Jan 192013

As we already know, search engines are such kinds of websites which help us to search any type of letter, word, phrase, document or file in the internet in a short time. These days, people are using search engines rapidly so as to save their time. Some examples of search engines are Google Search Engine (owned by Google Inc., U.S.A.), Bing (owned by Microsoft Corporation, U.S.A.), Yahoo! Search Engine (owned by

facebook Yahoo! Inc., U.S.A.) etc. They are very much popular due to their quick, reliable and efficient services.
Recently, famous social networking site, Facebook has started its initiatives to establish its own search engine. The name of the search engine of Facebook is kept as ‘Graph Search’. With the help of this search engine, the Facebook users will be able to search different materials like photos, videos etc. which are shared in Facebook. Not only that much, this search engine will not only help the users to search words, but also phrases and quotes.

While announcing Facebook’s own search engine feature, Facebook’s Co-Founder and Chief Executive Officer (C.E.O), Mark Zuckerberg said that Graph Search was not a web search engine which would challenge the most popular search engine of current time, Google.

But Graph Search will take help from Microsoft’s Bing search engine in order to find the materials which cannot be found by Graph Search. Due to this relationship of Graph Search with Bing, many people have taken this relationship as a direct challenge against Google. In spite of these types of thoughts of the people, Zuckerberg has hoped that Facebook users would use Graph Search only for searching the Facebook related materials rather than other internet related terms and materials.

Facebook, which has became successful to establish itself as the greatest social networking site of the world, contains huge amount of materials. These materials which have been posted, shared and connected by the site itself  have been defined  by Facebook as ‘Social Graph’. Zuckerberg also stated that in order to make the reach of the users to those materials or Social Graph reliable and easy, Facebook had introduced Graph Search. But critics have criticized about Graph Search by taking it as an incomplete as well as ineffective feature brought out by Facebook. So Zuckerberg has replied to this criticism by saying that there were many things that were left to do in Graph Search’s beta version and Facebook would soon make improvements in that. Currently, only limited numbers of users from United States of America are allowed to use and experience the Beta version of Graph Search. You can know more about Graph Search by clicking here.

Jan 182013

In biology, earthworm is also known as Pheretima. It is one of the organisms which can be found in most of the parts of the world. It lives in soil which is rich in decaying organic matters. Some examples of such places are lawns, gardens, fields, pastures, banks of rivers, lakes, ponds etc. It is nocturnal in nature so it becomes active at night only. These are some characteristic features of earthworm. Here, in this post,we are going to

discuss about the external morphology of earthworms which include the following factors:

  1. Shape and Size: The body of earthworm is long, cylindrical, narrow, bilaterally symmetrical and nearly circular in cross section. The anterior end is tapering while the posterior end is more or less blunt. A mature earthworm measures about 150 mm in length and 3 to 5 mm in thickness. The thickest part of the body is little behind the anterior end. The dorsal surface is marked by the presence of a dark median line of dorsal blood vessel which runs along the length of the body just below the skin. Likewise the ventral surface is marked by the presence of genital openings and papillae in the anterior part of the body. The body is of shiny dark-brown colour. The dorsal surface is darker than the ventral surface. The brown colour of worm is due to the present of pigment called porphyrin in the body wall.
  2. Segmentation: The body of earthworm consists of about 100-120 segments. The segmentation is true in which the external segmentation corresponds with the internal segmentation of the body. Hence, the segmentation in the earthworm’s body is known as metameric segmentation or metamerism. The whole body surface is divided by a distinct series of circular grooves. All the segments are alike except the first and the last.
  3. Peristomium: Earthworm has no distinct head, eyes and tentacles. The first segment of the body is called peristomium or the buccal segment, which bears a terminal, crescentric mouth. IT is prolonged anteriorly to a fleshy lobe known as the prostomium which overhangs the mouth of the earthworm.
  4. Clitellum: Clitellum is a girdle-like thick band of glandular tissue which is found towards the anterior end of the body. It is also known as cingulum. The clitellum is formed in mature worms and extends over 14th-16th segments. The glands of clitellum secrete mucus, albumen and egg case or cocoon for the eggs. Due to the presence of clitellum, the body is earthworm can be divided into pre-clitellar, clitellar and post-clitellar regions.
  5. Setae: Setae are chitinoid structures of faint yellow colour which are shaped like an elongated “S”. They have a swollen middle part which are called the nodulus. Except the first, the last and the clitellum segment, each segment contains a ring of about 80 to 120 chitinous setae which are embedded in the epidermal pit of each segment. Such an arrangement is known as perichaetine arrangement. About one-third of setae length projects above the surface of skin and the remaining gets embedded in a setal sac. The setae help in locomotion by holding the earth since they are directed backwards. Their movement is controlled by two types of muscles which are protractor and retractor.