Tuesday, May 16, 2006

DISCUSSION OF IDENTIFYING CHARACTERISTICS OF EACH ORDER OF PLACENTAL MAMMALS, INCLUDING A LIST OF ANIMALS REPRESENTING EACH ORDER

There are six orders which are found on placental mammals; these include Chipoptera, Pholidata, Carnivora, Perissodactyla (odd-toed ungulates), Artiodactyla (even-toed ungulates) and Cetacea. These orders have some characteristics which identifies them from each other.Chiroptera have long slender fingers covered with by sheet leathery skin. The skins are connected to their sides, legs and tails to make a wing.
The example for Chiroptera is bats. Bats have modified forelimbs which support wing membrane. Bats have most elongated parts of the limb are those of hands (metacarpal bones) and fingers. Numerous blood vessels and nerves are present throughout the wing membrane. Bats have five unique muscles present in the patagium and use addition muscle which is found in the chest and back to move the wings up and down. The hind limbs are unique.The examples of Artiodactyla are cow, sheep, pig, giraffe and hippopotamus. This is the order of even toed hoofed animals has only two toes on which it stands. Standing on two toes provides better control than on a flat foot. Animals which run very fast in this order are those that run either on all their toes or on one toe. The giraffes have unique elastic vessels which provide the ability to raise and lower the head. This species have high shoulders and slopping back. The front legs are much longer than hind legs. The body of the giraffe is covered with brown patches.
The examples of carnivore are dogs, cats, lion, skunk, walrus, sea and sea lion. Animals of the order carnivore hunt meat, and usually have sharp claws and long cone like. Carnivores have canine teeth which are used for seizing and stabling their prey. Some teeth are sharp and they act like scissor blades. They have furry or hairy coat. The main feature of the head is squarish snout. Their eyes are small and ears are internal. They have special air sacs below to their throats that allow them bob vertically in the water while sleeping.
The examples of animals that belong to order Cetacea include whales, dolphins and porpoises. Cetacea have bodies that are adapted for water but they are still air- breathing mammals that sticks their nostrils on the water every once in a while or they will drown. Cetacea have torpedo-shaped bodies, forelimbs that have been modified flippers and tails that are flattened side to side to become flukes. The majority of cetacean has no sweat glands and their skins are smooth and virtually hairless. Toothed whales are usually small to medium sized. They have skulls that that are bilaterally asymmetrically and it supports a round called melon. They have a single blowhole and a fused lower jaw.
Scaly anteater is the example of Pholidota. Pholidata are covered with large, overlapping scales made up of agglutinated hair. They have extraordinary long and strong tongue. The tongue passes over sternum and anchored to long process of the pelvis. They have ability to close eyes, nostrils and eyes apparently. The scales, coupled with the ability to curl into tight ball.Perissodactyla are a small order of herbivores which is comprised of species such as horse, zebra and rhinoceros. They are distinguishing from other ungulates by their odd number of toes.
The species of order Perissodacyla contained some largest land mammals such as Indricotherium, a relative of the rhinoceros which stood more than five meters tall at the shoulder and weighed estimated fifteen to twenty tons. Rhinocerotidae have three toes per foot. At the skull is elongated by stretching of the facial bones rather than the braincase. The nasal bones in the skull are expanded posteriorly and the project is freely for at least part of their length. Horns are present on the midline of the nasal or frontal bones in all members of Rhinocerotidae. However, these are dermal of origin and have no bony core as in the artiodactyls.

Chiroptera have long slender fingers covered with by sheet leathery skin. Artiodactyla is the order of even toed hoofed animals has only two toes on which it stands. Animals of the order carnivore hunt meat, and usually have sharp claws and long cone like. Cetacea have bodies that are adapted for water. Pholidata are covered with large, overlapping scales made up of agglutinated hair. Perissodactyla are distinguishing from other ungulates by their odd number of toes.
Reference

Wikipedia Contributor. Placental mammals, The free Encyclopedia [internet] 2006 May 06, 08:30 UT C [cited 2006 May 08] Available from: http://en.wikipedia.org/wiki/placental

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

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 specialized 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 UT C [cited 2006 May 08] Available from: http://en.wikipedia.org/wiki/multicellular

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DINOSAURS WERE WARM BLOODED ANIMALS

Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for more than one hundred and sixty million years, earliest appearing about two hundreds and thirty million years ago. For many years, scientists started to search evidence showing that dinosaur may be warm blooded. The evidence used include the way dinosaur 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. Dinosaurs were dynamic creature, and not just overgrown lizards.

The fossilized heart of Dinosaurs was found in the Northern part of South Dakota in 1993. Dinosaurs were classified under reptiles for many years until this view was seriously challenged by John Ostrom professor of palaeontology at Yale University and Robert Baaker. The two scientists from North Carolina States, Reese and Bill showers got a way. Reese and Bill determine the extremities of dinosaurs were sustained with same temperature with its body core or not. Scientists have used the isotopes method to determine the temperature of the body. Bones consist of mineral calcium phosphate (CaPO4); the calcium phosphate has an oxygen atom which occurs naturally in the form of two isotopes, 16O and 18O. the bond are formed by 18O (O Oxygen) atoms according to physists language this is the effect of isotopes, the oxygen atom taken up into newly formed bone tend to be preferentially. Barrick and Showers compared dinosaurs and reptiles. There was little or no difference between tail and rib in 16O/18O ratios. The unmineralized interior of Terex bones (T bones) rule out possible artifacts, the same results were obtained. The fossils of the reptiles were found in the same deposit showed similar characteristics of the cold blooded animals. The dog of the same size with dinosaurs indicated similar constancy of 16O/18O.

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.

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. Furthermore, evidence for rapid dinosaur growth can also be 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.

Ruben hauled a 70-watt ultraviolet lamp to Salerno, Italy to study the fossil of Scipionyx samniticus. It is the best preserved soft tissue of a dinosaur in the world. The fossil showed that the baby dinosaurs had a large intestine, liver, windpipe and muscles. The 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 indicate 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.

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. Dr Russell, a palaeontologist 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.

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

References

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
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
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

Wikipedia Contributors. Insects’ behaviour, The free Encyclopaedia [internet] 2006 May 06, 08:30 UT C [cited 2006 May 08] Available from: http://en.wikipedia.org/wiki/dinasaurs

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THE SIGNALS USED BY INSECTS TO ATTRACT A MATE FOR SEXUAL REPRODUCTION

Insects use different signals to attract their mates. These include the use of pheromones, nibbling, waving of abdomen, sound and display of mating behaviour. Insects use odors to attract male from a distance. Majority of insects have contact sex pheromones on their cuticles that allow each sex to clearly identify the other once they contact each other. Pheromones are usually used by social insects such as ant, termites and honeybees to differentiate nest mates and non nest mates.

In moth, the main determinant of female attractiveness is pheromone tilter. A virgin female, biosynthesize pheromones and release them to attract males. After mating they cease synthesizing and releasing pheromones. Pheromones biosynthesis in female moth is stimulated by a brain factor called pheromone biosynthesis activating neuropeptide. Male moths often trace a side to side zigzagging flight way as they follow the windborne pheromones to its source. When the male arrives where there is a female, the physical contact is made, mating proceeds almost instantaneously. However, in some moths, upon his arrival a male releases his unique courtship pheromones and fans it over female with wings.

American cockroach (periplanete Americana) begins when a mature female emits pheromones that attract male or many males on the mating ground. When the male accept this enticing signal, he approaches and flaps his wings to show his interest toward her. He will then probe the female with his abdomen as a way of searching for the origin of the omitted pheromones. Finally mating by males backing into the female and exchange sperm.

In some insects nibbling, waving of the abdomen and hissing are displays of mating behaviour. Some males will also emit sexual pheromones of their own initiate courtship and assume calling posture by exposing sexual gland of their abdomen called as tergites. If the female is next to the male, she will open her genital atrium widely thus exposing her atrium glands

Water striders or gerrids attract mates by using legs to create patterns of ripples on the surface of water. Some insects use sound signals to attract mates. They also pattern of light flashes from firefly or chirps from a cricket are conspicuous signals used to attract mate. Cricket, grasshoppers and cicadas attract mating partners by sounds which produce the process of stridulation. Cicadas make their sound by clicking a taut membrane. Among grasshoppers and cricket, stridulation involves rubbing one body part against another to produce sound. Both males and female they have a unique ears called tympana, for detecting one another’s calls or songs.

In Drosophila melanogaster, males are also attracted by female’s pheromones and female movement. The amount of courtship a female elicit from males is used as a measure of her attractiveness. A virgin female are vigorously courted by whereas mated female elcit less courtship. Some insects use antennae to hear sound made by other species members. For instance male mosquitoes use their featherlike antennae to hear sound of the female wing –beats. Female insects become less attractive to male insects after mating.

Some female insects stop releasing pheromones after mating for examples Gypsy moth lymantria dispar and brown-banded cockroach Supella longipalpa. However they rely on sperm to regulate their attractiveness. In contrast, Helicopverpa zea stop to release pheromones for only one night after mating. The process is accessory gland products that make up the spermatophore and not by sperm. Most of the insects use pheromones to attract mates.

References

Wikipedia Contributors. Insects’ behaviour, The free Encyclopedia [internet] 2006 May 06, 09:30 UT C [cited 2006 May 08] Available from: http://en.wikipedia.org/wiki/insects#Behavior
Randall T.N. Sexual Behavior Mechanisms in Cockroaches: How Have They Managed to Survive? [Internet] 2006 May 06, 13: 04 UTC [cited 2006 May 08] Available from: http://www.colostate.edu/Depts/Entology/courses/en507/papers-2001/ran%20dall.htm
Tram T & Wolfner M.F. Seminal fluid regulation of female sexual attractiveness in Drosophila melanogaster 2006 May 06, 09:30 UTC [cited 2006 May 08] Available from: http://www.pnas.org/cgi/content/abstract/95/7/4051

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COMPARISON BETWEEN THE PLACENTAL AND MARSUPIAL MODE OF REPRODUCTION

The strongly difference between the marsupial and placental mammals is the rate of gestation or time taken by offspring in the uterus. Marsupials and placental mammals differ powerfully in their reproductive anatomy and pattern.

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.

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. In Marsupial pregnancy does not interrupt the progress of the next oestrus cycles as it is interrupted in placental. However ovarian inhibition is mediated by lactation or suckling stimulus. 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.

Marsupial and placental mammals differ strongly in their reproductive anatomy and patterns. The reproductive tracts of marsupials are fully doubled. 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. The arrangement of ducts that become female reproductive tract do marsupial differ with that of placental mammals. In some marsupials female develop a pouch and it used as a place of are nursed. In males 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.

The majority of marsupial gestation period is short. It does not make much contribution to the child. Placental mammals nourished the developing embryo using the mother blood supply, allowing longer gestation. 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 oestrus cycle and the difference also exists between red and grey kangaroo. There is appears to be significant variability related to placental development. The placental develop from maternal and embryo tissue, and lifestyle difference between species various species appears to effect the specific of the complex. Different species among the placental may can take different form of placenta. These include change in degree of contact and number of layers of tissue between tissue maternal blood supplies

The mode of reproduction is very complex in marsupial than in placental mammals. The period of gestation is short comparing to the gestation period of placentals. 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.

References

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

Wikipedia contributors. Marsupials wikipedia, The free Encyclopedia [internet], 2005 May 08, 15:02 UTC [Cited 2006 may 11] Available from http://en.wikipedia.org/wiki/placenta
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DESCRIBE THE MORPHOLOGICAL DIFFERENCES THAT EXIST BETWEEN CARTTILAGENOUS AND BONY FISH.

Bony and cartillagenous are marine vertebrates. Cartillaginous fish are the earliest vertebrate to be developed. They are found worldwide, in oceans, rivers, streams, lakes and ponds. Bony fish belong to class Osteichthyes. The subclasses of bony fish are Sarcopterygill (ray-finned fishes) and Actinopterygill (lobe-finned fishes). Sarcopterygill contain fish such as coelanths and lungfishes. Actinopterygill contains fishes such as sturgeon, gars and bowfins. Cartilaginous belong to Chondricythyes. The subclasses of Chondricythyes are Elasmobranchii and Holocephali. They vary usually in structure. Bony and cartilaginous fishes vary in shapes.

The class Osteichthyes includes all bony fish. Bony fishes include snapper, groper and gurnard. . Bony fishes are the largest group of taxonomically. It has more than twenty species world. 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 as 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. These rays are bony, branched and jointed and called lepidotrich.

Furthermore, bony fishes have one pair of gill opening, pair of nostrils as well as pair of fins. Gas exchange in bony fish occurs across the gills. They have gills that are covered by operculum (cap), they remain stationary 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. The mouth is generally at front at front of the body whereas the tail fin at the top and bottom are nearly the same in size. Sharks have small eyes which are at the top of the head.

Cartillaginous fishes belong to this class Chondricythyes. 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. They are made up of cartilage not bones. Cartillaginous 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). The fin is supported by a large basal cartillage.

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. Most Cartillaginous 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 cartillaginous is found under the head. The male fish have claspers arch (hyoid) which involved in jaw suspension.

Cartillaginous are mostly covered with cartillage 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

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

Wikipedia contributors. [Internet].Wikipedia, the free encyclopaedia, 2006 May 09, 15:40 UTC. [Cited May 09]. Available from: http://en.wikipedia.org.wiki/Bony
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THE ADAPTATION REQUIRED TO MAKE THE TRANSITION FROM AQUQTIC TO TERRESTRIAL LIFE USING AMPHIBIANS AS EXAMPLE

Amphibians belong to the phylum chordate. Amphibians are organisms which live double life, both aquatic and terrestrial. In the aquatic environment, amphibians use gills to breath as opposed to the terrestrial environment where they lungs to breath. Even though amphibians can live on terrestrial environment but they do not have the ability to adapt on land. Their inability to adapt to the terrestrial environment can be attributed to some of the limiting factors such as population growth and diseases.

In the water algae are thought to be the producers. This means that algae can be able to produce their own food. Therefore animals in the aquatic environment will feed on algae. These also apply to the amphibians in the water, because they feed on the algae. Algae also help the amphibians during the laying of their eggs; the eggs are laid and remain hanging around the algae until hatching. The young tadpoles hatched will feed on the algae until their development into adult frog and move out of the water into the terrestrial environment.

Another example of the amphibian which has the double life is the crocodile. Crocodile also spend much of their time in water, where they find it easier to catch their preys such as goats and antelopes when they coming to drink water. In a sunny day they move out of the water to bask for the sun, but when their enemy comes the crocodiles run back into the water for hiding. They are able to live on both environments, aquatic and terrestrial because as like in frogs they possess both the gills and the lungs.

In almost all amphibians, an adaptation in the terrestrial environment is not easy. Their failure to adapt to the terrestrial environment can be attributed to many limiting factors such as population growth, climate change, urbanization and the drying out of the coal swamps. As the population continues to grow, this means that more land is occupied by the people and the buildings. The more the population grows, the higher would be the demand for the fossil fuels such as coal, oil and gases. The more the fossil fuels are burnt, the higher would be the temperature. The high temperature will affect the life of the amphibians in the terrestrial environment, because of the high rate of evaporation which will occur.

The adaptations in the terrestrial environment by the amphibians will continue to deteriorate as long as human beings continue to pollute the environment through their anthropogenic factors. As amphibians are surpassed by the reptiles in the terrestrial environment, in the aquatic environment such as the rivers amphibians were multiplying in numbers in the late Permian. Even today the most suitable environment for the amphibians is aquatic environment.

In concluding paragraph, it can be easily said that amphibians have not fully adapt to the terrestrial environment. Their failure to adapt to the terrestrial environment can be attributed to the many limiting factors such as climate and the drying out of the swamps. Lastly, the aquatic environment favours amphibians.

References

Wikipedia contributors. Amphibian [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 09, 00:20 UTC [cited 2006 May 09]. Available from: http://en.wikipedia.org.wiki/Amphibian
Wikipedia contributors. Chordata [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 08, 12: 15 UTC [cited 2006 May 09]. Available from: http://en.wikipedia.org.wiki.Chordata

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DESCRIPTIONS OF ALL MEMBERS OF HOMINIDAE

Hominidae are great apes that include human, chimpanzee, gorillas and orangutans. Originally the group was restricted to human and their extinct relative. However the classification was revised. Chimpanzees, gorillas and human are closely related species and orangutans are slightly less close phylogetically.

Humans are bipedal primates belonging to the mammalian. Humans have a highly developed brain capable of abstract reasoning, language and introspection. Human are social by nature. Human are particularly adapt to utilizing system of communication such as language for self expression and exchange ideas. Social structure of human consists of cooperating and competing groups. Human are also inborn appreciation for enjoyment, beauty and aesthetic which combined with a human desire for self expression, has led to cultural innovations such as art, literature and music.

Humans need to understand and influence the world around them, seeking to explain and manipulate natural phenomena through science, religion, philosophy and mythology. This natural curiosity has lead to the development of advanced skills and tools; human are only species that is able to make fire, cook their own food, exploration of spiritual concepts such as the soul and deities.

Gorillas are the largest primates. Gorilla are divided into species and either four or five subspecies, with 92-98% of its DNA being similar to that of human. Gorillas are the second closest relative of human after two chimpanzee species. Gorillas are knuckle walkers. The height of adult males ranges between 1.65mto 1.75m and in weight from 140 kilogram to 165kg. Gorillas are covered with brown hair in most of their body. They have a large head with a bulging forehead, tiny ears, and small dark to brown eyes. They exhort extreme sexual dimorphism, males being more twice than size of females. Gorillas live in open canopy place in order for them to access vegetation. Gorilla eats vegetation such as leaves, fruits, shoots and stems. Gorilla social system is usually composed of single adult male with many females. In general, female are not generally related to each other, their only link is that they like the same guy.

They are the only species which are existing species in the genus Pongo and family poningae. The majority of Orangutans are arboreal; this is clearly shown by anatomically in the structure of their hips and shoulders. Although they have mobile joints but they can not swing like gibbons. It is more like the climb around with hand Orangutans are too heavy to fling themselves. Sometimes they get down and walk from one tree to another. Orangutans also exhibit size of dimorphism. When they reach adulthood, males throat sacs and face flanges. Adult males are approximately 1.4m tall and up 82kg in weight. They are spending nearly all of their time on the trees, making a nest in the trees every night. Orangutans are really endangered. They are found in Sumutra and little on Borneo. Orangutans are also fruit eaters and they move slowly. Orangutans may move few hundred meters per a day. However, they can able cover many territories in a year. Orangutans have little social organization. Sometimes female will copulate with immature males who do not have secondary sex characteristics. Sometimes young males rape females which are unusually in primates other than human.

Chimpanzees (chimps) are knuckle-walkers, and are terrestrial. The majority of primates walk on the flat on their hands, but chimps walk on their knuckles with their hand turned over. The forearms are longer than the hind limbs, and the bonobo has a short thumb. The average mass for an adult male bonobo is approximately thirsty nine kilogram whereas the females are approximately thirty kilograms. They are covered with black hair on most of their body. Chimp exhibit less size dimorphism than other apes, the female’s prominent genital swelling when they are in estrus. Chimps have quite big testicle relative to size especially compared to gorilla. Chimps found a little in western Africa and across the Equatorial belt in mid-Africa. Chimps are mostly eat fruit but they also eat termites, ants, flowers, seeds, shoots, leaves, bark and shrub level forest. Male tend to hunt. They will eat monkeys, antelopes, pig and anything catches able. They are usually hunted in groups. Most of the grooming bouts and instances of food sharing occur between males and females. In chimps females to female relationships is strong.

References

Wikepedia Contributors. Human, Free Encyclopaedia [Internet] 2006 May 10, Cited on 2006 May 11, 10:12 UTC, Available from http://en.wikipedia.org/wiki/chimpanzee

Wikepedia Contributors. Gorillas, Free Encyclopaedia [Internet] 2006 May 10, Cited on 2006 May 11, 12:45 UTC, Available from http://en.wikipedia.org/wiki/Gorillas

Wikepedia Contributors. Human, Free Encyclopaedia [Internet] 2006 May 10, Cited on 2006 May 11, 13:30 UTC, Available from http://en.wikipedia.org/wiki/Human

Wikepedia Contributors. Orangutans, Free Encyclopaedia [Internet] 2006 May 10, Cited on 2006 May 11, 14:17 UTC, Available from http://en.wikipedia.org/wiki/Orungtans
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Monday, May 15, 2006

BIRDS ARE THE LIVING RELATIVE OF DINASAURS

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

The researchers said that a Tyrannosaurus rex dinosaur had soft thighbone tissues which strongly suggest that it was a female, and nearly to lay eggs. The bone tissue was strongly similar to that made inside the bones of female birds. Mary Higby Schweitzer of North Carolina State University in Raleigh indicated that no other living type of animal, when they are producing the hard shells of eggs just before they lay them. The emphasis to demonstrating gender, it also links the reproductive physiology of dinosaurs to birds very closely. It indicates that dinosaurs produced and shelled their eggs much more like modern birds than like modern crocodiles.

Mudge said that Dinosaurs were the ancestor of the birds or stock from which the latter have been derived by evolution. The bones of the hinds feet of a few species closely to look like those of birds, some of the bones were hollow that indicate that other resembles will be found and that bird was the outgrowth of reptiles. Dinosaurs had three toes like the bird, some of European and nearly of the entire American, have four and five toes and structure. When four toes were seen in the dinosaurs, the fourth never rotate 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.

Sinosauropteryx was the first dinosaur with non flying to have proto feathers and it was the earliest bird-like dinosaur. This clearly indicate that feathers arose before arose before flight. This also shows the common ancestor of bird 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 finds strengthen the theory that birds evolved from dinosaurs. Although these new species had some form of primitive feather, these feathers were symmetrical in cross-section which made then useless for flight. The dinosaurs' arm-length was also insufficient for flight. The feathers were most likely used as insulation, keeping in body heat. 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 specimen 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.

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 like bird are 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. 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 suggest some parental was used to feed young dinosaur, possibly the adult dinosaur go over nutrition into the mouth of 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. A number of feathered dinosaurs provided clear evidence of the close relationship between dinosaurs and birds.

References

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
Wikipedia Contributors. Dinosaurs are warm or cold blooded, The free Encyclopaedia [internet] 2006 May 06, 08:30 UTC [cited 2006 May 08] Available from: http://wikipedia.org.wiki.dinosaur
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DISCUSSION OF ECHOLOCATION IN BATS AND WHALES

The term echolocation refers to the ability that bats and toothed whales posses and enables them to locate and discriminate objects by listening for echoes. Bats and whales use echolocation for different purposes, for instance hunting, navigating and to judge the distance of the object.

Echolocation in bats was found in 1930s that bats use high pitched sounds like natural sonar to locate food and navigate. Bats are capable of hearing the object when it bounces off. When an object the hits an echo sound come back. They can able to judge the distance, movement as well as size of the objects in their path. Some of the bats are able to send their echolocation through their sound and through their nose but the majority of bats use their mouth. They hold their mouth open as they fly.

Different species of bats uses different pattern of echolocation frequencies to find food and navigate. The scientists used detector like Anatbat bat to record echolocation pattern for use of identifying different bat species at night and inside the dark caves. Bats have the ability to see through sound. The bats can identify objects by the sound of the echo. They can even tell the size, shape and texture of tiny insects from its echo.

In the basic principles of echolocation, Bats sound the same way as human by moving air past their vibrating vocal chord. Bats use this echolocation process to gather information in order to see the world around them. Scientists believe that the strange noise that structure found in some bats serves to focus the noise for more accurate pin pointing of insects and other prey. A bat emits a sound wave and listens carefully to the echoes that return to it. The brains of bats process the returning information the same way. The bats are able to detect if the insects is on the left or right by using the sound. If the sound reaches the right ear before it reaches the left ear it means that the insects are on the right. The bats have ears which have complex collection of folds of the outer ear that help it to determine an insect’s vertical position. Echoes coming from below will hit the folds of the outer ear at different point than sounds coming from above, and so will sound different when they reach the inner ear of the bats.

Whales used echolocation mainly for navigation and hunting. Toothed whales have developed the capacity of emitting sounds that travel from foreheads and reflect off objects. Toothed whales echo late by producing clicking sounds and then receiving and interpreting echo. Toothed whales use echolocation to sense objects. Whales sent out high pitched whales, the sound bounces off, the objects and some returns to the whales. The whale interprets this returning echo to determine the objects shape, direction and distance. Toothed whales produce sound to overlapping functions. That is communicating and echo locating.

Whales produce lower frequency, longer duration’s tones such as groans and moans. These sounds are very loud and they do travel very far. Whales may be able to use the echo’s produced by these sounds to navigate and the echo’s returned as allow frequency sound bounce off features in the oceans basis such as islands, sea mounts and continental shelves, and this could easily give the whales information about its environment. The sound also gave the whales little information about the other in the closer surrounding area.

Echolocation plays an important role to the life of bats and whales. Both whales and bats are able to hunt food, navigate and to judge the distance in which the insects is located. They have capacity to emit sound that travel like waves and reflect object.

References

Wikipedia contributors. Bats [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 09, 00:20 UTC [cited 2006 May 09]. Available from: http://en.wikipedia.org/wiki/bats

Wikipedia contributors. Whales [Internet]. Wikipedia, The Free Encyclopedia; 2006 May 08, 15: 15 UTC [cited 2006 May 09]. Available from: http://en.wikipedia.org/wiki/whales

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Tuesday, May 09, 2006

DESCRIBE HOW FIRST PLANT AND ANIMALS EVOLVED AND BECOME DEPENDENT ON EACH OTHER.

Plants and animals are complex organisms. They are consisting of much different kind of cells. The scientists believe that there are more than 260.000 of plant species. Some plants are very short, they can be hardly seen. However, other plants are bigger than human or animals. In California, there is one of the biggest living plants on the earth that is called sequoia trees. Some stand more than two-hundreds and ninety feet (eighty eight meters) high and measure more than thirty feet (nine meters).

The first fossils were formed during the origin of life. These were the fossil of bacteria. The bacteria consist of single cell. After three and half billion years the first animal evolved. Bacteria used sunlight to manufacture their own food. These cells were prokaryotic meaning that they had no nucleus inside of the cell. Bacteria are still prokaryotic even nowadays. Three billion later the first animals evolved.

It was earliest known multicellular eukaryotic animal fossil. These involved from “colonies” of single celled organisms. At this moment animals were small and simple (segmented worms, metazoans, coelenterates arthropods) finally evolve into all of the bigger and more multipart animals. At this moment, there was an unexpected “burst” of evolution, often called the Cambrian explosion. As results of explosion different type of invertebrates were involved in the ocean. The animals were consisted with hard shell which formed fossil after the death .These fossils include trilobites and brachiopods. At this moment the Oxygen in the atmosphere attained two percent. The first fish evolved.

The ozone layer was formed in the atmosphere due to high percentages of oxygen in the atmosphere. The ozone layer is essential because it blocks ultraviolet rays of the sun. It was nearly impossible for organisms to exist out of water because they would be killed by ultraviolet rays. As a result, it was possible for life form to involve on land. At this time, the ozone was sufficient to permit life on land. The earliest plants evolved. Plants existed on land before animals. The earliest plants were simple. The earliest plants were like the moss of nowadays.

Close to 2.5 billion years ago, the earth surface and atmosphere were stable enough to support primitive life. Single celled organisms started to develop in the seas that covered the planet. The blue algae appeared and across the seas. They used sunlight and water to manufacture their own food, during the process oxygen is created. As the blue-green grew on earth’s seas, they start to fill the atmosphere with oxygen. The oxygen which is produced by blue-green algae is used by other organisms to grow. This organism will produce carbon dioxide carbon dioxide, which algae needed to perform its functions.


Plants are very much essential in the nature cycle. The oxygen that animals breathe comes from plants. Through the process of photosynthesis, plants take energy from the sun, carbon dioxide from the air, water as well as from the soil. As a result, they give off water and oxygen. Animals take part through respiration.

References

Wikipedia contributor

THE WATER VASCULAR SYSTEM THAT CHARACTERIZES ANIMALS THAT OCCUR IN THE PHYLUM ECHINODERMATA

Enchinodermata are a phylum of marine animals found in the ocean at all depths. The echonodermata has six classes which are Asteroidea example starfish, Concentricycloipea example sea daises, Crinoidea example feather stars, Echonoidea example sea urchin, Holuthuroidea example sea cucumbers and Ophiuroidea example brittle stars. The phylum is containing approximately six thousands species and constitute the group of deuterostome invertebrates. Enchinodermata are characterizes by a unique vascular system.

The vascular system can be defined as a hydraulically controlled system consisting of a circumoral ring around the esophagus with connecting radial canals each leading to an ambulacrum. The vascular system can be closed and opened. Crinoids have an open vascular system. The water vascular system is used by echinoderm such as sea stars and sea urchins. They may be evolved from tentacular system similar to those of deuterostone phyla such as tentacle pterebranch hemichordates. However there are different kinds of derived features of the vascular system, these include an embryological origin from left mesocoel, podia arranged along branches (ambulacra), and a central curcumesophagel ring.

The characteristics of vascular system do differ according to class. Crinoid has madreporite with multiple pores and madreporite may be replaced by minute scattered openings called hydropores. It has no polian vesicles, tube feet suckers and ampullae on podia. Podia penetration is between plate and podia spacing is stumble. In asteroid madreporite of vascular system has aboral. Some asteroid have tube feet sucker whereas others do not have. Podia penetration is between plates. It has ampullae on podia.

In Ophiuroid, madreporite of vascular system has oral. It has a polian vesicles Ophiuroid does not tube feet sucker. Podia penetrations are found between plates. Podia spacing is paired. It does not have ampullae on podia. In Echinoid madreporite has aboral. It has polian vesicles, tube feet sucker may be present or absent. Podia penetration is paired through plates. Podia spacing is stagger. It has ampullae on podia. In Holothuroid madreporite are internal. It has polian vesicles. Tube feet sucker a may be present or absent. Podia penetration between suckers may be present or absent. Podia penetrations are found between plates. Podia spacing is stagger. It has ampullae on podia.


Vascular systems network canals to create hydrostatic pressure, to help the starfish to move. Water enters through sieve plate or madreporite on aboral surface into a short stone canal. Stone canal connects to a circular canal around the mouth called the ring canal. Five radial canals carry water to hundreds of paired tube feet. Bulb-like sacs or ampulla’s on the upper end of each tube foot contract and form suction to help move, attach or open bivalves’ mollusk shells and create suction to pull valves apart slightly. Starfish exerts its stomach through its mouth and inserts into prey. Stomach secretes enzymes to partially digest bivalve then stomach withdrawn and digestion completed inside the starfish.

The vascular systems perform different functions in echinoderm; these include locomotion, respiration, and feeding. Most of the sensory neurons are located at the podia which are also part of this organ. Most oxygen enters starfish through diffusion into the tube feet. This water vascular system can be used as a source of oxygen for respiration. Many sea cucumbers also have a complex respiratory tree. The surface of many echinoderms is perforated by extensions of the body wall. Through these thin membranes of the body wall respiration can take place.

The vascular systems are very essential to echonodermata. They are responsible for digestion, locomotion and respiration. Even though echonodermata do differ with some characteristics but they all have vascular system. The vascular system is either open or close.

References

Denning D & Russell B. The Biology of Echinoderms [Internet] 2006 May 05, 12:30 UCT [cited 2006 May 07] Available from: http://ebiomedia.com/prod/BOechinoderms.html%202000-2005

Wikepedia Contributors. Water vascular system [Internet] Wikipedia, The free Encyclopedia, 2006 May 05, 11:15 UCT [Cited 2006 May 07] Available from: http://en.wikipedia.org/wiki/water vascular

Gregory A.W. Echinodermata. [Internet] 2006 May 05, 14:10 UCT Available from: http://tolweb.org/Echinodermata
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