Please help!!!?

Question

I need to find out which of these are a charteristics of a Viruses.
These and these ONLY are what I need in my answer, help would be highly appriciated!

-Microscopic
-Submicroscopic
-Like Bacteria
-Pathogenic
-Parisites
-Reproduce by fission (I'm almost positive it isn't this...)
-Obtain nutrients from a host cell

Answer 1

Do your own homework.

Answer 2

They are submicroscopic. A virus is inactive, does nothing until it gets inside its host. When inside it takes over!
For example the HIV virus which has proteins on the outside of its caspid coat which enable it to enter the cell actually takes over the genome to a certain extent. It stops the cell from carrying out normal transcrition and instead instruct it to trnascribe viral genes. These include protein coats which protect from recognition from the immune system, viral genome...
Once the cell is loaded with Virus's, the cell burts leaving the viruses to infect other cells.

Answer 3

A virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism. At the most basic level, viruses consist of genetic material(DNA or RNA) contained within a protective protein coat called a capsid.Viral populations do not grow through cell division, because they are acellular; instead, they use the machinery and metabolism of a host cell to produce multiple copies of themselves.
it is still a mystry that whether viruses are living or non living.while outside the host they can be crystalized and can be stored in glass jar. but once inside the host they replicates in geometrical progression.some deadly viruses are HIV(causes AIDS), rhabdovirus(cuse rabies).
thank you

Answer 4

Viruses vary considerably in size and shape. Three basic structural groups exist: isometric; rod shaped or elongated; and tadpole-like, with head and tail (as in some bacteriophages). The smallest viruses are icosahedrons (20-sided polygons) that measure about 18 to 20 nanometres wide (one-millionth of a millimetre = 1 nanometre). The largest viruses are rod shaped. Some rod-shaped viruses may measure several microns in length, but they are still usually less than 100 nanometres in width. Thus, the widths of even the largest viruses are below the limits of resolution of the light microscope, which is used to study bacteria and other large micro-organisms
Human parasites include viruses, rickettsias, bacteria, fungi, protozoans, worms, and flukes. Viruses and rickettsias are not usually considered living organisms, but they have parasite-like methods of transmission between hosts and obtain all their nourishment from the host. In humans, bacteria and fungi cause the most common infectious diseases. Protozoans also cause disease. The lethal human disease sleeping sickness, for example, is caused by the one-celled organism Trypanosoma; a similar organism causes malaria. The debilitating disease schistosomiasis is caused by a liver parasite (see Fluke). Other human parasites include various species of worms (see Flatworm; Roundworm). See also Tropical Diseases.

III. PARASITIC PLANTS


Mistletoe Plant Growing in a Tree






Mistletoe Plant Growing in a Tree
A variety of small, parasitic, evergreen shrubs called mistletoe are native to Europe and the United States. These plants infest trees such as pine, fir, apple, and juniper. Some mistletoes are hemiparasites, relying on their host tree for some, but not all, of their nourishment.
Encarta Encyclopedia
Mark Hamblin/Oxford Scientific Films



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All parasitic plants feed on other plants. They may be either partial parasites, deriving some of their nutrients from the host, or total parasites, completely dependent on the host for food. Partial parasites have green leaves and are capable of synthesizing carbohydrates, proteins, and fats by the process of photosynthesis; however, they derive all their water, nitrogen, and mineral salts from the host.

Common examples of such parasites are the painted cup, parasitic on roots, and mistletoe, parasitic on branches. The mistletoe is typical of a group of parasitic plants that never form roots of their own; the seeds of these plants are carried from tree to tree by birds, and develop penetrating outgrowths, known as haustoria, that pierce the host and enter the conducting system. Total parasites have vestigial leaves without chlorophyll and never have functioning roots. In dodder, the seed germinates in the ground, forming a small root attaching the plant to the soil but deriving no food from the soil; a long, thin, pliable stem grows above the ground until it contacts a green plant, which it then climbs up.

The ultimate in total parasitism is exhibited by certain tropical plants of the family Rafflesiaceae, which have neither stems nor leaves; they grow only on specific species of green plants. The germinated seed sends haustoria directly into the host; the only other organs of the parasite are nonpetalled flowers, composed of five huge, fleshy sepals that give off the odour of decaying meat. Insects, attracted by this distinct odour, carry the

About 200 species of bacteria are pathogenic, or disease-causing, for humans. Pathogenicity varies widely among various species and is dependent on both the virulence of the particular species and the condition of the host organism. Among the more invasive bacteria responsible for human disease are those that cause cholera, tetanus, gas gangrene, leprosy, plague, bacillary dysentery, tuberculosis, syphilis, typhoid fever, diphtheria, undulant fever, and several forms of pneumonia. Until the discovery of viruses, bacteria were considered the causative agents of all infectious diseases
With aseptic canning, food is cooked and sterilized first, then canned under sterile conditions. This helps preserve flavours and nutrients, as much shorter heating times are involved. Radappertization is a process of preserving foods in vacuum-sealed cans or three-layered flexible pouches with sterilizing doses of ionizing radiation. The source of radiation may be gamma rays of cobalt-60 or caesium-137, X-rays, or electrons. Because the food is irradiated while frozen (-40° to -18° C or -40° to 0° F), the limitations of conventional heat sterilization are not encountered. As with frozen foods, radappertized foods, prior to vacuum sealing and freezing, must be heated to 70° to 80° C (158° to 176° F) to inactivate viruses and autolytic enzymes that cause loss in texture and flavour. Use of this method on a commercial scale awaits approval by national health authorities.

sorry could not find all ..... hope this will do some good

Answer 5

Submicro.
pathogenic
parasite

Answer 6

viruses are parasites,and they obtain nutrients from host cells

Answer 7

Viruses are different from anything else found on earth and are mainly characterized by their size, shape, and half alive/half dead existence.

The big difference between viruses and all else, is that fact that viruses are so small they can not be viewed without the help of an electron microscope. This is because viruses are, on average, smaller than a regular wavelength of visible light. In effect, the viruses can hide between light waves, thus making them colorless. They can not be seen by the naked eye or a regular microscope. Viruses are so small in fact, that the largest virus is equal in size to the smallest bacteria. The smallest virus measures only 20 nanometers in length. Because of their incredibly small size, viruses are extremely hard to study and understand.

Shape is also a defining characteristic of viruses. The basic shapes viruses tend to take are rods, filaments, crystals, helixes, polyhedrons and spheres, with added extensions. Almost all human viruses are close to being spherical. Every virus carry proteins and nucleic acids in a protective coat. This protective membrane is called the capsid. Extensions on any virus are called antigens. The antigens allow viruses to identify, attack, and enter its target host. Viruses are not classifiably alive or dead. They seem to be in limbo between each state. Viruses exist this way because they are strictly parasites. That is, they can not survive and thrive without a host or group of host cells. The hosts provide viruses with all the chemicals and molecules they need to survive and reproduce. You might think of viruses' as robots that need to take over a factory to make more of themselves. Without that, the viruses are dormant. Viruses can lie dormant within any host or environment until the proper conditions for their activity are provided. This is why we sometimes say that viruses have incubation periods of certain lengths. Some viruses are also classified as 'persistent viruses'. Such viruses can enter and exit host cells without killing them. Even so, each different virus is stimulated by different conditions and they all have different, specific functions they affect in their host. They are mysterious and dangerous creatures.

Scientists say, that viruses have existed since the beginning of life on Earth. Viruses have plagued animals, plants, fungi and protozoa as long as anyone can possibly trace back in time. Even as the years passed, and life evolved from a primitive 'primordial ooze' into more complex vertebrates, viruses maintained their reign of terror. But does this mean that viruses haven't changed at all over the millennia? Of course not. Just as life evolved, developed and adapted to the new and changing environment, so did viruses.

In their humble beginnings, viruses existed primarily as unprotected genetic strands that carried hereditary information from newly developed life to its offspring. They were messengers. Over time the ever-changing environment of Earth influenced many changes in the method of this transfer of information. The genetic messengers evolved as their hosts did, and they eventually developed protective outer casings to protect themselves from the elements. As life became more complex and cells began to self-reproduce, viruses lost their primary function. Cells took over the messenger role, and so viruses began to infect rather than exchange genes with their hosts. Almost seemingly set on revenge, the newly evolved viruses infected every living thing, and proscribed each cell with their own genetic formulas. They became parasites. They were unstoppable.

Continuing to progress, viruses developed the ability to jump from species to species by changing their genetic material to fit the new hosts' bodies. They were determined to survive throughout the centuries no matter the cost of life. The viruses of today are highly complex and elusive. Over their one million plus years on Earth, viruses have developed their own protection, means of survival and efficient ways of infecting their hosts. The medical researchers of today are constantly studying viruses in hopes that we will soon be able to understand them. But fighting viruses is like fighting an enemy who keeps up with every new advancement in weapons technology; the more time they have, the more precocious and powerful they become.

About 200 years ago Edward Jenner might as well have been known as the luckiest man alive. It was in the year 1796 that this country doctor made one of the most astounding discoveries ever. Of course, at the time Jenner didn't know the magnitude of the medical powers he was experimenting with. The experiment Jenner performed would now be considered extremely crude and dangerous. While practicing medicine in the small town of Gloucestershire, England, he decided to experiment with the effects of cowpox and smallpox. Cowpox was a common occupational hazard in the dairy country of England. Coming from sores on the udders of dairy cows, cowpox was a highly contagious disease with caused fever, nauseas and pustular sores on certain areas of the skin. Based only on an old wives' tale he heard as a teenage apprentice -- milkmaids who had been infected with cowpox never became infected with smallpox—Jenner decided to infected his first son with cowpox. A few days later, he infected Ed Jr. with smallpox. His son never got the disease.

With this encouraging result, Jenner decided to infect a young boy, James Phipps, with the contagious material of both diseases. This boy's cowpox infection also healed quickly, and he was back in perfect health after only a short amount of time. Afterwards James was injected with smallpox, but was seemingly unaffected, just like Jenner's son. Although no one at the time understood what exactly had prevented the boy from becoming infected with smallpox, it was certain that this obscure doctor had performed a miracle. Dr. Edward Jenner had discovered the first official vaccine, recorded on the 14th of May 1796. Throughout 1796, cowpox invaded the English countryside, providing Jenner with yet another opportunity to test his promising vaccination theories. He not only began investigating cases of milkers who were protected from smallpox by cowpox, but he also studied other inoculations for diseases such as swinepox and a number of bacterial infections. Jenner went on to publish papers on his experimentation. The paper describing the first discovered vaccination was appropriately titled, "An inquiry into the Causes and Effects of the Variolae Vaccineae, a Disease Discovered in some of the Western Counties of England, particularly Gloucestershire, and known by the name of the Cowpox by Edward Jenner, M.D. F.R.S. & C." Within two years, it was translated into many languages and reprinted all around world. Jenner became famous, but met both good and bad criticism. Newspapers and Magazines mocked his work. They would print cartoons showing vaccinated patients sprouting horns and mooing, with titles like "The Cowpock – or the Wonderful Effects of the New inoculation." Jenner had no idea why the vaccination worked, just that it did, but he spawned the first organized field of viral study. A year before he died in 1823, another great man that would change our view of the world was born.

Ninety years after Jenner's first vaccine experiments, a French chemist and renowned microbe hunter, Luis Pasteur, performed a similar marvel. Pasteur, at the time, had been studying the effects of another deadly disease of that time: rabies. He had done a great deal of research with animals, and had begun to notice certain things about infected body tissue. It seemed that as the tissue was transferred from species to species, it became less infective and less potent. Pasteur's theory, was that if this weakened tissue was somehow injected into humans already infected by rabies, that it would protect them from the disease's deadly effects. Pasteur, like Jenner, first tested his vaccination on a young boy, this one bitten badly by a rabid dog. This vaccination was also successful, and the boy remained rabies free for the rest of his life. Pasteur was more conscious of what he was doing than did Dr. Jenner, but he was never able to locate the 'bacteria' that he thought caused rabies.

Still, even with these amazing break-throughs in disease prevention, none of the scientist of the time had any clue to what kind of 'monster' they were dealing with. In 1892, Russian Dmitri Ivanovski discovered the very first clue that set these microbes in a class of there own. Even though he was not in the practice of studying human diseases, Ivanovski gave us the first proof that viruses so exist. Ivanovski's main research included the tobacco mosaic disease. Using special filters Ivanovski attempted to separate out the bacteria that was causing the infection. To his dismay, even after several iterations of the filtering process and exposing it to alcohol and fermalin, the tobacco plants continued to become infected and die.

Six years later, a Dutch botanist, Martinus Biejerinck performed a similar experiment. However, he had not read about Ivanovski's work since it was only published in not very well known Russian journals. He performed the same filtering method, but he took it a step further. Though the filtering method might have removed the bacteria, it might not have removed toxins created by bacteria. These toxins could also cause diseases. To see if it was the toxins, he infected a healthy plant and then tried to infect another plant with fluid from the now infected healthy plant. If it was toxins, the next plant would not be infected. It did however, telling Biejerinck that it wasn't toxins. Trying something different, he let the sap from an infected plant sit for three months and tried to infect a healthy plant. It still infected. He tried adding alcohol and formalin which would be enough to kill microorganisms. It did nothing to prevent the fluid from infecting again. So what was causing this disease in these plants if it wasn't toxins or bacteria? Perhaps it was bacterial spores? They could pass through the filters. To test this, Biejerinck heated the fluid to ninety degrees centigrade. All of a sudden, the fluid stopped infecting the plants! However, this didn't prove it was bacterial spores. Quite the contrary. It takes a hundred degrees centigrade to kill the spores, not ninety. This was something else completely.

Through their research, Biejernick and Ivanovski had discovered a new disease-causing agent. Biejernick believed this agent to be a fluid, he called it a "contagious living fluid." Later this liquid was renamed 'virus' for the Latin word poison.

The average virus experiences a rather dull presence on Earth. In fact, the sole purpose of a virus's existence is to duplicate itself and create more viruses.

There are basically three completely different 'types' of viruses. They are animal, plant and bacterial viruses. Each type of viruses is independent of the others. Meaning that a plant virus can not be transmitted to a bacterium and such. So far, there has never been any type of life found on Earth, which is not susceptible to viruses. Some species have more than one hundred different viruses plaguing their kind.

Within each classification, viruses are specific to a certain kind of cell. Viruses tend to be very picky about their hosts. They also have preferred ways of entrance into their hosts. A virus' method of entry is very specialized, and it is one of the main ways a virus is able to locate it's victims. Take, for example, a virus that targets host cells located in the stomach. If a person inhaled such virus particles they would not be harmed. On the other hand, if any virus molecules were ingested into the stomach, the hosts would immediately be infected. Some viruses even require cells to be in certain stages of life. These viruses may prefer actively dividing cells or cells that are younger.

Viruses use a simple marking process to identify the cells they attack. All viruses have special molecules on the outer covering that can search out and identify particles on cell surfaces. Every cell has a unique set of markers that identifies it to other cells. These surface molecules dictate the cells the each virus can recognize and infect. The interaction between the virus surface and the cell surface determines whether infection of the host will be successful or not. Host cells have to be of a very specific type or viruses will not be able to replicate and survive. All cells have surface receptors, which viruses use to identify the cell by their markers and if they match, attach themselves to it. Both sides have to be in good contact, and conditions have to be just right. When a virus securely attaches itself to a host cell in good condition, the infection begins.

Viruses do not possess any life sustaining characteristics, and do not require any nutrients. In fact, without a proper host viruses lie dormant indefinitely. Infection takes place when a virus comes in contact with its intended host. As soon as a virus encounters its victim, it attaches itself to the organism. Furthermore, most viruses prefer a certain type of host cell and a specific mode of entrance. Naked viruses, those without a structured casing, directly enter the cells while other types of viruses fuse themselves to the outsides of their victims and inject their genetic material inside the cell. Once the genetic material of a virus is transferred to the host cell, the virus can 'take over' by incorporating its DNA into the hosts DNA much like they used to do in the prehistoric days. The infected cell is essentially a factory in charge of virus manufacturing. In a process called budding, mature viruses leave the cell a few at a time. Lysis is the much more devastating cousin of budding. In lysis, the cell membrane of the host is completely destroyed, killing the cell. The new viruses are unleashed instantaneously. Almost all viral infections result in the death of the host, but in rare cases viruses leave their host cells alive. When this happens the cells are normally damaged beyond repair. With each successive transmission between hosts a virus is able to replicate itself thousands of times, and ensure the continuance of its reign of terror.

Most people relate viruses with 'the cold' and 'the flu,' viral infections that bring out a familiar set of symptoms, and then leave as quickly as they show up. These are examples of acute infections. Acute infections cause many of the minor illnesses that humans have experience with. This type of viral infection is, on the most part, rather harmless causing discomfort and minor indications of cell damage. Acute infections, however, can become much worse if they are recurring and do less damage to host cells. In this case acute infections become chronic infections. Chronic infections can be dangerous and sometimes deadly. In cases of chronic infection host cells may not be damaged at all, but their functions may be disturbed. This can cause serious recurring illness and disease. In many cases, chronic infections can be monitored and the viruses that cause them can be cultured in labs. However, scientists can not culture the types of viruses that cause latent infections. Latent infections come from viruses that can manage to evade attacks of the host's immune system. Latent viruses are persistent and frequently cause deadly diseases.

Answer 8

wat do u need help wit