Biodiversity

Saturday, May 06, 2006

ISSUES ON CHAPTER 2: BUGS

Hi Everyone

Vincent spotted that some text went missing on page 83 of Chapter 2 - see his posting http://bcb705.blogspot.com/2006/05/corrections.html.

I will try and sort this out shortly, but I think it is best to explain how this chapter was generated. It started off as a 450 page MS Word document that we add hidden code (called XML) using third parties (Connected Learning). I use CSS (cascading style sheets) to control the final look and feel of the site. The advantage of this is it automatically creates your Page and Chapter navigation - otherwise you would have to keep renumbering pages each time you inserted a new page (Weblogs get over this by only reporting in chronological order so there is no problem). In using this approach I have noticed a couple of bugs - the worst being when two hyperlinked words to different sites follow each other they get joined together as a single word losing their space. Please just bear with this while I contact the developer on this part of the project.

There is a second issue when inserting the code we can sometimes forget to close tags for the formatting and this is what Vincent has found - a missing classification or text caused by human error of not closing a tag. When you start your HTML - you will find that it is very easy to do a mistake like this.

There is also potential for a third issue/problem, when the material was prepared I did not have access to Wikipedia and its classification concepts for species classification - and therefore the classifications could vary slightly (similar to the Homo erectus and Homo ergaster problem identified earlier in the year). It is also possibly the Wikipedia can also be wrong or inconsistent. To illustrate this the lobe-finned fish http://http://planet.uwc.ac.za/nisl/biodiversity/Chapter2/page_93.htm called the Coelacanth Latimeria chalumnae (order Crossopterygii), if you search Wikipedia for "Crossopterygii" it will re-direct you to "Sarcopterygii". Sarcopterygii is actually the Class, and the main Wikipedia has directed you to this site and reports a different classification order "Coelacanthiformes" for the Coelacanth, but in its Wikibooks http://en.wikibooks.org/wiki/General_Biology/Classification_of_Living_Things/
1 Chordates
... and vindicates what I have put into the text.
A fourth point issue, I am aware of is the putting of species into italics is inconsistent - the actually scripting is tedious and we used students for the job, and well mistakes were made - but please remember there were 450 pages and more than 102 000 words, so inevitably mistakes will creep in (and we had literally a few weeks to develop the course).
If you find a mistake that is not a font-based italics or joining of two words that have independent hyperlinks (we know these are issue), then identify the page e.g. page_93.htm where there is a problem and attach as a comment to this BUG Page and in due course it will get fixed. Since when putting a change in - we have to re-compile the whole site which can potentiall change a pages url (and is literally an overnight computing task) these will not be done immediately.
Cheers
Rich




Dr Richard Knight
Co-ordinator: National Information Society Learnerships - Ecological Informatics
Department of Biodiversity and Conservation Biology
University of the Western Cape
Private Bag X17
Bellville 7535

Phone 27 + 21 + 959 3940
Fax 27 + 21 + 959 1237



THE VARIATIONS IN SHELL STRUCTURE THAT HAVE OCCURRED IN THE PHYLUM MOLLUSCA.

The phylum is a grouping of organisms used in the classification of life. The mollusca are large and varied group of organism that includes a variety of recognizable creatures well-known for their attractive shells or seafood. The common name for mollusca is mollusc or molluscs. The molluscs are triploblastic protostomes. It has thin shell, muscular foot that is used for movement and round mantle shell (1).


These range from tiny snails, clams and abalone to the octopus, cuttlefish and squid. The snail applies to most members of the mollusca class Gastropoda that have coiled shells. These snails are of herbivorous nature, found in fresh water, marine and terrestrial environment. The snails are also grouped in to, Pulmonata group (snails with lungs) and the Praphyletic group (snails with gills form). The snails move like earthworms by alternating body reductions with stretching, with proverbially low speed. They use mucus to reduce friction and chance of being injured. The mucus helps them to prevent dangerous insects like ants (1).


Mollusc are classified into nine classes of which eight of them are still living, these classes make up the 250 000 and more species of mollusc (2).Class Pelecypoda (Bivalvia) are compacted animals with two shells hinged on the animal’s dorsal surface. This class species are found in just about every marine environment. The clams are shelled marine of freshwater molluscs belonging to the class Bivalvia. They can live for 150 years old or longer. They can be hard shelled or soft shelled, according to the degree of calcification of their shells, according to species (1).


The abalone belongs to the large class of gastropods and the Haliotidae family. The shell is rounded to oval, with two to three whorls and the last one auriform, grown in to a large ‘ear’ giving rise to the common name ‘ear-shell’. ‘The cuttlefish are the animals of the order Sepiida, and are marine cephalopods, small relatives of squids and nautilus. They are having the internal shell, large eyes, and eight arms and two tentacles furnished with denticulate suckers’ (1). The squid are the large, varied group of marine cephalopods accepted as food in cuisines as widely separated as Korean and Italian. Class Caudofoveta are small (1 – 30 mm) class of the phylum mollusca, primitive deep sea molluscs. They are worm – like molluscs that live buried head down in the floor, lacking shells or distinct muscular feet (1).

Class Monoplacophora have a single cap-like shell and they superficially resemble limpets. The class Polyplacophora, usually known as chitons, have seven or eight dorsal shell plates. Class Scaphopoda or Tusk shells have a tapered, tubular shell that is unlock at both ends (1). Class Gastropoda are the largest most successful class of molluscs. Most of the approximately 40 000 living species of this class have shells; there are few groups that have either reduced or internal shells or no shell at all. The shelled forms are generally called ‘snails’ and the forms without shells are called ‘slugs’ (1).


“The slugs and snails move by contracting and relaxing their foot muscles. They are having two types of muscles fibres that are performing different work. When they are going forward they use one set, which is pulling the snail from the front and pushing it off towards the back. While the second pair pulls the outer surface of the sole forward. Usually the sole is not divided in the snails. There are some of the snails which their sole are splited lengthwise and are known as Pomatias elegans. They can both move separately, creating a sort of pedal like locomotion” (3).


References:


1. Wikipedia contributor, Mollusca [internet]. Wikipedia, the free encyclopaedia, 2006 May 03, 08:00 UTC cited, available [http://en.wikipedia.org/wiki/Mollusca].


2. Wikipedia contributors, Phylum [internet]. Wikipedia, The Free Encyclopaedia, 2006 May 03, 12:50, UTC. Available from [http://en.wikipedia.org/wiki/Phylum].


3. Arno Brosi. 2000. The biology of snail. [Internet]. Available from [http://members.tripod.com/arnobrosi/evo.html, accessed 16/05/2006, 14:34].


Ms Evelyn Maleka
CILLA CSIR
P.O. Box 395
Pretoria 0001
Tel: (012) 841 2133
Fax: 012 842 7024
Email: emaleka@csir.co.za
http://malekaevelyn.blogspot.com/