DIFFERENCES BETWEEN NEW WORLD MONKEYS AND OLD WORLD MONKEYS

Monkeys constitute 90 percent of the 145 living species of the suborder anthropoidea. They are the most successful primates in populating the earth. Monkeys are more intelligent and their eyes are well developed as compared to the prosimians.

However there are two different infraorders of anthropoidea that have been evolving independed of each other for many years. These are the platyrrihini (new world monkeys) and the catarrhine (old world monkeys, apes and humans). Both monkeys eat leaves, fruits, nuts, gums and some small insects. Both the old world monkeys and the new world monkeys share the same kinds of teeth. They both have the same kinds of specialised mammalian teeth of which they are used to eat a wide variety of foods.

Although they share some of their characteristics, they can be easily distinguished looking at their nostrils, ear region, tails, hand, infant care, premolars and molars.
These two diverse groups of species can be distinguished from each other quite a number of characteristics the new world monkeys are almost exclusively arboreal and they are smaller than the old world monkeys have the capability of grasping branches of trees using tails but the old world monkeys do not have this capability.

Many old world monkeys have hairless callous pads, on their rumps which may be adaptations for long periods of sitting or sleeping on rough branches and rocks but the new world monkeys do not have it. The new world monkeys have relatively large molars of which are far apart and open to the side. The old world monkeys have the down facing nose; nostrils are closer together and open down ward.

The new world monkeys have relatively large molars of which the last molar is comparatively small or absent and three pre molars. In contrast the old world monkeys have two premolars and the molars have sharply connected cusps. The ear region of the new world monkeys is a tympanic membrane connected to external ear by a bony ring whereas to the old world monkeys the tympanic membrane connected to external ear by a bony tube.

The old world monkeys have tails but lack prehensibility feature. They have a sitting pads around the tail region which is a thickly calloused skin areas supports the animal while they sit in trees or while resting, but the new world monkeys have a tail with prehensile tails. The old world monkeys have thumbs that are rotated and more opposable which look like of humans. They have toe tails and finger nails are present on all digits.


In the old world monkeys, the males are less involved in caring for the infants where as the males of the new world monkeys are more involved. When coming to their habitat these two differ in a way that the old world monkeys tolerate a wider range of habitats, form rain forest through savannah fringe and semi arid regions and they also spend much of the day on the ground. The other distinguishing factor is that the new world monkeys have developed way of defending territory in the top branches of their forest canopies with localisation of which they use their specialized larynx and throat.

All monkeys irrespective of new world monkey or an old world monkey, they are both intelligent and they behave like humans.


Reference:

1. Anthropology 1, new world (America) and old world (Africa and Asia) monkey: A comparison, [internet] [cited 2006 May 11] Available form:
http://www.cabrillo.edu/~crsmith/monkeycomparisons.html

2. New world monkeys, [internet] [cited 2006 May 11] Available from:
http://anthro.palomar.edu/primate/prim-5.htm


Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria,
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Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
Email: lmukwevho@csir.co.za
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WHY HERBIVORES DIET IMPOSES CERTAIN PROBLEMS FOR DIGESTION AND HOW SOME ANIMALS HAVE OVERCOME SUCH PROBLEMS

Herbivores are animals which eat only plants and no meat. This means leaves, flowers, fruits or even wood. Herbivores often do not have to search far to find food to eat. In some cases for example wood boring insects; they are entirely surrounded by their food. However the disadvantage for the herbivores is that it can be difficult to digest and is often low in nutrients. Sheep, horses, rabbits and snails are well known examples of herbivores which eat grass and leaves.

Herbivores can be classified as frugivores, which eat only fruit, and folivores, which specialize in eating leaves. The diets of some herbivorous animals vary with the seasons, especially in the temperate zones, where different plant foods are most available at different times of year.

They vary of diets in these classes of herbivores poses some problems. These problems are normally seen during digestion. Some of the animals are unable to digest completely the food they eat. Cellulose is another source of problem and it contains much of the energy. Since most of the herbivores digest food through enzymes, therefore it is difficult for the enzymes to broken down as it contains high organic substances. This cellulose composed of organic substances. only mechanical means such as extended chewing or fermetation can help to speed up the process of digestion.

Some animals have overcome these problems; most herbivores have tough mouth for chewing and grinding food. For example cattle have complex digestive system which contain micro organisms. These micro organisms play a role in breaking down of cellulose and other indigestible plant materials. These micro organisms help to turn the plant matter into nutrients that the animals can absorb.

Some herbivores are called ruminants (e.g. cattle, sheep and goats) which have two stomachs. They have two stomachs of which during the day, they chew their food in the same way as sheep. When they swallow in the food they go into the first stomach, called the rumen. During the evening the animal brings a mouthful of food back into its mouth from its first stomach and this is called regurgitating the food. During this process food is chewed and then swallowed into the second stomach.

The non ruminant (e.g. horse) herbivores depend on symbiotic micro-organisms for cellulose digestion. Their anatomical adaptations differ from true ruminants. Digestion of cellulose in the plant diet by microbial enzymes in adult cattle, sheep and goats on a normal diet occurs in the fore stomach, of which the rumen is the largest compartment; this organ therefore serves as the major source of energy in those species. Microbial fermentation is another way in which the herbivores adapted to make it simple for the digestion process. Therefore herbivores maintain continuous fermentation and absorption in their digestive tract.

Cellulose digesting enzymes called cellulases are present in the intestinal tract of several invertebrates that feed on wood and similar plant products. These enzymes are, however, absent for some reason from the digestive secretions of. Plant material is lower than meat in energy content, and the herbivore must consume a large quantity in order to satisfy its energy requirements.

Some animals have become large because of high metabolic process. These animals grew bigger in order for them to have a long digestive system that will allow a complete digestion for plants that are very very hard. Therefore they become larger in order for them to reach the plants matter that contains less cellulose.

Reference:

1. The gastrointestinal system, an introduction [Internet] [cited 2006 May 15]. Available from: http://www.chu.cam.ac.uk/~ALRF/giintro.htm
2. Knowledgerush.com, Herbivore [Internet]. Knowledgerush.com, 2003 [cited 2006 May 15]. Available from: http://www.knowledgerush.com/kr/encyclopedia/Herbivore

Mr Lufuno Mukwevho
CSIR Pretoria
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DESCRIBE HOW PLACENTAL MAMMALS HAVE COLONIZED LAND, WATER AND AIR

Placental mammals are diverse group whose young are born at relatively advanced stage (more advanced than the young of other mammals). The placental mammals include such diverse forms as elephants, whales, shrews, and armadillos. They include pets such as dogs and cats, as well as many farm and work animals, such as sheep, cattle, and horses. A human falls under the placental mammals.

The placentals mammals are by far the largest of all three mammal groups. Young placental mammals spend a relatively long time developing inside their mother’s body before birth. Warm and protected within the mother’s womb, the unborn young are nourished by a spongy organ called the placenta, which absorbs nutrients from the mother's blood and transfers them to the developing animal. By the time a young placental mammal is born it is usually fully formed, although it may not yet have fur or functioning eyes or teeth.

Some placental mammals have adapted to life and colonise water, land and air. Placental Mammals have developed different body shapes and sizes. These body size and shape were the other driving forces behind colonising water, land and air. Some are able to fly (with wings), those with four limbs to walk, bipedal and those with gills. Instead, most aquatic mammals eat animal as food, but they catch it in two quite different ways. Pursuit hunters, such as otters, seals, and toothed whales, chase individual prey through the water, much like carnivores chase their prey on land. However, the largest whales feed on much smaller animals, scooping them up in vast quantities. These whales do not have teeth, and instead strain their food with a screen of fibrous plates called baleen.

The whales, including the huge baleen whales and the dolphins, are well adapted as fast, open-ocean predators. The aquatic placental mammals still need to breathe because they can drown. , but whales and dolphins are truly pelagic, meaning that they wander far out into open water. These marine placentals mammals colonize areas where food is abundant, but where water temperatures are low. They survive the cold in two different ways. Some, such as sea otters and fur seals have a double coat of fur, with extremely dense underfur hairs that are so closely packed that the skin never gets wet. Whales have very sparse hair, and keep warm with a thick layer of fat called blubber.

The ways in which mammals move from place to place is greatly varied. Some mammals use four limbs to walk (such animals are referred to as quadrapedal) while others use only two (such animals are referred to as bipedal). The greatest differences in locomotion adaptation can be seen when comparing placental mammals from very different habitats. The jaguar, a terrestrial carnivore with explosive running power, is adapted for speed on land. The placental mammals that live on land mostly have four legs, which they use for walking on search for food. This carnivore colonise the land since it is a carnivore, most of its prey lived on land. They are warm-blooded, or endothermic, meaning that they maintain their body temperature within a narrow range despite changes in the environment.

The limbs of bats have evolved into wings enabling them to inhabit the skies and able to catch their prey on air.
The majority of bats also feed on insects, using different technique for catching their flying prey. Using a system called echolocation; a bat sends out bursts of high-pitched sound toward objects and interprets the returning echoes as images that guide a bat toward its prey so that it can hunt even in total darkness





Reference:

1. Mammal, [internet] [cited 2006 may 8]. Available from:
http://encarta.msn.com/encyclopedia_761561349/Mammal.html


Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria,
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Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
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COMPARISON BETWEEN PLACENTAL AND MARSUPIAL MODES OF REPRODUCTION

Placental mammals (subclass Eutheria) are highly developed mammals which give birth to young at a relatively advanced stage. There are almost 4,000 known species of placental mammals. The dominant ones are rodents and bats than other types of placental mammals. They are more advanced than the young of the other mammals, the monotremes and marsupials. Before birth, the young are nourished through a placenta. The placenta is a specialized embryonic organ that is attached the mother's uterus and delivers oxygen and nutrients to the young. Placental mammals are given this name because the placenta connects the growing embryo within the uterus to the circulatory system of the mother. It is the pathway provider for the nourishment of the foetus.

Marsupials are animals that belong to the order Marsupial and an infraclass Metatheria. The members of the class include kangaroo, koala, Tasmanian devil and the Virginia opossum. Marsupials are known to be the subdivion of mammals but they have a lot of characteristics. The marsupials are accepted as non-placental mammal. The female of these marsupials carries the young in the marsupial or pouch. This is where the young are provided with warmth and proper environment. They do have placenta which is non-invasive and functions in the transferring of nutrient and waste for limited period of time.


The different between the placental mammals and the marsupial are seen mostly through the mode of reproduction. The breeding season for the marsupial, takes place during December and continue through October and most of the infants are born between February and June. During mating the male attracts the female by making clicking sound by the mouth. The oestrous cycle of female opossum takes about of 28 days. During this period mating can take place. The sperm in the male opossums reproductive tract paired and then move through the lateral vaginal canals and become separate again in the female's tract. If fertilization occurs, the fertilized eggs move from the oviducts to the uteri where they will gestate for a short period before being delivered through the medial vagina or central birth canal. These normally give birth to infants weighing at 0.13 grams.


At birth, the infants make a long and difficult journey from where they got birth into the pouch and continue their development. The mother helps by licking the hair leading into the pouch, providing a moist path for the infants to follow.
The young remain in the pouch for about 2 1/2 months and at around 55-70 days the eyes open. As they become too large to fit in the pouch, they climb onto the mother's back and are carried as she searches for food. At this time the young are learning survival skills such as finding food sources and predator avoidance. If one of the young becomes separated from its mother it will make sneezing sounds to call her. She, in turn, will make clicking sounds.

The offspring of the placental mammals are born fully developed. This is one of the characters that distinguish this two. The placental mammals have a longer gestation period which results to the situation where off springs are able to develop fully. The extended maturation of placental is caused by the placenta which allows nutrients to travel from the mother's system to the embryo and waste to be carried away. The placenta is composed of several layers and these layers are supplied with blood and serve as immigration barrier letting nutrients to pass through. The embryo and the mother do not share the same blood supply


Reference:

1. Northwest creation network, Marsupial evolution and post flood migration [Internet] [cited 2006 May 11] Available from:
http://www.nwcreation.net/marsupials.html

2. Wgbh education foundation, convergence, marsupials and placental, 2001 [Internet] [cited 2006 may 11] Available:
http://www.pbs.org/wgbh/evolution/library/01/4/pdf/l_014_02.pdf

3. Opossum society of the United States, Opossum reproduction and life cycle, 2003 [Internet] [cited 2006 may 11] Available:
http://www.opossumsocietyus.org/opossum_reproduction_and_life_cycle.htm

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

THE GENERAL ADAPTATIONS BIRDS HAVE EVOLVED FOR FLIGHT, INCLUDING SECTIONS ON ANATOMICAL MODIFICATIONS, PHYSIOLOGICAL ADAPTATIONS, FEATHERS AND WINGS

Birds are warm-blooded, bipedal, oviparous vertebrate animals characterised by feathers fore limbs modified as wings. They differ in size ranging from small size to the huge birds such as ostrich. They are most diverse class of terrestrial vertebrates because they have 8,800-10,200 living bird species. They feed on nectar, plants, seeds, insects, rodents, fish and other birds.

Some birds are nocturnal (for example owls) and others are diurnal. Birds do migrate for long distance to find suitable living conditions. The Common characteristics of birds include a bony beak with no teeth, the laying of hard-shelled eggs, high metabolic rate, and a light but strong skeleton. Most birds are characterised by flight, though the ratites are flightless, and several other species, particularly on islands, have also lost this ability. Flightless birds include the penguins, ostrich, kiwi, and the extinct Dodo.

Birds have evolved some adaptations for flight purpose. Flight is the mode of locomotion used by most of the world’s bird species. This is important to birds for feeding, breeding and avoiding predators. Although the origin of bird flight is still not clear it believed that birds evolved this mechanism from small theropod dinosaurs. It seems likely that they evolved from ground living species, with developing after the evolution of feathers. Birds evolved this mechanism as a result of pursuing small airborne prey items such as insects and it became behaviour of adapting predator.

The flight is so energetically demanding birds have evolved several other adaptations to improve efficiency when flying. The most adaptation for flight on birds took place anatomically, modification, physiologically, on feathers and wings. Birds have hollow skeleton to reduce weight and many unnecessary bones have been lost for example the bony tail of the early bird Archaeopteryx, the toothed jaw of early birds which has been replaced by a light weight beak.
The birds have also adapted the vanes of the feathers with hook lets called barbules that zip them together, giving the feathers the strength needed to hold the airfoil. Birds evolved mono directional pulmonary system that provides the large quantities of oxygen required for the high respiration rate.

The large amounts of energy required for flight have led to the evolution of a mono directional pulmonary system, which provides the large quantities of oxygen required for the high respiration rate. However, birds do not suffer from the expected shortened life span as their cells have evolved a more efficient antioxidant system than those of other groups of animals.

Flight is more energetically expensive in larger birds, and many of the largest species fly by soaring (gliding without flapping their wings) most of the time. Many physiological adaptations have evolved that make flight more efficient. Birds evolved the digestive system which is simple but efficient (enabling them to pass food through their system quickly to minimize the extra weight of undigested food and the time it takes to extract energy from their food).

Today birds use flight for many purposes such foraging, to commute to feeding grounds and migrate between the seasons. It is still important in avoiding predators.



Reference:

1. Wikipedia contributors. Bird flight [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 10, 20:11[cited 2006 May 11]. Available from:
http://en.wikipedia.org/wiki/Bird_flight


Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria,
0001
Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
E-mail: lmukwevho@csir.co.za
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REVIEW OF THE EVIDENCE WE HAVE THAT DINOSAURS WERE WARM-BLOODED

Dinosaurs dominated the terrestrial ecosystem over 160 million years. These vertebrate animals first appeared approximately 230 million years ago. They are vertebrates animals because they were characterised by back bone. It is said that the dinosaurs suffered a disastrous extinction. Therefore going extinct ended their dominance in the land. However it is believed that birds are descendents of the dinosaurs. According to the scientist the earliest recorded dinosaurs fossils were found in Madagascar. They were slightly built and were of different diets, there were carnivores, herbivores, omnivores and others were insectivores.

According to the current studies by the scientist, it is believed that the dinosaurs were warm blooded animals unlike the early debates that they were cold-blooded animals. The current evidence by the scientist that the dinosaurs were warm blooded animals proved seems to be true based on the available evidence. Warm-blooded animals are animals that able to maintain thermal homeostasis, they keep their temperature at constant level in spite of the temperature of the surrounding environment. They are able to maintain their body temperature by regulating their metabolic rates.

The discovery of polar dinosaurs in Australia and Antarctica is also evidence that they were warm-blooded animals. This is because they were able to survive under very cooler condition. This mean that their body able to maintain the body temperature for them to survive. Their feathers may have played a role in providing regulatory insulation. The analysis carried on their blood vessels structures shows that of endotherms in dinosaurs bone.

The structure of the skeleton also suggests that dinosaurs had active lifestyles similar to that of endotherms. The body size of the dinosaurs is also another factor which the scientist believed that these animals were warm-blooded. This is because the size of animal plays a role in maintaining the body temperature. Their body size made them to be called bulk endortherms. These bulk endotherms are animals that are warmer than their environments through sheer size rather than through special adaptations like those of birds.

It is said that the warm-blooded animals grows faster than the cold blooded animals, there fore it was proved by Jack Horner that dinosaurs reach substantial size while they are still in the nests. This was proved through the isotope of their bones.
The above evidence is another way to believe that the dinosaurs were warm- blooded meaning that they manage to cope with different climatic conditions of the areas they existed.


Reference:
1. Wikipedia contributors, Warm-blooded [Internet]. Wikipedia, The free Encyclopedia, [Cited 2006 May 16] Available from:
http://en.wikipedia.org/wiki/Warm_blooded
2. Wikipedia contributors, Dinosaurs [Internet]. Wikipedia, The free Encyclopedia, [Cited 2006 May 16] Available from:
http://en.wikipedia.org/wiki/Dinosaurs

Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria,
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Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
E-mail: lmukwevho@csir.co.za
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THE ADAPTATIONS REQUIRED TO MAKE THE TRANSITION FROM AQUATIC TO TERRESTRIAL LIFE USING AMPHIBIAN AS EXAMPLE

The amphibians (example frogs) were the first vertebrates that managed a footing on land. Amphibians mean two lives, meaning that they can live in both water and land. They consist of a large group of different animals and frogs are the most familiar groups found in this class vertebrate. Amphibians are particularly interesting because they are an example of the vertebrate body plan in transition between the aquatic and terrestrial environment.

The transition from an aquatic life to terrestrial one, required modifications of several important body systems, to solve the problems of support and locomotion, gas exchange, desiccation, reproduction, feeding, and the function of some sensory systems. They adapted the different physical properties of water and air temperatures differences between water and land. They had to adapt with the drying out in the terrestrial ecosystem and had to change ways of giving birth. Transformation they had to change the way their circulatory system. When it comes to feeding, most amphibians feed well while they are in the aquatic environment. For example, crocodiles are very strong when they are inside the water when it comes to catching their pray.

The skeleton support was achieved by modification of the pelvic and pectoral fins and by strengthening the vertebral column. The skeletal support for the pectoral and pelvic fins was enlarged and strengthened, and the pelvic girdle became firmly attached to the vertebral column. The lower portions of the limbs were also greatly enlarged to provide an attachment area for powerful muscles. The vertebral column was strengthened by the development of interlocking processes and additional musculature.
The amphibians had to change their ways of locomotion for example in most fish, the propulsive thrust is provided by the tail and caudal fin which push against the dense water that cause the fish to move forward. In land the paired limbs with their strengthened girdles provided support for the body and also functioned in locomotion. When it comes to reproduction, amphibians had to adapt new ways of reproduction because reproduction in most frogs dependent on water as both fertilization and development. They adapted the way of excretion because most of these amphibians relied on large amount of water to wash away ammonia as excretory product. Therefore they had to use urea as their excretory product and it requires less water.

Although the amphibians managed to solve some changes, they were unable to solve one problem, reproduction in the terrestrial environment. . The problem is that the sperm, egg or developing embryo must be protected from desiccation. Amphibians must return to the aquatic environment to lay their eggs, and fertilize them, and it is there that the developing embryo grows until it is ready to move back up on land. Their adaptation from the aquatic environment to the land revealed a fantastic design that served them well in both environments.

References:

1. four feet on the ground, [internet] [cited 2006 may 9] Available from:
http://oscar.ctc.edu/access/geology100/life3.html#anchor583986

2. The move to land, [internet] [cited 2006 May 9] Available from:
http://instruct1.cit.cornell.edu/Courses/biog105/labs/deuts/movetoland.html

Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria,
0001
Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
Email: lmukwevho@csir.co.za
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MORPHOLOGICAL DIFFERENCES THAT EXIST BETWEEN THE CARTILAGINOUS AND BONY FISH

Fish are vertebrate animals that live in water, they have stream lined muscular bodies and they are cold blooded animals. There are three different classes of fish and these include the jawless fish, cartilaginous fish and bony fish. Fish can be found world wide and exhibit amazing adaptations to live in every kind of water habitat. Some fish live exclusively in saltwater, some in fresh water and others in mixed water.

Bony fish are fish that have a skeleton made of bone. They have teeth that are fixed into the upper jaw and have a swim bladder (an air filled sac that helps them with resilience) that opens into the gullet. They are the members of animals called vertebrate. These are animals with backbone. Several examples of this interesting and diverse group are found at sea. They do not have to swim to breath. Most of the fish are bony fish; however sharks, skates and rays are not bony fish.

Cartilaginous fish have the skeleton which is made of cartilage. These include sharks, rays and skates are cartilaginous. Fertilisation of eggs is internal. They have the scales that are placoid and are present all over the body surface. Once their scales are fully formed, they do not to grow but they replaced by new scale once they wear out.

These two fishes differs morphologically, the bony fish are the most diverse and numerous of all vertebrates. They differ from most of the cartilaginous fishes because they have a terminal mouth and a flap covering the gills most of them have a swim bladder which is ordinary use to adjust their buoyancy. Their skin has many mucus glands and is usually adorned with teeth. Most of their skeleton is bone that of sturgeon and few others is largely made of cartilage. In modern cartilaginous fish, lungs or swim bladder-like structures are absent efforts of swimming.

The bony fish have the skeleton with as small as amount of cartilage whereas the cartilaginous fish contains cartage only. Bony fish are able to swim backward and forward whereas the cartilaginous fish only able to swim forward. The cartilaginous fish consist of gill slits but no gills cover and the bony fish are covered with gill slits. The skin characterised of Slipper overlapping scales in bony fishes and in cartilaginous fish the skin is denticle rough sandpaper like placoid scales.


The bony have very good eyesight to avoid being prey. A swimming bladder keeps them floating just like fish on Earth. The unique thing about their swimming bladder is that they can efficiently extract oxygen from the water to fill their swimming bladders. The Cartilaginous fish do not have good eyesight; they make up for this with a good sense of smell. They are common in all the seas of Gump from the polar latitudes to the tropics.





Reference:

1. Hudson valley community college, 2000, life in the water, [Internet] Online Access: 2006 May 15 10:00 [cited 2006 May 16] Available from:
http://www.biologie.uni-hamburg.de/b-online/library/crone/3051/highli05.html

2. National geographic, 2000, fish of planet, [Internet] Online Access: 2006 May 15 13:00 [cited 2006 May 16] Available from: http://curriculum.calstatela.edu/courses/builders/planets2000/Gump/Limon/AQAnimal3/FISH.html#Bony

Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria,
0001
Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
Email: lmukwevho@csir.co.za
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SIGNALS USED BY INSECTS TO ATTRACT A MATE FOR SEXUAL REPRODUCTION

Insects are the most dominant species than any other kind of living creature. About 95% of all the animal species on the earth are insects. Million Insects can exist in a single acre of land. Insects are able to occur in large number because they can give a large number of off springs and they need only small amount of food. They can successfully live in most environments on earth for example desert.

Most insects mate and reproduce sexually between male and female. In insects females can still reproduce without male and this is common to the aphids. They may reproduce by laying eggs and in other insects, eggs hatch inside the female. Eggs can be laid in different places. For example locusts lay their eggs in a small hole until they hatched.

However, there are different signals which the insects use to attract a mate for sexual reproduction. Different semiochemicals are used by insects to attract mating partner. These chemicals mediate interaction between organisms. The chemicals are divided into allelochemicals and pheromones depending on the nature of interactions if it was interspecific or intraspecific. Allelochemicals are those chemicals that important to individuals of a species that are different from the source species. Pheromones are released by a certain species with the effect of having the attraction to the same kind of species.

Insects uses different ways to attract mating partner, which includes movement, colour, sound, vision and glands. For example, the female butterflies will develop some form of movement. The males will then chase those that show that behaviour and then the mating will take place. Male flies also form a compact swarms to attract females for mating. These insects also show some characteristics when coming to mating. These can be seen where male a required to have a form of gift or food to please the female. Fighting is another way where males compete for females, showing the survival of the fittest.

The female moths have scent glands on their abdomen which secrete pheromones to attract the male moth. The smell of these glands is easily detected by the male moth at a distance that can range from four to eleven kilometres. Sometimes the males secrete pheromone just to induce the females so that they mate.

The other interesting way in which insects attract each other for mating is through sound. Other insects that mostly use sound include mosquitoes, crickets, and grasshoppers. Female mosquitoes produce a note Sound which attracts the male mosquitoes. The male mosquitoes are attracted to the note or sound produced by the wing vibration of the wing. Female grasshoppers, crickets and cicadas are attracted by the sound produced by their males.
Some male insects have some special techniques they use to protect their sperms from other males. This includes guarding the female to prevent her from mating with other male. Genital plugging where accessory glands produce chemicals which plug the vagina allowing female to mate only once. Another technique is when the male scoop the sperms of previous males from female system using apparatus.
These special characteristics of insects prove that they are really the dominant in all living organism and they will continue to dominate every part of the earth.

Reference:

How do the sexes find each other, [Internet] [cited 2006 may 8] Available: http://bugs.bio.usyd.edu.au/Entomology/InternalAnatomy/reproduction.html

Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria
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Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
E-mail: lmukwevho@csir.co.za
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THE DIVERSITY OF FLYING INSECT LIFE THAT HAS EVOLVED

Insects are invertebrate animals which belong to the group of class insecta. They are the largest and most widely distributed taxon with the phylum anthropoda. There are about 925 000 known insect species. For example the dragonfly species, praying mantis, grasshopper, butterfly and moth, fly, tree bug, beetle, bees and ant species.

These insects are categorised in flying insects and non-flying insects. The flying insects such as bees, butterflies, grasshopper and dragon flies have developed their own different characteristics. Their characteristics are seen on the arrangement patterns of wings and their flying pattern. The grasshoppers characterised by two pairs of wing i.e. the inner wings which are very-very soft and the hard outer wings. The wings are attached to their abdomen.

The diversity of fling insects is seen with the example of dragon flies characterised by two pairs of wings which flap up and down synchronously. These two pairs of wings is a special characteristic for this insect because it can fly for long distance at a very high speed. The bees which are characterised by fore and hind wings linked together with hooks. Some of the flying insects have wings that can be folded over their back meaning that they can only spread them when in use. The indirect-flight muscle plays an important role in powering the wings for flying.

The flying ability by insects enable them diversify throughout the world. They gained the ability to explore more territory and find new kinds of food giving rise to more species. Insects easily produce large number of off-springs hence they need only small amount of food. This is another thing which able them to be more than other animals.

These flying insects are also ecologically significance/essential. They play a vital role and they are beneficial to the environment and to humans. Ecologically they facilitate the pollination process for plants that need to reproduce for example bees; butterflies receive rewards of nectar and pollen. They play a role in seed dispersal from one point to another. The evolution of different flying insects is very crucial because they produce useful substances such honey, wax and silk. Many of these have been cultured by humans for many years. Locusts serve as food for human.
Insects serve as food for other animals that are feed on insects thus insects are important in the food chain cycle.

Although the flying insects are diversified, they are facing threats. Through pesticides large numbers of insects are killed, although most tend to have some forms of resistance. These flying insects like locust are diversified in such a way that it is possible for them to invade a large portion of land.

Flying insects are very important to other plants and animals. In plants, this is seen during the process of pollination. Some plants cannot reproduce without the aid of the insects. Insects serve as food for other animals for survival.



References

1. A pair of wings took evolving insects on a non-stop flight to domination; [internet] [cited 2006 may 8]. Available from:
http://www.universityscience.ie/pages/scimat_evolving_insects.php


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

THE VARIATIONS IN SHELL STRUCTURE THAT OCCURRED IN THE PHYLUM MOLLUSCA

The phylum mollusca are known to be the largest of all phyla and provide some of the most familiar animals such as clams, mussels, squids and octopus. They are well known for their decorative shells or as sea food. The phylum Mollusca also includes lesser known forms such as the chitons, tusk shells, and solenogasters, among others.

The live in almost all parts of the world, from the deep water bodies like oceans to high up on mountains. The molluscs need moisture in order for them to stay alive; they must keep their soft bodies moist all the times. those which live in hot dry deserts environments, this is done by curling up in their shell, secreting a mucous plug and staying holed up until the next bit of moisture comes along.

The phylum Mollusca uses the chemicals and nutrients to build themselves protective shelters or shells. They have different shell structures however there are quite a few groups that have either reduced or internal shells, or no shell at all.

For example, the alplacophora are wormlike, bilaterally symmetrical animals living at moderate, to very great depths, usually on or in soft bottoms. They have no shell, but have calcareous spicules in the body surface. The bivalva or Apelecypoda does not have the shells because they live in water with ph greater than 5.

The polyplacophora have the shell consisting of eight, usually overlapping plates held together by a leathery strap. The polyplacophora or chitons are marine inhabitants and most make a living by grazing algae from rocks and other hard substrates. The most distinctive characteristic of chitons is their eight-piece shell.

The scaphopodia commonly known as tusk shells, they are bilaterally symmetrical and their elongate, tubular, tapering shells are open at both ends. The shell is usually an elongated, cylindrical tube; open at both ends, and slightly curved. However, some of the scaphoda shells are shaped more like a distended cucumber. The shell is usually heavily uneven and has small slits at the narrowest end.

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

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

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

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


References

1. Wikipedia contributors. Caudoveata [Internet]. Wikipedia, The Free Encyclopedia; 2006 April 9, 09:01 [cited 2006 May 4]. Available from:
http://en.wikipedia.org/wiki/Caudofoveata

2. Wikipedia contributors. Aplacopra [Internet]. Wikipedia, The Free Encyclopedia; 2006 April 20, 20:04 [cited 2006 May 4]. Available from:
http://en.wikipedia.org/wiki/Aplacophora

3. Wikipedia contributors. Polyplacophora [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 04, 15:32 [cited 2006 May 4]. Available from:
http://en.wikipedia.org/wiki/Polyplacophora

4. Wikipedia contributors. Monoplacophora [Internet]. Wikipedia, The Free Encyclopedia; 2006 April 22, 20:03 [cited 2006 May 4]. Available from:
http://en.wikipedia.org/wiki/Monoplacophora

5. Wikipedia contributors. Bivalvia [Internet]. Wikipedia, The Free Encyclopedia; 2006 April 23, 12:22 [cited 2006 May 4]. Available from:
http://en.wikipedia.org/wiki/Bivalvia

6. Wikipedia contributors. Scaphopoda [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 04, 20:07 [cited 2006 May 4]. Available from:
http://en.wikipedia.org/wiki/Scaphopoda

7. Wikipedia contributors. Gastropoda [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 04, 20:07 [cited 2006 May 4]. Available from:
http://en.wikipedia.org/wiki/Gastropoda

8. Wikipedia contributors. Cephalopod [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 3, 04:57 [cited 2006 May 4]. Available from:
http://en.wikipedia.org/wiki/Cephalopod



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

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

Fossilization is the process that involves non-living, which enable the remains of formerly living creature to be preserved after its death and following burial under sediment. This process only takes place in present of certain conditions or factors and these factors play a role in preserving the fossils. The process depends on chemistry of the environment and the biochemical makeup of the organism. Therefore because different organisms are made of different bio-chemical makeup not all organisms may be fossilised thus few in many organisms are fossilised.

The hard parts of dead animals are usually preserved as fossils; this includes shells, bones and teeth. The process begins with the dead of plants and animals. After they died, they are buried on the ground. The soft body parts decay and rot after death and the process is carried out by bacteria and scavengers. Different processes are involved in fossilization of plants and recrystalization. The body is buried under more and more layers of sediments overtime. Hard body parts are replaced by new minerals such as calcite or quartz or pyrite and this process is known as petrification. Sediments are further compacted further again by the weight of rocks above. At later stage the rocks are pushed up to form mountains fossils may be seen at later stage after million of years when the rocks are worn down to reveal the fossil.

Fossils are important as they allow the scientist called palaeontologists to find more information about biological organisms that existed in a period of time that predates our own. Knowing something about the kind of ancient life and the environment that existed long ago can tell us how Life become accustomed but also how the climate changes. Therefore by knowing something about the past we may be able to make a more informed prediction about what could happen in the future.

Fossils can also just tell us great stories about what was happening millions of years ago. For example fossilized footprints of a heard of dinosaurs running from danger or how they may have cared for their young. Discoveries of fossilised nests and eggs can tell us how they may have lived. The fossils are also important to tell more about the sizes and structure of organisms that existed in a period of time. These also help to understand the species that evolved longer than the other.

Currently, Fossils are also potentially economically. Quite big business, either directly by people finding examples and selling them or the industries like movies makes millions of dollars based on stories that come from fossil discoveries.


References

1. Fossilization, [internet] [cited 2006 may 5]. Available from:
http://www.museum.vic.gov.au/dinosaurs/sci-form.html

2. Fossilization, [internet] [cited 2006 may 5]. Available from:
http://www.musei.unina.it/Paleontologia/eng/3.2.4.1.htm


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