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
0001
Cell: 0820446442
Tell: 012 841 2133
Fax: 012 842 3676

DINOSAURS WERE WARM BLOODED ANIMALS

Many years ago, “different scientists started to search for evidence showing that dinosaurs were warm blooded. The evidence used included the way dinosaurs stood straight-legged like mammals, the big rib cages that could have held mammal-like hearts and lungs, and bones that had channels for quick blood circulation as found in the bones of the warm-blooded animals” (Payne 1999). Dinosaurs were very unique creature.

Scientists have determined the “extremities of temperature using bone isotopes. The results from the well preserved Tyrannosaurus bones suggested that its body was maintained within four degree Celsius. The temperatures uniformity with relatively high metabolism rate similar to known warm blooded animals" (Barrick and Showers 1994). “The studies of tiny dinosaur baby bones in hadrosaur were conducted by Jack. Results showed that Dinosaurs grow very fast. Horner showed that it reaches substantial size while still in the nest” (Morell 1987).

"Horner teamed up with Armand de Ricqles in an effort to investigate bone structure as a means to differentiate between endotherms and ectotherms. The two scientists did studies that analyzed the differences in bone structure during the growth series of a dinosaur, from embryo to adult. Through comparative anatomical studies of micro-thin sections of bone from dinosaurs, modern birds, and reptiles, the scientists found that both the dinosaur bones and the modern bird bones contained vascular canals within the bone, for blood vessels. This evidence suggested that there is a very significant similarity among bird and dinosaur bone, which indicated that the dinosaurs were warm blooded” (Morell 1987).

“Ruben also gave the evidence that dinosaurs were warm blooded animal. Ruben used seventy watt ultra lamp to study the fossil Scipionyx samniticus The fossil showed that the baby dinosaurs had a large intestine, liver, windpipe and muscles. The Ultraviolet (UV) light allowed Ruben and his team to see that the liver and guts of the Scipionyx were separated from the lungs and heart, which indicated the presence of a diaphragm, a layer of tissue found in mammals and modern crocodiles. "A diaphragm also allows for high levels of oxygen exchange" (Chang 1999).

“Examination of dinosaur fossils seemed to suggest they were indeed warm blooded. The remains of microscopic holes in the bone seemed to indicate tiny blood vessels had been trapped by the rapid growing bone tissue. The animal that grows fast is warm blooded” (Krystek 1996).

Furthermore, “evidence for rapid dinosaur growth was also being found in the microscopic structure of the bones. The bones of the dinosaurs were reached in the passage ways known as Halverson canals that transport nutrient laden blood to the cells that lay new bone. The fast growing bones of warm blooded mammals have the same high density of Halverson canals, whereas the slow-growing bones of cold blooded reptiles have far fewer” (Morell 1987).

“Beverly Eschberge believed that dinosaur have been only the warm blooded animals due to the structure of the bone and histology, growth rates, predator to prey ratios speed and agility, rate of evolution, similarities with birds as well as insulation .Most of the dinosaur bones which have been studied appear like the bones of modern ectodermic” (Eschberge 2001).

“Dr Russell, a paleontologist of North Carolina State University has indicated that the images of its chest which has enhanced suggested that it was a four chambered double pump heart with a single systemic aorta. The heart was more similar to of birds or mammals than reptile. ‘Willo’ fossilized heart suggested that the circulatory system was more advanced than that of the heart of reptiles. Longer periods of high activity were one of the vital aspects of warm blooded” (Eschberge 2001).

Evidence indicated that “dinosaurs were very active and they were able to move in high speed” (Eschberge 2001). The findings by “Reuben indicated the presence of a diaphragm, a layer of tissue found in mammals” (Chang 1999). “The way dinosaurs stood straight-legged live mammals. The bones that contained channels for quick blood circulation as found in warm blooded animals” (Eschberge 2001). The evidence which have been provided by scientists clearly indicates that the dinosaurs were warm blooded animals.

References:

1. Barrick R and Shower W.1994. Bones isotopes [Internet] Science; 2006 May 17, 15:04 UTC [cited 2006, May 16] Available from: http://www.dinoruss.org/de_4/5c52015.htm

2. Chang G. 1999. Dinosaurs were hybrid of cold-blooded, warm-blooded animals [Internet] Bell Globe media; 2006 May 09, 11:30 UTC [cited 2006, May 10] Available from: http://www.exn.ca/Html/Templates/topicpage.cfm?ID=19990122-51&Topic=Dinosaur

3. Payne J. 19Were dinosaurs warm-blooded or cold- blooded?[Internet] Kinetosaurs; 2006 May 09, 11:20 UTC [cited 2006, May 10] http://www.childrensmuseum.org/special_exhibits/kinetosaur/e2.html#q2

4. Eschberge B. 2001. Dinosaurs: warm or cold-blooded [Internet] 2006 May 09, 11:30 UTC [cited 2006, May 10] Available from:
http://www.priweb.org/ed/ICTHOL/ICTHOL04papers/13.htm

5. George J.1997. The isotopes in their bones suggest that dinosaurs were warm blooded [Internet] Onscience; 2006 May 09, 14:30 UTC [cited 2006, May 10] Available from: http://www.txtwriter.com/onscience/Articles/dinoblood.html

6. Discovery Channel (1997) Bird-like dinosaur found in Argentina [Internet] Onscience; 2006 May 09, 15:03 UTC [Cited 2006, May 10] Available from: http://www.exn.ca/Html/Templates/topicpage.cfm?ID=19970521-02&Topic=Dinosaur

7. Krystek L. 1996. An ultra attack: Did it kill in cold blood [Internet] Hot and cold running dinosaurs; 2006 May 17, 15:04 UTC [cited 2006, May 17] Available from:http://unmuseum.mus.pa.us/colddino.htm

8. Morell V.1987. Were Dinosaurs warm-blooded? Evidence supporting the claim that dinosaurs were warm blooded from strongest to weakest [internet] Essay and papers for students; 2006 May 07, 11:30 UTC [cited 2006, May 10] Available from: http://www.cheathouse.com/essay/essay_view.php?p_essay_id=12829

9. Wikipedia Contributors.2006. Dinosaurs. The free Encyclopedia [Internet] 2006 May 06, 08:30 UT C [cited 2006, May 08] Available: http://en.wikipedia.org/wiki/dinasaurs

Masiya Kedibone
CSIR PTA
0001
Cell No: 0732519071
Tel No: 0128412123
Fax: 0128423676
E-mail: kmasiya@csir.co.za
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DESCRIBE THE MORPHOLOGICAL DIFFERENCES THAT EXIST BETWEEN CARTTILAGENOUS AND BONY FISH.

Bony and cartilaginous fishes are marine vertebrates. Cartilaginous fishes live in only salt waters whereas bony fish live in all type of waters. Bony fish belong to class Osteichthyes. Cartilaginous belong to class Chondricythyes. Bony and cartilaginous fishes usually differ in structures.

Bony fishes include snapper, groper and gurnard. They have bony skeleton and scales. Their scales are found all over the body surface and they are slippery. The scales cease to grow when they are completely developed however they are replaced by new scales when they wear. The pelvic girdle consists of a single bone on each side of the body that is freely joined ventrally. "The girdles are embedded in muscle. In bony fish the basal have been lost entirely and ossified radials are reduced to a few short bones nearly hidden under the fish rays"(2).

Furthermore, bony fishes have one pair of gill opening, pair of nostrils as well as pair of fins. Gaseous exchange in bony fish occurs across the gills. They have gills that are covered by operculum (cap), they remain still and respire. They do not have to physically move to ventilate. Gills do not open separately. ''The bony fish have organs known as swim bladder, which gives the animals buoyancy, the ability to float"(2). The mouth is generally at front of the body whereas the tail fin is found on top and bottom and is nearly the same in size (2).

Cartilaginous fish comprises of chimaeras, sharks, skate, ratfish and rays. The skins are leathery, body covered by epidermal placoid scales (a bone-like tissue is present at base of placoid scales). Sharks as the example of cartilaginous have rough, sandpaper-like placoid scales. Sharks do not have a good insight because they cannot see things closer to them. Sharks have small eyes which are at the top of the head. They are able to see at a distance. They are made up of cartilage not bones. Cartilaginous fish have five to seven uncovered gills. “They have gill silt on both of the pharynx and they separate external opening and a heterocercal tail (may or not provide lift)”. Cartilaginous have large basal cartilages that are supported by fins. (1).

The pelvic girdle is not joined in the spine. They have a row of radial cartilages and many are thin, horny, unbranched, unsegmented fin rays called ceratotrich. Both upper and lower jaws are made up of cartilages. The jaws are short and mouth is protrusible. Teeth are usually hard and they are covered with denticles. The majority of Cartilaginous fish have rows of teeth in their mouths, so that when a tooth is lost another is already in place to roll up and forward and thereby replace the lost tooth. Mouth of cartilaginous is found under the head. The male fish have claspers arch (hyoid) which involved in jaw suspension (1).

Cartilaginous are mostly covered with cartilages whereas bony fish have true bones. Although Cartilaginous and bony fishes differ in shape but they have some similarities. They share common habitat. Both have gills and fins.

References

1.Wikipedia contributors.2006. [Online]. Wikipedia, the free encyclopaedia, 2006 May 09, 13:15 UTC. [Cited 2006, May 09]. Available : http://en.wikipedia.org/wiki/Cartilaginous

2.Wikipedia contributors.2006.[Online].Wikipedia, the free encyclopaedia, 2006 May 09, 15:40 UTC. [Cited 2006, May 09]. Available : http://en.wikipedia.org.wiki/Bony

Masiya Kedibone
CSIR PTA
0001
Cell No:0732519071
TelNo:0128412123
Fax:0128423676
E-mail:kmasiya@csir.co.za
Web log: http://kedibone-kedimasiya.blogspot.com/

COMPARISON BETWEEN THE PLACENTAL AND MARSUPIAL MODE OF REPRODUCTION

"The great difference between Marsupial mammals and placental mammals is the rate of gestation period or time taken by offspring in the uterus. Marsupials and placental mammals are also differing in their reproductive anatomy and pattern" (6).


In “Marsupials the developing embryo is separated from the body of its mother by amniotic membrane. Subsequent fertilization the embryo develops into a new organism. The immune system of the mother will attack it. The amniotic membrane of the mother separates the embryo from biological interaction with the parent. As there will be the boundary the nutrients will not cross from the mother to the embryo. In marsupial the birth occur earlier than in placental mammals and almost helpless fetus journeys to the pouch and become teat for a week or months depending on the species. Marsupials may stay approximately twelve days within the reproductive tract” (6)


"In placenta is composed of several layers which are richly supplied with blood vessels. And act as a barrier to allow nutrients to pass through and preventing the transfer of immune system" (6). In "Marsupial pregnancy does not interrupt the progress of the next estrus cycles as it is interrupted in placental"(2). However ovarian inhibition is mediated by lactation. The regulatory alteration is necessary as the baby is no longer carried internally; therefore negative feedback stimulus from the presence of the babies must come nursing from activity instead (2).


"Marsupial and placental mammals differ strongly in their reproductive anatomy and patterns. The reproductive tracts of marsupials are fully doubled"(6). "The right and left vaginae do not fuse to form a single body and birth take place through a new median canal called pseudovaginal canal. Right and left uteri are also unfused. Placental mammals do fuse. The right and left uterus do not fuse” (4). “In some but not all marsupial, the mother develops pouch on her in which to nurse young”(2). “The arrangements of ducts that become female reproductive tract of marsupial do differ with that of placental mammals. In some marsupials female develop a pouch and it used as a place to care. In males of marsupials penis is double. The scrotum lies in front of the penis in Marsupial and in the placental scrotum are on the posterior of the penis” (6).


The majority of marsupial gestation period is short “8-43 days depending on a species. It does not make much contribution to the child. Placental mammals have long gestation period. Placental mammals nourished the developing embryos using the mother blood supply"(3). “Marsupial has remarkable natural variation that is found among the gestation rates. The wide succession that occurs in the ovary and the genital tract of marsupial are the same but the general timing of events in the reproductive cycles is different from marsupial. And even between species and subspecies for instance kangaroo differ from basic marsupial pattern in that gestation and is extended from half to occupy almost all of the estrus cycle and the difference also exists between red and grey kangaroo" (6).


"The mode of reproduction is very difficult in marsupial than in placental mammals. The period of gestation said to be short comparing to the gestation period of placental. In marsupials reproductive tracts of marsupials are fully doubled and the embryo is separated from the mother. The embryo of placental mammals is attached to the mother"(6).


References:


1. Do- Whale J.Stone age mutant mammals [Online].Turtles; 2006 May 24. 10:05 [cited 2006 May 24]http://www.scienceagainstevolution.org/v4i12f.htm

2. Rincon P. 2003. [Online]. 2006 May 24. 09:25 [cited 2006 May 24].BBC News; Available from: http://news.bbc.co.uk/1/hi/sci/tech/3311911.stm

3. 2001 Marsupial-Placental dichotomy [Online].Bio 455 Mammalogy; 2006 May 24. 08:15 [cited 2006 May 24] Available from: http://www.usask.ca/biology/455/lecture8.ppt.

4. Wikipedia contributors.2006. Placenta. Wikipedia, The free Encyclopedia [Online]. 2005, May 08. 15:02 UTC [Cited 2006 may 11]. Available from: http://en.wikipedia.org//wiki/Marsupials

5. Wikipedia Contributors. 2006. Marsupials. The free Encyclopedia [internet], 2006 May 08, 15:02 UTC [Cited 2006 may 11] Available from: http://en.wikipedia.org//wiki/placenta

6. Wund M and Myers P. 2006.Infraclass Metatheria [Online].Animal Diversity; 2006 May 24. 11:25 UTC [cited 2006 May 24]http://animaldiversity.ummz.umich.edu/site/accounts/information/Metatheria.html


Masiya Kedibone
CSIR PTA
0001
Cell No: 0732519071
Tel No: 0128412123
Fax: 0128423676
E-mail: kmasiya@csir.co.za
Web log: http://kedibone-kedimasiya.blogspot.com/

HOW INSECTS FIND THEIR SOUL MATES

There are different mechanisms which insects use in order to attract their mates. Some of the insects use, sounds, display of beautiful colours and pheromones ("a chemical produced by an organism that transmits a message to the other members of the same species") (1).

Insects produce a trail pheromone to mark their path so that the females can find them easily (1). The females follow the smell until they find the males. Insects which use pheromones to locate or find their mating partners have to keep on releasing them because the scent disperses quickly (1). Moths use smell to attract mates (pheromones). Females produce chemical compounds called pheromones which male moths are able to detect with their large, feathery antennae but it had to continue producing the pheromone because it evaporates quickly(8).

Some insects like crickets, grasshoppers and cicadas rub together their body with the hind legs to create a sound (2). That sound attracts their mating partners (1). Similarly, the crickets’ males have ridges in their wings that act like a comb or file instrument to attract females (3). When they chirp they rub their wings or legs against each other, while they are busy rubbing a sound or song comes out (3). The song only attracts females and it is quite loud (3). Male crickets release two types of song depending on the situation that they are in. when the female is near the song produced is very quiet and when the female is far it is very loud so that the females can hear the sound (3).

Grasshoppers produce sounds when attracting their mating partners. They produce sound by strengthening their veins in the wings then they use the edge of their hind limb to rub against the wings (5). Only the males can be able to attract the female since they can sing and the females can not (5).

Cicadas use vibrations to attract their mates. They use their abdomen to make their vibrations which have two chambers. The two chambered abdomen is divided into the inner and the outer (7). The inner wall of the chamber is stiff and the abdomen moves in and out. When the chamber is moved muscles in the abdomen pulls the wall of the abdomen back which release a click sound which causes the abdomen to vibrate (7). When a female cicada hears the vibrations it knows that it is time for mating, then it follows the vibrations until it finds the male. Each species have its own sound which they can recognize and attracts their mates (7).

Moths, butterflies and mayflies display their colourful wings to attract their mating partners. Butterflies spread their multi colored wings to attract their mating partners. The wings have microscopic structures which spilt light rays to display different colours (pigments) (4). When the female sees the different colour it follows the male (4). When male mayflies spread their wings they attract females but of the same species since females are less colourful than males so males are the ones who attract females (6).

The main reason why insects use different signals to find their partners is because they want to reproduce so that they can increase in number. When they have found their soul mates they mate with them to produce eggs.


References:

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

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

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
0001
Cell number 072 351 8488
Tell [012] 841 2133
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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/

DOES HERBIVORES DIET IMPOSE CERTAIN PROBLEMS FOR DIGETION?

Herbivores diet impose problem on them because they only eat plants, but animals have some mechanism to cope with this problem. Herbivores are animals which eat only plants. Different types of plants contain different nutrients and the nutritional content varies from fresh leaves to old leaves. Fresh leaves have high nutritional content and are the favourite for animal consumption, while old or matured leaves are less palatable and contain hard cellulose and have low energy content (1).

Plants that are rich in cellulose pose some problems in the digestive system of certain animals such as elephants. Once high content of cellulose is eaten, animals have to depend on the microorganisms to fully digest that cellulose on their stomach. Other mechanism includes the development of long digestive tract to sort out the digestion problem. Once the food is in the stomach, it undergoes a process called fermentation. This is a process of breaking down the cellulose by bacteria called symbiotic bacteria (6). These bacteria also help in the extraction of energy from the food to be available for absorption by the body of an animal (7).

The physical appearance of herbivores animals is mostly determined by the type of food they eat. Animals such as elephant that feed by browsing branches have large bodies and are heavily built. Branches are hard to digest and have low nutrients (5). Elephants have to eat slowly so that they can be able to chew their food and as a result they have a slow metabolic rate (“is the rate at which cells of the body use energy” [8]). Because of that elephants deal with digestive problem by developing a long digestive tract. Nevertheless, about a quarter of food in the stomach of elephant is digested and the rest is excreted undigested with dung/waste (4).

Other species such as the Ruminants have a stomach with four chambers “rumen, reticulum, omasum and abomasums” to facilitate digestion (2). In the first two chambers (rumen and reticulum); food is mixed with saliva and separated into two layers (solids and liquid) of material. Solid material is put together to form a bolus which is then regurgitated. The food is then mixed with the saliva and then broken down into fibres especially cellulose (2). The symbiotic bacteria and protozoa break down this cellulose into glucose (2). After the fibre is broken down; which would be in the form of liquid, it is passed to the next stomach chamber, the omasum where water is removed. After the food is digested it is then moved to the last chamber, the abomasums and then to the small intestine where nutrients are absorbed (2).

Herbivores are the healthiest animals on earth because they eat raw plants which contain a lot of enzymes and nutrients (7). Herbivores have different digestion mechanisms to digest their food. Herbivores have slow metabolic rate because of it they start to have large stomachs in order to accommodate the food that is in the stomach (1).



Reference:

1. Wikipedia contributors. Herbivores [Internet]. Wikipedia, The Free Encyclopaedia; 2006 Apr 30, 00:26 UTC [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Herbivorous
2. Wikipedia contributors. Ruminants [Internet]. Wikipedia, The Free Encyclopaedia; 2006 Apr 22, 23:58 UTC [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Ruminants
3. Wikipedia contributors. Bovid [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 2, 05:19 UTC [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Bovid
4. Wikipedia contributors. Elephant [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 11, 23:26 UTC [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Elephant
5. Lindroth, L.R. Food conversion efficiencies of insect herbivores [Internet] Updated 1993 Mar, Cited 2006 May 25. Available from: www.hollowtop.com/finl_html/conversion.htm
6. Olsen, L. Digestion and anatomy of the canine. [Internet] Updated 2005 Sept, Cited 2006 May 25. Available from: http://b-naturals.com/Sep2005.php
7. Muiioz, V. Natural diet versus Traditional diet [Internet] Updated 2000 Aug 23, Cited 2006 May 25. Available from: http://www.blogger.com/www.artisticliving.com/LivingfoodsvsSADdiets.htm
8. Google Web definitions: for metabolic rate. [Internet] updated anon, Cited 2006 May 25. Available from: www.kentuckyawake.org/templates/glossary/

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

THE DIFFERENCES BETWEEN NEW AND OLD WORLD MONKEY

The scientific name for the New World monkey is Platyrrhini (2) and The Old World monkeys are Catarrhini. Old World monkeys are found mostly in Africa and Asia but some are also found in Europe (1). New World monkeys are only found in South America (5).New monkeys differ slightly from the Old World monkeys in many aspects e.g. their physical features, the way they live and the way they take care of their infants.

The nose is the feature that is used mostly to differentiate the New monkey from the Old monkeys (2).The New World monkeys has a flat nose, with side facing nostrils which are far apart and Old World monkeys have New World monkeys have down facing noses with nostrils which are close to each other (6). New World monkeys have three premolars, large molars and their last molars are small or absent while the Old World monkeys have two premolars and their molars have sharp cusps. Old World monkeys’ ears have a tympanic membrane connected to their inner ear by a bony tube while New World monkeys’ ears are also have a tympanic membrane connected to the inner ear but by the bony ring (6).

New World monkeys have a long prehensile tail and they use their tail as their fifth hand (2) while the Old World monkeys have tails but they are not prehensile (1). Old World monkeys have rotated thumbs which are more opposable and they have finger nails even on the toes and the New World monkeys have thumbs whose orientation lies on a line with other digits and they finger nails on their big toes (6).

New World monkeys spend most of their time in trees and they live in arboreal habitat “small” and they prefers living in groups of about 18 individuals (2) while the Old World monkeys spends most of their time on the ground; they climb trees occasionally especially when they are going to sleep (1) and they live in wide range areas (6). Old World monkeys such as Mandrills are omnivores and they get their food by foraging plants, insects and smaller animals while the New World monkeys like to eat nuts, berries and insects (3).

Many New World monkeys prefers having one partner for sexual reproduction and the males helps with the raising of the young (2) while in the Old World monkeys there is no paternal care the offspring are looked after by their mother until they are adults (1). New World monkeys (Howler monkeys) range from 56 to 92 cm in size and have a life span of 15 to 20 years (4). The Old World monkeys weighs up to 30 kg and they can grow 1 m long. Old World monkeys can survive up to 25 years (3).

Old World monkeys have more colourful faces than the New World monkeys and they are more dominant than the New World monkeys.

Reference:

1. Wikipedia contributors. Old World monkeys [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 11, 18:58 UTC [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Old_World_monkey
2. Wikipedia contributors. New World monkeys [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 7, 15:12 UTC [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/New_World_monkey
3. Wikipedia contributors. Mandrill [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 8, 01:47 PTA [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Mandrill
4. Wikipedia contributors. Howler monkeys [internet]. Wikipedia, The Free Encyclopaedia; 2006 May 9, 00:44 UTC [cited 2006 May 12]. Available from: http://en.wikipedia.org/wiki/Howler_monkey
5. Anon. The New World monkeys [Internet]. Updated Anon, [cited 2006 May 25]. Available from: http://www-personal.umich.edu/~phyl/anthro/platy.html
6. Anon. New World-Old World Monkey Comparisons [internet]. Updated Anon, [Cited 2006 May 25]. Available from: http://www.cabrillo.edu/~crsmith/monkeycomparisons.html

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

HOW CELLS HAVE BECOME SPECIALIZED TO PERFORM DIFFERENT FUNCTIONS IN A MULTICELLULAR ORGANISMS

Multicellular organisms are made up of more than one cell. The examples of multicellular organisms are all plants and animal. Multicellular organisms have cells which are different. Example the cells that build skin of human are different from those that build the inner organs. The cells of almost every multicellular organism are generated by repeated division from a single original cell; they form a clone. Normal human development and volvox were used as examples of multicellular organisms.

All different kinds of cells were derived from the fertilized egg cell through the process of differentiation. The process of differentiation allows the unspecialized cells to become specialized into one of the many cells that make up the body such as heart, liver or muscle cell. During the process of differentiation, there are certain cells which become inactivated while other genes are activated. Consequently, the cell which was differentiated expand with a specific structure that is shape and size to perform a specialize function. The process is complex to regulate.

The mammalian body is made up of three fundamental cells, these include germ line, somatic and stem cells. Germ line cells produce gamete (egg and sperm) and proceeds through the generation. Stem cells have ability to divide for imprecise period and produce specialized cells. When a sperm fertilizes an egg, the single cell is created which has ability to form the entire organism. The cell split into identical cells. The cells split at the earliest hours after fertilization. In humans, just about four days after fertilization and after several cycles of cell division. Consequently, the identical cells start to specialize by creating a hollow sphere of the cell.

Furthermore, humans have a cell mass and cells which are found in the inner cell mass create all tissues in the body. Even if cells in the cell mass can virtually every type of cell found in human, they cannot form organism. These cells are called pluripotent. Pluripotent stem cells go through cell specialization into a stem cell. This process produce cell that have special function. Examples include blood cell produce red blood cells, white blood and platelets and skin stem cell produce various kinds of skin cells.

Moreover, there are specialized part within the cells that are responsible for transportation of material, energy capture and release, protein building, excretion, passing information and also movement. A group of specialized tissue work together to form tissue, for instance muscle. Different tissues are in turn cooperating to make larger functions that serve the entire organism.

Volvox which some of whose species have as many as 50,000 or more cells linked together to form a hollow sphere. Volvox is more like a multicellular organism than a simple colony. Its entire flagella beat in synchrony as it spins through the water, and the colony is structurally and functionally polarized and can swim toward a distant source of light. The reproductive cells are usually limited to one end of the colony, where they divide to form new miniature (baby) colonies, which are firstly sheltered inside the parent sphere, its cells become specialized, and they cooperate. By specialization and assistance the cells combine to form a coordinated single organism with more capability than any of its component part.

Cells become specialized to perform different function in multicellular organisms through differentiations. Stem cell which is unspecialized cell is transformed in certain condition to perform specific functions. As a results stem cell become a specialized cell to perform special function.

Reference

Wikipedia Contributor. multicellular organisms, The free Encyclopedia [internet] 2006 May 06, 08:30 UTC [cited 2006 May 08] Available from: http://en.wikipedia.org/wiki/multicellular

Masiya Kedibone
CSIR PTA
0001
Cell No: 073 2519071
Tel No: 012 8412123
Fax: 012 842 3676
E-mail:kmasiya@csir.co.za
Weblog: http://kedibone-kedimasiya.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
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URL: http://www.blogsoccer-peter.blogspot.com/

BIRDS ARE THE LIVING RELATIVES OF DINOSAURS

Birds have some characteristics which are similar to Dinosaurs. A Tyrannosaurus rex dinosaur that died sixty eight million years ago provided some of the strongest evidence that birds are the closest living relatives of dinosaurs. Dinosaurs had bone similar to female birds. Both Dinosaurs and birds shared common ancestors. Embryos of Dinosaurs were found without teeth.

The researchers said that a Tyrannosaurus rex dinosaur had soft thighbone tissues which strongly suggest that it was a female, and ready to lay eggs. The bone tissue was strongly similar to that made inside the bones of female birds (Chang, 1999). Mary Higby Schweitzer of North Carolina State University in Raleigh indicated that no other living type of animal, produces the hard shells of eggs just before they lay them. The emphasis was placed on gender, as it links the reproductive physiology of dinosaurs to birds very closely. It indicates that dinosaurs produced and shelled their eggs much more like modern birds (Discovery channel,1999).

"Mudge said that Dinosaurs were the ancestors of the birds or stock from which the latter have been derived by evolution"(George, 1997). The bones of the hind feet of a few species closely look like those of birds, some of the bones were hollow that indicates that other resemblances will be found and that birds were the outgrowth of reptiles. Dinosaurs had three toes like the birds, some of European and nearly all of the entire American dinosaurs, have a four and five toed structure. When four toes were seen in the dinosaurs, the fourth never rotated backward like that of the birds. Dinosaurs had the tibia and fibula which are separated always whereas the birds have these bones joined. The termination of the caudal vertebrata of the dinosaur was always small and did not tend toward the plowshare structure of birds (Morell, 1987).

Sinosauropteryx was the first non flying dinosaur to have proto feathers and it was the earliest bird-like dinosaur. This clearly indicated that feathers arose before flight. This also indicated the common ancestor of birds and dinosaurs. The fossil had features that the birds have for instance plumage.

Paleontologists have discovered two new bird-like dinosaurs with simple feathers and many other bird-like features. These findings strengthen the theory that birds evolved from dinosaurs. Although these new species had some form of primitive feathers, these feathers were symmetrical in cross-section which made them useless for flight. "The dinosaurs' arm-length was also insufficient for flight. The feathers were most likely used as insulation, keeping in body heat" (Morell, 1987).

These new dinosaurs Protarchaeopteryx robusta, and Caudipteryx zoui, together with the recently found Sinosauropteryx prima, have characteristics common to both theropod (beast-footed) dinosaurs and to birds. All three, plus many specimens of a very primitive bird (Confuciusornis Sanctus) were found in the period from 1996 to 1997 in an ancient lake bed in Liaoning Province, in China (Discovery Channel, 1999).

The carnivore dinosaurs had a complex system of air sacs similar to the setup of birds of nowadays. According to the research led by Patrick O'Connor of Ohio University, the lungs of carnivores that are bipedal with the feet similar to birds most likely pumped air into hollow sacs in their skeleton. "Comparisons between bird and dinosaur skeletons, as well as cladistic analysis, strengthen the case for the link, mostly for a branch of theropods called maniraptors "(Chang, 1999). Skeletal similarities include the neck, pubis, wrists (semi-lunate carpal), arm and pectoral girdle, shoulder blade, clavicle and breast bone.

A dinosaur embryo was found without teeth, which suggests some parental means was used to feed young dinosaurs, possibly the adult dinosaur putting nutrition into the mouth of a young dinosaur. This type of behaviour was seen in many modern bird species. "The skeletal similarities include the neck, pubis, wrists, arm and pectoral girdle, shoulder blade clavicle and breast bone" (Chang, 1999). A number of feathered dinosaurs provided clear evidence of the close relationship between dinosaurs and birds. Fernado Novas said that because birds are dinosaurian descenants, they are dinosaurs...birds are living dinosaurs.

References

1.Chang G. 1999. Dinosaurs were hybrid of cold-blooded, warm-blooded animals [internet] 2006 May 09, 11:30 UTC [cited 2006 May 10] Available from http://www.exn.ca/Html/Templates/topicpage.cfm?ID=19990122-51&Topic=Dinosaur
2.Discovey Channel.1997. Bird-like dinosaur found in Aigentina[internet]2006 May 09,11:45 UTC [cited 2006 May 10]
3. George J. 1997. The isotopes in their bones suggest that dinosaurs were warm blooded [internet] 2006 May 09, 14:30 UTC [cited 2006 May 10] Available from: http://www.txtwriter.com/onscience/Articles/dinoblood.html

4. Morell V. 1987. Were Dinosaurs warm-blooded? Evidence supporting the claim that dinosaurs were warm blooded from strongest to weakest [internet] 2006 May 07, 11:30 UTC [cited 2006 May 10] Available from: http://www.cheathouse.com/essay/essay_view.php?p_essay_id=12829

5. Wikipedia Contributors.2006. Dinosaurs are warm or cold blooded, The free Encyclopaedia [internet] 2006 May 06, 08:30 UT C [cited 2006 May 08] Available from: http://en.wikipedia.org/wiki/dinasaurs

Masiya Kedibone
CSIR PTA
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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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Fax: 012 842 7024
Cell: 0723175626
E-mail: lmukwevho@csir.co.za
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COMPARISON BETWEEN THE PLACENTAL AND MARSUPIAL MODES OF REPRODUCTION

Marsupials are mammals such as Kangaroos. The name marsupial originate from the fact that the female marsupials has a pouch “bag” which is used to carry its young during early childhood (1). Marsupial females have two vaginas and males have two penises for reproduction unlike the placental where the males have one penis and the females have one vagina. The two vaginas of marsupials have only one opening which leads to the outside (1). The two penises are only used to pass sperms unlike in the placental where the penis is used to pass both the sperm and urine (1).

Placental mammals are mammals such as humans. A placenta is an organ which is only present when a female placental is pregnant or during gestation (2). The fetus (baby) inside the placenta is attached to the wall of the uterus. When the fetus is in placenta it receives nutrients and oxygen from the mother. Whatever the mother eats the fetus also eats so if the mother is not eating nutritious food the fetus is also starved of the nutrients (2). The placental membrane or barrier protects the fetus against some harmful substances which can harm the fetus (2). Some substances such as alcohol can penetrate the membrane; harm the baby and the baby could end up suffering from fetal alcohol syndrome (2).

Marsupial females have a yolk sac when they are pregnant. The fetus gets its nutrients from the yolk sac (1). The baby in the placental mammals gets all the nutrients from the mother but through the umbilical cord (3). The marsupials give birth early than the placental mammals. They carry the baby for a month in their stomachs while the placental mammals carry their babies for nine to ten months. Marsupial baby develop fully when they are in their mothers pouch where there are nipples (1). When the baby has developed it can leave its mothers pouch to go play and when they are through the baby return to its mother pouch for warmth (1). Placental mammals’ baby develops in the mothers’ womb until it is fully developed (2).

Placental mammals differ from the marsupial mammals in the way they reproduce. Placental mammals develop a complex placenta to protect the fetus from the mothers’ immune system while the marsupials do not have to develop a complex placenta (1). Marsupials give birth earlier than placental mammals; they do not have to carry a large fetus to full-term. The placental mammals (e.g. humans) carry their babies in the womb for nine months but the marsupial mammals (e.g. Kangaroos) carry their babies in the worm for a month (“thirty-one to thirty six days") (4). If a placental mammal gives birth early before the baby has fully developed (prematurely). Then the placental mother is going to take care of the baby the same way as the marsupials. The mother is going to use a blanket and put the baby inside the blanket on the mothers’ stomach. The blanket act like a pouch in the marsupials and the method that humans use is called the Kangaroo care. Marsupials and mammals take care of their offsprings but in different ways.
Reference:

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

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

BIRDS EVOLVE FROM DINOSAURS

BIRDS EVOLVE FROM DINOSAURS

In general dinosaurs were animals which lived on earth 160 millions back. Dinosaurs went through an extinction, which ended their existence on land. Modern birds are considered as direct descendants of theropod dinosaurs (3). Birds are bipedal (two feet moving) warm-blooded animals which have feathers, forelimbs modified as wings and hollow bones (1).

Most palaeontologists argue about where do birds evolve from some says birds evolve from Cryptovolans and some says from Saurichian dinosaurs. All the palaeontologists agree on one thing that birds evolve from dinosaurs but they do not agree on which type of a dinosaur (1). Some Palaeontologists discovered that modern birds evolve from Cryptovolans than Archaeopteryx. Ornithischian (bird-hipped) dinosaurs have the same hip structure as birds, but some paleontologists believe that birds originate from the saurichian (lizard-hipped) dinosaurs

Some Palaeontologists believe that birds are the descendants of theropod dinosaur (2). Descendants of a single common ancestor are related. Some palaeontologists believe that since modern birds are dinosaurs therefore dinosaurs have not become extinct. Modern birds are classified by most paleontologists as belonging to the subgroup Maniraptora, “which are coelurosaurs, which are theropods, which are saurischians, which are dinosaurs" (3). Paleontologists refer to birds as avian dinosaurs and to all other dinosaurs as non-avian dinosaurs. Dinosaurs are referred "to as a synonym for non-avian dinosaur, and bird as a synonym for avian dinosaur (meaning any animal that evolved from the common ancestor of Archaeopteryx and modern birds)" (3).

Birds are living dinosaurs because birds evolved from theropod dinosaurs which means when the dinosaurs died out birds continued with the legacy. Some of birds resemble dinosaurs like the ostrich; they have feathers but cannot fly the same as some dinosaurs. They are both warm blooded animals and they take care of their offsprings. Some paleontologists believe that birds are dinosaurs so dinosaurs did not die out because birds are carrying the dinosaurs’ legacy. Where do birds really evolve from does anyone know where they do or it is another argument from paleontologists? Are birds rely related to the dinosaurs?

Non-avian (dinosaurs) theropods shows a clear distinction between a bird and non-bird and the non-avian theropods were closely related to birds. In northeast China scientists discovered that the small theropod dinosaurs had feathers just like the modern birds (2). Since modern birds and dinosaurs have common ancestor then dinosaurs did not die out. Palaeontologists agree on one thing that modern birds are dinosaurs but they are not sure about the type of dinosaurs. Most of the dinosaurs could not fly just like some birds such as Ostrich.

Reference:

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

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