Disease And Average Life Span Biology Essay

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The average life span at the beginning of the 20th century was about 50 years old. By the time the century came to a close, the average life span had risen to roughly 76. It has changed drastically because over time scientists have discovered large amounts of information about diseases. They have uncovered certain characteristics each disease has, including their different affects on the body. The characteristics and different affects have been important information for doctors and other health care professionals when making a diagnosis. Many times, different diseases have the same affects on the body. In those cases, doctors depend on medical tests such as blood draws, and x-rays to confirm which disease has been acquired.


The spread of disease across the world has been one of the most influential biological factors throughout the world. The World Health Organization (WHO) estimates that over 35 million people die each year of chronic disease (Caribbean Community Secretariat, 2007). In 2005, the National Center for Health Statistics reported that there were 27.6 million office visits to physicians and 3.5 million emergency room visits for diseases in the United States (Alic, 2009). This paper will discuss the difference between a communicable and non-communicable disease, various disease causing organisms, and ways to prevent disease.

Diseases are harmful changes that interfere with the normal appearance, structure, or function of the body and its parts. They have various causes which can be differentiated into two broad groups: communicable and non-communicable. Communicable diseases can spread from one person to another and are caused by microscopic organisms that invade the body. Physicians refer to these disease causing organisms as pathogens (Ehrlich, 2009). Sometimes a disease does not develop because of the actual organism, but instead the toxin that the organism produces after entering the body. Many communicable diseases spread in more than one way. (Wisconsin Department of Health, 2010).Communicable diseases can spread from one infected person to another, from an animal or insect to a human, and even from touching contaminated objects and surfaces such doorknobs, counter tops, and tables. A few examples of communicable diseases include lower respiratory infections, tuberculosis, measles, meningitis, diarrheal diseases and HIV/AIDS.

Non-communicable diseases are not known to be caused by infectious agents, and are not communicated from one person to another. Unhealthy diet and physical inactivity are the leading causes of non-communicable diseases (Mehan, 2006). High blood pressure, high cholesterol, poor ingestion of fruits and vegetables, excess weight, physical inactivity, and tobacco use are significant risk factors in obtaining a non- communicable disease (Mehan, 2006). Some of these diseases include osteoarthritis, osteoporosis, and Alzheimer's disease. These are degenerative disorders that involve the progressive breakdown of tissues and loss of function of body parts. Non communicable diseases causes blood vessels to clog with fatty deposits, bones to become weak and break easily, and joints to become stiff and hard to move. The majority of non-communicable disease deaths are from heart disease, cancer, and type two diabetes (Mehan 2006).

Pathogens are different disease causing organisms that carry or cause communicable diseases. Handshakes, hugs and kisses are examples of how many pathogens are spread from person to person. These pathogens leave one person through the wounds, mucous membranes, and body openings and enter another person through similar paths (Science JRank.org, (2010). Pathogens can also be spread through moisture droplets when an infected person sneezes or coughs, just as sexually transmitted diseases are transmitted during sexual contact. Other pathogens, such as an insect, must have a carrier. For example, a mosquito would be considered a carrier when biting a person because they distribute a malarial parasite into a person’s blood stream. Several types of pathogens are passed on through contaminated food and water, and other pathogens can only be passed on by contaminated food or water. Most pathogens that infect people include different types of bacteria, viruses, fungi, and protozoans (Science JRank.org, 2010).

Bacteria are a large group of microorganisms. Generally they are one celled and found in humans, animals, plants, soil, air and water (Marieb, 2009). Some species of bacteria are harmless and beneficial to humans; these are called resident bacteria. On the other hand, some infectious bacteria are pathogens that cause harmful diseases such as cholera, leprosy, pneumonia, strep throat, tetanus, and tuberculosis (Elrich, 2009). Bacteria that are pathogenic in humans include bacilli, rickettsia, spirochetes, staphylococci, and streptococci. Bacilli are rod shaped spore forming bacteria. Tetanus is causes by the bacillus clostridium tetani and is transmitted through a cut or wound. Rickettsia is a small bacterium that lives in lice, fleas, ticks, and mites (Elrich, 2009). Rocky Mountain spotted fever is caused by Rickettsia rickettsii and is transmitted to humans by the bite of an infected tick. Spriochetes are spiral shaped bacteria that have flexible bodies and are capable of movement. Lyme disease which is caused by Borreleia burgdorferi is transmitted to humans buy the bite of an infected deer tick. Staphylococci are a group of about 30 species of bacteria that form different groups that sometimes resemble grapes. Most staphylococci are harmless and reside normally on the skin and in mucous membranes of humans. However, others are capable of producing very serious infections. Strepococci are bacteria that form a chain. Many streptococcal species are harmless, while other members of this group are responsible for illnesses including strep throat, meningitis, endocarditis and necrotizing fasciitis (Elrich, 2009).

Viruses are much smaller than bacteria and live only by invading other cells (Elrich, 2009). They are not cellular but are a genetic substance surrounded by a layer of protein. A virus has genes made of DNA or RNA which allows it to make copies of itself, but they are only able to survive and reproduce inside a living cell. Once inside the living cell, it instructs the cell to make new virus particles. The new virus particles are then released to surrounding tissues and continue to infect more and more cells. Diseases caused by viruses include mumps, measles, influenza, rabies, hepatitis, poliomyelitis, smallpox, AIDS, and certain types of cancer (Brown, 2000). Herpes zoster, also known as shingles, is an acute viral infection and occurs when the dormant varicella virus from chicken pox is reactivated later in life. Measles is an acute highly contagious infection caused by the rubeola virus and is transmitted by mucous droplets from the respiratory system. Rabies is a viral infection that is transmitted to humans by the bite or saliva of an infected animal, and the west nile virus is spread to humans by the bite on an infected mosquito.

A fungus is a simple parasitic organism and there are over 100,000 different species. Fungi are various small organisms that lack chlorophyll and get their food from living or dead organic matter. They reproduce from spores and survive for a long period of time. Many fungi are beneficial while some cause problems in the human body. Since they do not have chlorophyll, fungi must absorb food from others. They also do not need light to make food so fungi thrive and live in damp, dark places. Fungi are supposed to "eat" things when they are dead but sometimes they start eating when the organism is still alive (Kwon-Chung, 1992). A fungus is a simple parasitic organism. Tinea pedis, also known as athlete’s foot, is a fungal infection that commonly develops between toes and on the feet. Yeast is also a type of fungus. Candidiasis, also known as a yeast infection, is caused by the pathogenic yeast candida albicans. This fungus can thrive on the skin or mucous membranes in the warm moist areas such as the vagina or mouth.

Protozoa are the smallest one celled animals. Most can only be seen if using a microscope. They move, reproduce, and breathe, just like multi cells animals. Pathogens in this group live in wet, damp places, and include paramecium, the euglena, and the ameba. The ameba is one of the simplest and smallest structured protozoa and look like a grey splotch under a microscope. They can be found in ponds and rivers, and even on the leaves of plant that live in water (MCWDN.org, 2009). One special characteristic of the ameba is the false feet that are called pseudopodia. These feet extend out and the rest of the body follows. The paramecium is larger than the ameba, but can also be found in ponds. Paramecia are covered in cilia and they eat plants, and algae. They look like the sole of a shoe under a microscope. The euglena is unique because it possesses the same characteristics as a plant and an animal. Euglena contains chlorophyll, a substance that plants use with sun light to create food. While in the darkness, they are able to get food like an animal, by eating plants and animals, just like the ameba and paramecium (MCWDN.org, 2009). The euglena is pear shaped and has a tail called the flagellum, which allows them to move through water. Protozoan diseases vary from mild to life threatening reactions. The deadliest disease cause by a protozoa is malaria, an infectious disease that causes over two million deaths each year (CDC, 2010). Other protozoan diseases include amoebiasis, sleeping sickness, toxoplasmosis, and trichomoniasis.

There are many different ways that the body prevents disease from infestation. There are also many ways for people to prevent disease as well. The body’s first defense mechanism is the mucous membranes. Most pathogens cannot pass through skin unless there are wounds or cuts. The membranes that line the respiratory, digestive, urinary, and reproductive systems secrete mucous that traps foreign microscopic microbes (CDC, 2010). Small, hair like projections in the lining of the nose, throat and bronchial tubes work with the mucus to trap unknown substances. In the ears, there is wax and small hairs that offer protection against germ entry. Tears that are secreted by the lachrymal glad wash away germs that may enter through the eyes, and contain a protein that kills certain germs. White blood cells called phagocytes constantly travel through the body looking for foreign substances. If they find a foreign substance, they surround it, and digest it.

Prescribed antibiotics are important when it comes to fighting disease. Antibiotics should be used exactly as prescribed and for the full course of time prescribed. In addition, antibiotics should not be used for cold or other nonbacterial illness (RIDH, 1998-2010). Keeping immunizations for children, adults and pets up to date is just as important as washing hands often. Hands should be washed after using the bathroom, before preparing, or eating food, after changing a diaper, and after coughing sneezing and blowing noses. Not many people realize that washing hands after caring for someone who is sick or after playing with pets can really have an impact on the transfer of disease. When preparing food, people should use caution. Raw meat, eggs, chicken, and seafood should be kept away from foods that are ready to be eaten. Food should never be placed on an unwashed plate that held any of the previous raw items. Foods should be kept either hot or cold, until they are cooked. Cutting boards and knives should be thoroughly cleaned with hot, soapy water. Food that is left over should be placed in the refrigerator within two hours of cooking, and should be thrown away after three or four days (RIDH, 1998-2010). People should avoid areas where there are lots of insects. Insect repellant should be used on skin and clothing when in areas where mosquitoes or ticks are common. Lastly, when people are sick, they should allow themselves time to heal and recover. By taking a few days of work or school, washing hands, and covering mouths when coughing or sneezing, disease spreading can be stopped.

Nowadays, longer life spans are due to the overcoming of diseases. Diseases result from the infestation of pathogens and by the reactions of the hosts they infect. The severity of the disease results from the pathogens ability to damage the host. Also, the severity of diseases pathogens cause is based on their need to reproduce and spread. Vaccines, antibiotics, surgical tools and medical miracles are all responsible for treating diseases. Medical knowledge should be easily accessible to all people of the world. The more knowledge that is gained, the easier it will be for others to understand, treat, and prevent diseases.