CROP CIRCLES


Crop circles are the strange patterns that occur in plants such as wheat, corns, grass, oats and barley. These crop circles are very beautiful. They do not occur every where and at any time, but there are specific countries such as USA, Israel, Russia and UK. Some scientists believe that these circles are man made and while others believe that crops circles do occur naturally. They further say that most of these crop circles occur between 11 pm and 4 am. There are different types of crop circles.


Crop circles are found only in the Northern Hemisphere which is surprising. Some of the countries in which crop circles are found include USA, Israel, Russia and UK. In the Southern Hemisphere we do not hear any reports about the availability of the crop circles. Lack of information about the crop circles in the Southern Hemisphere can be attributed to misunderstanding of what the crop circles are.


Each crop circles have its unique shape. Some are triangle, squares, circles, rings and hexagons etc and it is believed that each circle shape has its meaning. The triangular crop circles are found in USA. The evidence or the samples that are taken inside the circle and outside the circle were not the some. The colours of the crops that are found inside the circles are brown in colour while the crops that are outside the circle are green in colour. The information of the different colours inside and outside of the crop circles has been found by studying the soil samples in the laboratory.


There is still no valid information which confirms how the crop circles are made. Some scientists believe that the energy which is present in the formation of the crop circles is affected by the equipments which are used to take photos and other instruments. On the other side people who do visit the crop circles have also reported a wide range of psychological, physiological and emotional effects. While agriculturalists believe that the pesticides are the once responsible in the negative effects in the crop circles.

From the Video viewed, crops found inside the crop circles were found flattened as opposed to the crops found outside the crop circles which were standing firm. The bending of the crops which were inside the crop circles is attributed to the natural causes. In my opinion crop circles are not hoax but real phenomenon.

In conclusion, there are different types of crop circles which are also found in different parts of the world such as USA, Russia, England and Israel. The crop circles also differ in their shapes such circular, ring, triangular, squares and hexagons. The controversy surrounding whether the crop circles are man made or occur naturally remain sketchy. This is because the disagreement among the scientists is still continuing even today.

References:
1. Anon. Crop Circle Theories [Internet]. Crystalinks. [cited 2006 May 5] Available from: http://www.crystalinks.com/crop theories.

2. Herby, T. 2000. Crop circles. [Internet]. 2000 January 01. [cited 26 May 2006]. Available from:
http://www.geocities.com/Area51/Shadowlands/6583/crop.html

3. Wikipedia contributors. Crop circles [Internet]. Wikipedia, The Free Encyclopaedia; 2006 May 26, 00: 36 UTC [cited 2006 May 26]. Available from:
http://en.wikipedia.org/wiki/Crop_circles

4. Wikipedia contributors. Geometry [Internet]. Wikipedia, The Free Encyclopaedia;
2006 May 23, 15: 46 UTC [cited 2006 May 26]. Available from:
http://en.wikipedia.org/wiki/Geometry


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
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ECHOLOCATION IN BATS AND WHALE


Echolocation is the biological sound used by mammals such as bats, dolphins and whales to emit sound waves that encounter objects and these sound waves create a complex sound that returns back to the ears. Echolocation is some times known as Biosonar. Bats that echolocate are of the suborder Microchiroptera from the mammals order Chiroptera. The bats of Microchiptera suborder produce all manner of sound for echolocation and they do for the purpose of catching prey such as insects.


Human ear can not hear echolocation of the bats can not be heard by the human ear because their sonar pulses are beyond the range of human hearing. It is also said that not all bats echolocate, but bats of the sub-order Microchiroptera do echolocate. Furthermore, members of this sub-order produce all manner of the sounds through echolocation. The sub-order of this group also does echolocate in order catch many preys and other many insects. On the other side bats of moustached are said to be highly dedicated to the task of echolocation and are also said to be an excellent species.


The ear of the human is thought to be unable to hear the echolocation abilities of the bats. Bats are also said to produce different types of sounds during the echolocation process for example, mustached bat is thought to produce a bisonar sound consisting of a frequency which is constant which. Bats catch their prey by flying around, they do so by using their sonar signals as information about the food in the area. The sonar signals which are used by bats act like the waves of the sound, because sonar signals that the bat produce return in the form of the echo, which the bat detect with auditory structures.


On the other side whales use echolocation to sense their objects. In echolocation highly pitched sound is sent by the whale. The sound is sent in this way, the sound bounces off the object and some returns to the whale. Therefore, the returning echo is interpreted by determining the shape of the objects, direction, distance and the texture. Teeth of the echolocation start with a series of the low-frequency. The echoed sound waves are received in the flat-filled cavities of the bone of the lower jaw. These sounds are conducted through the bone to ear and the brains where as the location of the object is interpreted. The whale can determine the distance to an object, its size, shape, the speed that the object is travelling and its texture.


It is also possible that the whales may use other types of sound to perform similar functions as the traditional sonar signals of the dolphins. While on the other hand whales do not produce high frequency, broad band, short duration clicks. They also produce lower frequencies as compared to the mustached bat. The echoes returned as the low frequency sound bounce off features in the ocean. In conclusion, one can say that the echolocation process is useful in bats because it seems unique in bats. This is because echolocation is only unique to the bats.

References:

Wikipedia contributors. Echolocation [Internet] Wikipedia, The Free Encyclopedia 2006 May 07, 18: 16 UTC [cited May 15, 16: 10]. Available from: http://en.wikipedia.org/wiki/Animal_echolocation

Wikipedia contributors. Echolocation [Internet] Wikipedia, The Free Encyclopedia 2006 May 13, 00: 49 UTC [cited May 15, 16: 10]. Available from:
http://en.wikipedia.org/wiki/Whale


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com

BIRDS HAVE BEEN DESCRIBED AS THE LIVING OF THE RELATIVES OF DINOSAURS


Dinosaurs and birds are vertebrate animals that are found on land or terrestrial environment. These two species are omnivores meaning that they feed themselves on plants, meat seeds and fruits from the trees. Dinosaurs have four legs and they do not have wings. The birds have legs and wings which are used fly. Both birds and dinosaurs have back bone. The evidence that the paleontologists have about the close relationship between the dinosaurs and birds is unclear or controversial. It is because some paleontologists believe that dinosaurs are ancestors of birds resemble to dinosaurs. Paleontologists made their decision suggesting that birds are living relative of the dinosaur’s species.


Some Paleontologists suggested that recorded fossil of birds and dinosaurs. Indicates that there is a closely relationship between them. It is said that because a fossil of confuciousornis species in China which was a resemblance of Archaeopteryx species, and this species have wing claws like a modern birds and they had no teeth like the birds. Confuciousornis and Archaeopteryx fossil look like the birds and they did fly like birds.


Some paleontologists came up with the negative thoughts about the relationship between the birds and the dinosaurs and they gave the evidence on the bones. They said that the birds have different number of the toes. They said that some birds have three toes, some have five and some have more toes but depending on the area where they found. It said that some of the bones toes of the birds resemble of the reptiles are ancestors of the birds.


Paleontologists also disagree about the ribcage in the fossils of dinosaurs which was compressed more from back to their belly. Some scientists believe that the similarities between dinosaurs and birds are very imported. They said that by comparing the bones in the wings of birds with the front feet of the dinosaurs. The evidence indicates that these bones are similar to the bones of any other species and birds and dinosaurs had similar behavior.


Some paleontologists believe that birds developed from the reptiles before dinosaurs. They compared birds with the reptiles than dinosaurs, reptiles and birds have many features that they share and which are common in both species. The characteristics of the birds and the dinosaurs include wings with four functional fingers, long bone, slender, vertebrate tail recurved teeth, set in socket and vertebrate biconcave etc are different from those which are found in dinosaurs such as very hallow bones etc.


Birds and dinosaurs look the same because they live in the similar environment and they also did things to survive in a similar way. It is said that the birds live at the same time with the dinosaurs did fly but not as well as a modern birds. It is because of their features which are the same with the reptiles. The features of the birds and dinosaurs are touted as the missing link between them. The relationship between birds, dinosaurs and evolution of flight is more complex. It is because some paleontologists believe that birds developed from dinosaurs where as some paleontologists believe that some dinosaurs developed from the birds.


Reference:


Wikipedia contributors. Birds [Internet] the free encyclopedia, 2006 May 14, 23:56 UTC [Cited 2006 May 14:00]. Available from:
http://en.Wikipedia.org/Wiki/Birds

Wikipedia contributors. Dinosaurs [Internet] the free encyclopedia, 2006 May 15, 04:56 UTC [cited 2006 May 15:23]. Available from:
http://en.Wikipedia.org/Wiki/Dinosaurs


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com

WHY HERBIVORES IN THE FOREST LIVE ALONE OR IN PAIRS, WHILE HERBIVORES IN OPEN GRASSLAND LIVE IN GREGARIOUS GROUP


Herbivores are animals that depend on plants for their survival and they are sometimes referred to a vegetarian. Herbivores can be classified or divided into groups such as fungivores and folivores. Fungivores are animals that feed themselves on fruits and folivores are animals that feed themselves on leaves. Many fruits and animals that eat plants, roots and seeds. Herbivores animals are found in savanna, open grassland and tropical rain forest etc. Forest is the large area of trees which grow close together and the dominated species at this area are trees compared to the grass, herbs and shrubs etc. Grassland is the area or the land covered with wild grass and the dominant species are grasses.


Herbivores that are found in both open grassland and forest environment include insects such as grasshoppers and many other insects which are living in the dapple shade of the forest. Other herbivores include birds such Ross’s turaco which depend on dense cover or vegetation and the large and small animals such as elephant, gorillas, pygmy hippo, bongo, okapi, zebra, giraffe, rhinoceroses, hippopotamuses, rabbit and hares etc. All these animals feed on fallen fruits, seeds, sapling, twigs, shrubs, leaves, flower etc.


Zebras are one of the herbivores that are found in open grassland environment. These animals preferred to live in gregarious groups, it is simple and easy for them to communicate to each other if their enemies are close to them. Zebras feed themselves on grass for their survival. Living in social units helps the grassland animals cover more area with their eyes so that they can find their food and their predators faster. The other things that protect zebras from their enemies are their stripes which confuse their predators during the attack. There is no enough space to hide in open grassland; herbivores have to use speed to escape from their predators.


Another example of the herbivores found in the forest is giraffes. These animals have long neck to reach leaves about the floor or on the top of the trees. They are found in tropical rain forest. They have stripes legs which help them the blend into the shadow of the forest. Giraffes live in pairs and are not easy for them to see their enemy and they are not easily to be killed because they are big animals. They do not want to live in group because most of the animals feed on leaves they are scared that there will be a shortage of leaves that is why they preferred to live in pairs.


Okapi animals are found in forest and they live in pair. They feed on the foliage which is avoided by other forest animals. Animals such as deer are also feed on foliage but they live in a gregarious group compared to the okapi. It is simple foe the herbivores that found in forest to hide themselves from their enemy compared to those herbivores live in grassland; they have the chance the run to the tress as some of them are using trees as their living place.


Duikers are found at rain forest and they feed on fallen fruits and seed. Bird such as Ross’s turaco etc is herbivores that depend on dense cover or vegetation in order to protect themselves from their predators. The other herbivores that are found in grassland are grasshoppers, rabbit, snails and slugs. Malay tapir is a largest species which related to horses and rhinos. Tapir feeds on grass, leaves and fallen fruits and it lives alone or in a pairs because it does not want to be disturbed by other animals.


Herbivores that are found in open grassland can run fast away from their predators compared to those herbivores found in forest. Since there is no enough space to hide in grassland, living in social units help them to cover more area with their eyes so that they can see their predators faster and run away. Herbivores found in forest live alone or in pairs are selfish because they do not want to share their food with other animals, they want to eat alone.

Reference:

Wikipedia contributors. Herbivores [Internet]. Wikipedia, the free encyclopedia 2006 May 30, 00:26 UTC [Cited May 12, 12:45]. Available from:
http://en.Wikipedia.org/Wiki/herbivores


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
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THE PROCESS OF FOSSILIZATION AND THE IT’S SIGNIFICANCE IN THE INTERPRETATION OF THE EVOLUTIONARY EVENTS.


Fossils refer to the remains of plants and animals that existed many or long time ago and it is mostly occurring in sedimentary rocks and the process of fossilization occurs when living organisms such as animals and plants dies. This process of fossilization mostly occurs near the river where there is a lot of sand. Fossilization mostly occurs on big organisms that have hard body parts such as bones, teeth, clews and shells. It is impossible for small animals to be fossilised because they have a soft bodies and they do not live for the long time, so they can became extinct.

When the animals died, their meat is eaten by their enemy or predators and leaves their bones. These bones will be left untouched, and when the wind blows the sand and sediments, these bones will be covered and place underground. The organism must be covered by sediment soon after they died or decaying process and the sediments will continue cover up the bones until they are hidden far underneath the ground. After they have been covered with sediment they become solid and they will be covered into rock and organic remains replaced with a minerals and it is called diagenesis form.

During the process of fossilization minerals, calciums and hydroxyapatite found in the bones replace by the minerals that are found in the sand and after many years, and there will be a lack of an organic materials in the bones because they will turn to solid rock and end up to being a fossils. There are two types of fossils, namely: organic fossils which were once part of living organism and trace fossils which are the trackways, burrows, footprints, eggshells, nests and worms holes.

The fossils of small animals such as insects, spider, and small lizards can be found in the mudstone or sandstone and psedofossills are produced by natural occurring in the geological process and same of these fossils such as dendrites are formed by naturally occurring in the rock that filled up with the percolated minerals. Other examples of the psedofossils are kidney ore and moss agaster.

The reef-building corals fossils show that the rocks were deposited in warm and were found in the tropical seas where sunlight can pass through the water to reach the their photosynthesising algae within their cells. Fossils may be formed close to the edge of the body of water. The Koonwarra fossil includes fossilised fish, plants, insects spiders and bird feathers. These fossils show that the deposit was formed in the dip part of the large freshwater lake because the insets are living in cool mountain streams and in lakes. These insects were not transported far after their death.

Most of the fossils are found in the sedimentary rocks that have been formed by the consolidation of the soft sedimentary such as sand and mud. Fossils which are found in igneous rocks are hidden from a molten state or in the metamorphic rocks that have undergone intense pressure and heat. The fossils occur in sediments such as rocks, and incorporated as an integral part of the rock formation. Unconsolidated sediments such as sand or muds are good for burial. The other thing is that fossilization is the process of the hard part of the skeletons and shells etc and these were fossilized under high favourable conditions.


References

Wikipedia contributors. Fossilization [internet]. Wikipedia, The Free Encyclopedia; 2006 May 4, 13:36 UCT [cited 2006 May 8] available from:
http://en.wikipedia.org/wiki/fossils

Wikipedia contributors. Fossilization [internet]. Wikipedia, The Free Encyclopedia; 2006 May 5, 13:49 UCT [cited 2006 May 6]. Available from:
http://en.wikipedia.org/wiki/Fossils

Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Telephone number [012] 841 2133
Fax number [012] 842 3676
E-mail mmaluleke@csir.co.za
weblog: http://mmaluleke.blogspot.com

COMPARISON OF MODE OF REPRODUCTION BETWEEN THE PLACENTAL MAMMALS AND MARSUPIALS


The placental mammals are female vertebrate animals having an organ part where the baby grows before it is born. Marsupials are invertebrate animals and placental mammals are vertebrate animals. There are differences between the marsupials and placental mammals during the process in which the babies grow inside the body of their mother before they born and this process is known as gestation. The development of an embryo in marsupials vertebrate animals is isolated from body of their mother by the amniotic membrane.

The differences between the marsupials and placental mammals are their rate of gestation. I marsupials the mode of their reproduction is more difficult compared to the placental mammals meaning that their reproductions is not difficult. 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 and it also protect them not to be assaulted.

The short and long gestation in marsupial vertebrate occurs as differ to the placental mammals. 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. The birth rate in marsupials occurs at the early stage. 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. The process of gestation in off spring starts to full develop.


The other differences between placental and marsupial’s reproduction occurs in the mode reproduction and any pattern. The pregnancy in marsupials does not interrupt the development of the oestrus cycle and the pregnancy in placental interrupt the development of the oestrus cycle. 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.


In marsupials the right and left uterus are not complex compared to in plantation meaning that the right and left uterus is complex. 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. The male in marsupials have double penis and their scrotum is found in the anterior part of the penis. In placental mammals the scrotum is found at the posterior at the end of the penis.


There are differences between the placental mammals and the marsupials on their reproduction anatomy and pattern because marsupials are invertebrate mammals while as placental mammals are vertebrate mammals. They are also differences during their gestation. Their birth occurs at different times, in marsupials’ birth occurs earlier compare to placental meaning that in placental birth occurs later. In marsupials the pregnancy does not interrupt the oestrus cycle and in placental the pregnancy is interrupt. The reproduction in marsupials it said to be full developed compared to in placental mammals.


Reference:

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

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



Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com

BIRDS HAVE BEEN DISCRIBED AS THE LIVING OF THE RELATIVE OF DINOSAURS


Dinosaurs and birds are vertebrate animals that are found on land or terrestrial environment. These two species are omnivores meaning that they feed themselves on plants, meat seeds and fruits from the trees. Dinosaurs have four legs and they do not have wings. The birds have legs and wings which are used fly. Both birds and dinosaurs have back bone. The evidence that the paleontologists have about the close relationship between the dinosaurs and birds is unclear or controversial. It is because some paleontologists believe that dinosaurs are ancestors of birds resemble to dinosaurs. Paleontologists made their decision suggesting that birds are living relative of the dinosaur’s species.


Some Paleontologists suggested that recorded fossil of birds and dinosaurs. Indicates that there is a closely relationship between them. It is said that because a fossil of confuciousornis species in China which was a resemblance of Archaeopteryx species, and this species have wing claws like a modern birds and they had no teeth like the birds. Confuciousornis and Archaeopteryx fossil look like the birds and they did fly like birds.


Some paleontologists came up with the negative thoughts about the relationship between the birds and the dinosaurs and they gave the evidence on the bones. They said that the birds have different number of the toes. They said that some birds have three toes, some have five and some have more toes but depending on the area where they found. It said that some of the bones toes of the birds resemble of the reptiles are ancestors of the birds.


Paleontologists also disagree about the ribcage in the fossils of dinosaurs which was compressed more from back to their belly. Some scientists believe that the similarities between dinosaurs and birds are very imported. They said that by comparing the bones in the wings of birds with the front feet of the dinosaurs. The evidence indicates that these bones are similar to the bones of any other species and birds and dinosaurs had similar behavior.


Some paleontologists believe that birds developed from the reptiles before dinosaurs. They compared birds with the reptiles than dinosaurs, reptiles and birds have many features that they share and which are common in both species. The characteristics of the birds and the dinosaurs include wings with four functional fingers, long bone, slender, vertebrate tail recurved teeth, set in socket and vertebrate biconcave etc are different from those which are found in dinosaurs such as very hallow bones etc.


Birds and dinosaurs look the same because they live in the similar environment and they also did things to survive in a similar way. It is said that the birds live at the same time with the dinosaurs did fly but not as well as a modern birds. It is because of their features which are the same with the reptiles. The features of the birds and dinosaurs are touted as the missing link between them. The relationship between birds, dinosaurs and evolution of flight is more complex. It is because some paleontologists believe that birds developed from dinosaurs where as some paleontologists believe that some dinosaurs developed from the birds.


Reference:


Wikipedia contributors. Birds [Internet] the free encyclopedia, 2006 May 14, 23:56 UTC [Cited 2006 May 14:00]. Available from:
http://en.Wikipedia.org/Wiki/Birds

Wikipedia contributors. Dinosaurs [Internet] the free encyclopedia, 2006 May 15, 04:56 UTC [cited 2006 May 15:23]. Available from:
http://en.Wikipedia.org/Wiki/Dinosaurs


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.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. Hominidae share 97 % of their DNA with the modern human. Chimpanzees, human and gorillas species are closely related to each other but their DNA are different. The DNA of a common chimpanzees and pygmy differs at about 0.7 % while at between human and chimpanzee differ at about 1.6% of their DNA even if the share 97 %.


Orangatans are the species of great apes with long arms and the ward orangutanas means man of the forest. They are the rain forest inhabitant and they spend their time in the trees making new nests. Orangutanas weight at about 82 kilograms and the height of the males is 1.4 mitres tall and the females are smaller than the females. They have reddish and brown hairs. They are extant species in the genus Pongo and subfamily Pongonae. Orangutanas are very clever species, passive and violence toward other orangutanas is very common. They are friendless animal and they can be violently protective.


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 had a robust built with arms and short legs. They have a massive chest and broad hand. They are knuckle walking, and they have a long and hair which insult it from the living cold at high elevation.


The body of the gorillas is covered by brownish hairs and they have a big head with building forehead thin ears and small dark brown eye. They have facial features like wrinkle around the nose. Gorillas use both arms and feet to walk. The height of male adult ranges between 1.65 m and 1.75 m tall. Their weight ranges between 140 and 165 kg. Females are about half of weight of males. Gorillas have bloated stomach and all share the blood type B.


The chimpanzees have a very long arms and short legs. Their body is covered by black hairs. They have a slight brow ridge, large ears and small nostrils. 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 are walking with two feet. And they are belonging to the Homo sapiens which mean wise man. Human have develop brain, of abstract reasoning, language and introspection. They have body types which are determined by their genes. They are also omnivores meaning that they eat meat and plants. Human and chimpanzees are closely related to each other. Hominidae share 97 % of their DNA with the modern human and all these Hominidae ate related to each other.

Reference:


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
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com

COMPARISON OF MODE OF REPRODUCTION BETWEEN THE PLACENTAL MAMMALS AND MARSUPIALS


The placental mammals are female vertebrate animals having an organ part where the baby grows before it is born. Marsupials are invertebrate animals and placental mammals are vertebrate animals. There are differences between the marsupials and placental mammals during the process in which the babies grow inside the body of their mother before they born and this process is known as gestation. The development of an embryo in marsupials vertebrate animals is isolated from body of their mother by the amniotic membrane.

The differences between the marsupials and placental mammals are their rate of gestation. I marsupials the mode of their reproduction is more difficult compared to the placental mammals meaning that their reproductions is not difficult. 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 and it also protect them not to be assaulted.

The short and long gestation in marsupial vertebrate occurs as differ to the placental mammals. 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. The birth rate in marsupials occurs at the early stage. 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. The process of gestation in off spring starts to full develop.


The other differences between placental and marsupial’s reproduction occurs in the mode reproduction and any pattern. The pregnancy in marsupials does not interrupt the development of the oestrus cycle and the pregnancy in placental interrupt the development of the oestrus cycle. 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.


In marsupials the right and left uterus are not complex compared to in plantation meaning that the right and left uterus is complex. 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. The male in marsupials have double penis and their scrotum is found in the anterior part of the penis. In placental mammals the scrotum is found at the posterior at the end of the penis.


There are differences between the placental mammals and the marsupials on their reproduction anatomy and pattern because marsupials are invertebrate mammals while as placental mammals are vertebrate mammals. They are also differences during their gestation. Their birth occurs at different times, in marsupials’ birth occurs earlier compare to placental meaning that in placental birth occurs later. In marsupials the pregnancy does not interrupt the oestrus cycle and in placental the pregnancy is interrupt. The reproduction in marsupials it said to be full developed compared to in placental mammals.


Reference:

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

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



Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com

ADAPTATION REQUERED TO MAKE THE LAND LIFE TRANSITION FROM THE WATER TO LAND LIFE USING AMPHIMBIANS GROUP AS AN EXAMPLE


Amphibians are vertebrate animals that can inhabit on both land and in water, which lay their eggs in water. Some of these species have four feet and they do not have amniotic eggs. Amphibians was classify at the Amphibia. It was said that their transition from land to water was not completed because they live in water and this means that they require a transition from the aquatic to terrestrial environment and they first adapt air from the terrestrial environment. Species such as frog, tatropods and salamander etc are the example of amphibian’s animals.


The frog animals adapted to an arid and semi arid environment need water to lay their eggs meaning that water plays an important role during their reproduction. They lay their eggs inside the water, then the eggs will be hatched inside the water and the young eggs developed into adult. Small or adolescent fogs live in water and breathe with gills and adult live on land breathe through lungs. When adolescent reach sexual maturing stage, they goes back inside the water and spend a lot of time inside the water. Frogs feeds themselves on algae plants in water and when they are on land they eat insects such as flies etc. They depend on absorbing oxygen through their thin, wet skin.


Some of the amphibians manage their adaptation on land. Amphibian’s metamorphosis has four legs to support their body on the land. Their gills are replaced after being terrestrial dwellers and they also started to use lungs for breathing. Their skin change and develops glands to avoid loosing a lot of water from their body and this process is dehydration. They also develop eyelids on their eyes and they start to adapt vision when they are outside the water. They also develop an eardrum that locks off their middle ear. The species such as frog and toas lost their tails. Frogs uses their legs to swim in water and they jump when they are on land.


Early reptiles and other living organisms succeeded their adaptation on the land but frogs did not succeed because of the low biomass on the land and dry environment in dry areas. Amphibians are semi terrestrial inhabitant. Their skins are soft and moist meaning that they are at the higher risk of dehydration in the dry area. Their eggs were unprotected meaning that were not covered by the waterproof, these eggs must be laid near the plants that are found inside the water where they are fertilised. Some of these species place their eggs within their mouth and some place their eggs at their stomach after the external fertilization.


The declines in amphibian’s populations include population crashes and mass localization extinction and this is the threats to the global biodiversity. Amphibians started to decline after becoming a terrestrial dwellers and this caused by the limitation factors such as over exploitation, climate change, population growth, diseases, habitat distruction and modification. Most of an amphibians run away from the water to the land because of the above factors. The species manage to survive are frogs, tetrapod etc.
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Tetrapods species do not have amniotic eggs and they have adaptations to a terrestrial environment. Amphibians such as crocodiles lay their eggs in a mass of dead vegetation. Amphibians animals are adapted to the wetland or wet environment. They also have a skeleton bone and four legs which support them to stand on the land. The wetland is good for both arid and semi arid animals because water play an important role during their reproduction and on land they maintain their body temperature.


References:

Wikipedia contributors. Amphibians [Internet] wikipedia, the free encyclopaedia 2006 May 09, 12:25 UTC [cited May 11]. Available from http://en.wikipedia.org/wiki/Amphibians


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
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THE FORMS OF SOCIAL LIFE THAT OCCUR IN INSECTS


Insects are small living animals which have four wings and usually wings, for example ants, butterflies, and flies etc. Insects are invertebrate animals in the class insecta. Their adult bodies are divided into head, thorax and abdomen. These animals have three pairs of segmented legs which are attached thorax and one pair of antennae. Insect that are fall under subclass Pterygota have two pairs of the wings and the insects fall under the subclass Apterygota does not have wings. Insects are ecologically important as other animals such as herbivores, predators, parasites and scavengers. They are also considering being the most successful group of organisms on the Earth.


Insects have a complex life cycle consists of many small part transformation known as metamorphoses. Insects have different body shapes, functions and behaviours at each stage of metamorphoses. Butterflies, moths and true flies are the insects that have more complicated life cycle which also have four stage including eggs, larva, pupa and adult. Spring tails and bugs are the insects that have less complex development which include eggs, nymp and adult stages. Most of the insects are non-social and some species have developed complex social behaviours, they are living together and caring for eggs. The young once are the offspring of a single female known as the queen and this system is common in insects such as bees, wasps, ants and termites.


The life of insects is in danger in many ways. They may be eaten by other insects, birds, and some other animals etc. Human being may kill them by crushing, burning or poisoning them. The parasites which are the animals, who feed on living animals, may kill and eat them; and disease may also kill them. Insects may also killed by cold weather. The other things is that a dry spell may cause the plant the shrink, dries up and dies and this means that insects that depend on that plant may suffer and end up dieing. Even if the insects and other species can survive these dangers, it means that there will be running out of the food supply and it also means that they will die because of the shortage of their food.


An insects developed many ways of their life survival. They adapted themselves to a living conditions and developed many ways to get away from their enemies. Most of insects spend a lot of time on eating and reproducing and everything they do is related to those two activities. Insects can also communicate to each other and they can get the message by touching and smelling, for example, the queen releases airborn chemicals called pheromones and foreign insects can be attact by this chemicals. Social insects also share information about food, for example, ants lay scent trails that lead to feeding site and bees returning to the hive dance that shows the direction of the food sources. So with this information, other insects can find sources of food away from that area.


Communication is an important for mating and defence among the nonsocial insects. Insects such as grasshoppers, crickets and cicadas produce their sound which can attract mating parterners and this process is called stridulation. Stridulation involves rubbing one body part against another to produce sound and cicadas produce sound by clicking a taut membrane. Their ears are called tympana and they use them to detecting one another’s song. Some insects use their antennae to hear sound made by other species members. Mosquitoes use their featherlike antennae to hear the sound of the female wing-beats and water strides use their legs to attract.


References:

Wikipedia contributors. Arthropod [internet].wikipedia, The Free Encyclopaedia, 2006, May 8, 3:40 UCT [cited 2006 May 6]. Available from: http://en.wikipedia.org.wiki/Arthropod

Wikipedia contributors. Insects [internet]. Wikipedia, The Free Encyclopaedia, 2006, May 8, 3:40 UCT [cited 2006 May 6]. Available from: http://en.wikipedia.org.wiki/insects



Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com

THE WATER VASCULAR SYSTEM THAT CHARACTERISES ANIMAL THAT OCCUR IN THE PHYLUM ECHINODERMATA


The water vascular system is a system of canal branching through the body that branch in many sections known as tube feet which era also 2 000. These tube feet can penetrate the body wall and skeleton in ambulacral grooves in enchinoders. Water vascular system also refers to the hydraulic system used by an enchinoderms such as sea fish and sea urchins. The water vascular system develops from tentacular system and it has feature such as podia arranged along the branches, an embryological origin from left mesocoel and central circumesophageal ring.


The important functions of water vascular system in echinoderms are for locomotion, respiration and were transportation as well as feeding. The water found in pore, in the body wall of an echinoderms are very important for feeding and respiration and this indicate that this system is an internal closed system of reservoirs and ducts containing water fluid. The water vascular system is also the canal that joins all the canals creating hydrostatic pressure to help the star fish to move. The water inside this system move through modreporite on aboral surface and go straight to the stone canal, which connects to a circular canal around the mouth known as ring canal.


These animals have five radial canals which are extend down each arm and they are connected to the ring canal. These radial canals transport water to the tube foot which contract and create suction to help these animals to move and attach or open bivalves. Their stomach secretes enzymes to digest bivalve, so the stomach withdrawn and the digestion takes place in the stomach of star fish. This system has separate sexes. They have two gonads in each arm and these gonads produce eggs or sperm. They only have external fertization. The females produce about 200 000 000 eggs per season and fertilized eggs produce into bipinnaria larva which live to the bottom of a sea after two years and changes into adult. They have an asexually which by reproduced by regenerating arm.


The water vascular system use cilia and ampullae to keep things moving. An Ionic imbalance causes water to flow into madreporite and also allow water to inter to the water vascular system. Some of the water is directed to the different part of the animals such as coelon. Some of the water directed where it is circulated by the beating of cilia. Phylum Echinodermata are marine animals such as sae star, sand dollar, sea urchins, brittle star and sea cucumber and they are found in the ocean. These animals are also known as spiny-skinned animals and they are also endoskeleton made by calcium plate or ossicles with protruding spines.


Echinodermata are free-swimming larva to sessile and undergo metamorphosis from bilateral. The larva stage known as a bipinnaria and the adults have pentaradia symmetry. They have a segmentation or metamerism and they have coelomate. They use skin gills for breathing and they are capable of extensive regeneration. Bipinnias mouth is found at the oral surface which is the lower surface and its anus is at the aboral surface which is the upper surface. Bipinnaria do not have head or brain, they have a nervous system. They have tube feet as an arm which helps them to move and eat. Echinordermata divided in to five classes and are as follow.


Asteriodea class are star fish or sea fish. Their body have more arms. They are predators in much marine system and also prey on bivalve molluses such as clams and oysters. They have five arms projected from the central disk that can be regenerate. They have mouth on the oral surface. Crinoidea class are animals such as sea lilies and feater stars which are most primitive of the echinoderms. They have long stalk with branching arms that attach them to rock and the bottom of the ocean. Their mouth and anus are located on the upper surface. They have 5 to 200 arms with sticky tube feet to help them to capture the food and take in oxygen. They are also nocturnal feeders.


Echinodea are animals such as urchins and dollars. They do not have arms and their bodies are covered with movable spines and they use tube feet to move. Sea urchins and sand dollars also have differences. Sea urchins have a spherical shape, and sand dollars have flattened body. Urchins live in the bottom of the ocean, and dollars live where there is sand along the coastlines. Holothuroidea are animals such as sea cucumbers and they are found at the bottom of the ocean and hide themselves during the day. These animals do not have arms; they have a soft body with a tough and leathery outer skin. They can scare predators by ejecting part of their internal organs and regenerate this structure during the day.


The last class is ophiuroidea. These are the animals such as basket stars and brittle stars. These animals are found on the bottom of the oceans under stone and in holes. They have long and narrow arms which resemble tangle of snakes. They move faster than a star fish and they feed themselves by standing in the food with arms.


References:

Wikipedia contributors. Water vascular system [internet] wikipedia, The Free Encyclopaedia, 2006 May 8, 12:13 UCT. Available from: http://en.wikipedia.org/wiki/Water-vascular-system


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com

THE DINOSAURS WERE WARM-BLOODED ANIMALS


Dinosaurs were the warm-blooded vertebrate animals living on land for over 160 million years and it also said that they first appeared about 230 million years ago and their hearts was resembled of crocodiles. These organisms have back bone skeleton and also have four legs. Dinosaurs were discovered in the 19th century and species such as pelycosaur Dimetrodon, the pterosaurs were found on the land. Another example of dinosaurs that were found in the water is ichthyosaurs, plesiosaurs, and mosasaurs. These species suffered a catastrophic extinction which made them dominated on land.


During 1970s scientists started looking the evidence indicating that the dinosaurs may be warm blooded animals and the evidence shows that the dinosaur started to stand straight and walk like animals because their legs were like the animals. They also have big ribs cages like a mammal’s heart and lungs. The other thing is that they also had bones containing channels for quick blood circulation which was also found in warm blooded animals.


The palaeontologist believed that some of the dinosaurs were warm-blooded animals but at the beginning were believed to be the cold-blooded animals because of they were closely related to the cold-blooded animals known such as reptiles. The warm-blooded do not rely on the environment, chemical reaction help them to create heat inside their body and this means that they can regulate their body temperature rather than relying their on the environment, they can also hunt anytime any where.


Beverly Eschberg says that dinosaurs were believed to be related to the reptiles, but some of these species behave like the warm blooded animals. It said that the dinosaurs were active and moving at a high speed. Other scientist says that they fossils about the warm blooded animals that suffered from the heat in warmer climate were recognised. Beverly says that the evidence such as bones, growth rate, histology, predators to prey, high speed, and rate of evolution etc shows that the dinosaurs are warm blooded animals and all these evidence convinced her that the dinosaurs were the warm blooded animals.


The palaeontologist discovered the fossils of the dinosaur’s heart and they decided to name it Willo. Russell believed that this heart shows that this species was a warm blooded animal. Warm blooded animals can maintain their body temperature at any environment and they can also control it by increasing their metabolic rate when the temperature decreases. Ostrom and Baaker are the ones of the Palentologists determined that dinosaurs are the warm blooded animals because they believed that these species grow quickly and cold blooded animals grow slowly.


In 1992 the scientists by names of Shower and Barrick believed that dinosaurs were warm blooded animals because of the temperature that they were maintaining at their body core. They provide the evidence of bones, so the isotopes from the dinosaur’s bones indicated that the dinosaurs were warm blooded animals. This is also because the bones are composed of minerals and calcium phosphate (CaPO4) so the oxygen in this process exist in the form of two isotopes,160 and 180 and this ratio can be measured and this means that the species is warm blooded animals. The bones of dinosaurs are rich in halversia canals that transport nutrients from the blood to the cells that down new bones.


Pateontologists have different thoughts about the evidence of the dinosaurs. There are some scientists who believed that dinosaurs were warm blooded animals and others believed that these animals were cold blooded animals and both have the evidence to prove their believe. I concluded saying that the dinosaurs were warm blooded animals because they can maintain their body temperature at favourable and unfavourable environmental conditions.


Reference:

Wikipedia contributors. Dinosaurs [Internet] wikipedia, the free encyclopaedia, 2006 May 09, 18:48 UCT [Cited 15:00 May 10]. Available from: http://en.wikipedia.org.wiki/Dinosaurs


Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com

THE MORPHOLOGICAL DIFFERENCES THAT EXIST BETWEEN THE CARTILAGINOUS AND BONY FISH


Fishes are marine vertebrate animals with back bones, dwelling in ocean, sea and in rivers. They are found under the rocks, in sand and mud. Fishes are divided in to three different classes such as Chondrichthyes, Osteichthyes and Agnatha classes. Agnatha fishes are the small animals that have a mouth like a hole in the head that have no movable parts. These fishes do not have paired fins and they have large gills which serve food filters and respiratory organ.


Chondrichthyes fishes have strong jaws and also have pairs fins, nostrils, scales, two chambered heart and skeletons made by the cartilage. Their mouth located underside of the head and they use their nose to sense where their food is and same of them use electrosensory system because they are unable to see their food see their food because their eyes are fond on top of their head..


Sharks, rays and chimaeras are fishes falls under the class chondrichthyes. The other name of chondrichthye is cartilaginous fish. Their skeleton bones are cartilage meaning that they do not have true bones. They have five to seven gills slits. They use gills to breathe and during their breath, water passes through mouth, over their gills and out through their gills slits. Their eyes are found at the top of their head and they can not see food as it enters to their mouth.


Sharks fish are the one species known as jawed fishes. They also have also have spiracle behind their eyes at the top of the head. Shakes are the biggest fish, they have big mouth and they have brown with yellow or white dots on their back. Sharks have five to seven pairs of gills and chimaeras fish have only one pair of gills. The ghost shark has an external smooth skin and one also have one pair of the external gills opening. Cartilaginous fish have fins which help them not to go under the ocean because they do not have air bladder.


Rays fishes have enlarged pectoral fins; their tails are thin and it ranges from short to long in length. These fishes use their pectoral fins to swim by waving them and sharks their tails to swim. Rays mouth is facing downwards and they have flattened teeth. These fishes feed themselves on the species that are found at the bottom of the ocean. They change the way of breathing in order to avoid sucking up the bottom mud.


The other name of Osteichthyes is true bony fish. These fishes live in all types of water. This class is divided into two classes which are Sarcopterygii and Actinopterygii. Class Osteichthyes include coelacanths and the lung fishes and Sarcopterygii include gars, sturgeons, bow fish and telelosts. The skeleton of the bony fishes made by bone and most of them have a scales. Most of bony fish species have two sets of paired fins and some have one set of paired fins and some have no fins at all. The species that falls under the class Osteichthyes are snapper, grouper and gurnard fishes. The difference between the bony fishes and the cartilaginous is that the bony fishes have cartilage skeleton bone and the bony fishes have a true bone.


References:

Wikipedia contributors. [Internet]. Wikipedia, the free encyclopaedia, 2006 May 09, 10:15 UTC. [Cited May 09]. Available from: http://en.wikipedia.org/wiki/Cartilaginous

Wikipedia contributors. [Internet].Wikipedia, the free encyclopaedia, 2006 May 09, 11:50 UTC. [Cited May 09]. Available from:
http://en.wikipedia.org.wiki/Bony




Lizzy Maluleke
CSIR PTA
0001
Cell number 072 351 8488
Tell [012] 841 2133
Fax [012] 842 3676
E-mail mmaluleke@csir.co.za
Weblog: http://mmaluleke.blogspot.com