Biodiversity

Friday, May 05, 2006

CORRECTIONS

Some notes on Chapter 2 of biodiversity need editing, like E: section two:Fossil evidence for the first chordates, is incomplete. Rich please note this. Cheers


VINCENT MUCHAI WAIRIMU

Biodiversity and Conservation Biology

University of the Western Cape

Private Bag X17 Bellville

TEL: +27825103190

Email: 2648463@uwc.ac.za

Website:http://www.muchai.iblog.co.za

SIGNALS USED BY INSECTS TO ATTRACT A MATE FOR SEXUAL REPRODUCTION

Insect use sight, smell and sound for their courtship. A combination of any of the three or a single one is used by a particular group to achieve attracts members of the opposite sex.

Pheromones is a chemicals released by organisms to send a message to members of similar species1. They serve different purposes like alarming other animals, marking territories, marking food trails, sexual attraction among others. Sexual pheromones are mostly produced by females indicting their availability for mating and this applies also for insects but males also produce pheromones to indicate what species they are1. An example of insects that use pheromones are the moths which when produced will be detected by males using their feathery antennae which are large6.

Other insects make calls (noises) which attract members of the opposite sex and repel competing members of same species. The calls vary from species to species as they are produced differently. Male Crickets make calls known as chirp using their wings which have ridges that is more similar to a "comb and file" instrument. They achieve this by rubbing their wings or legs over each other, and the calls are conspecific (for similar species). This type of calls are for attracting females and repelling males (calling song) and are loud as compared to the courting song which is produced when the male is near a female and the sound is more quiet. The chirp sounds vary from species of cricket to the other and depend on temperature of the environment. The chirping in most cases is temperature dependent and is higher at higher temperatures and less in lower temperatures. This relationship between the chirping rate and temperature is described by a law known as Dolbear's Law.2

Cicadas and grasshoppers produce sounds just like the crickets do. Sound in grasshoppers is produced by rubbing the notched edge of the legs against the wings6. Sound is received by a membrane located between the two deep slits on the first thigh pair. Sometimes they use the visual display of their sometimes brightly coloured legs5. As for the cicadas the stomach has got two chambers. The inner wall of every chamber is stiff and pulled by a big muscle found in the stomach moving up to six hundred times per second and as it is pulled it makes a click. 6 The click (stridulation) is created is made loud in the abdomen “by a hollow vibrating plate and two hollow rectangular resonators and sound is received from eardrums on either side of the thorax of the cicadas” 6. Male cicadas are called tymbals and modulate their calls by moving their abdomens to and away from the tree that they sit on3. The sounds produced are different for each and every species hence its success and they can be amazingly loud. The different kinds of rubbing the body to produce sound are known as stridulation3.

Other species like the moths, butterflies and mayflies display their wings especially during the mating season. The wings are created in such a way that they have scales that have pigments and microscopic structures that split light reflect different form of light rays displaying different kinds of colours. These colours are conspecific and serve to attract species of the same species for mating. This members display sexual dimorphism (males having different colours and structure than the females). The displaying of colour is used during the mating season6.

References:

1. Wikipedia contributors. Pheromone [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 13:28 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Pheromone&oldid=51522169.

2. Wikipedia contributors. Cricket (insect) [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 14:55 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Cricket_%28insect%29&oldid=51531343

3. Wikipedia contributors. Cicada [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 19:47 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Cicada&oldid=51568000. .

4. Wikipedia contributors. Stridulation [Internet]. Wikipedia, The Free Encyclopedia; 2005 Sep 24, 16:53 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Stridulation&oldid=23924839.

5. Wikipedia contributors. Grasshopper [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 27, 13:10 UTC [cited 2006 May 5]. Available from: http://en.wikipedia.org/w/index.php?title=Grasshopper&oldid=50416744.

6. Knight, R. BCB Biodiversity chapter 2 The Swarming Hordes (Cited 2006 May 4) http://planet.uwc.ac.za/nisl/biodiversity/Chapter2/page_40.htm



VINCENT MUCHAI WAIRIMU

Biodiversity and Conservation Biology

University of the Western Cape

Private Bag X17 Bellville

TEL: +27825103190

Email: 2648463@uwc.ac.za

Website:http://www.muchai.iblog.co.za

THE VARIATIONS IN SHELL STRUCTURE THAT OCCURRED IN THE PHYLUM MOLLUSCA

The phylum mollusca are known to be the largest of all phyla. They provide some of the most familiar animals such as clams, mussels, squids and octopus. They are well known for they provide shells used for decoration as well as sea food. The phylum Mollusca also “includes lesser known forms such as the chitons, tusk shells, and solenogasters, among others”. (1)

They live in more or less “all parts of the world, from the deep water bodies like oceans to high up on mountains” (1). For them to stay alive; they need enough moisture to keep their body moisturised all the times. Those that live in hot dry deserts environment, they keep their bodies moist by curling up in their shell there by secreting a mucous plug and staying holed up until the next bit of moisture comes along.

The protective shells or shelters of the phylum Mollusca are made up of chemicals and nutrients. These shells or shelters are however different and quite a few groups have reduced or internal shells, or no shells at all. (1)

The aplacophora “are wormlike bilaterally symmetrical animals living at moderate, to very great depths, usually on or in soft bottoms” (2). They have no shell, but have calcareous spicules in the surface of their bodies. The bivalva or Apelecypoda does not have the shells because they live in water with ph greater than 5. It is difficult for them to develop shell because the ph value of the water. (2, 4)

The polyplacophora have the “shell consisting of eight, usually overlapping plates held together by a leathery strap” (4). They live in water and most survive by grazing algae from other hard substrates and rocks. The most distinguishing characteristics of chitons are that they have eight-piece shell.

The scaphopodia which are commonly known as tusk shells, “are bilaterally symmetrical and their elongate, tubular, tapering shells are open at both ends” (5). “The shell is usually an elongated cylindrical tube; open at both ends, and slightly curved” (5). However, some of the scaphoda shells are shaped more like a bloated cucumber. The shell is usually heavily not level and has small slits at the narrowest end.

The cephalopoda class includes octopus, squid, cuttlefish and nautilus. “Tentacles surround the head and a funnel coming from the mantle produces jet propulsion” (6). Externally, the shell of the nautilus is creamy white with broad reddish-brown stripes. Inside it is brilliant, iridescent mother-of-pearl.

The Gastropods generally “have a single-valved shell, which is usually spiralled; this brings their organs from a posterior position to an anterior position behind their head” (7). In most cases, the soft animal is able to pull back into their shells for protection.

The Monoplacophorans have a single, large, bilateral shell. “The shell is a simple depressed limpet or disk -shaped valve, less than 25 millimetres across usually and is often thin and fragile” (8).

The shell serves both protective and supportive purposes. The one feature common to all molluscs is the presence of a fleshy mantle. This is a fold or lobe of fleshy material, which secretes, modifies and lines the shell.


References

1. Wikipedia contributors. Mollusca [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 18, 21:38 UTC [cited 2006 May 23]. Available from:

2. Wikipedia contributors. Aplacophora [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 18, 05:55 UTC [cited 2006 May 23]. Available from: http://en.wikipedia.org/w/index.php?title=Aplacophora&oldid=53815532.

3. Wikipedia contributors. Chiton [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 12, 14:07 UTC [cited 2006 May 23]. Available from:
4. Wikipedia contributors. Bivalvia [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 5, 12:59 UTC [cited 2006 May 23]. Available from:
5. Wikipedia contributors. Tusk shell [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 23, 12:22 UTC [cited 2006 May 23]. Available from:
6. Wikipedia contributors. Cephalopod [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 21, 05:56 UTC [cited 2006 May 23]. Available from:
7. Wikipedia contributors. Gastropoda [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 20, 06:36 UTC [cited 2006 May 23]. Available from:
8. Wikipedia contributors. Monoplacophora [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 21, 01:25 UTC [cited 2006 May 23]. Available from: http://en.wikipedia.org/w/index.php?title=Monoplacophora&oldid=54281584.

Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria
0001
Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
E-mail: lmukwevho@csir.co.za
My blog URL: http://mukwevholufuno.blogspot.com


VARIATIONS IN SHELL STRUCTURE THAT HAVE OCCURED IN THE PHYLUM MOLLUSCA

The phylum mollusca include organisms which are having internally and reduced shell, but in some of the phylum mollusca the shell is absent at all (Edwards, 1997). For examples, the phyllum mollusca include gastropoda, and cephalopoda. Under the phylum mollusca, we find different classes which are also different in their structural body form. These classes include ''polyplacophora; cardofoveata and solenogastres; gastropoda; scaphopoda; bivalvia; cephalopoda and monoplacophora'' (Edwards, 1997). The variations in shell structure of the above mentioned classes of the mollusca may be attributed to various locations or the evolution of the species themselves.

Mostly, the phylum mollusca have their shell structures which are planispiral flat coil in shape. Cephalopoda have head and foot which are fused together to form the anterior end and they also have atendency towards reduction and loss of shell. Although the majority of the mollusca have the planispiral flat coil structure, some of them have ''partially straight, partially coiled partially uncoiled shell, helically coiled and superficially coiled'' (Edwards, 1997). Along the period of evolution, some shells of the phylum mollusca started to become diverse during the cretaceous part. However, some shells of the phylum mollusca appear to be three dimensional while some appear to be smooth without the spines.

Gastropoda are logorithmically spiraled shell that is 180 degree rotation during its development. According to the paleoanthropologists and the geologists the rapid evolution of the mollusca provided them with the useful information about the fossils. This is because paleoanthropologists can easily link each class of the mollusca according to its variation in relation to their location. Usually the majority of the mollusca live above the seafloor. Therefore when the ''mollusca die, their remains sink down into the seafloor where they remain buried as a fossil'' (Wikipedia contributors, 2006).

As it has already been mentioned in the introductory paragraph that some of the classes of the mollusca lack shells. This is evidence in the ''two classes solenogastres and caudofoveata'' (Edwards, 1997). The lack of shells in the two classes can be attributed to their habitat which is soft sediments which are usually found in deep sea. While on the other side polyplacophora consists of an overlapping shell plates which can also be attributed to its habitat, rocky shore. The class bivalvia consists of two values of shell which are held together by the ligaments as opposed to the class gastropoda which consists of a spirally coiled shell.

Although the shells in the majority of the phylum mollusca are complex, there is a different ways in which the shells can be modified. Mostly, the shells composed of three things. These three things are periostracum, outer cover and the inner layers of the calcium carbonate. Edwards (1997) also says that the outer cover of the shell protects the inner calcareous layers of the shell against erosion or heavy storm. On the other hand periostratum acts as a microscopic shell structure.

In concluding paragraph, one can say different classes of the phylum mollusca possessed different shell structure. This is because all the classes of the phylum mollusca are not found in the same place, even though the majority of them are found in the sea. After dying while in the sea, the fossils of the remains of the mollusca provide paleoanthropologists with the evolutionary information. The fossils found in the sea will enable paleoanthropologists to make both the prediction and postdiction about the primitive and modern life of the species of the phylum mollusca.

References:

Edwards, L. A. 1997. The shell structure. [Online]. Available from:
http://www.arches.uga.edu/~amylyne/GSC/shellmakers.html

Wikipedia contributors. Mollusca [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 13:39 UCT [cited 2006 May 6]. Available from: http://en.wikipedia.org/wiki/Mollusc

Wikipedia contributors. Mollusca [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 5, 14: 15 UCT [cited 2006]. Available from: http://en.wikipedia.org/wiki/Molluscs

Peter Muvhali
CSIR PTA
0001
Tell no 012 8142133
Fax 012 8423676
E-mail smuvhali@csir.co.za
URL: http://blogsoccer-peter.blogspot.com/

THE PROCESS OF FOSSILIZATION AND ITS SIGNIFICANCE IN THE INTERPRETATION OF EVOLUTIONARY EVENTS

The process of ''fossilization is the one which occurs when the animal or plant remains are preserved underneath the ground without any disturbance'' (Wikipedia contributors, 2006). The process takes different forms; these forms include carbonization, permineralization, drying, and asphalt, freezing and amber. The final results of fossilization are the fossils. Fossils are either plant or animal remains embedded underneath the ground. These fossils help scientists to analyze and make postdiction about how life started on our planet earth. The analyses are done by using either radiometric dating or geological time scale.

The process of fossilization begins when the plant or animal remains are buried underneath the ground. In order for fossilization to occur naturally without any disturbance such as erosion and washing away by precipitation or floods, the remains are then safe for fossils to occur. As it has already mentioned in the above introductory paragraph that fossilization does occur differently. It may occur through the process of ''permineralization where the plant or animal remains are preserved as a rock'' (Nedin, 1998). Permineralization occur when the remains of either plant or animal become crystallize and then leaving the original appearance of the original remains.

On the other side during ''carbonation, both plants, animals, reptiles and all other aquatic organisms leave carbon when they die'' (Wikipedia contributors, 2006). The carbon which is left provides scientists with the information about the species. The information which can be provided by studying the carbon may be found by using the carbon-dating method. Mostly, fossilization starts when plants, animals and reptiles fall in craves, drown into the river or remained buried underground.

Sand or mud often protects the remains of organisms after the process of decomposition. Therefore after the burial of the remains, the process of fossilization will continue slowly as compared to the immediate death of the organisms. It must also be taken into consideration that the process of fossilization occurs in the absence of oxygen while the remains are already under the ground. The absence of oxygen discourages the bacterial activities which are responsible for the decaying of plant or animal remains.

After the rapid events of death and burial of the plants or animals, the events which follow take thousands to millions of years. Nedin (1998) says that the slow process of fossilization is due to the build up of materials such as sediments over the remains. After the build up of sediments over the remains, the remains may either changed into one of the different types of rocks such as calcite, gypsum and phosphates.

Therefore, in concluding paragraph one can say by studying and analyzing the fossils which are buried underneath the ground scientists can make possible postdiction about the evolution of life on the earth from the primitive periods until today. The piecing together of each fossil whether plant or animal provides the scientists with the linkage of the primitive species and the present species. This is because fossils provide scientists with the information about the history of evolution. The evidence which the fossils can provide can be whether the species were abundant or rare previously as compared as compared to the present.

References:

Nedin, C. 1998. Fossilization. [Online]. Available from:
http://home.tiac.net/~cri/1998/taphonomy.html [24 February 1998, 13: 24]

Wikipedia contributors. Fossilisation [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 13:36 UCT [cited 2006 May 5]. Available from: http://en.wikipedia.org/wiki/Fossilisation

Wikipedia contributors. Fossils [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 5, 13: 49 UCT [cited 2006 May 6]. Available from: http://en.wikipedia.org/wiki/Fossils


Peter Muvhali
CSIR PTA
0001
Tell no 012 8142133
Fax 012 8423676
E-mail smuvhali@csir.co.za

URL: http://blogsoccer-peter.blogspot.com/

THE STRUCTURE AND SIGNIFICANT OF DNA TO LIFE

The DNA (Deoxyribonucleic acid) is "a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information’' (1, 4). It is regularly in the form of a double helix, having the hereditary instructions indicating the biological development (the study of the process by which organisms grow and develop) of all the cellular forms of living and micro organisms (1). It is very long molecule consisting of structural unit of nucleotides and encodes the series of the amino acid remains in the protein using the hereditary code, a ''triplet code of nucleotides" (1).


The DNA is often called the molecule of genetics, because of its responsibility to hereditary propagation of mainly inherited traits. "It is replicated and can be transmitted to offspring during duplicating in the process of cell division. The DNA is a pair of molecules joined by the hydrogen bond’. All the DNA strands are chain of the nucleotide. There are about four types of nucleotides namely: (A) Adenine, (C) Cytosine, (G) Guanine and (T) Thymine. A is paired with T while G with C, that is A+T, T+A, C+G, G+C are possible combination and A+T is not the same as T+A as well as C+G is not the same as G+C (1).The DNA contains the hereditary information that is innate by the brood of an organism; ‘this information is determined by the sequence of the base pair along its length"(1).


The DNA strand has an area "that regulate genes and areas where the functions are yet unknown or they do not have a function. The DNA is found throughout the body in cells, within cells in chromosomes and within each chromosome in genes. The body is formed from between 50 and 100 trillion cells. These cells are organised into tissues, such as skin, muscle and bone. Humans have two sets of 23 chromosomes in every cell, the Y chromosome and the X chromosome, the Y is for male and X for female therefore a human cell contains 46 of these chromosomal DNA molecules" (1, 2).


The DNA helps in identifying people. "We use the DNA tests to find out about our relatives, families and also to trace the criminals. No matter how differently we appear, in hair colours, facial structures, our movement, habits and other characteristics. These differences result from very little differences in their DNA sequences. The DNA of any two people on Earth is in fact, 99.9% identical. We inherit one copy from each parent, we have two copies. In order to understand fully our DNA sequences, both inherited copies of genes need to be carefully examined" (1).


The Deoxyribonucleic acid can be used to trace a criminal by comparing the "DNA data from the crime sight to the DNA profiles of the suspects using the CODIS sites, if the DNA samples match absolutely at the 13 regions used in the FBI’s CODIS system, then the probability that they come from two related people are 100%. This method helps in the identification of a relevant person for the scene" (1).

Reference:

1. Wikipedia contributors. DNA. [Internet]. Wikipedia, The Free Encyclopaedia, 2006 May 3, 10:11, PTA Available from: [http://en.wikipedia.org/wiki/DNA ].


2. Wikipedia contributors. Gene [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 02, 10:00, PTA. Available from: [http://en.wikipedia.org/w/index.php?title=Gene&oldid=50087668].

3. Wikipedia contributors, biological development [internet]. Wikipedia, The Free Encyclopaedia, 2006 May 03, 12:50, PTA. Available from [http://en.wikipedia.org/wiki/Developmental_biology].


4. Wikipedia contributors, biological development [internet]. Wikipedia, The Free Encyclopaedia, 2006 May 03, 12:50, PTA. Available from [http://en.wikipedia.org/wiki/Nucleic_acid].

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/

BIODIVERSITY COURSE CALENDAR ADDED

Hi Everyone,

Really exciting news - and I hope it works your end! We have been
developing a course calendar for the Weblog that works from our BCB
servers. You can see this added to the right hand side - and each day's
task are highlighted by a link with some instructions to guide your pace
of learning. When the tasks are listed and you want to see the entire
calendar you follow the link that says

Return to calendar for BCB705

Here is also a link to large Calendar with all details for the next
weeks workplan.

http://planet.botany.uwc.ac.za/calendar/calendar/largecal.asp?view_date=5/5/2006&calendarname=BCB705

Please confirm that you have read this email by adding your comments
and that you a) understand the use of the calendar, b) you have viewed
your workplan for the week ahead and c) you are happy about editting and adding the assignments via your blogger.com accounts

We are unfortunately going to have to pick up a little speed on this
course so that it is completed by the end of the month.

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

Email Rknight@uwc.ac.za

Web http://nisl.uwc.ac.za

LINKS TO NEW CHAPTERS ON BIODIVERSITY UPDATED

Hi Guys

Please note that the links to the first four chapters are now up.


It is really important that you review Chapter 1 and then tackle Chapter 2 with seriousness.  All assignments in Chapter 2 need to be completed by the end of next week so that we can proceed to next stage of Biodiversity.  The UWC based students David and Karin are doing Biodiversity in the past through revision of material and preparing it eventually as a Web Page.  The Pretoria Students will explore Biodiversity from a Genetic Perspective and those lectures will  become available from the 15th May.
 
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