Monday, May 15, 2006


The old world monkeys are from the superfamily Cercopithecidea, they are found in the continents of Africa and Asia. The new world monkeys are found in Central and South America. They are the four families of primates namely, the Cebidae, Aotidae, Pitheciidae and Atelidae and these families are called the Platyrrhini parvorder.

The monkeys are the animal’s species of the suborder Anthropoidea. These suborders have two distinct infraoder that have evolved independent of each other for 30,000,000 years, namely the Platyrrhini and the Catarrhini. The Platyrrhini refers to the new world monkey and catarrhini refers to the old world monkey. These two groups of species can be differentiated from each other by their physical appearance.

The nose of the Platyrrhine is flat as compared to the one of the catarrhine, their nostrils are separated by a wide septum, while of the catarrhine are separated by a small septum. Platyrrhine have three molars which are large as compared to the one of the catarrhine which are two and sharply connected cusps. Besides the physical characteristics of this species, they can also be differentiated by their behaviours. The males of the platyrrhine are involved in the infant care, most of the time the males will caring the infant and give them to their females for nursing. On the other side there is no involvement.

The platyrrhines are confined arboreal habitats and are herbivorous; they only eat leaves, fruits, nuts, gums and occasional small preys such as insects. While the catarrhines tolerate wider habitats, couples of them spend most or some of their day on the ground. These monkeys have hairless callous pads, ‘on their rumps which may be adaptations for long sitting or sleeping on rough branches and stone’ and the new world monkeys do not have that.

The new world monkeys are having long tails, often prehensile tails. Most of this tails are small, arboreal and nocturnal, while of the old monkeys are easily observed, they never had a prehensile tails. The new world monkeys sometimes use their tails as their third hand. Another difference between the two monkeys is their body; the old world monkeys are having large body size as compared to the new world monkeys. And the old world monkeys are having bright colourful colours especially in their face; on the other side the new world monkeys are having dark colours.

In conclusion, it is easier to differentiate the old world from the new world monkeys simply by their appearance, when you are distanced from them you can check their colours, body weight and when you are not far you can also check their facial appearance as they are different.

1. Wikipedia contributors. Monkeys [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 12, 08:30 PTA [cited 2006 May 12, 15:15]. Available from: [].

2. [, accessed on 12/05/2006, 10:00].

3. [, accessed on 12/05/2006, 10:30].

4. Wikipedia contributors. Monkeys. [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 12, 10:40 PTA [cited 2006 May 12, 15:15]. Available from, [].

5. Wikipedia contributors. Monkeys. [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 12, 11:00 PTA [cited 2006 May 12, 15:15]. Available from, [].


The marsupial animals belong to the Marsupial order; they share the infraclass metatheria with the kangaroo, koala, Tasmanian devil and the Virginia opossum. They are the non placental mammals, the female marsupials carriers her young in a pouch. The Concise Oxford Dictionary describe pouch, as a ‘pocket-like abdominal receptacle in which marsupials carry their young during lactation’.

The placenta mammals are named because of its function; it connects the growing embryo within the uterus to the circulatory system of their mother. The placenta is the pathway provider for the nourishment of the fetus. Most of the placenta mammals are investing most of their time in the stage of growth.

The main difference between the marsupial and placental mammals is the rate of gestation, or the time the offspring take inside the uterus. The Concise Oxford Dictionary explains gestation as the process of carrying or being carried in the womb between conception and birth. The stage of mating happens throughout the year in the marsupial mammals than in any other species. The marsupial females use the amniotic membrane to separate the developing embryo from their body. The functions of the amniotic membrane is to protect the embryo, it protect it by isolating it from all biological interactions with the parent. The amniotic membrane play important role, because when fertilization took place the embryo becomes a new organisms and the immune systems attack it, but because of the protection the attacker becomes unsuccessful.

The fewer the nutrients in the egg will result in the few nutrients of marsupial embryo, because they depends on the egg yolk for their nutrients. The type of egg yolk reproduced determines the period of gestation in marsupials. The marsupials give births very fast, the longest period they can spend in a reproduction are only twelve days. On the other side, the placental mammals takes weeks and months which is longer compared to the marsupials mammals.

The placental mammals have a long gestation period because their offspring is born being well developed. The placenta allows the nutrients to travel from the mother systems to the embryo and waste are carried out, and this allows the extension of placental maturation. The placenta is composed of numerous layers of blood supply; the mother and embryo have their own blood supply.

In conclusion, indeed there are difference mode of reproduction between the placental and the marsupial. During pregnancy of the marsupials the oestrus cycle occur, while in the placental does not until the whole period of pregnancy is over. The embryo of the marsupial is not connected to the mother while of the placental is connected. The marsupial gives birth very fast as compared to the placental. The main difference between the marsupial and placental mammals is the rate of gestation, or the time the offspring take inside the uterus.


1. [, accessed on 12/05/2006, 08:00].

2. Wikipedia contributors. Placenta. The free Encyclopedia [internet], 2006 May 12, 09:00. PTA. Available from [].

3. Wikipedia contributors. Marsupials. The free Encyclopedia [internet], 2005 May 12, 10:30 PTA [Cited 2006 may 11] Available from [


The placental mammals are the largest group of the mammals, it comprises about 4300 species. They are known to be the third subclass of the mammals. The placental mammals are biologically classified into nineteen orders. The largest group of these mammals contains the rodents, such as rats, mice, squirrels, and porcupines. Bats are found in one of the largest group of mammals. The young placental mammals are born at a comparatively advanced period. These mammals include elephants, whales, shrews and armadillos, it also includes pets such as dogs and cats, it includes also the farm and work animals like; cattle, sheep, and horses. The humans are also regarded as the placental mammals.

Some of the placental mammals are found on land, water and in the air, and they differ in their shape and body size. They also differ in their method of surviving, some are carnivores, and some are omnivores while some are herbivores. The differences are also in those that colonized the land, they live in different shelters, for example: human live inside the house while the sheep and cattle in the kraal.

The placental mammals that live on the land are having feet, those who occupied the water are having gills and those who colonized the air are having the wings. The seals, including the sea lions and the walruses can not reproduce in the open oceans, however they spend most of their time in the open oceans, and they depend on the land for reproduction. The largest plant eating mammals that spend the entire lives in water are dugongs and manatees. The bats are the only group of placental mammals to occupy the air.

The jaguar is found to be occupying the land simply because its preys are colonized on the land. ‘The whales, including the huge baleen whales and the dolphins, are well adapted as fast, open ocean predators’. These marine placental mammals occupy areas where there are large amount of food, but where the water temperature is low. These mammals survive the cold conditions in two different ways. Some have very sparse hair and blubber, which helps them to become warm. And others have a double coat of fur, with extremely dense underfur hairs closely packed, and this prevent the skin from being wet.

The majority of the aquatic mammals in the world live in the ocean, nevertheless, some live in the freshwater, for example: river dolphins, and otters adapted to life in fresh water habitats. The rodents are found to have successfully occupied the land, air and the water. They managed to colonize these three habits because they are small in size and this serve as their advantage to evade the extreme conditions.

In conclusion, the placental mammals colonized the air, water and the land very successfully. The humans would not colonize the air because of lack of wings, but they colonized the land. The bats colonized the air. The seals live both aquatic and terrestrial life, they spend most of their time in the water, but they still have to come to land so that they can reproduce.


1. Wikipedia contributors. Placenta. The Free Encyclopedia [internet], 2006 May 12, 09:00. PTA. Available from [].

2. Msn contributors. Mammal. The Online Encyclopedia [internet], 2006 May 12, 10:00. PTA. Available from [].

3. Msn. Contributor. The Online Encyclopedia [internet], 2006 May 15. Available from, [http://Encarta.msn/text_761561349_1/Mammal/html].

Friday, May 12, 2006


The birds are the phylum chordate, from the class Aves. They are the avian dinosaurs and birds are technically considered as reptiles because they descended from certain diapsids dinosaurs. The earliest species of the class Aves to be known is Archaeopteryx. They are characterized by the bony beak without teeth, the laying of hard – shelled eggs, high metabolic rate and a light strong skeleton. The most important characteristic of the bird is flight or that they fly.

The dinosaurs were the subphylum of chordates, specifically, those with backbones or spinal columns that conquered the terrestrial ecosystem over 160 million years. They are a group of diapsids reptiles that firstly evolved from archosauriform ancestor during the olenekian, like modern crocodilians. They first appeared about 230 million years ago, and became extinct 65 million years back at the time of cretaceous, and they were no longer dominant on land. The clade maniraptoran is the group of the theropod dinosaurs that many paleontogists believe birds were derived from some 150 or so million years ago, in the Jurassic period on the other side of the phylogenetic taxonomy birds are by definition maniraptoran and other maniraptoran are their closest relatives.

The birds are the direct descendants of meat eating dinosaurs (eoraptor). However, the dinosaurs are not birds or reptiles at all. They are a separate special group, having straighter legs. They had unique movement, walked with their legs underneath them. The little dinosaur meat-eaters were probably the ancestors of birds. The dinosaurs also laid eggs, even though their eggs differ somewhat from those of birds, and at least some dinosaurs nested in colonies and cared for their young in the nest as the birds do, they take care of their young one until they are able to fly on their own.

The birds and the dinosaurs were comparable, because the birds have hollow bones, but so did pterosaurs. Dinosaurs walked upright as birds do and meat-eating dinosaurs have very similar skulls to birds. Some of the smaller dinosaur meat-eaters have bodies and arms similar to birds' as well. The first bird, archaeopteryx, looks nearly identical to the small meat-eating dinosaur of the same time, compsognathus, except it has feathers.

The birds share many characteristics with their extinct relatives and those characteristics enable them to fly. ‘The birds have evolved remarkable specializations for flight, they resembled the flight from the Ornithomimids and other small theropods.: a unique "one-way" breathing system, light yet strong hollow bones, a skeleton in which many bones are fused or lost, powerful flight muscles, and -- most importantly – feathers’.


1. [, accessed on 10/05/2006, 09:00].

2. [, accessed on 10/05/2006, 09:40].

3. [, accessed on 10/05/2006, 12:00].

4. [, accessed on 10/05/2006].

Thursday, May 11, 2006


The amphibians are the simplest Tetrapods, and are the first class of the vertebrate to invade the land. The Tetrapods includes approximately 18100 existing species of amniotes (birds and their dinosaur ancestors, reptiles and mammals) and approximately 300 existing species of amphibians (frogs, salamanders and caecilians). The term Tetrapoda refers to species with ‘four feet’ and forms the largest group of the terrestrial vertebrates.

Most of the Tetrapods lived in terrestrial ecosystem, but, others still live in the aquatic environment, where their distant ancestors lived. Aquatic Tetrapods include various salamanders (sirenids, cryptobranchids, proteids, etc.), frogs (pipids), some caecilians (typhlonectids), leatherback turtles, sea snakes, pinnipeds (seals and walruses), and whales. Some Tetrapods are capable of flight (birds and bats), while others glide, such as flying squirrels, dermopterans (sometimes called "flying lemurs", even though they are not primates), and the flying dragons (Draco Volans).

Indeed, some of these animals have lost their limbs. However, their common ancestor had two limbs in front and two in back, where fins once flicked instead. When we talk about the limb we are referring to a leg, wing or arm of an animal. To understand where the limb originates, this could bring us to two major hypotheses that were discovered, namely, the fin-fold hypothesis and the gill arch hypothesis.

Some of the known animals, which lost their limbs or limbless animals includes snakes and whales. The whales are any range of marine mammals of the order Cetacea, and they are have the common form of a fish with forelimbs adapted to form flippers, a tail with horizontal flukes and a single blowhole for breathing. The whales open its blowhole and start to breathe out before reaching the water surface and hold its breathing when they are below the water surface.

Reasons were suggested on why the snake became limbless. It was suggested that the snake might have ‘burrowed underground searching for food in small crevices’. I turn to agree with this suggestion, because even to date snakes spent much of their times in small holes (hibernate). Most of the times, snake are seen during summer times, when they are searching for foods and sometimes when they are feeling hot in their habits. It is suggested that snakes lost their limbs and wide shoulders and pelvis that supported their limbs when they were struggling to enter the small holes.

The loss of limbs is very common in all lineages of vertebrates. Both the fishes and the amphibians evolved several times and they both move by using the limbs. The axial muscular mammals and the archosaurs are not able to support the animals, so if they can lose their limbs they will not make it. At least one group of mammal (whales) has ever lost either of the limbs. They survived only because they developed a larger, broad tail which is significantly strengthened their axial muscular. The loss of the limbs of these animals might also be caused by changes in environmental conditions.


1. [, accessed on 09/05/2006, 10:00].

2. [ , accessed on 10/05/2006, 12:30].

3. [, accessed on 10/05/2006, 12:30].

Wednesday, May 10, 2006


The bony fishes are the fish of the large class Osteichthyes differentiated by a skeleton of bone and comprising the majority of the modern fish. They are the most plentiful, varied and multifaceted group of fishes. They outnumber all other fishes twenty to one and include more species as compared to all other vertebrates combined. They have bony skeleton and slimy, scales that cover their bodies.

The first bony fishes had streamlined bodies and well – developed fins. The bony fishes had large eyes and mouths, aids in evasion and food gathering helped them to thrive in lakes, streams and the sea. They also developed specific adaptations to unique environments. The oldest bony fishes had thick enamel scales, which in the later forms became lighter. In the actinopterygian forms the fins are supported by many slender ray-like bones.

The early forms were substituted in Mesozoic times by the surviving holeosts that include the garpike and bow fish. Most of the holeosts were also replaced in the time of the cretaceous by the teleost ray fins which included almost all living fish. The lobe fins or choanichthyes include also the lung fish, fins are supported by a strong bony axis and the nostrils open into the mouth.

The (Chonndrichthyes) cartilaginous fish are fish (animals) having only cartilage as hard connection tissue. The cartilage is a type of impenetrable connective tissue. The cartilage is composed of fibres consisting of collagen and elastic fibres, a matrix and cells called chondrocytes which are dispersed in the matrix. These cell types are the only cells available in cartilage and they generate and maintain the matrix of the cartilaginous.

The cartilage is found in the joints, rib cage, and the ear, the nose, in the throat and between invertebral disks. The cartilage functions as the framework provider upon which the deposition of bone can commence. There are three major types of cartilage namely, hyaline, elastic and fibrocartilage. The hyaline type of cartilage is found lining bones in joints and inside bones, serving as the centre for bone growth.

The bones of animals are collectively known as the skeleton. However, both the bones and the cartilage derived from the mesoderm, they have the different composition. The process in which cartilage is formed from condensed mesenchyme tissue that distinguishes into chondrocytes and begins secreting the materials that form the matrix is found to be the Chondrification.

There are two different types of growth that takes place in cartilage, namely the appositional and the interstitial. The appositional increases the diameter or thickness of the cartilage and the interstitial increases the mass of the cartilage and occur within.


1. The wikipedia contributor, the free encyclopaedia [internet] cited PTA, accessed on 08/05/2006, 16:00 available from []

2. The wikipedia contributor, the free encyclopaedia [internet] cited PTA, accessed on 08/05/2006, 15:300 available from []

3. Frank H.T, Herbert S, Paul R. (1965) Fossils, a guide to prehistoric life. Page 136 – 137.

Tuesday, May 09, 2006


Insects are small animals around us; they are animals of the class Insecta, the largest and most widely distributed taxon within the phylum Arthropoda. They are invertebrate animals consisting of six legs and the three body parts namely; the head, thorax and abdomen. Most of the insects have one or two and even three pairs of wings.

Ancient types of insects have been available since early dinosaur days and they have been flying before the some of the birds could fly. The sub class Apterygota is divided into two orders, the microcoryphia known as dragonflies, damselflies and the zygentoma known as silverfish, fibre brats. These insects were known to be jumping insects as they were wingless and their habits were, indoors under sinks, stones, bookshelves, in bathrooms, grass, feed, rubble or in woods.

The dragonflies and the damselflies are the insects of the subclass Apterygota that evolved in to the subclass zygentoma, all the insects in the sub class Apterygota are wingless. The reason why these early insects were unable to become very diverse was because they did not have wings. Later the insects gained the ability to explore more territory and find new type of food which increased more species. This resulted as when they evolved the ability to fly. For example: the insects from the microcoryphia order evolved into the Odonato order. These insects had about two pairs of wings and they were regarded as the best fliers, they were eating other insects caught on fight.

The early flying insects developed wings that stuck straight out - as demonstrated by the mayflies and dragonflies, the oldest flying insects alive today. The past 300 million years , other insects had evolved folding wings. This modernism really gave the diversity of insect’s improvement. 'Those insects can keep their wings safely tucked away as they move slowly through leaf litter, squeezed under tree bark or even dived into water'.

The evolution of insects was success and would not be successful without the plants as the insects depend on plants for their survival, because plants provide a large amount of food for the insects. 'The insects evolved defences against the sophisticated chemical weapons in plants. Some of the insects, like monarch butterflies, can recycle poisons from plants they eat, making themselves poisonous to birds and other predators'.

Evolution happens every where, just like in insects evolution took place. 'Some of the insects descended from other insects, for example fleas descend from mosquito and like the insects called scorpion flies, they have long wings and powerful eyes, aiding them in finding insect carcasses for food'.

The knowledge on how the scorpion flies evolved into fleas comes from the fleas' closest living relatives, known as boreids or snow fleas. ‘These 24 species walk across snow in late winter to feed on moss. Unlike other scorpion flies, snow fleas have tiny wings that are useless for flying. They don't have the keen eyesight of other scorpion flies, probably because they need their eyes only to detect predators’.


1. [, accessed on 07/05/2006: 09:00].

2. [, accessed on 07/05/2006: 10:00]

3. The family tree, [, accessed on 06/05/2006, 12:00].

Monday, May 08, 2006


Insects are small animals around us; they are invertebrate animals of the class insecta, the largest and most widely distributed group of animals within the phylum Arthropoda. An insect consists of six legs and the three body parts, namely a head, a thorax and an abdomen.

The insects were probably the first animals to fly. Most of the insects have one or two or even three pairs of wings which they developed millions of years before bats and birds. They are known to be excellent fliers, they fly in big groups and they like doing trick flying. There are over 800,000 different kinds of insects that are known and being discovered daily. They live almost everywhere in the world and they are very adaptable. Many insects such as butterflies and moths go through the four stages of growing. They are firstly an egg to being like a worm (larva) then goes to pupa where they take a nap. Finally the new insect will break out of their pupa and therefore, an adult insect.

The insects are categorized into three different groups, namely
Holometabolous (the complete metamorphosis), the pupae is formed in this stage, and the examples of these insects are beetles, flies, bees, lacewings, butterflies, ants and caddis flies.
Hemimetabolous (the incomplete metamorphosis) there is no pupae in this stage and the examples of these insects are crickets, true bugs, termites, grasshoppers and cockroaches.
Ametabolous is without the metamorphosis, example is silverfish.

There are about two subclass of the class insecta namely: Apterygota and Pterygota, and they are further divided into the orders. The Aptergota into microcoryphia known as dragonflies, damselflies and Zygentoma known as silverfish and firebrats while the subclass Pterygota is divided into twenty one orders namely Ephemeroptera known as mayflies, shadflies. Odonata known as dragonflies and damselflies. Dictyoptera are known as cockroaches and mantids. Isopteran are known as termites and white ants. Athoptera are known as grasshoppers, locusts, katydids and crickets. Phasmida are known as stick and leaf insects. Dermaptera is known as earwings. Grylloblattodea are known as rock crawlers, ice insects. Plecoptera is known as thrips. Psocoptera is known as scorpion flies. Trichopterais is known as caddisflies. Coleopteran is known as beetles. Neuropteran are known as lacewings, mantispids and ant lions, and the Hymenoptera known as bees, wasps and ants.

However, insects are known to be excellent fliers but there are still some of the insects without wings. These types of insects are jumping insects, for example: silverfish, fibre brats, fleas, etc. The true flies are the most known excellent flier. The mantids are known to be the excellent pest control, because they eat other insects in the garden and their large species can also eat frogs, lizards and even hummingbird. The fleas depend on the blood of their hosts like dogs, cats, birds and humans to survive.

The insects fly for couples of reasons, some fly to survive, others fly in order to find insects that they can mate with, while others fly to get better foods, all in all they fly to escape they predators. There are some of the insects that fly during the day, like butterflies while some like moths’ flies at night. There are also seasonal insects, butterflies comes out in summer and spring. During winter the insects migrate to escape the killing temperature, while others are hibernating as larvae, others as nymphs, others as eggs, others as pupae and others hibernate as adults. Insects can survive the cold condition easily only when the temperature is stable. Many insects can get shelter and nourishment through the winter in the variety of micro – habits.


1. [, accessed on 06/05/2006, 09:00]

2. Using live Insect (1997) The University of Arizona
[, accessed on 06/05/2006, 09:30].

3. [, accessed on 06/05/2006, 10:00].

4. [, accessed on 06/05/2006, 10:20].

5. The k8 Aeronautics Internet Textbook site, [, accessed on 06/05/2006, 11:40].

6. The family tree, [, accessed on 06/05/2006, 12:00].

7. [, accessed on 06/05/2006, 12:30].

8. Wikipedia contributor, insect [internet]. Wikipedia, the free encyclopaedia, 06/05/2006, 12:40 PTA cited, available].

Saturday, May 06, 2006


The DNA (Deoxyribonucleic acid) is a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. It is regularly in the form of a double helix that has the genetic instructions specifying the biological development (the study of the process by which organisms grow and develop) of all the cellular forms of live and bacteria. It is very long molecule consisting of structural unit of nucleotides and encodes the sequence of the amino acid residues in protein using the genetic code, a triplet code of nucleotides.

The DNA is often called the molecule of heredity, because of its responsibility to genetic propagation of most inherited traits. It is replicated and can be transmitted to offspring during reproduction in the process of cell division. The DNA is a pair of molecules joined by the hydrogen bond. Every DNA strand is a chain of chemical ‘building blocks.’ 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.

The DNA contains the hereditary information that is inherited by the offspring of an organism; this information is determined by the sequence of base pair along its length. The DNA strand has genes, area that regulate genes and area that regulate genes and areas that either function are yet unknown or the does not have 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.

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 do we appear, in hair colours, facial structures, our movement, habits and other characters. This differences results 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.

Using the DNA to trace a criminal, we compare the DNA data from the crime scene 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. Wikipedia contributors. DNA [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 3 10: 11 PTA Available from: [].

2. Wikipedia contributors. Gene [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 02, 10:00, PTA. Available from: [].

3. Wikipedia contributors. Nucleic acid [internet] Wikipedia, the free Encyclopaedia, 2006 May 03, 11; 30, PTA. Available from [].

4. Wikipedia contributors, biological development [internet]. Wikipedia, The Free Encyclopaedia, 2006 May 03, 12:50, PTA. Available from [].


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

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

Mollusc are classified into nine classes of which eight of them are still living, these classes make up the 250 000 and more species of mollusc.

Class Pelecypoda (Bivalvia) are compacted animals with two shells hinged on the animal’s dorsal surface. This class species are found in just about every marine environment. The clams are shelled marine of freshwater molluscs belonging to the class Bivalvia. They can live for 150 years old or longer. They can be hard shelled or soft shelled, according to the degree of calcification of their shells, according to species.

The abalone belongs to the large class of gastropods and the Haliotidae family. The shell is rounded to oval, with two to three whorls and the last one auriform, grown in to a large ‘ear’ giving rise to the common name ‘ear-shell’. ‘The cuttlefish are the animals of the order Sepiida, and are marine cephalopods, small relatives of squids and nautilus. They are having the internal shell, large eyes, and eight arms and two tentacles furnished with denticulate suckers.’

The squid are the large, varied group of marine cephalopods accepted as food in cuisines as widely separated as Korean and Italian. Class Caudofoveta are small (1 – 30 mm) class of the phylum mollusca, primitive deep sea molluscs. They are worm – like molluscs that live buried head down in the floor, lacking shells or distinct muscular feet.

Class Monoplacophora have a single cap-like shell and they superficially resemble limpets. The class Polyplacophora, usually known as chitons, have seven or eight dorsal shell plates. Class Scaphopoda or Tusk shells have a tapered, tubular shell that is unlock at both ends.

Class Gastropoda are the largest most successful class of molluscs. Most of the approximately 40 000 living species of this class have shells; there are few groups that have either reduced or internal shells or no shell at all. The shelled forms are generally called ‘snails’ and the forms without shells are called ‘slugs’.


Wikipedia contributor, Mollusca [internet]. Wikipedia, the free encyclopaedia, 2006 May 03, 08:00 PTA cited, available [].

Wikipedia contributors, Phylum [internet]. Wikipedia, The Free Encyclopaedia, 2006 May 03, 12:50, PTA. Available from [].