Biodiversity

Friday, May 12, 2006

THE DIFFERENT BETWEEN NEW WORLD MONKEY AND OLD WORLD MONKEY

Monkeys are arranged into two main groups. That is, new world monkey and old world monkey. Animals that exit in new world monkeys are known as platyrrhines while those that occur in old world monkeys are known as catarrhines. "The new world monkey are found in South America while the Old world monkey are found throughout tropical Africa and Asia"(1). Animals that exist in new world monkey are not the same as those that are existed in Old world monkey. They are differ interms of charecteristics and its behavior.

The new world monkeys are small to medium and those monkeys are "related to apes and humans"(2). The new world monkeys have 3 premolars while on the other hands the old world monkey has 2 molars. All new world monkeys differ slightly from old new world monkeys in many aspects. The important thing is differ in nose."Platyrrhines and catarrhine differ in shape of the nose. New world monkeys have flat nose. The nostrils of new monkey are far apart and open to the side while in the old world monkey, nostrils are closer together:(1)
The new world monkey has big, and it has sharp canines with a distena. Distena means the gap between canines and incisors. Old world monkeys are larg than new world monkey. For examples males baboons are the biggest old world monkey. "According to the hands of new world monkey, thumb lies in line. In the new world monkey, spider monkey has no thumbs. And some of the species have fingernails on big toe. Where as in the old world monkey, thumbs are turn and they are like human, and baboons"(1).
It has finger nails and toenails on all digits. The new world monkeys have relatively large molars. the last molars are relative small. Some they do not have molars. Remember that, the old world monkey have two premolars. “Premolars are found in the mandible side are sectorial” http://www.cabrillo.edu/~crsmith/monkeycomparisons.html
The ear regions of new world monkey, especialy the tympanic membrane, they are connected to external ear by a bony ring while in the old world monkeys, tympanic membrane are connected to external near by a bony tube.”(1) “In the new world monkey some species have pensile tails while in the old world monkey all have tails but lack of prehensility feature. Few species in the new world monkey have one male multifemale group like many of the old world monkey species. New world monkey have scent glands rely more on scent to mark territories than old world monkey.”(1) http://www.cabrillo.edu/~crsmith/monkeycomparisons.html
“New world monkey confined to arboreal habitats and rely heavily on fruit and less on foliage with compare to old world monkeys. Old world monkeys spend some or most of the day on the ground and they tolerate in a wider range of habitats from rainforest through savannah fringe”(2). Most of the new world monkeys are closely related. Cebidae and Atelidae families are found in new world monkey. Cidibae include animas like, squirrel, capuchin, owl and monkeys. Atelidae include animals like spider and howler monkeys.

References

1. Anthropology 1, New world (America) and Old world (Africa and Asia) Monkey: A comparison, [Internet] [Cited 2006 May 12] Available from: http://www.cabrillo.edu/~crsmith/monkeycomparisons.html

2. Wikipedia Contributor Monkeys (internet) Wikipedia, the free Encyclopedia, 2006 May 12, 17:33 UTC [Cited 2006, May 12, 17:25] Available from:
http://en.wikipedia.org/wiki/Monkeys

3. Anthropology 1, New World (Amarica) & Old World (Africa and Asia) Monkey: A comparison, [Internet]. [Cited 2006 May 11]. Available from: http://www.cabrillo.edu/~crsmith/monkeycomparisons.html
Linette Netshiheni
CSIR
Pretoria
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Cell: 0820446442
Tell: 012 841 2133
Fax: 012 842 3676

THE MEMBERS OF THE FAMILY HOMINIDAE.

The family of Hominidae consists of the gorillas, chimpanzees, orangutanas and human and all of them are known as the great ape. It is said the true membership of the Hominidae are not clear. Chimpanzees, human and gorillas species are closely related to each other but their DNA are different. Chimpanzees and hunan are closely related to each other and they share 99.4 percent of their DNA." (2).

Orangatans are the species of great apes with long and strong arms which are about 2.2 metres. Their legs are short and week. The word orangutanas means man of the forest meaning that they are found or living in the forest environment. They spend their time in "the trees making new nests" (4,5). The weight of the males orangutanas were differ compared to the females. Males weight ranging "between 50 and 90 kilograms and females weight ranging between 30 and 50 kilograms" (3). The height of the males is 1.4 metres tall and the females are smaller than the females. They have "reddish and brown hairs and high sloping fore head" (3, 5). They are existing species belonging to the genus Pongo and subfamily Pongonae. Orangutanas are very "clever species, passive and violence toward other orangutanas is very common and this means that they are friendless animals and they can be violently protective" (5).

Gorillas are the chief of the chimpanzee or an ape and their genus name is gorilla. Gorillas are herbivores animals meaning that they feed themselves on plants and fruits from the trees and shoots. These species are found in the forest of central Africa. They share 92 to 98 % of their DNA with the human and this means that they are closely related to a human. Gorillas have a strong body, arms and their legs are short. They have a strong chest and broad hand. They are " knuckle walking”(1,5), and they have a long hair which protect them from the living cold at high slope.

The body of the gorillas is covered by brown hairs. They have a big head with forehead, thin ears and small eyes which are dark brown in colour. They have facial features like “wrinkle around the nose" (5). Gorillas use arms and feet to walk. The height of "male adult ranges between 1.65 m and 1.75 m tall" (1,5). Their weight ranges between 140 and 165 kg. Females are about half of weight of males. All gorillas share the blood type B. Scietists believe that gorillas are active in the mornig like a human, It is because they wake up early in the morning and go around in search for their food so that they can feed themseves and their babies. They also take a good care for their children like the human being.

The chimpanzees have a long arms and short legs. Their body is covered by black hairs. They have a "slight brow ridge, large ears and small nostrils" (5). The genus name of chimpanzees is Pan. Chimpanzees are divided in to groups such as common chimpanzees and pygm chimpanzee. These species are omnivores meaning that they feed themselves on animals, plants and fruits. They found in forest and they are walking with two feet.

Human beings are bipedal meaning that they walk with two feet. They belong to the Homo sapiens which mean wise man. Human being develop "the brain which allow them to bring ideas and solving problems, language and introspection" (3,5). All this indicates that they "developed a high nervours system and they have a strong senses" (4). They are also omnivores meaning that they eat meat and plants. Human, gorillas and chimpanzees are" closely related" (3,4) to each other.

In coclution, Hominidae are closely related to each other. All Hominidae family have large brain and their weight ranging from between 48 and 120 kilograms. Their arms are strong and well developed and also have a strong bodies. They are all walking with two feet.


References:

1. Csomos, R. 2001. "Gorilla gorilla" [Internet], Animal Diversity Web. Accessed May 2. [cited 25 May 2006, 11:10]. Available from:
http://animaldiversity.ummz.umich.edu/site/accounts/information/Gorilla_gorilla.html

2. Hecht, J. 2003. Chips are human, genes study implies. [Internet]. Accessed 19 May 2003, 22:00 [cited 25 May 2006, 09:30]. Available from:
http://www.newscientist.com/article.ns?id=dn3744

3. Millhouse, C. 2003. "Gorilla gorilla gorilla" [Internet]. Animal Diversity Web. Accessed May 19, 2006 [cited 2006 May 24, 09:58]. available from:
http://animaldiversity.ummz.umich.edu/site/accounts/information/Gorilla_gorilla_gorilla.html

4. Myers, P. 2001. "Hominidae" [Internet], Animal Diversity Web. Accessed May 19, 2006. [Cited 2006 May 19, 12:11]. Available from: http://animaldiversity.ummz.umich.edu/site/accounts/information/Hominidae.html.

5. Wikipedia contributors. Great Apes [Internet]. Wikipedia, The Free Encyclopedia, 2006 May 10, 02:58 UTC [cited 2006 May 12, 15: 45]. Available from:http://en.wikipedia.org/wiki/Great_Apes


Lizzy Maluleke
CSIR PTA
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Cell number 072 351 8488
Tell [012] 841 2133
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E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.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" (1). They are 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 the "most diverse class of terrestrial vertebrates and there are about 8,800-10,200 living bird species" (1). 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 hooklets 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" (1). 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" (1). 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)" (1).

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,
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Tel: (012) 841 2133
Fax: 012 842 7024.
Cell: 0723175626
E-mail: lmukwevho@csir.co.za
My blog URL: http://mukwevholufuno.blogspot.com/

HOW PLACENTA MAMMALS HAVE COLONIZED LAND, WATER AND AIR

The placental mammals are very diverse species and range from elephants, whales, shrews, and armadillos. They also include pets such as dogs and cats, as well as many other animals such as sheep, cattle, and horses. It is also recognised that human being are also the placental mammals. They form a very diverse group of species and their young are born at relatively advanced stage as compared to other mammals.

The placentals mammals include about 4300 species, making it by far the largest of all three mammal groups. Young placental mammals spend a relatively long time developing inside the body of their mother before birth. They are protected within the womb, which is nourished by a spongy organ called the placenta. This serves to absorb nutrients from the blood of the mother and transfers them to the developing animal. By the time a young placental mammal is born, it is usually fully developed, although it may not yet have fur, functioning eyes or teeth.

Some placental mammals have adapted to survive in the water, land and air. They have developed different body shapes and sizes, which act as the driving forces behind colonising water, land or air. They have wings to survive in air, feet to survive in land and gills to survive in the water. Species such as Seal, sea lions and walruses as for example, have adapted to live in both land and in the water. These species do sleep and feed in the ocean but they return to land in order to reproduce. Manatees and dugongs are large, plant-eating mammals that spend their entire lives in the water (2)

In the same manner, whales and dolphins are well adapted as fast, open-ocean predators. Most aquatic animals 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 and where the water temperatures is low. They survive the cold temperature in two different ways; firstly -Others such as sea otters and fur seals have a double coat of fur, with extremely dense under fur hairs that are so closely packed that the skin never gets wet. Secondly -whales have very sparse hair, and keep warm with a thick layer of fat called blubber. Such characteristics enable this species to survive even in low temperature.

In addition, "dolphins have adapted for an aquatic lifestyle, by having flippers that help them glide through the water. The manatees and dugongs are large, plant-eating mammals that spend their entire lives in the water. Contrary, the jaguar, a terrestrial carnivore has explosive running power, which enables them to survive on land. This species colonise the land and most of its prey lived on land. Other species such as bat have evolved limbs into wings that enable them to inhabit the skies"(1). Generally, mammals have adapted to some of the most extreme habitats on earth. They are warm-blooded, or endothermic, meaning that they maintain their body temperature within a narrow range despite changes in the environment.

Reference

1. Wikipedia contributors, Whales [Internet] The Free Encyclopedia, 2006 May 12; 12:35 UTC[ Cited 2006 May 12]
Available From:
http://encarta.msn.com/encyclopedia_761565254_2/Whale.html

2. Wikipedia contributors. Mammal, [Internet] Wikipedia, The free encyclopedia; 2006 May 12; 12:04 [Cited 2006 May 12] Available From:
http://encarta.msn.com/encyclopedia_761561349/Mammal.html

Dianah Nangammbi
Cilla CSIR
P.O Box 395
Pretoria
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Tel: +27 12 841 2133
Cell: +27 73 121 3589
Email: dnangammbi@csir.co.za
http://wwwdianah.blogspot.com/

CHARACTERISTICS OF ORDER OF PLACENTAL MAMMALS AND LISTS OF ANIMALS REPRESENTING EACH ORDER.


Placental mammals contain different types of orders. They are twenty orders. These orders include: Chiroptera, Carnivora,Perissodactyla, Cetacea, Artiodactyla, Dermoptera, Hyracoidea, Insectivora, Lagomorpha, Macroscelidea, Primates, Proboscidea, Rodentia, Scandentia, Sirenia, Condylarthra, Afrosoricida, Tubulidentata, and Xenarthra. Each order consists of different animals. They are also differs in terms of characteristics. "These animals hold their young within the mother until development is well along"(2).

The order Chiroptera is found in placentalmammals. These are only mammals that are truly fly and well furred bodies. Animal that fall under this order have very poor vision. These animals have wings, and they used those wings for flying purpose. They also eat insects and vegetation. Animal which are found in the order Chiroptera are bats.

Carnivora are another order of placental mammals.Carnivora are strictly meat eaters. Carnivora are large in size. Although Carnivora have heavy skulls. They all have hair in their bodies. The teeth of these animals are well developed. However all carnivores have sharp canine’s teeth. All Carnivora have simple stomach. The eyes of Carnivora are facing front. Dogs, bears, raccoons, seals, walrus and sea lion are the animals that are found in order Carnivora. http://www.nhptv.org/Natureworks/mammalia.htm

The order Perissodactyla have hooves. They are odd toed, meaning that they are unpaired. They are hoofed. Animals that fall under Perissodactyla have no gall bladder. All Perissodactyla are large animalsnot small animals. One can say that, animal fall under this order have complete set of incisors. It has longer skull. However these animals do not have true horns. Animals which are found under Perissodactyla are Horses, Rhinos, Tapirs, Zebras and donkeys.

Cetacea is one of the order of placental mammals. The body of Cetacea are fairly robust. On top of the head are open. Animals found here are warm blooded animals and they have few hairs on their bodies.” organism or animals which belong to this order are usually have the following characteristics, large body size, bubbler, usually hairless, sensory abilities such as large brain and they are good in swimming. These are the animals such as whales, Dolphins, Porpoises”.(5)

The orderArtiodactyla have four chamber stomachs. They lack upper incisors. All have long limbs. Many Artiodactyla have horns that grow from frontal bones of their skull. These horns are not the same as those of Perissodactyla.
The order Artiodactyla includes deep, pigs, cattle, goats, giraffe, camels and sheep. The toes of these animals are covered by large honey hooves.

The order Dermoptera has only one family having two species. Although these species are flying lernurs like squirrel, and Colugos. Their arms are covered by flap skin. They also have well- developed gliding membrane. According to the skull of these animals are unique.

"Insectivora is found on order of placental mammals. Inscetivora are insects eaters. These are animals such as Moles, Shrews and Hedgehogs. Many of Insectivora have poor developed eyes, and small ears. They use hearing and smell to find prey"(2).

Animals that found in the order Lagomorpha have long ears. They also have short tails. Its back legs are strong. They have two pairs of incisors. However these animals have no canine teeth and molars but they have spongy bones in the upper jaws. Animals that are found here are Rabbits, Hares and Pikas. It has short tails.

Macroscelidea is one of the group of placentalmammals. Animals that are found under this order are Elephant shrews. Their back leg is long. They also have big ears and eyes. Their tails are short.

Primates is one order of placental mammals. Lemurs, monkeys, marmosets, apes and human are found under this order. They also have forward facing eyes. However in the chest, they have one pairs of mammae.” Its unique characteristics are the grasping fingers aid in power grip that they have. They have opposite thumb and foot are plantigrade “(6).

Lets look at order Proboscidea. These animals have thick skin and it also have the little hairs. These are the animals such as elephant. Most of these animals have horns. Most of the animals found here are big.

Order Rodentia, all the animals that are found here are rodents. They are small animals. However these are the animals that have one pairs of chisel. Animals that are found under Rodentia order are squirrels, chimpmunk, rats, mice, voles, and beavers and bemmings. They have diastema between premolars and incisors.

Order Scandentia have small body size but they have long tails. Its eyes are facing forward and they have poorly developed claws. The animals belongs here are Typayas

In the order Sirenia,we found examples of animals such as Dugongs and Manatees. Most of these animals do not have teeth but they have flat tail.

Tubulidentata is one of the order of placental mammals. They have very thick skin. They also lack incisors and canines in adult. The teeth are also rootless. Animals that are found here are aardvark.

I n the order of placental mammals we found Xenarthra sometimes they called Edentata.They have long and sticky tongues. They also have long claws on the front feet and five toes on the hind feet. Animals that are found under this order are Sloths, Armadillos and true anteaters.

Afrosoricida is found in the order of placental mammals. Animals that are found here are goldens moles and terecs.

Just conclude Eutheria is the largest subclass of mammals. Each orders have different charecteristics and different animals. For examples, animals that are found under Insectivora eat only insects where as animals found in carnivores, are strickly meat eaters. It is easy for one to identify which animals belong to whch orders.

References

1. Moreillon,J. 2000-2005, Orders of Mammals in Sabino Canyon
[Online]. Available from: http://storytrail.com/SabinoCanyon/orders.html©


2. Wikipedia contributors.Eutheria [Internet]. Wikipedia, The free Encyclopedia, 22:55, 25 May 2006 UTC [Cited 29 May 2006 10:15] Available from: http://en.wikipedia.org/wiki/Eutheria

3.Wikipedia contributors. Mammal [Internet]. Wikipedia, the free Encyclopaedia, 00:51, 10 May 2006 UTC [Cited 12 May, 2006, 5:25] Available from
http://en.wikipedia.org/wiki/Mammals

4. Murphy, W.J; Eiziric,E, E. 2001. Molecular dating and biogeography of the early placental mammal radiation. [Online]. Available from:
http://jhered.oxfordjournals.org/cgi/content/full/92/2/212 [2006 May, 12]

5. Byers, R. 2005. Post-Flood Marsupial Migration Explained. [Online]. [Cited 12 May, 2006, 11:20]. Available from:
http://www.rae.org/marsupials.html [19 October 2005, 12: 20]

6. Durham, N.H. Nature works mammals. [Online] [Cited 25 May, 2006 15:10]. Available from:http://www.nhptv.org/Natureworks/mammalia.htm

7. Murphy, W.J 2001. Molecular phylogenetics and the origins of placental mammals. [Online]. Available From:http://www.museums.org.za/bio/mammals/eutheria.htm

Linette Netshiheni
CSIR
Pretoria
0001
Cell: 0820446442
Tell: 012 841 2133
Fax: 012 842 3676
tnetshiheni@csir.co.za
Weblog:
http://tnetshiheni-linette.blogspot.com/

HERBIVOROUS DIET "IMPOSES" CERTAIN PROBLEMS FOR DIGESTION

Herbivores are animals that feed only on plants. These are animals like rabbits and elephants. Some of the herbivores eat a certain part of the plant. "Herbivores are further classified into various sub-groups such as frugivores and folivores. Frugivores are animals that feed only on fruits whreas folivores specialise in eating leaves. Most of the fruit and leaf eaters also eat other parts of the tree such as roots and seeds. The diet of herbivourous differ s according to the season "(1). There are some seasons at which plants loose some leaves, so the folivores will have to change their diet for that period until the leaves develops again.

The problem that herbivores face with their digestion is caused by cellulose.Their diet contains a lot cellulose because plant cells are made up of cellulose. Enzyme cellulase is used for the breaking down cellulose, so it is difficult for cellulose to be broken down due to the fact that it contains high organic substances. In some vertebrates enzyme cellulase is not present in the digestive secretions of some vertebrates and these vertebrates digest cellulose and depend on it as their source of energy. They behave like this because inside their gut there are symbiotic micro-organisms which can digest cellulose. Animals like ruminants solve this problem esily. Ruminants are those animals with stomach having "four chambers rumen, reticulum,omasum and abomasum"(2). Most ruminant animals include cattle, sheeps and goats and these are animals provide us with meat and milk. Ruminants chew their food during the feeding and when they are at leisure the food comes back to the mouth and they rechew it again. By doing this they are helping on breaking down of cellulose.

"In rumens extensive microbial fermentation of the plant diet occurs in a specialized region of digestive tract prior to digestion by alimentary enzymes. Some of the non-ruminant animals depend on symbiotic micro-organism for the digestion of their cellulose. Non -ruminant herbivores have large stomach with several compartments. The digestion of ruminants and non- ruminants is very similar, the only exception is that in non- ruminants there is no regurgitation and rechewing of food. The major fermentation of cellulose in herbivorous mammals takes place in a large diverticulum from the caecum. Microbial fermentation in caecum is similar to fermentation in the rumen"(1). The only difference is found by comparing the faeces. The faeces of the ruminants (taking cattle as an example), are watery and smooth, whereas the faeces of the non- ruminants (horse) have coarse fragments of food.

It is true that animals with high metabollic process grow very fast as in case with herbivores who eat cellulose. In order to solve this problem some animals just grow massively. The advantage is that they will have a long digestion which will allow them to digest tougher plants. This allows larger herbivores to protect themselve by their body size from predators and they feed on higher foliage while small herbivores are feeding on small grass. Most of the predators fear to attack them.Everything that the herbivores eat have a great impact on the structure of their body. The body size help them to have acess to all the types of the plants. Taller herbivore will depend on taller plants and shorter herbivores will feed on sort plants and grass so there is a balance.

Reference

1. Findlay, A.L.R. 1998 The Gastrointestinal System: an introduction Carnivores, Omnivores and Herbivores [Internet] 2006 May 11; 10:33 UTC [cited 2006 May 11] Available From:
http://www.chu.cam.ac.uk/~ALRF/giintro.htm


2. Wikipedia Contributors. Ruminant. Wikipedia, The free Encyclopaedia, [Internet] 2006 May 12; 11:10 UTC [Cited 2006 May 12] Available From:
http://en.wikipedia.org/w/index.php?title=Ruminant&oldid=49674058.

Dianah Nangammbi
Cilla CSIR
P.O Box 395
Pretoria
0001
Tel: +27 12 841 2133
Cell: +27 73 121 3589
Email: dnangammbi@csir.co.za
http://wwwdianah.blogspot.com/

PLACENTAL AND MARSUPIAL MODES OF REPRODUCTION

Placental mode of reproduction is a process that occur in mammals, “is a temporary organ that develop during pregnacy”.[1] The growing embryo connects with the uterus through umbilcal cord to the mother,in this process the fuetus gets feed from the blood of the mother.the embryo grow inside the womb of the mother and it takes 12 months period for gestation. while the marsupial mode develop the yolk sack and it have short period of gestation, the embryo of the marsupial do not develop inside the womb of the species.[1]

Marsupials develops a pouch that they used to carry their early infant, this pouch develops in the belly of the species. “where the infant crawls ups and attach itself to the nipple for feeding, it can stays acttached to the nipples for period until it can pass the stage where it can live its mothers pouch. They will only returns to its mother for warmth and nourishment”.(2)[3]

During reproduction placental mammals develops placenta that protects the fetus from their mother s immune system. “while in marsupials they does not develop a complex of fetus, because they does not need any protection for the fetus from the immune system that the mother have”.[2]

Marsupials mode of reproduction and placental mainly differ interms of gestation period. In marsupials it takes short period, close to twelve days of the embryo of marsupials in the reproductive track. but this also influence by the type of egg yolk. while the placenta gestation takes takes 9 months , this occurs because the embryo of placental mammals need to be fully developed before birth. But if the placental mammals give birth before time,the fetus become prematurely and it will need care which is similar to marsupials.[3]

This two mode of reproduction also differ in the way their embryo develops,in marsupials the embryo is separeted from the body of the mother, while in placental the embryo is connected to the mother.it get all the support from nutrient ,oxygen through blood.marsupials only feed its fetus for short period and then start to breast feed the infant.[2]

Difference also seen when the placental mammals are pregnant the process of oestrus cycle does not happen until the end of pregnancy. Whereas in marsupials the oestrus cycle does not stop it takes place. “In marsupial the ovarian inhibition is mediated by lactation or suckling stimulus. These regulatory modifications are important because the baby will no longer be carried internally so negative feedback stimulus from the presence of the infant must come from nursing activity”.[3]

Mating system also differ and this can determine the mode of reproduction. in marsupial is different through out the year. Some species are single and they only come together to mate and this pattern of social behaviour reflect promiscuous mating systems.while in placental after mating male and female take time together, and this sometimes depend on the type of species.some males takes care of their infant.

In conclusion mode of reproduction differs with type of species and also the size of the species involve to the way in which species reproduce. Species that reproduce by placental must have big body as they have to carry the embryo for couple of months, while those with small bodies do not carry embryo in their belly they reproduce by marsupials process.as they have to carry infant for short period,which will enable them to move because they have small bodies.

Reference:

1. Wikipedia contributors. Placenta [Internet]. Wikipedia, the Free Encyclopedia; 2006 May 15, 13:52 UTC [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Placenta

2. Wikipedia contributors. Marsupials [Internet]. Wikipedia, the Free Encyclopedia; 2006 May 19, 22:51 UTC [cited 2006 May 10]. Available from: http://en.wikipedia.org/wiki/Marsupials

3. Ashcraft.C.W. Marsupial Evolution And Post Flood Migration.[Internet]cited 2006-May-10] Available from: http://www.nwcreation.net/marsupials.html

Mr Elelwani Muanalo
NISL- Ecological Informatics Student
CSIR Pretoria
Tel: +27 12 841 2133
Fax: +27 12 842 7024.
Email: emuanalo@csir.co.za
My bloger URL: http://www.emuanalo.blogspot.com

DISCUSION OF THE CHARACTERISTICS WHICH IDENTIFY EACH ORDER OF THE PLACENTAL MAMMALS AND LIST OF ORGANISMS

Placental animals are organisms which maintain their young in the body of the ''mother until the end of the period of the gestation'' (Wund and Myers, 2006). There are several orders of organisms which are found under the placental mammals which also have different unique or diagnostic features. These orders include ''Chiroptera, Artiodactyla, Rodentia, Logomorpha, Carnivora, Insectivora, Cetacea, Tubulidentata, Pholidota, Primates, Dermoptera, Proboscidea, Sirena, Scandentia, Edentata, Perissodactyla, Xenarthra, Embrythopoda, Creodonta and Condylarthra'' (Wund and Myers, 2006) . Under each order there is an also different animals such as Pigs and Deer.

In the order artiodactyla variety of characteristics and animals are found. These unique characteristics include two or four toes. ''Pigs, Deer, Cattle and Goats'' are examples of the order artiodactyla (Wund and Byers, 2006). Pholidota, in this order diagnostic features such as ''long toque and imbricate scales which tend to overlapp'' (Byers, 2005). The examples of animals which are found in this order include only Pangolins. Primates, the diagnostic features which primates possess include ''brain with a posterior lobe, claviculate and unguiculate'' (Wund and Myers, 2006). The examples of animals in the order primates are Monkeys, Lemurs and Chimpazees.

The order cetacea include animals such as Dolphins, Whales and Porpoises. The organisms which belong to the order cetacean usually have the following unique characteristics which is their ''highly specialized aquatic lifestyle'' (Byers, 2005). In the other side Logomorpha have two pairs of the upper incisors and molars without roots. Examples of animals which are found in this order are Rabbits, Hares and Pikas. In the order Chiroptera, only one example of animal is found. The animal which is found is Bats. The unique characteristic which Chiroptera possess is their modified forelimbs.

The order Carnivora include examples of animals such Dogs, Cats and Bears. The diagnostic feature which distinguish this order from others is their adptation on eating meat. Insectivora have these unique features, ''small brain, unspecialzed teeth, poorly developed eyes, small ears and a long pointed snout'' (Wund and Myers, 2006). Examples of animals found in the order Insectivora include Moles and Shrews. In the order Rodentia, examples of animals such as Mice, Rats, Squirrels and Gophers are found. The distinguishing characteristics in which Rodentia possess are one pair of chisel-like incisors and they have no canine teeth. Tubulidentata is the order in which only one example of animal is found. This animal is Aardvark. Tubulidentata possess a unique structure of the teeth. In adults canines and incisors are absent. The only teeth which are found are at the back of the jaw.

Animals which belong in the order Dermoptera have the unique features such as ''incisors which are specialized for comb-like teeth'' (Murphy and Eizirik, 2001). The adaptive incisors are also used for grooming. Examples found in these order Dermoptera include only Flying lemurs. Proboscidea is the order which include animals such as Elephants, Mammoths and Mastodons. Wund and Myers (2006) say that the diagnostic features which are found in this order include horns which consist of parietal bones and manatees. Sirenia is the order which include only one animal which is Sea cow. The only unique feature in this order is the absent of the teeth. Scandentia is the order in which animals such Tree shrews.

In the order Edentata, unique characteristics such as ''large claws for digging and lack of teeth are found'' (Murphy and Eizirik, 2001). The examples which are found in the order Edentata are Sloths and Armadillos. Byers (2005) says that Perissodactyla is the order which possess the following unique characteristics, hoofed forms and odd toed. Examples of animals which are found in this order include Horses, Donkeys and Zebras. Xenarthra is the order which possess the following unique characteristics ''long sticky tongues, long claws on their front teeth and small brain'' (Wund and Myers, 2006).

In conclusion, it is easy to say that in all orders mentioned above some examples of animals are faced with extinction. This is because that in other order such as Chiroptera we only find one example which is that of Bats. On the other side, as opposed to Chiroptera, in certain orders such as Primates we find more than one examples of animals. It is also common that in each order there is one or more diagnostic or unique characteristics.


References:

Byers, R. 2005. Post-Flood Marsupial Migration Explained. [Online]. Available from:
http://www.rae.org/marsupials.html [19 October 2005, 12: 20]

Murphy, W. J.; Eizirik, E. 2001. Molecular Dating and Biogeography of the Early Placental Mammal Radiation. [Online]. Available from: http://jhered.oxfordjournals.org/cgi/content/full/92/2/212 [February 2001, 07; 12:42]

Wund, M. and Myers, P. 2006. Order Insectivora. [Online]. Available from:
http://animaldiversity.ummz.umich.edu/site/accounts/information/Mammalia.html [cited 25

May 2006, 15: 17]
Peter Muvhali
CSIR PTA
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Tell no 012 8142133
Fax 012 8423676
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URL: http://www.blogsoccer-peter.blogspot.com/

COMPARISON BETWEEN PLACENTAL AND MARSUPIAL MODES OF REPRODUCTION

Placental mammals “are highly developed mammals which give birth to young at a relatively advanced stage” (1). There are “almost 4,000 known species of placental mammals” (1). They are more advanced than the young of the other mammals, the monotremes and marsupials. Before birth, the young are nurtured through a placenta. The placenta is attached to the mother uterus and it is a specialised embryonic organ. These help to deliver oxygen and nutrients to the young placental mammals.

Marsupials are mammals in which the female typically has a pouch in which it rears its young through early infancy. Marsupials are “animals that belong to the order Marsupial and an infraclass Metatheria” (2). “The member of the class includes kangaroo, koala, Tasmanian devil and the Virginia opossum” (3). Marsupials are known have a lot of characteristics and they are not considered to be non-placental mammal. “The female marsupials “carries the young in the marsupial or pouch” (3). This is where the young are provided with warmth and proper environment. They are characterised by non-invasive placenta which is used in the transferring of nutrient and waste for limited period of time. (3)

“Placental mammals differ from the marsupials in that their young develop to a relatively mature stage within a uterus attached to the mother by an allantoic placenta. The placenta allows the foetus to plug into its mother's circulation and share her respiratory and excretory systems, and the nutrients carried in her blood. Mammals, like marsupials, feed their young with milk and care for them for prolonged periods until they can look after themselves” (4).

The marsupials differ from placental mammals in the way in which reproduction take place. The “female has two vaginas and both of which open externally through one orifice but lead to different compartments within the uterus” (3). The “male marsupials have two penis which only passes sperm” (3) and these two penis corresponds to the females two vaginas. ”The pregnant female develops a kind of yolk sack in her womb” (3) which delivers nutrients to the embryo. “The embryo is born at a very early stage of development (at about 4-5 weeks), upon which it crawls up its mothers belly and attaches itself to a nipple” (3). It remains attached to the nipple for a number of weeks. The offspring later goes through a stage where it temporarily leaves the pouch and then return for warmth and nourishment.

The “early birth of marsupials removes the developing young much sooner than in placental mammals, and marsupials have not needed to develop a complex placenta to protect the young from its mother's immune system” (5). “The early birth places the tiny new-born marsupial at greater risk, but significantly reduces the risks associated with pregnancy, as there is no need to carry a large fetus to full-term in bad seasons” (5).

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 while they are still inside their mothers. The extended maturation of placental is caused by the placenta which allows nutrients to travel from the mothers 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. Enchated Learning.com, Placental Mammals. 1998 [Internet] [Cited 2006 May 24] Available from:
http://www.enchantedlearning.com/subjects/mammals/Placental.shtml

2. Wikipedia contributors. Marsupial [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 19, 22:51 UTC [cited 2006 May 24]. Available from:

3. Opossum society of the United States, Opossum reproduction and life cycle, 2003 [Internet] [cited 2006 may 24] Available from:
http://www.opossumsocietyus.org/opossum_reproduction_and_life_cycle.htm

4. Matthews B.E and Preston, M.P. The placental or true mammals, Joint museum curators, Edinburgh, 2001 [Internet] [Cited 2006 May 24] Available from: http://www.nhc.ed.ac.uk/index.php?page=24.134.166

5. 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

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
My bloger URL: http://mukwevholufuno.blogspot.com

COMPARISON OF MODE OF REPRODUCTION BETWEEN THE PLACENTAL MAMMALS AND MARSUPIALS

Placental mammals are vertebrate animals that have placenta that join the growing embroy inside the womb of the mother and marsupials are invetebrate mammals. There are differences between "the marsupials and placental mammals during the process of gastation" (2,3) in which the babies grow inside the body of their mother before they born. This placental give the species away of feed fetus and during this process it will also reach maturity during the birth.


The rate of gestation between marsupial and placental mammals is not the same. In marsupials, their reproduction is more difficult compared to the placental mammals. "Embryo becomes a new organism during the process of the fertilization and auto immune system from their mother will assault it. The amniotic membrane work together with the mother inorder to protect them not to be assaulted" (2,3).

The marsupial mammals give birth at short period and placental mammals give birth at long period. The short gestation qualified to the development of the yolk type reproduction. The longer gestation in marsupials qualified to the fully developed off spring. Marsupials and placental mammals also differ during their birth" (1). The birth rate in marsupials occurs at "the early stage and they carries their baby in the puch" (2). It takes a week or a mouth for unborn organism to pouch and attached to a teat depending on that particular species. In placental mammals, the birth rate occurs at late stage and this can cause the process of gestation develop fully during the orocess of off spring.

The other differences between placental and marsupial’s reproduction occurs in the mode reproduction and any pattern. The pregnancy in marsupials do not disturd the development of the oestrus cycle and placental disturb the development of the oestrus cycle" (1,2,3). The reproduction in marsupials it said to be full developed and there is no combination in both right and left of marsupial’s vaginae to from a single body through psyeodoraraginal canal"(3).


In marsupials "the right and left uterus complex compared to in placental" (2,3) . During the embryo in marsupials mammals the process of development female reproductive tract is different compared to the one which is found in the placental mammals. In marsupial, the marsupiums develop in females in order to look after the babies and they also have two reproductive. The male marsupials have "two penis and their scrotum is found in the front part of the penis" (3). In placental mammals "the scrotum is found at the end of the penis" (3).


The placental mammals have long period of gestation and this will cause a full development of the off spring. The maturation of placental allows nutrients to move from the mother's system to the embryo and waste to be carried away. The placenta is made by layers which also provide blood to it.

Reference:

1. Roach, J. 2002. Earliest known ancestor of placental mammals discovered. [Online]. Available from: http://news.nationalgeographic.com/news/2002/04/0423_020425_firstmammal.html [24 April 2002, 15:45]

2. Wikipedia contributors. Placental [Internet]. Wikipedia, the free encyclopaedia, 2006 May 07, 18:21 UTC [Cited 2006 May 12, 10:21]. Available from:
http://en.wikipedia.org/wiki/Placental

3. Wikipedia contributors. Marsupials [Internet]. Wkipedia, the free encyclopaedia, 2006 May 09, 17:16 UTC [Cited 2006 May 12, 11:10]. Available from: http://en.wikipedia.org/wiki/Marsupials

4. Wund, M. and P. Myers. 2006. "Metatheria" (On-line), Animal Diversity Web. Accessed May 24, 2006 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Metatheria.html.


Lizzy Maluleke
CSIR PTA
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Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com/

GENERAL ADAPTATIONS BIRDS HAVE EVOLVED FOR FLIGHT

Birds belongs to a class called aves. They are the only group of animals to posess feathers and they are best known for their ability to fly. These warm blooded vertebrates have feathers covering their skin and their forelimbs. The taxanomic point of view shows that there are about 8.800-10.200 living bird species and their size range from the tiny hummingbirds to the huge ostrich.

Fossilisation shows that dinosaur and reptile are the only great ancestors of the birds. According to the skeletal bones it was found that bone the close ancestor of the birds were arboreal or evolve flight from the trees nor they were physiologically intermediate between typical reptiles and living birds, nor that their feathers evolved for flight. The ancestors of birds were terrestrial,fast growing and active animals.

Feathers are made of a protein called keratin. They are made of thousands of branches called barbs. Feathers grow in specific areas called feather tracks. Between the feathers tracks there are down feathers which are used to keep the body weight. The spine down the middle, called the shaft, is hollow. The vanes are on the two halves of the feather. They are made of thousands of branches called barbs. Because there are many spaces between these barbs, a feather has as much air as matter. They grow from a bump of skin. Growth starts by a tip of a feather. After the bird hatches then the tip separates and looks like fuzz on the baby bird. Pin feathers are rolled inside the sheath. For a bird to survive it depends on the condition of its further. They take a lot of time caring for their feathers and this is called preening. Their feet and beaks are used to arrange and to clean their feathers. They chew each feather from the base to the tip meaning that they bath a lot. Feathers protect the skin of the bird, during winter they can be fluffed up and in summer they can be squeezed down. They also help in making the nest.

Different birds have different types of feathers but all birds have feather on their wings. The wing on a bird serves as the basic structure for flight. The shape of the wing allows the bird to fly. During the flight the tail of the bird also plays an important role, it acts as the rudder balancing and steering the bird. If the tail is turned downward it acts like a brake, helping the bird to stop. Everything about the bird is made perfectly for flying. The entire body inside and outside is designed for flight. Every part must give maximum power with a minimum of weight. The heavier the bird the bigger its wings need to be and the bigger the wings, the more muscles are needed to move them.

The easiest way to fly is to be light. Birds have feathers that are very light in weight. The bones that birds have are made for lightness. Birds have fewer bones than most animals. The bones they have are hard but thin. The biggest bones in flying birds are the breast bone and the shoulder bones. The shape of the wing is called the airfoil. When the wing moves the air goes above and below. The air moving over the upper surface has to be faster than the air on the lower part of the wing. The shape of a wing is called an airfoil. As the airfoil moves through the air, air goes above and below. The air flow over the upper surface has to move farther than the lower part of the wing. In order for the air flows to make it to the edge of the wing at the same time, the top air must go faster

Reference

1. Wikipedia contributors. Animals Wildlife [Internet] Wikipedia the free encyclopedia [Cited 2006 May 12] Available From: http://animals.about.com/z/js/o.htm?k=birds&d=Birds&r=http%3A//animals.about.com/od/birdsastudyguide/a/introtobirds.htm

2. Wikipedia contributors. Birds [Internet] Wikipedia, The free encyclopedia; [Cited 2006 May 12] Available From:
http://animals.about.com/od/birdsastudyguide/a/introtobirds.htm

Dianah Nangammbi
Cilla CSIR
P.O Box 395
Pretoria
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Tel: +27 12 841 2133
Cell: +27 73 121 3589
Email: dnangammbi@csir.co.za
http://wwwdianah.blogspot.com/

EVIDENCE WHICH SHOW THAT DINOSAURS WERE WARM-BLOODED ANIMALS.

Dinosaurs fossils were found about 230 million years ago. It was suggested that they were vertebrate animals. They dominate the terrestrial environment for 160 years before extinction. This left many Paleothropologist with suggestion that relate modern bird to be the direct descendent of Dinosaurs. (2)


Most of the species found on land was suggested to be warm-blooded this include birds and mammals.paleothropologist also suggest that because of the body and characteristics that the dinosaurs have, can regarded it as warm-blooded animals. This because most mammal or birds with large body, they have high metabolic rate that can regulate their body temperature.


In warm-blooded animal it was suggested that their body can retain heat for long period and also the chest cavity can hold huge hearts that increase metabolism. The bone structure that the dinosaurs have also suggested that it play a part on heat retation, the parallel rows of plates on dinosaurs has been interpreted as additional temperature –control mechanism. This plate is made of bone-like sponge consists of many blood vessels that can absorb heat from the environment or disperse excess heat. (1)


The characteristics that dinosaurs have for living also indicate warm blooded animal, its character of migrating, instead of hibernation during cold periods shows that they can adapt any environmental change they encounter. Which is impossible for cold blooded animals? (2)


The anatomical analyses of dinosaurs suggest that they were active animal, moving fast which increase endothermic metabolism rate. Also the diet they have also increase the metabolic rate, this because the herbivorous dinosaurs require hundreds kilos of vegetation a day to sustain their enormous bulk and that they had a unique endothermic metabolism fuelled by the heat given off by non-stop digestion. The metabolism rate was the insulator of heat in dinosaurs because they do not have feathers and hairy skin; its skin is consisting of hides with scaly and bony bumps that do not insulate. (3)


Some paleothropologist suggest that dinosaurs maybe in between the warm blooded or cold blooded animal. But with the DNA test of the bones it shows that dinosaurs are warm blooded. “This because warm blooded animal grow fast than cold blooded ,this was proven by scientist Jack Horner through the bones of a tiny baby dinosaurs found in hadrosaur nests. But as scientist has conflicts other suggest that the heart of herbivores dinosaurs consist of four chambers instead of three which is common to warm blooded animal.”(2)

Evidence studied can reveal that dinosaurs were warm blooded animal, this because they can maintain their body temperature by increasing the metabolic process through eating lots of vegetation that will need non stop digestion. And also by moving fast which increase the endothermic metabolism. It was suggested that dinosaurs have large body that can regulate temperature, because they have high metabolic rate.


In general warm blooded animal maintain their body temperature at their constant level, this regulation of metabolic rate helps them to adapt any environment as they can increase or reduce their depending the surrounding environment.

Reference:


1. Were Dinosaurs Warm-Blooded .1999. [Internet] [Cited 2006-May-09] Available from: http://www.dinoruss.com/de_4/5c51d90.htm


2. Wikipedia contributors. Dinosaurs [internet] Wikipedia, The Free Encyclopedia [cited 2006-May-09] Available from: http://en.wikipedia.org/wiki/Dinosaurs


3. Dinosaurs [internet] [cited 2006-May-09] Available from: http://teacher.scholastic.com/researchtools/articlearchives/dinos/evolut.htm,


Mr Elelwani Muanalo
NISL- Ecological Informatics Student
CSIR Pretoria
Tel: +27 12 841 2133
Fax: +27 12 842 7024.
Email: emuanalo@csir.co.za
My bloger URL: http://www.emuanalo.blogspot.com

THE DINOSAURS WERE WARM - BLOODED ANIMALS

The dinosaurs were the subphylum of chordates, specifically, "those with backbones or spinal columns that conquered the terrestrial ecosystem for over 160 million years” (5). They are a group of diapsids reptiles. They evolved “from archosauriform ancestor during the olenekian, like modern crocodilians” (5). They were seen 230 million years ago, and disappeared 65 million years back. The clade maniraptoran is the “group of the theropod dinosaurs that many paleontogists believe birds were derived from some 150 million years or so ago in Jurassic period on the other side the phylogenetic taxonomy birds are by definition maniraptoran and other maniraptoran are their closest relatives” (5).


There was an argument among the scientists about the dinosaurs being warm blooded animals. Some of the palaeontologists believed that they were the warm – blooded animals just “like the modern birds and mammals are” (4). Other scientists believed that they were cold – blooded. They just imagined other cold blooded animals related to the dinosaurs and they concluded that they were also cold blooded animals, example of cold blooded animals closely related to them are the reptiles. And other scientist were neutral (4).


By saying that the dinosaurs were warm blooded animals, they meant that they were able to “adjust their body temperature internally instead of relying on their environment” (3). As far as (fact monster, 2005) is concern, the cold blooded animals depend on the temperature from the environment. They need the environment to regulate their temperature so that they can become warm (3). It seems as if there is only one way that the cold blooded animals can become warm, “basking at the sun” (3). I believe these types of animal hate winter at all, because during winter it is very cold. However the sun is available it is still cold and the day is very short while the night is long. In most cases it is cold at night.


The dinosaurs seem to be different from other group of reptiles, they had unique metabolism. The heart of the dinosaurs was found with about four “chambers which is more than other warm blooded mammals. Most of the reptiles were found with three chambers in their hearts. The cold – blood animals are having three chambers in their heart” (2). The are differences between the cold and warm blooded animals. The cold – blooded animal seems not to be growing quickly as compared to the warm – blooded animals. “More evidence was found from the dinosaur’s bones, the bones are found to be rich in the passage ways called Halversian canals which acts as transportation for nutrient – laden blood to the cells that lay down new bone” (5). This evidence was confirmed from the fast – growing bones of warm blooded mammals. “The results were the same; the warm blooded mammals had the same high density of Halversian canals” (5).


The dinosaurs became so “plentiful and abundant for a long time because they were warm – blooded animals. All the large predators available on earth today are warm blooded, except for crocodiles that occupy only one very specific area, which is water” (5).


In conclusion, the dinosaurs were the warm – blooded animals, they were very active, moving at very high speeds and they were able to hunt at any time of the day and in any season unlike the cold – blooded animals which were unable to survive the cold conditions (5).


References:


1. [http://www.priweb.org/ed/ICTHO4papers/13.htm, accessed on 11/05/2006, 13:00].

2. Science news, (2000) Telltale Dino Heart Hints at Warm Blood, [http://www.sciencenews.org/articles/20000422/fob1.asp, accessed on 11/05/2006, 13:11].

3. Fact monster (2000).Were dinosaurs warm-blooded? [http://www.factmonster.com/ipka/A0862622.html, accessed on 10/05/2006, 10:00].

4. [http://pubs.usgs.gov/gip/dinosaurs/warmblood.html, accessed on 10/05/2006, 11:00].

5. Wikipedia contributors. Dinosaurs. [Internet]. Wikipedia. The Free Encyclopedia; 2006 May 10, 11:16. UTC [cited 2006 May 3]. Available from: http://en.wikipedia.org/wiki/Dinosaurs.


Ms Evelyn Maleka
CILLA CSIR
P.O. Box 395
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Fax: 012 842 7024.
Email:emaleka@csir.co.za
http://malekaevelyn.blogspot.com/

THE DIFFERENCES BETWEEN NEW WORLD MONKEYS AND OLD WORLD MONKEYS

“A monkey is any member of two of the three groupings of simian primates. These two groupings are the New World and Old World monkeys of which together there are 264 known extant species” (1). They range in size and weight, some live in trees and others in savanna. Their “diets differs amoung the various species but may contain any of the following: fruit, leaves, seeds, nuts, flowers, insects, spiders, eggs and small animals”. (1)

“Although monkeys everywhere have similar external appearances, a closer look reveals unique and distinctive differences between the American and Old world monkeys” (1). Both the old world and the new world monkeys share some of the characteristics. They both share the same type of teeth which are much specialised. These specialised mammalian teeth are used for eating different of different foods. “Some characteristics are shared among the groups; most New World monkeys have prehensile tails while Old World monkeys do not; some have trichromatic colour vision like that of humans, others are dichromats or monochromats. Although both the New and Old World monkeys, like the apes, have forward facing eyes, the faces of Old World and New World monkeys look very different though again, each group shares some features such as the types of noses, cheeks and rumps” (1).

The hairless callous pads are present on the old world monkeys and this may be adaptations for long periods of sleeping and sitting on rocks and branches which are rough but the new world monkeys do not have this characteristic. “All New World monkeys differ slightly from Old World monkeys in many aspects, but the most prominent of which is the nose. This is the feature used most commonly to distinguish between the two groups” (2 ). The “old world monkeys have the down facing nose; nostrils are closer together and open down ward” (3).The molars of the new world monkeys are large and have three pre-molars. In contrast the old world monkeys have two premolars and “the molars have sharply connected cusps” (3). 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” (3).

The old world monkeys “have tails but lack prehensibility feature” (3). 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 prehensile tails” (1, 4). Prehensile tail refers to “the tail of an animal that has been adapted for use as a fifth hand” (4). These are mostly used to hold while eating foods and during manupulation of objects. The old world monkeys have “thumbs that are rotated and more opposable which look like of humans” (3).

The males of the old world monkeys are less involved in taking care of the young monkeys and interestingly the males of the new world monkeys are more involved in taking care of the infants ( meaning that not only females are responsible in making sure that the youngs are nurtured, rather it is also the male responsibilities). 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” (3). Unlike the new world monkeys prefer specific areas.

Monkeys are intelligent and they sometimes behave like human.


Reference:

1. Wikipedia contributors. Monkey [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 21, 05:33 UTC [cited 2006 May 25]. Available from:
http://en.wikipedia.org/w/index.php?title=Monkey&oldid=54309251.

2. Wikipedia contributors. New World monkey [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 21, 15:12 UTC [cited 2006 May 25]. Available from: http://en.wikipedia.org/w/index.php?title=New_World_monkey&oldid=54360388.

3. Anthropology 1, New world (America) and Old world (Africa and Asia) monkey: A comparison, [Internet] [Cited 2006 May 25] Available form:
http://www.cabrillo.edu/~crsmith/monkeycomparisons.html

4. Wikipedia contributors. Prehensile tail [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 8, 10:38 UTC [cited 2006 May 25]. Available from:
http://en.wikipedia.org/w/index.php?title=Prehensile_tail&oldid=52121683.

Mr Lufuno Mukwevho
CSIR Pretoria
P.O. Box 395
Pretoria
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Tel: (012) 841 2133
Fax: 012 842 7024
Cell: 072 317 5626
E-mail: lmukwevho@csir.co.za
My blog URL: http://mukwevholufuno.blogspot.com

COMPARISON OF THE MODE OF REPRODUCTION BETWEEN PLACENTAL MAMMALS AND MARSUPIALS

Marsupial and placental mammals have the main difference between them which is their ''rate of gestation'' (Wikipedia contributors, 2006). Both the marsupials and the placental mammals are also different when coming to the pattern and the reproductive anatomy. The mode of reproduction is also said to be more complex in marsupials as compared with the mode of reproduction in the placental mammals which is not complex. Placental mammals are vertebrates while on the other side placental mammals are invertebrates.

It is also said in the introductory paragraph that the mode of reproduction in both the marsupials and the placental mammals is totally different. In marsupials, it is said that the reproductive tracts are fully doubled. There is no fusion in both the left and the right varginae of the marsupials in order to form the single body as they occur in all placental mammals. Marsupials also give birth through a ''new median canal which is known as the pseudovaginal canal'' (Wund and Myers, 2006). Both the right uterus and the left uterus are not fused in marsupials as opposed to the placental mammals; where fusion of both the right and the left uteri do occur differently.

In the embryo of the marsupials which is still in the process of the development, ''female reproductive tract which is formed as the result of the arrangement of ducts is also totally different with the one which is found in the placental mammals'' (Wund and Myers, 2006: 1). Still in marsupials, marsupium or pouch develops in the females in order to nurse the young once. The penis in the male marsupials is doubled like in the female marsupials. In placental mammals, the scrotum is found in the posterior end of the penis, unlike in the marsupials where the scrotium is found in the anterior part of the penis.

It is also said that gestation also differs between the two species, marsupials and the placental mammals. In marsupials both short and long gestation does occur as opposed to the placental mammals. The occurrence of the short gestation is attributed to the development of the york in the type of reproduction. While on the other side the longer gestation in marsupials is attributed to the offspring which are born well fully developed. The rate of birth between marsupials and the placental mammals also takes place differently. In marsupials, birth takes place early as compared with the placental mammals where birth takes place late. Furthermore, an important difference also do occur between the two species, marsupials and the placental mammals in their mode of reproduction. Wund and Myers (2006: 2) further say that pregnancy in placental mammals interrupts the development of the oestrus cycle as opposed to pregnancy which does not interrupt the development of the oestrus cycle.

In conclusion, one can say that there is a huge different between the marsupials and placental mammals, when coming to the comparison of their mode of reproduction. The huge difference can also attribute to the fact that the two species are totally different. Marsupials are not vertebrates while placental mammals are thought to be invertebrates. Gestation period in both species is also different. Marsupials have both short and long period when coming to gestation as opposed to the placental mammals.

References:

Wikipedia contributors. Placenta [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 07, 18:21 UTC [cited 2006 May 11, 15:31]. Available from: http://en.wikipedia.org/wiki/Placenta

Wikipedia contributors. Marsupials [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 09, 17:16 UTC [cited 2006 May 11, 15:12]. Available from: http://en.wikipedia.org/wiki/Placenta

Wund, M. and Myers, P. 2006. Animal Diversity Web. [Onlike]. Available from: http://animaldiversity.ummz.umich.edu/site/accounts/information/Metatheria.html


Peter Muvhali
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COMPARISON BETWEEN THE PLACENTAL AND MARSUPIALS MODES OF REPRODUCTION

There are huge differences between the marsupials and placental mammals. The different between marsupials and placental mammals is the mode of reproduction and gestation period. They are also differs in gestation period. Marsupials have very short gestation whereas the placental have usually longer gestation. "The neonate are incompletely developed in marsupials where as neonate are anatomically complete in the placental. In addition, the reproductive tracts of marsupials in the females are fully doubled. Nevertheless, the right and left vagina do not combine to form a single body as they do in placental mammals"(2)Thus, in the marsupial’s mammals, birth takes place through new canal, that is pseudovaginal canal. http://www.nwcreation.net/marsupials.html

"The longer gestation period that in the placental mammals are occurs in the offspring that are born, and fully developed. One can say that, the mature time in placenta compared to other vertebrates it depends on placenta, which allows nutrients to move from mother system to embryo"http://www.nwcreation.net/wiki/index.php?title=Main_Page. "The mother and embryo do not share the same blood supply, but the placenta is richly supplied with blood vessels, nutrients metabolites pass through and prevent the transfer of immunity system"(3). In Marsupials pregnacy does not break the continuance of the next oestrus cycle, because it is not in the placenta.

However birth in marsupials occurs much earlier as opposed to the placenta mammals. The fetus to the pouch becomes attached to teat just for a weeks or a months. This depends on the type of species, but marsupials spend 12 days in the reproductive tract(1)". http://www.nwcreation.net/wiki/index.php?title=Main_Page

“Marsupials and placental birth may not equal. Gestation length indicates the direct exchange between advantageous for child as is not like to the mothers. Marsupials’ reproduction is more beneficial, by reducing the death especially related to child mother union. The length and time of marsupials’ gestation are important through the evolutionary genetic recombination. The young placenta mammals spend long time to develop inside the mother body before birth.”(2)


The development of marsupial embryo, the arrangement of ducts that become the female reproductive tract differs from the placental. The placental mammals have penis, which look like the female vagina, whereas the marsupial’s males have a forked, and scrotum penis in the front. As for instance, wolf animals have many marsupials that are essentially identicall to the placental mammals. “Marsupial and placental mammals have evolved coincidently as a results of common environmental exposures”(2). The hands indicates that, each marsupial is unique kind from their placental twin. http://www.pbs.org/wgbh/evolution/library/01/4/pdf/l_014_02.pdf

Just to conclude, marsupials birth takes place through a median canal. Its marsupium is used for nursing young, but this, does not happen in all the marsupials species. On the other hand, the placental species has no marsupium. Some marsupials have chorioallantoic placenta, with no villi, while in the placenta have extensitve villi. Left and right vaginae and uteri of marsupials do not fused to form a single body, where as left and right vaginae of placental is fused. Penis in placenta is not forked, scrotum lies in the posterior of the penis. According to the degree and development of young in placental, gestation period is long and the young are born with functional organs and have short lactation period where as in the placental mammals lactation period is prolonged . In marsupials degree of development the young have short gestation, which can takes 8 to 43 days depending on species. Development takes place in pouch(1).

References

1. Wikipedia Contributors. Coordinated universal time. Marsupials evolution[Internet]. Wikipidia, The free encyclopedia; 2006 May, 10, 04:55 UTC [cited-2006 May, 12]. Availabe from:
http://www.nwcreation.net/wiki/index.php?title=Main_Page

2. Andriene, L. 2001. The Human Evolution Coloring Book [Internet] [Cited 2006 May, 12]. Available from:
http://www.pbs.org/wgbh/evolution/library/01/4/pdf/l_014_02.pdf

3. Northwest creation Network, Marsupials Evolution and post flood migration [Internet] [Cited 2006 May, 12] Avalable from:
http://www.nwcreation.net/marsupials.html

Linette Netshiheni
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