Figure 22.13
This lip blister, or cold sore, is caused by a herpes virus. The virus is closely related to the virus that causes genital herpes. The genital herpes virus causes similar blisters on the genitals. If youve ever had a cold sore, you know how painful they can be. Genital herpes blisters are also painful.
Hepatitis B is a disease of the liver. It is caused by a virus called hepatitis B, which can be passed through sexual activity. Hepatitis B causes vomiting. It also causes yellowing of the skin and eyes. The disease goes away on its own in some people. Other people are sick for the rest of their lives. In these people, the virus usually damages the liver. It may also lead to liver cancer. Medicines can help prevent liver damage in these people. There is also a vaccine to protect against hepatitis B.
HIV stands for human immunodeficiency virus. It is the virus that causes AIDS. HIV and AIDS are described in the Diseases and the Body’s Defenses chapter. HIV can spread through sexual contact. It can also spread through body fluids such as blood. There is no cure for HIV infection, and AIDS is a fatal disease, although the onset of AIDS can be significantly delayed with proper medication. Researchers are trying to find a vaccine to prevent HIV infection.
In Latin America, many women are infected with HIV. They are often treated unfairly just because they have the virus. For example, they may be rejected by their family or fired from their job. A woman from Argentina named Patricia Pérez has been working to change that. She was infected with HIV in the 1980s. Ever since then, she has been fighting for the rights of women with HIV. In 2007, Pérez was nominated for a Nobel Peace Prize for her work.
Other Reproductive System Disorders
Many disorders of the reproductive system are not STDs. They are not caused by pathogens, so they don’t spread from person to person. They develop for other reasons. The disorders differ in males and females. In both genders, the disorders range from causing little more than discomfort to potentially causing death.
Disorders in Males
Most common disorders of the male reproductive system involve the testes. For example, injuries to the testes are very common. In teens, injuries to the testes most often occur while playing sports. An injury such as a strike or kick to the testes can be very painful. It may also cause bruising and swelling. However, such injuries seldom do lasting harm.
Varicocele is also quite common, especially during puberty. A varicocele is a swollen vein in the scrotum (Figure below). A varicocele doesn’t usually cause pain or other symptoms. If it does cause symptoms, it can be treated with surgery.
Figure 22.14
Do you see the wormlike structures under the skin of the scrotum shown here? They are swollen veins, called varicoceles. This condition usually isnt harmful.
Another disorder of the testes is cancer. Cancer of the testes is most common in males aged 15 to 35. It occurs when cells in the testes grow out of control. The cells form a lump called a tumor. If detected early, cancer of the testes usually can be cured with surgery. Early detection of tumors of the testes is best accomplished via regular self examination. The technique for the examination may be seen at http://tcrc.acor.org/tcexam.html
Disorders in Females
Disorders of the female reproductive system may affect the vagina, uterus, or ovaries. They may also affect the breasts. One of the most common disorders is vaginitis. This is redness and itching of the vagina. It may be due to irritation by soap or bubble bath. Another possible cause of vaginitis is a yeast infection. Yeast normally grow in the vagina. A yeast infection occurs when the yeast multiply too fast and cause symptoms. A yeast infection can be treated with medication.
Endometriosis is a disorder that may affect several organs. It occurs when tissues that normally line the uterus grow elsewhere. The tissues may grow on the uterus, ovaries, or Fallopian tubes (Figure below). The disorder causes pain. It can also cause abnormal bleeding. In some cases, it prevents a woman from becoming pregnant. It is usually treated with hormones or surgery.
Figure 22.15
In endometriosis, tissues that normally grow inside the uterus start growing on the outside of the uterus. They may also grow on other reproductive organs.
A common disorder of the ovaries is an ovarian cyst. A cyst is a sac filled with fluid or other material (Figure below). An ovarian cyst is usually harmless. However, it may cause pain. Most cysts gradually disappear and do not need treatment. Very large or painful cysts can be removed with surgery.
Figure 22.16
Ovarian cysts, like this one, are common. They generally do not need to be treated unless they cause symptoms. Most go away without treatment.
Many teen girls have painful menstrual periods. They typically have cramping in the lower abdomen. Generally, this is nothing to worry about. Taking a warm bath or using a heating pad often helps. Exercise may help, as well. A pain reliever like ibuprofen may also be effective. If the pain is severe, a doctor can prescribe stronger medicine to relieve the pain.
The most common type of cancer in females is breast cancer. It occurs when cells of the breast grow out of control and form a tumor. Breast cancer is rare in teens. It becomes more common as women get older. If breast cancer is detected early, it usually can be cured with surgery.
Keeping the Reproductive System Healthy
What can you do to keep your reproductive system healthy? You can start by making the right choices for overall good health. To be as healthy as you can be, you should:
eat a balanced diet that is high in fiber and low in fat.
drink plenty of water.
get regular exercise.
maintain a healthy weight.
get enough sleep.
avoid using tobacco, alcohol, or other drugs.
manage stress in healthy ways.
You should also keep the genitals clean. A daily shower or bath is all that it takes. Females do not need to use special feminine hygiene products. In fact, using them may do more harm than good. They can irritate delicate membranes.
Abstinence from sexual activity is the best way to prevent STDs. You should also avoid other behaviors that can put you at risk. Risk behavior are those that might lead to contact with another person’s blood or other body fluids. For example, never get a tattoo or piercing unless you are sure that the needles have not been used before.
If you are a boy, you should always wear a protective cup when you play contact sports. Contact sports include football, soccer, and hockey. Wearing a cup will help protect the testes from injury. You should also do a monthly self-exam to check for cancer of the testes (Figure below). See also http://kidshealth.org/teen/sexual_health/guys/tse.html
If you have any questions, ask a health care provider. It may be embarrassing, but it could save your life.
Figure 22.17
Teen boys should learn how to examine their testes for lumps that could be a sign of cancer.
If you are a girl and use tampons, be sure to change them every 4 to 6 hours. Leaving tampons in too long can put you at risk of toxic shock syndrome. This is a serious condition. You should also get in the habit of doing a monthly self-exam to check for breast cancer. Although breast cancer is rare in teens, it's a good idea to start doing the exam when you are young. It will help you get to know what is normal for you. You can learn how to do the exam at http://freemedicalmovie.blogspot.com/2007/10/breast-self-exam.html
Ask a health care provider if you have any questions.
Lesson Summary
Sexually transmitted diseases are caused by pathogens. They spread through sexual contact.
In males, other disorders of the reproductive system include varicocele and cancer of the testes. In females, other disorders include vaginitis and breast cancer.
One way to keep the reproductive system healthy is by making the right choices for overall good health. Other ways are keeping the genitals clean and avoiding sexual activity.
Review Questions
What is a sexually transmitte
d disease?
In the U.S., what is the most common STD caused by bacteria?
Which of the following STDs can be prevented with a vaccine? genital warts, Chlamydia, gonorrhea, hepatitis B
What is a varicocele?
What is the best way to prevent STDs?
Explain why bacterial STDs are treated differently than viral STDs.
It is especially important for females to be protected from HPV infections. Why is this the case?
Why should males start doing self-exams of the testes by age 15?
How could a person become infected with an STD without ever being sexually active?
Explain how girls can reduce their risk of developing toxic shock syndrome.
Further Reading / Supplemental Links
CK–12.org, High School Biology, Chapter 40, Lesson 4
http://focus.hms.harvard.edu/2008/030708/licensing.shtml
Rajasingam S. Jevendran and Megan Hollingsworth. Sex, Sperm, and STDs: What Every Teenage Boy Needs to Know. iUniverse, Inc., 2006.
Robie H. Harris. It’s Perfectly Normal: Changing Bodies, Growing Up, Sex, and Sexual Health. Candlewick, 2004.
Steve Parker. The Reproductive System: Injury, Illness, and Health. Heinemann Library, 2004.
Tricia Kreitman, Fiona Finlay, and Rosemary Jones. The Period Pocketbook: Honest Answers with Advice from Real Girls. Ulysses Press, 2006.
http://kidshealth.org/parent/general/body_basics/female_reproductive_system.html
http://womenshealth.about.com/od/stds/a/stdmythsvsfacts.htm
http://wrongdiagnosis.com/h/hepatitis_b/prevalence.htm
http://wrongdiagnosis.com/s/syphilis/prevalence.htm
http://www.cdc.gov/stdconference/2008/media/summaries-11march2008.htm
http://www.cdc.gov/STD/stats04/trends2004.htm
http://www.ehow.com/how_2076825_care-female-reproductive-system.html
http://www.faqs.org/health/Body-by-Design-V2/The-Reproductive-System.html
*[http://www.ipsnews.net/news.asp?idnews=37705 http://www.gardasil.com/; *[http://www.ipsnews.net/news.asp?idnews=37705
http://www.niaid.nih.gov/dmid/stds/herpevac
http://www.nlm.nih.gov/medlineplus/malereproductivesystem.html
http://www.nlm.nih.gov/medlineplus/malereproductivesystem.html
http://en.wikipedia.org/wiki
Vocabulary
breast cancer
Most common type of cancer in females that occurs when cells of the breast grow out of control and form a tumor.
cancer of the testes
Type of cancer common in teens and young men that occurs when cells of the testes grow out of control and form a tumor.
Chlamydia
Most common STD in the U.S. that is caused by bacteria.
endometriosis
Disorder in which tissues that normally line the uterus grow outside the uterus and cause pain and bleeding.
genital herpes
Common STD that is caused by a virus called herpes.
genital warts
Common STD that is caused by a virus called HPV.
gonorrhea
Common STD that is caused by bacteria.
hepatitis B
STD that damages the liver and is caused by a virus called hepatitis B.
ovarian cyst
Sac filled with fluid or other material that develops in an ovary.
sexually transmitted disease (STD)
Disease that spreads through sexual contact and is caused by a pathogen.
syphilis
Very serious STD that is caused by bacteria.
vaginitis
Redness and itching of the vagina that may be due to irritation or a yeast infection.
varicocele
Swollen vein in the scrotum.
Points to Consider
A healthy reproductive system is important if you plan to have children when you are older. The birth of children, in turn, is one of the main factors that affect the growth of a population. We turn our attention next to ecology.
Ecology includes the study of populations. What factors do you think affect population growth? How might a rapidly growing population affect its environment?
Chapter 23: From Populations to the Biosphere
Lesson 23.1: Introduction to Ecology
Lesson Objectives
Define what ecology is.
Explain what organisms and environments are.
Describe how organisms can interact with their environments.
Describe levels of organization in ecology.
Check Your Understanding
What is adaptation?
What is the scientific method?
Introduction
Organisms can be studied at many different levels, from biochemical and molecular, to cells, tissues and organs, to individuals, and finally at the ecological level: populations, communities, ecosystems and to the biosphere as a whole. Because of its focus on the higher levels of the organization of life on earth, ecology draws heavily on many other branches of science. Can you think of what some of these might be?
What is Ecology?
Ecology is the scientific study of how living organisms interact with each other and with their environment. Because of its broad scope, ecology draws from other branches of science, including geology, soil science, geography, meteorology, genetics, chemistry, and physics.
The study of ecology can also be broken down into sub-disciplines. Thus, if you were focusing on, for example, how the physiology of an organism influences the way that organism interacts with the environment, you would be studying the sub-discipline of ecophysiology. Similarly, you could come up with terminology for studying the roles of behavior, populations, communities, ecosystems, landscapes, evolution, and even politics!
You could also sub-divide ecology according to the species of interest into fields such as animal ecology, plant ecology, insect ecology, etc., or according to biome, an ecological formation that exists over a large region, such as the Arctic, the tropics, or the desert (Figure below). Perhaps you can come up with some of your own terms for combining some of these specialties, or think of some other specialties yourself!
Figure 23.1
An example of a biome, the Atacama Desert, in Chile.
Finally, because of the way ecologists study their discipline and because of the number of other fields involved, many methods can be employed to study how organisms interact with each other and their environment. Can you think of what some of these methods might be?
One obvious type of research that comes to mind is field studies, since ecologists generally are interested in the world of nature. This involves collecting data in the natural world, as opposed to laboratory settings with controls. One example of this kind of study is determining how many organisms occupy a specific geographical area. This usually involves a technique called sampling, where an area is divided into a certain sized plot, and the number of organisms in that area is counted.
Ecological principles can be studied in the laboratory as well. Perhaps you can think of some ways in which some aspects of ecology can be isolated in the lab. Statistical analysis is also used for analyzing both field and laboratory data. Finally, ecologists often use computer simulations to model complex ecological systems and to help predict how future environmental changes can affect a system. Can you think of some possible environmental change in the future that could be studied?
Organisms and Environments
All organisms have the ability to grow and reproduce, properties which require materials and energy from the environment. An organism’s environment includes physical properties (abiotic factors), such as sunlight, climate, soil, water and air, and biological properties (biotic factors), which comporise the other living organisms, of the same or different species, that share its habitat. Biotic and abiotic factors will be further discussed in the Ecosystems lesson.
An example of how biotic factors influence the environment in which an organis
m lives can be seen in the primitive atmosphere. The first photosynthesizing organisms on Earth produced oxygen. This led to an oxygen-rich atmosphere, which caused life forms for which oxygen was toxic to die, and other organisms which depend upon oxygen to evolve.
Levels of Organization in Ecology
Ecology can be studied at a wide range of levels, from the smallest unit, at the individual level, to the largest, or most inclusive, the biosphere (the portion of the planet occupied by living matter (Figure below)) (Table (below) ). Between the individual level and the biosphere, from smallest to largest, is the population (organisms belonging to the same species that occupy the same area and interact with one another) level, the community (populations of different species that occupy the same area and interact with one another) level, and the ecosystem (a natural unit composed of all the living forms in an area, functioning together with all the abiotic components of the environment (Figure below)) level.
Figure 23.2
The global biosphere, which includes all areas that contain life, from the sea to the atmosphere.
Figure 23.3
Satellite image of Australias Great Barrier Reef, an example of a marine ecosystem
Ecological Range Level Definition
population organisms belonging to the same species that occupy the same area and interact with one another
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