Lethabo

im 22 years old, female doing my honns in ecological informatics at csir(pretoria)

Name:
Location: pretoria, gauteng, South Africa

i completed my Bsc (microbiology physiology) degree in 2005 at University of Limpopo, now im doing my honns in ecological informatics at university of the western cape.

Wednesday, March 28, 2007

KEEP ON GOING

I like these words by Amy Candy which says that "you should always learn, with life comes wisdom and with wisdom comes the courage to live your life selflessly. The more you learn about yourself and the experiences surrounding your life. The more opportunities you have to make your life better and more fulfilling." i think each and everyone one of us owe it to herself/himself to be the best they can possibly be in life

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

KEEP ON GOING

I like these words by Amy Candy which says that "you should always learn, with life comes wisdom and with wisdom comes the courage to live your life selflessly. The more you learn about yourself and the experiences surrounding your life. The more opportunities you have to make your life better and more fulfilling." i think each and everyone one of us owe it to herself/himself to be the best they can possibly be in life.

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

Thursday, January 18, 2007

NEW BABOON SPIDER SPECIES DISCOVERED IN KRUGER NATIONAL PARK

NEW BABOON SPIDER SPECIES DISCOVERED IN KRUGER NATIONAL PARK

Martin Paulsen and Ian Engelbrecht have discovered a new species of baboon spider (Ceratogyrus paulseni) at Letaba region of the Kruger National Park. They said that the baboon spider comes from four different genera and it is difficult to tell the genera that the baboon spider may fall into. The baboon spider has a horn on its cephalothorax and the horn is similar to the common horned baboon spider (Ceratogyrus becaunichus). This discovery makes one to think about evolution and whether everything is still evolving. The discovery of the baboon spider forms part of the researches of South African National Survey of Arachnids (SANSA) headed by Dr Ansie Dippenaar-Schoeman of the Agricultural Research Commission (ARC). They are trying to discover and describe an inventory of the South African arachnoid fauna. There about 220 species of arachnoids found in Kruger National Park which are known. Kyle Harris, a C•I•B student is conducting a masters (M.sc) research on the “effects of alien invasive plants on spider assemblages within the KNP” [1].

[1]. http://academic.sun.ac.za/cib/news_new_baboon_spider_species.htm

Friday, May 26, 2006

CROP CIRCLES OR FAIRY CIRCLES

What are these crop circles some says that they are patterns that no one can explain and others says that they are similar crops that some of the crops are flattened to form different types of shapes.

Some people think that crop circles are natural and others thinks that are manmade. Some people think that it is a “foot print of intelligence” [1]. Those who have seen crop circle been made said that it takes just few minutes to make a crop circle. For an example Doug Bower and Dave Chorley said that they know how to make these circles and they have been making crop circles in England since 1978 [2]. They said they were using planks, ropes, wires and hats to make the circles.

So who or what really made these crop circles is it the witches/wizards or lightning or aliens or just super natural powers or man. I think nobody really knows the answer to this question because each and everyone want to prove that his/her point to be right. Those who are saying that they are witches or wizards’ making this circles they said that the circles are made by witches/wizards while they are dancing and they dance in rings or circles. As for the different circles they says that witches/wizard do not serve the same master so it depends on which master they are serving and they call crop circles as “fairy circles”. Some people say that is a way that aliens communicate with people so what people has to do is just to figure out what the circle means. As for the lightning they say that the lightning has burst from the clouds in a circular way then when it reaches the ground it makes crop circles [3].

Why are this crop circle happening is it just to decorate the field or is there any other reason. Those who are making these circles they are just making them for fun just like Doug and Dave were making these circles just to make people think that aliens’ spacecraft had landed there just because they have read about crop circles from a book [4]. But those who believe that crop circles are made by aliens said that on the night this crop circle appeared they saw unusual light and they also heard some weird sounds and some says that they smelt a “smoky foul smell” in the early mornings [5]. As for those who believe that crop circles are natural thinks that everything can be explained by the “Plasma vortex theory” where air from the top of a hill whirls up and produce electrically charged particles which flattens the crops [6].

In the soil of some crop circles especially were the crops were bent there were small particles of magnetic iron which were found inside the circles were more than those found outside the circle? The soil inside the circle differs from the soil outside in such a way that the soil which is found inside the circle is more fertile than the one which is outside. The nodes on the stalks of plants which are inside the circle are different from those outside so if it was man-made how do they change the nodes of plants? Why the do not make mistake because all the crop circles that are available are all perfect. Where do they get time to make this circle? What is keeping the shape of the circles? Why are these crop circles only found in certain plants such as wheat, corns or oat but not in spinach field or pumpkin field? Why do they occur only during the night between 11 pm to 4 in the morning [7]?

These crop circles have effect on other peoples lives and some of the people who have seen then says that the crop circles leaves a feeling of gratefulness in them [1].

The way the crop circles are made the are so beautiful so some of them I can believe that they are made by man but some I do not believe; they way the are so complicated I do not think they can make them. From this website [8] explains how artificial crop circles were made so my question is how did the change the nodes on the plants or is just another technique used to become rich and famous? So I personally think some of the crop circles occur naturally and some are man-made.

References:

1. Quest for the truth. [Video] available from: http://video.google.com/videoplay?docid=974931714241227503&q=crop+circles
2. Wikipedia contributors. Crop circles [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 18, 03:27 UTC [Cited 2006 May 19]. Available from:
http://en.wikipedia.org/w/index.php?title=Crop_circle&oldid=51207130
3. Plot, R. The natural History of Stafford-Shire. [Internet]Updated 2006 May8, 2:31 am [Cited 2006 May 23]. Available from: plotshistorystaffordshireabbrev.pdf
4. Anon. Crop circles [Internet]. Updated 2006 May 26, [Cited 2006 May 26]. Available from: http://www.bbc.co.uk/science/space/life/aliens/cropcircles/human.shtml
5. Anon. Are crop circles made by Aliens? [Internet]. Updated 2006 May 26, [Cited 2006 May 26]. Available from: http://www.bbc.co.uk/science/space/life/aliens/cropcircles/alien.shtml
6. Anon. Are crop circles a Natural phenomenon? [Internet]. Updated 2006 May 26, [Cited 2006 May 26]. Available from: http://www.bbc.co.uk/science/space/life/aliens/cropcircles/vortex.shtml
7. Anon. Crop circle theories [Internet]. Updated Anon [Cited 2006 May 19]. Available from: http://www.crystalinks.com/croptheories.html
8. Krystek, L.Crop circles from outer space? [Internet]. Updated 2000, [Cited 2006 May 26]. Available from: http://www.unmuseum.org/cropcir.htm

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
Mail: http://www.blogger.com/lmosomane@csir.co.za
http://lmosomane.blogspot.com/

Tuesday, May 16, 2006

ADAPTATION REQUIRED TO MAKE THE TRANSITION FROM AN AQUATIC TO A TERRESTRIAL ENVIRONMENT- AMPHIBIANS

In general Amphibians are ectotherms and spend part of their time on land. They live both in water and on land but they spend most of their time in water. Amphibians are soft bodied; they are hunted after as food by larger predators. The common European Toad (Bufo bufo) inflates its body and stands on its toes to appear as large as possible and thereby discourage any potential predator. More active defence occurs in the fire-Bellied toad produce a mucous for protection which keeps the skin moist and it is also extremely bitter tasting. The poison (mucous) which frogs produce is lethal to mammals and local people use its poison to tip their arrows. Defence that frogs use-producing a poisonous mucous- it is of a little value because their attacker dies after they themselves have been eaten.

When amphibians are in water they use gills to breath but when on land the gills are replaced by other respiratory organs i.e. lungs. They change their skin and develop glands in order to avoid dehydration. Amphibians eyes develop eyelids and adapt to vision outside the water. An eardrum develops to lock the middle ear and the tail disappears.

Limitations to an amphibians terrestrial life

Amphibians are only partly successful in their colonization of land, since their limbs are short and they need to flex their body in order to take reasonable strides. Their skin is permeable and in dry atmospheres they dehydrate quickly. Amphibians do not have the mechanisms to drink water while they are on land. Their skin must be moist in order to supplement respiration since their lungs are comparatively simple and not totally adequate for its needs. These limitations restrict amphibians to moist environments. Amphibians are entirely dependent on water for reproduction sine their eggs have no water-proof covering and their larvae (tadpoles) which are quite like fishes. These larvae initially have no legs they use their long tail in order to swim and they use external feathery gills to breathe.

Amphibians use terrestrial environment mostly for laying eggs you have just said they lay their eggs in the water? Because for them it is a much safer site for the development of their offspring than an aquatic environment which has many predators (especially fish). Anurans have evolved mechanisms to exploit the terrestrial environment for the breeding of their young. Some amphibians like the midwife toad Alytes obstetricans live in holes close to water and mate on land. After fertilization the long strands of eggs are twisted around the hind leg of the male toad. The male carries them around until the tadpoles are ready to hatch and then takes them to water.

In dry habitats, amphibians development is limited by moisture not by temperature. For example the rain frogs Breviceps which live in dry regions only come (out of burrows) above ground during heavy downpours. Adults emerge from their underground burrows and absorb rainwater through their skins, thus replenishing their body fluids. Amphibians fill their bladder with water. Some frogs are able to hold water; they minimize their dependence on water under dry conditions. When it rains they absorb lots of water and bury themselves deep inside the sand and then they secrete a membrane around themselves which prevents water loss.

Many frogs are able to absorb water directly through the skin, especially around the pelvic area. However, the permeability of a frog's skin can also result in water loss. Some tree frogs reduce water loss with a waterproof layer of their skin. Others have adapted behaviours that conserve water, including engaging in nocturnal activity and resting in a water-conserving position.

References:

1. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 Mar 27, 22:44. PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Permeable
2. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 00:20. PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Amphibians
3. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 02:38. PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Frog
4. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 30, 18:42. PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Nocturnal
5. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 03:32. PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Microhylidae
6. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 Feb 8, 17:35. PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Midwife_toad
7. Wikipedia contributors. Amphibians [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 02:38. PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Anurans

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

WHY REPTILES ARE BETTER ADAPTED TO A TERRESTRIAL ENVIRONMENT THAN AMPIBIANS

Reptiles are cold blooded animals (ectothermic). Their cellular metabolism produces some heat but reptiles do not generate enough to maintain a constant body temperature (1). Reptiles rely on gathering and losing heat from the environment to regulate their internal temperature, for example they move between sun and shade. They also move warmed blood into their body core, while pushing cool blood to the periphery. In their natural habitats, most species are adapted to the mechanism and they can maintain their core body temperatures within a fairly narrow range. While this lack of adequate internal heating imposes costs relative to temperature regulation through behaviour, it also provides a large benefit by allowing reptiles to survive on much less food. While warm-blooded animals move faster in general, an attacking lizard, snake or crocodile moves very quickly.

Lizards the Scincomorpha family, which include skinks, often have shiny, iridescent scales that appear moist. However, like all other lizards, they are dry-skinned and generally prefer to avoid water. All lizards are able to swim if needed, however, and a few are comfortable in aquatic environments (2). For example marine iguana (a lizard which live in the water) when it is cold it is unable to move effectively, which is makes it more vulnerable to predators. Marine iguanas are very aggressive before they have warmed up since they are unable to run away (3).

The physiology of frogs is generally like that of other amphibians but differs from other terrestrial vertebrates (5) because oxygen may pass through their highly permeable skin and reptiles uses their nostrils. This unique feature allows frogs to "breathe" largely through their skin. Because the oxygen is dissolved in an aqueous film on the skin and passes from there to the blood, the skin must remain moist at all times; this makes frogs susceptible to many toxins in the environment, some of which can similarly dissolve in the layer of water and be passed into their bloodstream (4). Reptiles skin mostly consists of scale and it is not permeable. There is a lack of moisture on land so in order for amphibians to survive they require a lot of mosture unlike the reptiples. Ampibians depend mostly on the amount of mosture available unlike the reptiles.

Many frogs are able to absorb water directly through the skin, especially around the pelvic area which makes it more vulnerable to absorb a lot of poisonous gases from the atmosphere. The permeability of the skin of a frog can also result in water loss especially on land unlike the reptiles (3). The skin of reptiles acts as a structure for protective features e.g. scales (5).

Amphibians and reptiles are both ectothermic- can not maintain their body temperature- they maintain their body temperature by basking on the sun. They absorb a lot of heat so that they can be active. The problem is amphibians can not survive on land for long periods unlike the reptiles which basically live on land. When the amphibians are on land their skin loses a lot of water since they spend most of their time in water. When amphibians are on land mostly they absorb a lot of heat within a short period of time so that by the time they dry out they should have collected enough heat and they also minimize the period of lethargy after emerging from the water. Reptiles can maintain and retain their water inside unlike some amphibians.

Reference:

1. Wikipedia contributors. Reptiles [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 10, 02:57. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Reptiles
2. Wikipedia contributors. Lizards [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 10, 07:12. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Lizard
3. Wikipedia contributors. Anura [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 10, 02:38. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Anura
4. Wikipedia contributors. Marine Iguana [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 8, 23:48. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Marine_Iguana
5. Wikipedia contributors. Vertebrate [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 7, 13:12. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Vertebrate

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

MORPHOLOGICAL DIFFERENCES BETWEEN CARTILAGINOUS AND BONY FISH

Bone fishes also referred to as Osteichthyes-osseous tissue is a hard endoskeletal (internal support structure of an animal) connective tissue. Bones give the body posture structures support and also help in facilitating movement (1). Bony fishes are characterised by a relatively stable pattern of cranial bones and rooted teeth. The head and pectoral girdles are covered with large dermal bones and the eyeball is surrounded by a sclerotic ring of four small bones. They also have an operculum, which helps them to breathe without having to swim (4).

Cartilage is a type of dense connective tissue and it is composed of cells called chondrocytes. Chondrocytes are dispersed in a gel-like ground substance called matrix (2). Cartilage is a vascular (contains no blood vessels) and nutrients which are diffused through the matrix. Cartilage is mostly found in the joints, the ear, nose, rib cage and in the throat. Cartilages provide a framework for fish which do not have bones (2). The cartilaginous fishes are also referred to as Chondrichthyes which have jaws with paired fins, paired nostrils, scales, two-chambered hearts and a skeleton made of cartilage(3). Cartilaginous fishes have a tough skin which is covered with dermal teeth also called placoid scales or dermal denticles which make the fish feel like sandpaper (3).

Cartilaginous fishes do not have any bone marrow; the red blood cells are produced in the spleen and special tissue around the gonads. In the bony fishes the red blood cells are produced in the bone marrow like in humans. Cartilaginous fishes have a special organ where red blood cells are produced called Organ of Leydig and it is only found in the cartilaginous fishes. Another unique organ is named epigonal organ, and plays a role in the immune system (3).

Cartilaginous fishes have a relative brain which relative brain weight comes close to that of mammals, and is about ten times of bony fishes of the same size. The bony fishes have a relative brain size to be compared with the brain size of humans. One of the explanations why cartilaginous fishes have such large brains is because they are using much less energy. The density of nerve cells in cartilaginous fishes are much lower than in the brain of bony fishes, making it less energy demanding and allows it to be bigger(3).

Bony fishes have various types of calcified tissues: dentine, enamel (or enameloids) and bones. Endochondral bone of the bony fishes begins as a cartilage then it later turns to a bone (4). Cartilaginous fish gets calcium from a cartilage called hyaline (3).

Bony fishes get most of their calcium from the bones but the cartilaginous fishes get their calcium from hyaline articular cartilage. Basically bony fishes consist mostly of a cartilage when the fish is still young the bone only develops when the fish starts to grow so even the bony fish use cartilage because cartilage is much more flexible than bones. Cartilaginous fishes are lighter in weight than the bony fishes which are much heavier for example Marlin (5) which weighs up to 820 kg.

References:

1. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 7, 20:02 PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Bone
2. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 3, 21:28 PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Cartilaginous
3. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 5, 20:22 PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Cartilaginous_fish
4. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 7, 12:50 PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Bony_fish
5. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 15, 09:47 PTA [cited 2006 May 9]. Available from: http://en.wikipedia.org/wiki/Marlin

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

MUTUAL RELATIONSHIP BETWEEN PLANTS AND ANIMALS

Many insects are considered pests by humans. Insects commonly regarded as pests include those that are parasitic (mosquitoes, lice, bedbugs), transmit diseases (mosquitos, flies), damage structures (termites), or destroy agricultural goods (locusts, weevils). Many entomologists are involved in various forms of pest control, often using insecticides, but more and more relying on methods of biocontrol(2).

Many insects are beneficial to the environment and to humans. Some help in pollinating flowering plants (for example wasps, bees, butterflies, ants). Pollination is the transfer of pollen grains to the plant-ovule (1). An exchange between plants that need to reproduce and pollinators receive nectar and pollen. Population of pollinator insects has been declined and numbers of species of insects are now cultured primarily for pollination management in order to have enough pollinators (1).

Insects also produce useful substances such as honey, wax, lacquer and silk. Honeybees have been cultured by humans for honey, although contracting for crop pollination is becoming more significant for beekeepers. Fly larvae (maggots) were formerly used to treat wounds to prevent or stop gangrene, as they would only consume dead flesh. This treatment is finding modern usage in some hospitals. Insect larvae of various kinds are also commonly used as fishing bait.

There are different types of animals which help with pollination (carrying pollen grains-male- to other plants-female plant) (3). There is pollination by insects like bees which is called entomophily (4) and pollination by animals such as birds or bats called zoophily(5).

Bees travel from flower to flower, collecting nectar (which is later converted to honey), and in the process they pick up pollen grains. The bee collects the pollen by rubbing against the anther (found on top of the filament and it is a male organ-stamen) (6). The pollen is collected on the hind legs, in dense hairs referred to as a pollen basket. As the bee flies from flower to flower, the pollen grains are transferred onto the stigma of the female flower part.

Nectar provides the energy for bee nutrition; pollen provides the protein. When bees are rearing large quantities of brood (7) (young of honeybees collectively), bees will deliberately gather pollen to meet the nutritional needs of the brood. A honeybee that is deliberately gathering pollen is up to ten times more efficient as a pollinator than one that is primarily gathering nectar and only unintentionally transferring pollen(3).

Good pollination management seeks to have bees in a "building" state during the bloom period of the crop, thus requiring them to gather pollen, and making them more efficient pollinators. Thus the management techniques of a beekeeper providing pollination service are different from, and somewhat incompatible with, those of a beekeeper who is trying to produce honey.

Plants provide bees with nectar and bees transfer pollen grain from one plant to the other. Some animals lay their eggs in some flowers then the flower will act as a shelter for those eggs. This shows a mutual relationship between plants and animals because both species benefit from each other.

References:

1. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 4, 20:22 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Pollination
2. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 8, 08:09 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Insects
3. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 4, 20:22 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Pollination#Types_of_pollination
4. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 5, 10:13 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Entomophily
5. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 3, 09:26 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Zoophily6. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 Apr 28, 13:40May PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Anthers
7. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2005 Aug 25, 02:08 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Brood_(honeybee)

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

VARIATION IN SHELL STRUCTURE OCCURRED IN THE PHYLUM MOLLUSCA

The mollusks constitute one of the largest phyla of animals, both in numbers of living species and in numbers of individuals. All mollusks have a soft body, which is protected by a hard, calcium- containing shell. Mollusks are triplobastic (ovum which has three primary germ layers-ectoderm (outer), mesoderm (middle) and endoderm (inner layer) protostomes. A significant characteristic of mollusks is their possession of a coelom, a fluid-filled cavity that develops within the mesoderm. The coelom functions as a hydrostatic skeleton which also provides space within which the internal organs can be suspended by the mesenteries. The body cavity is filled with blood. Mollusks have a mantle (fold of the outer lining of the shell and a muscular foot that is used for motion-movement). Many mollusks mantle produce a calcium carbonate-external shell and their gills extracts oxygen from water (1).

Phylum Mollusca are divided into different classes which have different types of shells:-

· Class GastropodaMost of the approximately 40,000 living species of gastropods have shells, however there are quite a few groups that have either reduced or internal shells, or no shell at all. Although most Gastropods are marines, there are numerous forms in both freshwater and terrestrial environments. Most members have a shell which is in one piece and typically coiled or spiralled which usually opens on the right side (2). Some species have an operculum which operates as a trapdoor in order to close the shell.

· Class Pelecypoda (Bivalvia )They have two part shells with both parts being less or more symmetrical. The class include scallops, clams, oysters and mussels. Their shells are composed of calcium carbonate and the shells are very strong. In some bivalves the shell is made up of calcium carbonate known as aragonite which is not very strong (3).

· Class Cephalopoda This class includes species like squid, octopus and cuttlefish. Their shell is either internalized or is absent. The cuttlefish is the only modern shelled cephalopod. It occupies only the outermost portion of its elaborate and beautiful shell, the rest of which serves as a flotation chamber. In the squid and its relative, the cuttlefish, the shell has become an internal stiffening support, and the octopus does not have a shell entirely (4).

· Class MonoplacophoraThey have a single, flat, rounded bilateral shell which resembles chitons. Their shells are often thin and fragile and their shell apex is forward (5).

· Class PolyplacophoraThis class include the chitons which have seven or eight dorsal shell plates embedded in the tough muscular girdle that surrounds its body. Their calcareous armour shell that they carry dorsally acts as a protective measure. Their shell is made up of aragonite and colored (6).

· Class ScaphopodaThey are also called the tusk shells because their shell is openly curved plan spiral tubular shell which opens at both sides and the shell resembles an elephant tusk. They have tapered, tubular shells that open at both ends (7).

Reference:

1. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 3:39 PTA [cited 2006 May 4]. Available from: http://en.wikipedia.org/wiki/Mollusc
2. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 3, 20:07 PTA [cited 2006 May 4]. Available from: http://en.wikipedia.org/wiki/Gastropoda
3. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 3, 19:00 PTA [cited 2006 May 4]. Available from: http://en.wikipedia.org/wiki/Bivalvia
4. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 03: 04:57 PTA [cited 2006 May 4]. Available from: http://en.wikipedia.org/wiki/Cephalopoda
5. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 22, 20:03 PTA [cited 2006 May 4]. Available from: http://en.wikipedia.org/wiki/Monoplacophora
6. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 04, 15:32 PTA [cited 2006 May 4]. Available from: http://en.wikipedia.org/wiki/Polyplacophora
7. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopedia; 2006 Apr 23, 12:22 PTA [cited 2006 May 4]. Available from: http://en.wikipedia.org/wiki/Scaphopoda

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

HOW INSECTS FINDS THEIR SOUL MATES

Insects use different ways in order to attract their partners. Insects use sound, smell, colour and pheromones (is a chemical produced by an organism that transmits a message to the other members of the same species).

Pheromone is a chemical which is produced by living organisms that transmits message to other members of the same species. Insects produce a trail pheromone and some insects use pheromones to mark their path. The pheromones have to be continually renewed because they evaporate quickly. Some insects use pheromones in order to locate or find their mating partners.

Some insects like crickets, grasshoppers and cicadas use the process of stridulation (produce sounds by rubbing together two parts of their body) when attracting their mating partners.

Crickets males have a chirp (their wings have ridges that act like a comb or file instrument) which they use to attract the females. They chirp by rubbing their wings or legs over each other, and the song is specific. Crickets have two types of songs which they sang in order to attract their females. The songs are the calling song and a courting song. The calling song attracts only females and repels males, and the song is fairly loud. The courting song is used when a female cricket is near, and is a very quiet song. Female crickets have a long needlelike egg-laying organ (ovipositor).

Grasshoppers produce sounds when attracting their mating partners. They produce sound by sawing the notched edge of their hindlimb against the strengthened vein of the wing. Only the males are able to sing in order to attract females. After mating, the female cuts slits into the bark of a twig and deposits her eggs there. She may do so repeatedly, until she has laid several hundred eggs. When the eggs hatch, the newborn nymphs drop to the ground, where they burrow and start another cycle.

Cicadas attract their mates by vibrations. They have abdomens which have two chambers, the inner wall of the chamber is rigid and when the abdomen moves in or out it makes a click sound. There is a large muscle in the abdomen which pulls the wall back; the noise is amplified in the abdomen using a hollow vibrating plate and two hollow rectangular resonators. Sound is received from eardrums on either side of the thorax in cicadas, but grasshoppers use a membrane situated between two deep slits along their first pair of thighs. With each species having a unique sound, they can recognize and attract appropriate mates of the same species.

Moths, butterflies and mayflies display their colourful wings to attract their mating partners. Their wings have scales that have pigments and microscopic structures that split light and reflect different form of light rays displaying different kinds of colours. When they spread their wings they attract females but of the same species since females are less colourful than males so males are the ones who attract females. Moths use smell to attract mates (pheromones). Females produce chemical compounds called pheromones which male moths are able to detect with their large, feathery antennae but it had to continue producing the pheromone because it evaporates quickly.

Insects use different way in order to attract their mating partners or in finding their soul mates. Some animals use smell, sounds, displays beautiful colours and some use pheromones.

Reference:

1. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 7, 16:15 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Pheromones
2. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2005 Sep 24, 16:53 [cited 2006 May 8]. Available from: http://en.wikipedia.org/w/index.php?title=Stridulation&oldid=23924839
3. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 4, 14:55 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Crickets
4. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 8, 03:48 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Butterfly
5. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 6, 15:20 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Grasshopper
6. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 Apr 28, 18:49 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Mayflies
7. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 7, 09:49 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Cicadas
8. Wikipedia contributors. Council of Science Editors [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 8, 13:21 PTA [cited 2006 May 8]. Available from: http://en.wikipedia.org/wiki/Moth

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

DOES A HERBIVOURS DIET IMPOSE CERTAIN PROBLES FOR DIGESTION?

Herbivorous animals eat only plants and it demands particular skills and structures to stick to one particular diet. Vegetables are not particularly nutritious and great quantities of material needs to be extracted to obtain enough calories to sustain large animals. In animals such as elephants their diet is so woody it takes a long time for them to digest their food. It takes an elephant two and a half days to digest its food and for most of the time the food will be in the stomach being stewed with digestive juices and bacterial broth. All plants contain cellulose and there is no animal that can digest cellulose what about rabbits? So animals depend mostly on stomach bacteria to break down cellulose by the process of fermentation (1).

All herbivorous animals have a four chambered stomach which allows most of them to digest foods which are low in nutrients. Most of the herbivorous animals develop big stomachs. Bovids, for example, elephants only digest half of what they eat in order to make up for a lack of efficiency of their digestive system. An elephant only digests 40 % of its food and the rest of the food leaves the elephants body undigested (4). Animals like cows take their food into their rumen, a chamber of the stomach which contains a particularly rich brew of bacteria. While the food is still in the rumen, the food is churned back and forth for several hours, and then the food is squeezed by a muscular bag, while the bacteria attach to the cellulose (3).

Ruminants have a stomach with four chambers rumen, reticulum, omasum and abomasums. The first two chambers (rumen and reticulum); food is mixed with saliva and separates into layers of solids and liquid material. Solid material is clumped together to form a bolus which is then regurgitated, chewed slowly to completely mix it with saliva which is then broken down into fibres especially cellulose. Cellulose is then broken down into glucose by symbiotic bacteria and protozoa. The fibre which was broken down which is now in a liquid form it is passed to the next stomach chamber, the omasum where the water is removed. After the food is digested it is then moved to the last chamber the abomasum. In the abomasum food is digested in the same way humans digest their food, and then sent to the small intestine where nutrients are absorbed (2).

Mature leaves contain a high amount of hard to digest cellulose and have relatively low energy. Some herbivorous animals tend to have long digestive tracts and slow metabolism (biochemical modification of chemical compounds in the living organisms and cells) rate. If an animal has slowed its metabolic rate it gets large or fat in order to accommodate the food which is in the stomach. So they solve the problem by growing big and having large stomachs. Many of the herbivorous animals depend on the symbiotic bacteria to release nutrients into their diet (1).

Herbivorous animals have to eat very fast (grab as much food as possible) and cautiously because if they relax they will be at great risk of being eaten by predators (animals which eat only meat). For example the African Giant Rat gets out of its burrow (hole) at night when there is no danger; it loads its cheek pouches with food and when the pouches are full then it goes back to its burrow. Herbivorous animals eat only one type of food (plants) so they do not get enough nutrients in their bodies like proteins.

Reference:

1. Wikipedia contributors. Herbivorous [internet]. Wikipedia, The Free Encyclopaedia; 2006 Apr 30, 00:26 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Herbivorous
2. Wikipedia contributors. Ruminants [internet]. Wikipedia, The Free Encyclopaedia; 2006 Apr 22, 23:58 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Ruminants
3. Wikipedia contributors. Bovid [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 2, 05:19 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Bovid
4. Wikipedia contributors. Elephant [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 11, 23:26 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Elephant

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

THE DIFFERENCES BETWEEN NEW AND OLD WORLD MONKEY

The scientific name for the New World monkey is Platyrrhini. The New monkeys are the four families of primates found in Central and South America. New monkeys differ slightly from the Old World monkeys in many aspects, but mostly concerning the nose. The nose is the feature that is used mostly to differentiate the New monkey from the Old monkeys. The New World monkey has a flat nose, with side facing nostrils. New World monkeys have a long, prehensile tail (their tail has adapted to be used as the fifth hand). Many of them are small (arboreal), spend most of their time in trees or in the bushes and they sleep during the day and are active during the night (nocturnal). Many New World monkeys like to form monogamous pair bonds (remain with one partner for sexual reproduction and the raising of the young) and they show a substantial paternal care (fatherly care) of their young (2).

The Old World monkeys are called the Cercopithecidae which are a group of primates. They fall into the superfamily of Cercopithecoidea in the clade Catarrhini. They are found mostly in Africa and Asia but are also known to come from Europe. The Old World monkeys are unlike apes in that most of them have tails (tailed apes) when they are viewed from the superficial point of view. Their tails are never prehensile unlike the New World monkeys. The distribution of catarrhines (Old World monkeys) from the platyrrhines (New World monkeys) depends on the structure of the nose and the distinction of Old World monkeys from apes depends on dentition (1).

Most of the Old World monkeys have anatomical oddities. For example the colobus monkeys have a stub for a thumb; the Proboscis monkey has an extraordinary nose while the snub-nosed monkeys have almost no nose at all. The male Mandrill has a red coloured penis and the scrotum is a lilac colour while the face has bright coloration like the genitals. This develops only in the dominant males of a multi-male group (1).

Old World monkeys (e.g. Mandrills) are omnivores and acquires their food by foraging (mainly plants, insects and smaller animals) and the New World monkeys like to eat nuts, berries and insects (3). New World monkeys spend most of their time in trees and the Old World monkeys climb trees occasionally especially when they are going to sleep. There is no paternal care in the Old World monkeys like in the New World monkeys the offspring are looked after by their mother until they are adults. Old World monkeys have narrow noses or they do not have noses at all while the New World monkeys have flatter noses.

New World monkeys (Howler monkeys) range from 56 to 92 cm in size and have a life span of 15 to 20 years. They live in groups of about 18 individuals (4). The Old World monkeys weighs up to 30 kg and they can grow 1 m long. Old World monkeys can survive up to 25 years (3). Old World monkeys have a longer life span than the New World monkeys. Old World monkeys are more colourful than the New World monkeys.

Reference:

1. Wikipedia contributors. Old World monkeys [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 11, 18:58 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Old_World_monkey
2. Wikipedia contributors. New World monkeys [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 7, 15:12 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/New_World_monkey
3. Wikipedia contributors. Mandrill [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 8, 01:47 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Mandrill
4. Wikipedia contributors. Howler monkeys [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 9, 00:44 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Howler_monkey

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

COMPARISON BETWEEN THE PLACENTAL AND MARSUPIAL MODES OF REPRODUCTION

The placenta is a temporary organ which is only present in females especially during pregnancy (gestation) (2). The placenta is composed of two parts the genetically and biological part of the fetus and the other part of the mother. The fetus (baby) is implanted in the wall of the uterus where it receives nutrients and oxygen from the blood of the mother and passes out waste (2). Substances which could be harmful to the baby are filtered out by the placental barrier but some substances are not filtered out like alcohol and chemicals from cigarettes. Some types of viruses can also penetrate the barrier.

Marsupials are mammals in which the female has a pouch (marsupium) in which it rears its young through early infancy. Marsupials differ from placental mammals in their reproductive traits. A marsupial female has two vaginas which both open externally through one orifice (hole) but lead to different compartments within the uterus (1). Males have two penises which correspond to the females two vaginas. Marsupials have a cloaca (posterior opening that serves as the only opening for the intestinal, urinary, and genital tracts) that is connected to an urogenitals sac in both sexes. Marsupials’ males have two prolonged penises which are used to pass only sperm. Waste is stored before expulsion.

A pregnant Marsupial female develops a yolk sack in her womb which delivers nutrients to the embryo. The embryo is born at an early stage of development; it then crawls up into its mothers belly and attaches itself to a nipple. It attaches to the nipple for a number of weeks. Then the offspring passes a stage where it can leave its mothers pouch temporarily and returns for warmth and nourishment (1).

In placental mammals the placenta transfers gases and nutrients and the placenta has metabolic and endocrine (secrete hormones) activity. The placenta produces other hormones, progesterone which is important in maintaining pregnancy and somatomammotropin (placental lactogen). Placental lactogen increases the amount of glucose and lipids in the maternal (mothers) blood and this results in increased sugar levels during pregnancy (2). The placenta is connected to the fetus through the umbilical cord (3) (tube-like structure) which is composed of blood vessels and connective tissue. The placenta is delivered after the delivery of the baby (fetus) (2).

Placental mammals develop a complex placenta to protect the fetus from the mothers immune system and the marsupials do not have to develop a complex fetus. Marsupils give birth earlier than plancental mammals, they do not have to carry a large fetus to full-term. The plancental mammals e.g. humans carry their babies in the placenta for nine months but the marsupial mammals e.g. Kangaroos carry their babies in the placenta for thirty-one to thirty six days(4).If a placental mammal gives birth early before the time comes (prematurely) the baby is mostly taken care the same way as the marsupial take care of their babies. The baby is wrapped with a blanket on the mothers stomach like a Kangaroo and this method is called the Kangaroo care. Marsupials and mammals take care of their offspring but in different ways.

Reference:

1. Wikipedia contributors. Marsupials [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 9, 17:16. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Marsupials
2. Wikipedia contributors. Placenta [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 7, 18:21. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Placenta
3. Wikipedia contributors. Umbilical cord [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 8, 18:02. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Umbilical_cord
4. Wikipedia contributors. Kangaroo [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 11, 10:30. PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Kangaroo

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

ARE BIRDS LIVING RELATIVES OF DINOSAURS?

In general dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years ago. At the end of the Cretaceous period 65 million years ago, dinosaurs suffered a catastrophic extinction, which ended their dominance on land. Modern birds are considered to be the direct descendants of theropod dinosaurs (3). Birds are bipedal (two feet moving) warm-blooded animals which are characterized by feathers, forelimbs modified as wings and hollow bones (1).

There is evidence that birds evolved from theropod (beast foot) dinosaurs, specifically, members of Maniraptora, a group of theropods which includes dromaeosaurs and oviraptorids, among others (2). Non-avian (dinosaurs) theropods which were closely related to birds were discovered, which shows a clear distinction between non-birds and birds. In northeast China scientists discovered that the small theropod dinosaurs had feathers just like the modern birds (2).

Paleontologists discovered that Cryptovolans are better examples of birds than Archaeopteryx which is from where modern birds evolve. Ornithischian (bird-hipped) dinosaurs share the same hip structure as birds, but paleontologists believe that birds originate from the saurichian (lizard-hipped) dinosaurs. Dinosaurs are descendants of the most recent common ancestors of modern birds and Triceratops (1).

Modern birds are classified as Neornithes, which are split into the Paleognathae and Neognathae. The paleognaths include the tinamous (ancient groups of birds) and the ratites (flightless birds). The ratites are large flightless birds, and include ostriches, cassowaries, kiwis and emus (1).

Paleontologists believe that birds are the descendants of theropod dinosaurs. Descendants of a single common ancestor are related, modern birds are dinosaurs and dinosaurs have, therefore, not become extinct!. Modern birds are classified by most paleontologists as belonging to the subgroup Maniraptora, which are coelurosaurs, which are theropods, which are saurischians, which are dinosaurs. Paleontologists refer to birds as avian dinosaurs and to all other dinosaurs as non-avian dinosaurs. Dinosaurs are referred to as a synonym for non-avian dinosaur, and bird as a synonym for avian dinosaur (meaning any animal that evolved from the common ancestor of Archaeopteryx and modern birds) (3).

Birds are living dinosaurs because birds evolved from theropod dinosaurs which means when the dinosaurs died out birds continued with the legacy. Some of birds resemble dinosaurs like the ostrich; they have feathers but cannot fly the same as some dinosaurs. They are both warm blooded animals and they take care of their offsprings. Some paleontologists believe that birds are dinosaurs so dinosaurs did not die out because birds are carrying the dinosaurs legacy.

Reference:

1. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 8, 20:26 PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Birds
2. Wikipedia contributors. Theropoda [Internet]. Wikipedia, The Free Encyclopaedia; 2006 Apr 2, 04:52 PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Theropoda
3. Wikipedia contributors. Council of Science Editors [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 9, 17:38 PTA [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Dinosaurs#Evolution_of_dinosaurs

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com

ECHOLOCATION IN BATS AND WHALES

Bats and whales use high frequency sounds like sonar and radar to locate objects in the surrounding environment (echolocation) (2).

“Toothed whales use echolocation to sense objects. Whales send a high-pitched sound (usually a click sound). The sound bounces off the object and some returns to the whale. The whales then use the returning echo to determine the shape, direction, distance, and texture of an object” (1). Echolocation in a toothed whale starts with a series of low-frequency clicks (called a train) produced by the animal.” This train passes through the melon of the whale (a fat-filled organ in the head of the toothed whale that focuses the sound wave). The train of clicks is focused into a beam that bounces off objects and reflects (echoes) back to the whale”. “The echoed sound waves are received in the fat-filled cavities of the lower jaw-bone. These sounds are conducted through the bone to the ear and the brain, where the location of the object is interpreted. The whale can determine the distance to an object, its size, shape, the speed that the object is travelling, and its texture” (1).
Bats also use the process of echolocation in order to find their prey in the dark. Bats produce the sound by rushing air from their lungs past their vibrating vocal chords. “These vibrations cause fluctuations in the rushing air, which forms sound wave (sound wave is just a moving pattern of fluctuations in air pressure). The change in air pressure pushes surrounding air particles out and then pulls them back in. These particles then push and pull the particles next to them, passing on the energy and pattern of the sound. In this way, sound can travel long distances through the air. The pitch and tone of the sound are determined by the frequency of the air-pressure fluctuations, which is determined by the way you move your vocal chords” (3).

Some bats emit the sounds from their mouth, which they hold open as they fly and others emit sound through their nose. It's not fully understood how the bat's sound production works, but scientists believe that the strange nose structure found in some bats serves to focus the noise for more accurate pin-pointing of insects and other prey. In the case of most bats, the echolocation sound has an extremely high pitch. “The sound travels through the air as a wave, and the energy of this wave bounces off any object it comes across. A bat emits a sound wave and listens carefully to the echoes that return to it and processes the returning information in its brain. By determining how long it takes a noise to return, the bat's brain figures out how far away an object is” (3).

The bat can also determine where the object is, how big it is and in what direction it is moving. The bat can tell if an insect is to the right or left by comparing when the sound reaches its right ear to when the sound reaches its left ear: If the sound of the echo reaches the right ear before it reaches the left ear, the insect is obviously to the right. The bat's ears have a complex collection of folds that help it determine an insect's vertical position. “Echoes coming from below will hit the folds of the outer ear at a different point than sounds coming from above, and so will sound different when they reach the bat's inner ear. A bat can tell how big an insect is based on the intensity of the echo. A smaller object will reflect less of the sound wave, and so will produce a less intense echo. The bat can sense the direction in which the insect is moving. If the insect is moving away from the bat, the returning echo will have a lower pitch than the original sound, while the echo from an insect moving toward the bat will have a higher pitch”(3).

Whales use their tooth to locate their objects while bats use their mouth or nose to make the sounds. The mechanism that these animals are using is safer because they can sense how far an object is and they can also tell the direction in which the object is travelling.

Reference:

1. Echolocation –Whale Glossary. [Internet] 2006 http://www.enchantedlearning.com/subjects/whales/glossary/Echolocation.shtml
2. Google definition: [Internet] 2006 museum.nhm.uga.edu/gawildlife/glossary/gawwglossary.html
3. How stuff works “How Bats Work”. [Internet] 2006 http://science.howstuffworks.com/bat2.htm

THE STRUCTURE AND SIGNIFICANCE OF DNA TO OUR LIVES

Deoxyribonucleic acid (DNA) is a nucleic acid (“a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information”) (2) that are in the form of a double helix. It is able to replicate itself due to its double helix structure. “DNA contains genetic instructions that specify the biological development of all cellular forms of life. DNA is a long polymer of nucleotides and it encodes the sequence of the amino acid residues in proteins using the genetic code mostly a triplets code of nucleotides” (1).

The DNA molecule is a chemically linked chain of nucleotides. Each DNA molecule consists of sugar (deoxyribose-it has five Carbons and three Oxygen), a phosphate and one of five kinds of nucleobases (bases). “DNA strands are composed of nucleotide subunits called polymers. DNA has five kinds of nucleotides which are commonly referred to by the identity of their bases (1). The bases are adenine (A), thymine (T), uracil (U), cytosine (C) and guanine (G). Uracil (U) is found in the DNA when cytosine (C) is chemically degraded”.

"DNA is sometimes referred to as a heredity molecule because it carries genetic propagation (when more DNA is produced from the original strand) of most inherited traits. DNA can be transferred after been replicated from the parent to the offspring during reproduction”. Each and everyone of us has DNA; we have inherited our genomes from our parents. “A genome of an organism carries the whole hereditary information of an individual that is encoded in the DNA” (4). Each individual inherits 23 chromosomes from each parent including the X-chromosome (mitochondrial DNA that we inherit from our mothers and Y-chromosome from our fathers (1).

The way in which the DNA strands stay associated is determined by complementary pairing. Each base forms hydrogen bonds A bonds with T and G with C. the hydrogen bonds between A to T is a double bond and between G to C is a triple bond.Since DNA is a double stranded helix it can also unfold into two single strands by the process called DNA replication. “The two resulting double strands which are identical, each synthesize a new strand by the process called semiconservative replication (the method in which DNA is replicated in all known cells) (5).

The DNA molecule is always double stranded when it unfolds another strand is synthesized unless the DNA is mutated (change in genetic material).DNA contains the genetic information that is inherited by the offspring and this information is determined by the sequence of the base pairs. A DNA strand contains genes and areas where gene regulation takes place. Genes can be viewed as a cookbook or blueprint” (3).

The significance of DNA to us as human beings is that we are able to trace back our ancestors for example scientists used DNA in order to try to find the missing link between “Apes to Man”. Scientists used DNA in order to trace African Eve eight daughters so DNA is so important. DNA contains genes that parents pass on to their children so the generations can be traced back to our ancestors.

Reference:

1. Wikipedia contributors. DNA [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 01, 23:16. PTA [cited 2006 May 3]. Available from: http://en.wikipedia.org/wiki/DNA
2. Wikipedia contributors. DNA [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 01, 12:48.PTA [cited 2006 May 3]. Available from: http://en.wikipedia.org/wiki/Nucleic_acid
3. Wikipedia contributors. DNA [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 2, 04:25 PTA [cited 2006 May 3]. Available from: http://en.wikipedia.org/wiki/DNA_replication
4. Wikipedia contributors. DNA [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 3, 04:39 PTA [cited 2006 May 3]. Available from: http://en.wikipedia.org/wiki/Genomes
5. Wikipedia contributors. DNA [Internet]. Wikipedia, The Free Encyclopedia; 2006 Feb 3, 04:39 PTA [cited 2006 May 3]. Available from: http://en.wikipedia.org/wiki/Semiconservative_replication

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
mail: lmosomane@csir.co.za
http://lmosomane.blogspot.com/

Friday, April 21, 2006

Writing a scientific paper

Hi everyone on the 20 April 2006 I attended a small presentation about scientific writing at CSIR in Pretoria NRE (Natural Resources and Environment) building. Writing a scientific paper was presented by Peter Ashton. He talked about the different papers for example book reviews, discussion document, newsletters. When writing a scientific paper you should include all authors but with their permission and try writing as a team in that way you will be sharing the load and information. He talked about how to structure your paper before writing and the most important thing is that you should follow instructions. For more info send me an e-mail.

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
e-mail: lmosomane@csir.co.za
blog: http://www.lmosomane.blogspot.com

NASA Faked the Moon landing

Neil Armstrong and his team were the first people to land on the moon and they also put a United States of America flag on the moon but Bill Kaysing said that the chance of landing a spacecraft on the moon was 0.0017 which means 1 in 600 so Neil Armstrong and his team could not have gone to the moon (2). Neil Armstrong and his team brought back an 11.7 Kg Moon rock from the moon and it was prove to show the world that they actually went to the moon. The rocks from the moon are different from the rocks on earth. Moon rocks have isotopes which were created by nuclear reactions with the highest-energy cosmic rays and earth rocks are protected by the atmosphere and magnetosphere from the radiation (3). Moon rocks also have almost no water trapped in their crystal structure and earth rock has water trapped inside but Dr Marc Norman said that they have found fresh particles of fresh glass in the Moon rocks and the glasses were produced by a volcanic explosion activity(3).

Neil Armstrong and his team managed to take some photographs and video of the moon. They used Lunar Module antenna to send the pictures of the Apollo 11 landing to earth (2). “Apollo 11 was limited to using black and white, slow-scan TV camera with a scan rate of 10frames per second at 320 lines per frame. The pictures were converted to the commercial TV standard (EIA) first before they were displayed on a 10-inch black and white monitor and a vidicon camera. The pictures were scanned at the EIA standard. Kodak said that it is impossible to take photographs on the moon because temperature on the moon is 250ºF and the film will melt (2). The National Aeronautics and Space Administration (NASA) said that they have designed special transparency film for environments like the moon by wrapping it with a material which has a reflective surface (usually a white material). Bill Kaysing said that the pictured lacked stars and the stars should be visible because the pictures were taken from the moon (2) and the sky was black. NASA said that the stars were not visible on the photographs because they are too faint to be seen and also the moon surface is brightly lit by the sun; they are also wearing white suites so the stars cannot be seen on the pictures(1).

I do not think that NASA landed a spacecraft and no man also landed on the moon because the earth orbital is surrounded by the dangerous Van Allen Radiation Belts which are too dangerous since it is consists of small molecules which can penetrate the spacecraft and the space suite. On the video 2 (4) one of the Astronauts jumped and there was dust but surprisingly the dust managed to come down to the moon surface. What I know is that the is no gravity on the moon so how come did the lunar manage to go down, is it that the dust should remain being suspended on space just like the things(e.g. food that they were passing to each other) that they were using remained suspended until someone takes it . None of the people who went to the moon wanted to be interviewed by the CNN news on video 3(5); if they were not hiding anything they could have told people how it was to be on the moon because they used their money and they should also thank them for their support. They should have done what Mark Shuttleworth did, he went to space and when he came back he reported how it was like to go to space to show that he has nothing to hide. So what is it that Neil Armstrong and his team running from, why did they not want to be interviewed? If they went to the moon why did they fake their pictures because all their pictures have the same background, some have more than one light source how that can be possible. Since at the moon gravity is absent and also airless how come the flag on video 2(4) was flapping? The whole is just like the Piltdown

References

1. http://www.badastronomy.com/bad/tv/foxapollo.html
[Accessed 19 April 2006, 15:47]

2.
http://www.braeunig.us/space/hoax.htm
[Accesssed 19 April 2006, 09:58]

4.
http://video.google.com/videoplaydocid=1481909519678263426&q=Apollo+debrief&pl=true [Assecced 19 April 2006, 14:00]

5.
http://video.google.com/videoplaydocid=2265515730495966561&q=Did+we+land+on+the+moon&pl=true [Accessed 20 April 2006, 14:00]

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: +27 12 841 2133
Fax: +27 12 842 3676
E-mail: lmosomane@csir.co.za
Blog: lmosomane.blogspot.com

Thursday, April 13, 2006

Neanderthals mate with modern humans

Neanderthals are best known and least understood in all of human ancestors. Neanderthals were powerfully-built species and they were evolved to cope with the changing climate of Ice Age Europe. Their brains were larger than modern human and they were more robust and heavily built than human (3).

The scientists found a hybrid skeleton of a four year old boy (which was found in Portugal and the skeleton had both human and Neanderthals characteristics (3). The skeleton had a pronounced chin and teeth of modern human, but its sturdy limbs were more characteristics of the Neanderthals. From the skeleton found the scientist believe that Neanderthals interbreed with modern human.

Mark Stoneking of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany did a genetic variation between modern human and Neanderthals and the DNA showed that the two species were interbreeding(1). Some researchers said that modern human and Neanderthals did not interbreed because they were reproductively incompatible (2). Professor Lupo (4) said that Neanderthals interbred with some of the modern humans and that there is a little bit of Neanderthals in each person.

Neanderthals were powerfully-built species and they were evolved to cope with the changing climate of Ice Age Europe. Their brains were larger than modern human and they were more robust and heavily built than human (3).
Some researchers said that modern human and Neanderthals were physically isolated from each other so it was difficult for them to have interbreeded with each other (2).

From the skeleton that they have found it shows that modern human and Neanderthals interbreeded because the skeleton had both features of a modern human and Neanderthals. The skeleton inherited the features of both but other scientists do not agree that modern human and Neanderthals mate.
CSIR
Pretoria
0001
Tel: 27 12 841 2133
Fax: 27 12 842 3676
e-mail: lmosomane@csir.co.za

Reference:
1. www.signonsandiego.com/uniontrib/ 20050223/news_1c23neander.html
2. www.discover.com/issues/ sep-95/features/theneanderthalpe558/
3. http://dsc.discovery.com/news/briefs/20050919/neanderthal.html
4. www.wsu.edu/DrUniverse/nean.html

Wednesday, April 12, 2006

Elegant Universe

This is a movie, where scientists want to make the wireless connection possible. Isaac Newton discovered a force that pulls materials to the ground, which later called a force of gravity or heaven and earth. Gravitational force was the first force to be understood but little was not known on how gravity works. They discovered that if the sun could be distracted the earth will fly out of the orbital because the earth follows the sun curves.

Albert Einstein came up with a theory called the string theory, which was compared to the strings of a violin or piano or as reality meets science friction. He explains that everything is at its microscopic level when it is consisting of combinations of vibrating strands. A string theory provides a single explanatory framework capable of encompassing all forces and matter. Everything Force of particles consists of electromagnetic forces, weak and strong nuclear force and force of gravity.

Albert Einstein also researched about the light and found that nothing can travel faster than the speed of light even gravity. When an atom is split apart into neutrons and protons it gives out a very powerful explosion called nuclear force. No one was able to put general activity of quart theory together (gravity, electromagnetic, strong and weak nuclear forces). The universe is smaller, harder and denser, but it is ruled by the quantum mechanics and general activity. All these scientists were trying to explain everything in the world but they could not accomplish their unification.

Lethabo Mosomane
CSIR
Pretoria
0001
Tel: 27 12 841 2133