tectonics carried the earths continents to some strange places; for example, much of what would later become Australia and Antarctica protruded into the northern hemisphere! Biologically, these early continents were important only insofar as their coastlines provided sheltered habitats for shallow-water marine organisms; no life of any kind had yet conquered land. Marine Life During the Ordovician Period Invertebrates. Few non-experts have heard of it, but the Great Ordovician Biodiversity Event (also known as the Ordovician Radiation) was second only to the Cambrian Explosion in its importance to the early history of life on earth. Over the course of 25 or so million years, the number of marine genera around the world quadrupled, including new varieties of sponges, trilobites, arthropods, brachiopods, and echinoderms (early starfish). One theory is that the formation and migration of new continents encouraged biodiversity along their shallow coastlines, although climatic conditions also likely came into play. On the other side of the evolutionary coin, the end of the Ordovician period marked the first great mass extinction in the history of life on earth (or, one should say, the first for which we have ample fossil evidence; there were certainly periodic extinctions of bacteria and single-celled life during the preceding Proterozoic Era). Plunging global temperatures, accompanied by drastically lowered sea levels, wiped out a huge number of genera, although marine life as a whole recovered fairly rapidly by the start of the ensuing Silurian period. Vertebrates. Practically all you need to know about vertebrate life during the Ordovician period is contained in the aspises, especially Arandaspis and Astraspis. These were two of the first jawless, lightly armored prehistoric fish, measuring anywhere from six to 12 inches long and vaguely reminiscent of giant tadpoles. The bony plates of Arandaspis and its ilk would evolve in later periods into the accoutrements of modern fish, further reinforcing the basic vertebrate body plan. Some paleontologists also believe that the numerous, tiny, worm-like conodonts found in Ordovician sediments count as true vertebrates; if so, these may have been the first vertebrates on earth to evolve teeth. Plant Life During the Ordovician Period As with the preceding Cambrian, evidence for terrestrial plant life during the Ordovocian period is maddeningly elusive. If land plants did exist, they consisted of microscopic green algae floating on or just underneath the surface of ponds and streams, along with equally microscopic early fungi. However, it wasnt until the ensuing Silurian period that the first terrestrial plants appeared for which we have solid fossil evidence.

Everything You Need to Know About Having a Part-Time Job

Everything You Need to Know About Having a Part-Time Job Don’t want to work full-time but aren’t sure what the alternative is? If you’re not exactly certain what a part-time job entails, hours-wise, here’s a primer to what you might expect. The HoursEssentially, a part-time job is a position that offers you flexibility- of scheduling or decreased hours. The number of hours varies from company to company: anywhere from 5 to 35 per week. The company has the discretion here, as to what they consider part-time. It isn’t regulated by the Fair Labor Standards Act- and the ACA only differentiates full from part-time work (at 30 hours per week) for the purposes of health insurance benefit eligibility.The  OpportunitiesThere is a bit of stigma attached to â€Å"part-time† work, making it seem as though it isn’t real work, but there are many professional gigs that fall under the part-time umbrella. It’s not just retail and hospitality either! It can be particularly useful for stay-at-home par ents, students, retirees, and any other workers who prefer not to have the time commitment of a full-time position.The PerksIt’s even occasionally possible to start with part-time employment and transition into full-time work at that company, if you play your cards right- making part-time work a useful way to get your foot in the door somewhere.It’s also possible to gain access to benefits- though not as extensive as full-time packages, and not universally.If you think part-time work might be an ideal situation for you at this stage in your career, try looking for positions that have flexibility and at least some baseline benefits. And remember, what works for you works for you. Don’t worry about what anybody else thinks.

Writer's Autobiography Assignment Essay Example | Topics and Well Written Essays - 500 words

Writer's Autobiography Assignment - Essay Example This gave me an opportunity to read extensively. As such, I gathered knowledge on how to approach different topics. My tutor told me that, to develop fluency in language, there is a need to read extensively. This will not only develop my fluency in writing, but will also develop my speech. In my pre-school years, I remember playing reading games. This gave me exposure to the English language as I learned new vocabularies with each passing day. Apparently, some of the words were confusing. This encouraged me to search a dictionary to enable me understand the vocabularies. However, this was tricky. For example, some new vocabularies are not included in the older versions of dictionaries. Therefore, as I progressed in the reading games, I had to look for the latest dictionary. This proved a prudent approach in knowing new vocabularies. In the turn of events, I started to develop a passion of writing about any trending story. As such, I noted that I had developed an undying passion of writing for enjoyment. One thing i remember about writing is that, it helps in grasping different topics and giving the topics a different approach. For example, I could write about the same story using three different approaches. This was like playing with words to suit the same topic. I re member most of my classmates making requests for my writings to develop their language. I felt that my writing was appreciated in class. As a fact, this elevated my passion in writing. I felt that I could do better with enhancement in the efforts I made towards writing. Consequentially, I started concentrating in some of the topics that proved a hurdle. For example, physical geography involves visiting places and doing lots of research. However, I started writing about physical geography, though I had not visited some of these places. This sparked my imagination to a higher level as I had to do massive research on the places. I was astonished