Self Evaluation

1. What were the three aspects of the assignments I've submitted that I am most proud of?

I am proud of the first compendium review and I did well on the two tests.

2. What two aspects of my submitted assignments do I believe could have used some improvement?

The second Compendium and the ethical issues essay.

3. What do I believe my overall grade should be for this unit?

I am not so sure on this unit, whatever you think is best.

4. How could I perform better in the next unit?

I was away in Washington DC at an important meeting most of this unit and my work suffered. I should have started much earlier and been better prepared.

1. At what moment during this unit did you feel most engaged with the course?

I enjoyed the information on reproduction and ecology.

2. At what moment unit did you feel most distanced from the course?

I have issues with macro evolution.

3. What action that anyone (teacher or student) took during this unit that find most affirming and helpful?

Professor Frolich, I think you are a great teacher, I have never been this engaged in an online class. You put a lot of work into this course and it shows. Good Job!

4. What action that anyone (teacher or student) took during this unit did you find most puzzling or confusing?

None

5. What about this unit surprised you the most? (This could be something about your own reactions to the course, something that someone did, or anything else that occurs to you.)

I guess I enjoyed the lab more than I thought I would. I am also glad I don't have to worry about getting my work done anymore.

What is the Problem?

This has been a fascinating year. Not only has our economy hit the skids, but earlier in the year we saw food and fuel costs skyrocket to record levels. Why did costs go up so quickly. The buzz in newspapers and on blogs was China had become a new "super consumer" and was gobbling up all the resources. I heard one commentator say that the people of China had been eating rice for years and they were ready for something different. The Chinese are also driving more vehicles, therefore using more fuel. Now we know that China has has over a billion inhabitants but the fertility rate is currently under 2.0. Is the problem with the population or is it attitude?

Here in the USA everyone is worried about the economy, people have lost jobs and are losing their homes. Yet how much are we really suffering? This is a country where you can be "poor" but still have a cell phone and subscribe to cable. One American consumes the same amount of resources as 30 people in India!? Population is not the issue in the US, it is our culture of self indulgence.

Residents of other countries have somewhat of a love/hate relationship with the west, on one hand they hate us and see us as greedy and self indulgent, on the other hand they wish they could live like we do. I visited Thailand several years ago and was amazed by how much they all loved Americans. The people there made me feel like a celebrity. But why do they like us? It makes me think of those popular kids in school that we all hated but wanted to be friends with. The American lifestyle is an ideal.

It seems to me that it has something to do with human nature. I once heard this story about a monkey trap, (I don't know if it's true) I like the idea behind the story. Apparently poachers put a piece of fragrant fruit in the bottom of a jar with a narrow opening and bury it with the opening exposed. A monkey smells the fruit, reaches in and grabs it but can't get its fist out while it is holding the fruit. Refusing to let go of its prize the monkey is easily captured by the poachers. I think it is the same way with people we are so caught up in our own self gratification that we are completely unable to see how it may lead to our own demise.

Demographics Online Lab

1. What was your high fertility rate country and what was its fertility rate?

My country was Laos in Asia. The fertility rate was 6.30.

2. What was your low fertility rate country and what was its fertility rate?

My low fertility rate country was Canada with a rate of 1.80 children.

3. The initial demographic "shape" of your high fertility rate country should have been a pyramid, with high population in young age groups. Explain why high fertility rate results in a high percentage of young people in the population. How does this affect future population growth?

Often in less developed countries where there is not access to birth control there are high fertility rates. The life expectancy is also lower, as in Laos, the life expectancy is only 50 years. Because of a lack of good medical care, nutrition etc, the older and more frail die. The younger and stronger live and upon reaching reproductive age have more children, resulting in a younger population.

4. Your low fertility rate country might have had a more oval-shaped curve with high population in middle age groups. This is especially exaggerated if the fertility rate is below 2.00. Explain why low fertility rate leads to lots of middle-aged people.

There is a higher standard of living in these countries with access to better nutrition and medical care. People live longer.

5. Write ten adjectives or descriptive phrases for what you might expect life, people's attitudes, conditions on the streets, etc. will be like in each of those situations. Imagine a situation with lots of middle-aged and older people in the population and write ten quick "brain-storm" descriptors for you think it would be like (Prescott, Arizona?). Then do the same for a situation with lots of children in the population.

Lots of Middle aged older people:

1. Materialistic

2. Individualistic

3. Emphasis on heritage

4. Rich history

5. More sedentary society

6. Xenophobic

7. Less diversity

8. Educated

9. Wealthy

10. Resistant to change

Lots of Children:

1. Diverse

2, energized

3. Innovation and creativity are prevalent

4. Crime and death rates are higher

5. Scarcity

6. Unemployment

7. Emphasis on family

8. Pollution

9. Emphasis on religion and spirituality

10. Accidents

Compendium Review: Human Landscapes and Ecology

Photo taken from www.all-creatures.org/hope/

I Introduction

II Evolution

III Global Ecology

IV Population and Resources

V Conclusion

Introduction

I think the origin of life is a fascinating subject. From time to time we all have those moments where we question the origins of life and how our universe, planet, and life in general came about. Evolution is an interesting theory and I appreciated reading more about it. The interactions of species and our ecosystem was even more interesting to me. Looking at how species are linked and serve different roles was thought provoking.

Evolution

According to the text, chemical evolution is a possible source of the origin of life. Around 10-billion years ago our primitive earth included sources of energy like volcanoes, lightning, radioactive isotopes, meteorites, and ultraviolet radiation. The theory is that through this energy primitive gases reacted with each other to form organic compounds like amino acids. An experiment was done by Stanley Miller that simulated this primitive and came out with small organic molecules. It is believed that macromolecules were then formed, possibly RNA from the joining of these organic molecules. A protocell may have been the next link in the chain followed by a true reproducing cell. The earliest cell were probably prokaryotic cells lacking a nucleus.

A graphic showing chemical evolution taken from Human Biology page 468, Sylvia S. Mader

Biological evolution is defined as the process by which a particular species changes over time. There are two components of evolution, adaption and the descent from a common ancestor. Charles Darwin, during his observations in the Galapagos Islands ,began gathering evidence that life-forms change over time. The evidence he found included fossil, anatomical, and biogeographical.

Fossils are the remains or evidence (like footprints or droppings) of lifeforms that lived on earth at least 10,000 pears ago. These are the best evidence of evolution. The fossil record is the history scientists have been able to record by studying fossils.

Biogeographical evidence is the occurrence of unique species in different parts of the world. For example, Darwin noticed there were no rabbits in South America and concluded that this is because rabbits evolved somewhere else. the finches of the Galapagos Islands are an example of biogeographical evidence.

Anatomical evidence is found in the similarities in the skeletons of varying species. When a anatomically similar structures are inherited from a common ancestor they are said to be homologous. Analogous structure may have the same function but are not constructed the same and do not share a common ancestor.

Biochemical evidence is the presence of the same biochemical molecule like DNA and ATP.

Darwin also proposed the idea of natural selection. Natural selection is process by which individuals of a species possessing certain characteristics (like long necks on giraffes) suited to the environment are more likely to thrive and reproduce. The result is that most of the new offspring will possess the original characteristic, for example the long neck of the giraffe.

Humans are primates and therefore probably share a common ancestor with other primates. Humans did not evolve from apes. Primates have mobile limbs and five digits on the hands and feet. An opposable thumb, found in humans and chimpanzees creates a more powerful grip. Having both eyes positioned at the front of the head makes depth perception possible for humans and apes. Humans and apes also have a reduced birth rate and larger more complex brains.

A chart showing the evolution of primates taken from Human Biology page 478, Sylvia S. Mader

Humans are known as hominids, and that is where we branch away from the other primates. Our ability to walk on two feet is one of the traits that separates us from other primates. Our brain size is another feature that separates us.

The earliest hominid fossil was found in Chad and is called Sahelan-thropus tchadensis. Other fossils and evidence of hominids have been found. Homo habilis is believed to be an ancestor tohumans. Homo erectus is another ancestor and has a larger brain and flatter face. Homo erectus is the first hominid to utilize fire and more advanced tools.

Chart showing human evolutions taken from Human Biology page 481, Sylvia S. Mader

Global Ecology

The bioshere is that area of the earth where living organisms are found. An ecosystem is community where species can interact with each other and the physical and chemical environment.There are different terrestrial ecosystems including the tropical rain forest, savanna, prairie, desert, taiga, and temperate forest. Aquatic ecosystems are separated by salt water or fresh water.

Ecosystems are composed of living and nonliving things. Living things are biotic and nonliving are abiotic. Autotrophs need inorganic nutrients along with an outside energy source in order to live. Autotrophs are producers because the produce food for other organisms. Algae and plants are examples of autotrophs. Heterotrophs are consumers and require organic nutrients. Heterotrophs can be herbivores, consuming only plants or algae, or they can be carnivores, meaning they eat other animals. Omnivores eat both plants and animals, like humans. Fungi are examples of decomposers, meaning they break down dead organic matter. All organisms have a niche, that is a role in an ecosystem.

It is important to understand the flow of energy between organisms. When a producer is consumer by a consumer only a portion of the energy possessed is passed on to the consumer. A food web is a diagram that illustrates feeding relationships. The one below is an example of a grazing food web beginning with a tree and grass. A food chain is the order by which a population feeds on one another.

An example of a food web taken from Human Biology page 496, Sylvia S. Mader

Biochemical cycles are pathways by which chemicals circulate through ecosystems. The different biochemical cycles include the water cycle, carbon cycle, nitrogen cycle, and phosphorus cycle. Each of these cycles is important to the various ecosystems and can be altered by human activities.

Graphic of the water cycle, Human Biology page 499, Sylvia S. Mader

Graphic of the Carbon Cycle, Human Biology page 500, Sylvia S. Mader

Carbon dioxide and other gases produced by human activities like the burning of fossil fuels are contributing to global warming. Global warming can lead to serious changes like the melting of the polar ice caps.

Graphic illustrating global warming, Human Biology page 501, Sylvia S. Mader

Population and Resources

The population of earth is currently experiencing exponential growth and is now at about 7 billion people. Less-developed countries have higher growth rates than more-developed countries. Countries with a younger population also have a higher growth rate. As the population grows the need for resource like food, water, and fuel increases. Some resources like food and water are renewable, meaning they can be replenished. However sometimes the need for the resources comes faster than our ability to replenish them. Pollution can contaminate resources, making them unusable. Nonrenewable resource are those that have a limited supply, like fossil fuels. These resources will eventually run out.

It is important for us to find ways to use our resources without squandering them. Conservation is very important. The USA consumes much of the fossil fuels produced but contains only a fraction of the world populations. Alternative energy sources like wind and solar power can be developed to replace non renewable resources.

Pollution, habitat loss, and climate change are effecting biodiversity. Many species are in danger of extinction. This effects ecosystems. The loss of certain organisms can have a direct effect on human life.

Conclusion

Our world is a complex place. What we do has a direct impact on the environment. I think it benefits us to have an understanding of where we came from and where we want to go as a species. These chapters gave me a lot to think about.

Works sited

Human Biology, Sylvia S. Mader

www.all-creatures.org/hope/

Lab Project: List of Species

Cat: Scientific name is Felis domesticus. This is my cat Sting (Named after Sting from the Police). I list him first because he is usually the first thing I see in the morning. I would say our relationship is definitely mutualistic although it is hard to say if it is me who is in charge or him. I will tell you that I didn't wake up at 5 am before he came along. So I feed him and I get to enjoy his company, we both benefit. He does have a predatory relationship with the other species that live around us and he leaves evidence of this on our doorstep if I let him outside. House cats are a domesticated species.

Humans: Homo sapiens; Obviously I interact with people everyday. First and foremost I spend the most time with my family. I also have a very social career which requires lots of interaction with both coworkers and members of the community. The photo above shows me hiking with my family. So, we interact in many different ways with each other depending on the relationship. Sometimes the is animosity or rivalry between people or groups of people that can lead to negative outcomes. We are not different species but I guess you can say that we humans have a symbiotic relationship with each other. In some cases it may be mutualistic, as with very young children.

American Crow: Corvus brachyrhynchos; Crows seem to have done pretty well for themselves, at least here in the US, although I did see some species of crow in Asia when I visited Thailand in 2003. I see lots of crows everyday at work when I go on my walk, they hang out at the garbage bin. As far as I can tell they are omnivores as they seem to eat almost anything. They also feed on carrion. I think our relationship with crows is mutualistic (they eat our garbage and dead animals after all) and we have been co-evolving with crows as they seem to thrive in areas where people are, whether it's in the city or more rural like a farming community.

Live cultures in Yogurt: Every morning I eat Yoplait yogurt with live cultures. The live culture supposedly help my stomach. I also eat it because I need the calcium (I have osteopenia). There are actually two organisms lactobacillus bulgaricus and Streptococcus thermophilus, and they convert pasteurized milk to yogurt during fermentation. From what I've read, yogurts are required to have these organisms. Some yogurts contain Lactobacillus acidophilus, Bifidus and other cultures. Referring to the PowerPoint you could almost say this is a domesticated species because of the way we use it. The interaction is weirdly mutualistic as it benefits while the yogurt is around and we consume it.

Dust mites: Scientific name is Dermatophagoides farinae. This picture grosses me out and my daughter was scared of it. Dust mites are microscopic bugs that live on dead skin cells. I learned that about 100,000 mites can live in one square yard of carpet, yikes. Even worse, tens of thousands live in the average mattress! A problem with dust mites is the can cause serious allergy problems. The website I got this info from state that dust mites are not parasites in the typical sense, but if I am understanding the Power Point correctly they actually are parasites as we can be harmed by them in the form of allergies. I guess we have co-evolved with dust mites as they seem to thrive on our dead skin cells.

Eyebrow Mites: Demodex folliculorum and D. brevis; We have lots of mites and bacteria that live on and in our bodies, many do not actually harm us. That is the case with the eyebrow mite which lives in our eyebrows. The interaction is commensal as the mite benefits and we do not even know it is there. It is not domesticated in the traditional sense but I guess that you could say it has co-evolved with us and must have adapted over time to detergents and soaps as they don't seem to be washed off easily.

Bacteria on Skin: Propionibacterium acnes; This is a bacteria that lives harmlessly on our skin in which case the interaction would be commensal. However, sometimes an excess of oil on the surface of this skin can cause an overgrowth in this bacteria which can result in acne. Sometime this is brought on by stress or hormones and even diet. Often upsets in the balance of bacteria in different parts of the body can lead to a change in the normal environment causing a bacteria or fungus to proliferate which in turn leads to infection. Overuse of antibiotics and antibacterial soaps have sometimes led to these types of problems.





Little Black Ants: Monomorium minimum; Every summer these creatures attempt to invade our home. It seems like no matter how careful I am they find a way in. Eventually I resort to insecticide along my windows and door frames, although I hate it, and this usually stems them off for a time. I would say the interaction is commensal up until I kill them at which time I become the predator. Personally, I find them disgusting but they actually do not do us any harm as far as I know.

Willow Tree: Salix pendulina; We have this huge willow tree at the corner of our yard. I like it, it provides shade, but I hate cleaning up after it.I guess it is a mutualistic relationship. We both benefit. I water it and take care of it and therefore get to enjoy it. I think it is sort of domesticated. People seem to like the look of Willow trees and so they are cultivated for that reason.

Common King Snake: Lampropeltis getula; Our cat caught this snake back in September, we rescued it and let it loose in our back yard where we discovered several baby king snakes. Personally, I am not afraid of snakes (I grew up around them) and I consider them a good thing to have around as they eat small rodents which are dirtier animals. I think it is a common king snake although it may be a California King. Our interaction is commensal, with humans benefiting. However many people are afraid of snakes and will kill them whether they are dangerous or not. King snakes have been domesticated as pets and I think we do co-evolve together because of the fact that king snakes will live where food is available, which is often close to where humans are.



Javelina: Pecari tajacu; We have a lot of these near our home. They like to eat plants, especially prickly pear. I have come across them while walking but give them a wide berth as I have heard they can be aggressive. I don't like that they eat my plants. I would say that javelina are prey to humans. We are infringing on their habitat for sure. They are not domesticated in any sense that I can think of.



Prickly Pear: Opuntia phaeacantha; The prickly pear is an interesting plant that has adapted to its environment quite nicely. I think it is interesting that you will have them in the Mojave desert as well as here in the mountains of the Prescott area. Of course both are arid climates. Many Arizonians plant prickly pear because it is easy to grow and takes little water. It also produces beautiful fruit and flowers. I guess in some sense it has been domesticated, but I don't think it is really co-evolving in the sense that the PowerPoint talked about. I would also say that the Prickly Pear seems to be prey to javelina.

Nobel Fir Christmas Tree: Abies procera; Our family prefers the Nobel Firs as Christmas Trees as they seem to be easier on my son's and husband's allergies. In the sense that Professor Frolich was describing in his PowerPoint, I guess you could say that we have domesticated the Nobel Fir in a way that has been a benefit to its species. These are considered the "highest quality" Christmas trees by many and are therefore being cultivated more and more. I guess our relationship is mutualistic although some would argue the point since we chop them down.



Tomatoes: Solanum lycopersicum; This year we grew our own tomatoes, they were delicious. I chose not to use insecticide and grew them from organic compost from my own compost heap. This was somewhat of an experiment. They did not look as beautiful as those in the supermarket, but they tasted much better. Still I wondered what little bugs I may have ingested. The interaction is mutualistic, although we ate the fruit of the tomato I took care of the plants and expect them back next year.



Tomato Worms: Manduca quinquemaculata; I hate these and they are definitely predators to the tomato plants. One plant died because of these little critters. I was unable to find a way to get rid of them without insecticide. If you know of a way let me know. I guess my interaction with tomato worms is as a predator because I mean them harm. They are not domesticated as far as i can tell although they are adapted to feeding off of tomato plants.


Aphids: Aphis gossypii; Aphids are little bugs that love to eat plants, particularly my roses. They are definitely a parasite for plants but I don't think they do humans any real harm. I guess normally our interaction is commensual, but because I don't like them harming my plants I become predator.

Ladybugs: Coccinella septempunctata; Actually beetle not bugs, ladybugs are beneficial to any garden, mainly because they eat aphids. These creatures were my solution to my aphid problem. You can buy them at Home Depot cheap. Anyway, they did not kill all the aphids but they did a good job of controlling the problem. This was definitely a symbiotic relationship.


Dogs: Canis lupus familiaris; We don't own a dog ourselves but all of our neighbors do. I would say that my interaction with dogs is symbiotic as it is with most humans. We feed them, play with them etc. and we benefit from the interaction. There have recently been studies done showing how interaction with dogs is beneficial for the terminally ill. Some hospitals even purchase dogs for this purpose. Dogs are domesticated and it is obvious that this has been a good relationship for them as a species.

Domestic Chicken: Gallus domesticus; Lately we've been eating a lot of chicken. My husband was practically raised on a chicken farm as his grandmother worked on one. My interaction with chicken is as a predator as I eat it. Chicken are domesticated and are therefore found in abundance.

Spinach: Spinacea oleracea; Spinach is one of my favorite foods, I buy it every week and eat it raw in salads. Spinach is supposedly good for a lot of reasons including its benefit as the "broom of the stomach." The interaction I guess is predator prey but the fact that it is being cultivated more and more is a benefit to the species.

Reproduction online lab

Event 1: Fertilization- This is the beginning of the pregnancy. I don't know if it counts but it seem significant to me since this is where it all begins. Sperm and egg meet and form a zygote. The zygote divides over and over as it travels down the oviduct.




Event 2: Implantation- Happens during week two. The zygote implants on the uterine wall. Woman is now officially pregnant.

Event 3: Heart begins to form- Happens at around 21-23 days gestation. This is significant because at this point many women do not even know they are pregnant! Important development of body systems happens early on.

Event 4: Formation of body stalk- This occurs at about 4 weeks. The body stalk becomes the umbilical cord which will connect the developing embryo to the placenta. The umbilical cord is vital for the survival of the fetus.

Event 5: Formation of the linbs- Little buds appear around the fifth week, these buds will become arms and legs. Again important because this early dvelopment is often happening before the woman knows she is pregnant. The embryo is still only about 7 mm long.

Event 6: Bone is starting to replace catilage- At around the 11th or 12th week bone begins to 1replace cartilage. Ossification centers begin to appear in most bones. I find it fascinating that all of this is going on inside the womb.

Event 7: Circulatory system- By the 16th week the circulatory system is functioning and the heart is pumping about approximately 24 quarts of blood a day. Significant because this is such a vital system.

Event 8: First movement felt- Times vary from person to person but this usually occurs around the fifth month. At this point in development the fetus is large enough for the mother to actually feel movement. This is an important "bonding" moment for mother and child.

Event 9: Immune system develops- Around 32 week the immune system begins to develop. This system is important for fighting infections.

Event 10: Child turns head down- Sometime during the last month the child will turn so the head is positioned for birth. Of course in some cases this does not happen and a child is in the breech position. This can complicate the birth.

Compendium Review: Reproduction

An image from an electron microscope showing sperm fertilizing an egg, taken from www.sciencemuseum.org.uk/.../lifecycle/40.asp

I. Introduction

II. Human Life Cycle

III. Male Reproductive System

IV. Female Reproductive system

• Ovarian Cycle

V. Birth Control

VI. STDs

VII. Stages of Development

• Pre-Embryonic
• Embryonic
• Fetal

VIII. Birth

IX. Aging

X. Conclusion

Introduction

I enjoyed reading these units because they deal with subjects I have been immersed in over the last 13 years. I spent my early days as a health educator in a women’s health clinic and now serve as the project coordinator of an aging program. I suppose I’ve come full circle. I guess the biggest lesson I have learned from working in a women’s clinic and through these chapters is the importance of understanding your body and how it works. So many women are completely unaware of how their reproductive systems work and are therefore woefully unequipped when making important decisions on pregnancy, contraception, and STD protection. The same is true of men. My husband knew something was “different” when he discovered his cancer but it was not until we looked it up that he knew he might have a serious problem. Over the next few paragraphs I will describe the male and female reproductive organs and their functions, discuss contraception and protection from STDs, and provide an overview of development, pregnancy, and birth.

Human Life Cycle

During puberty, between ages 11 – 13 for girls and 14 – 16 for boys, children reach sexual maturity. Sexual maturity means an individual is now capable of producing children. The reproductive systems of males and females differ significantly but have some similar functions.

Both produce gametes, in males, sperm are produced in the testes, in females the eggs are formed in the ovaries

Eggs reach the uterus via the fallopian tubes, and sperm are carried through ducts through the penis and are ejaculated. The penis delivers sperm to the vagina during sexual intercourse.

Testes and ovaries produce hormones that result in male/ female features and in females facilitate pregnancy. The uterus is the female organ that allows a fertilized egg to grow and develop.

In the human life cycle meiosis occurs in the ovaries (females) and testes (males) resulting in eggs and sperm. Sperm and eggs each contain only 23 chromosomes as compared to other cells that contain 46. Ordinary cells undergo division called mitosis resulting in another cell containing 46 chromosomes. Meiosis requires two cell divisions resulting in the haploid 23 chromosomes. During fertilization the sperm and egg meet to form the zygote which has 46 chromosomes.

Graphic of the human life cycle taken from Human biology page 320, Sylvia S. Mader

Male Reproductive System

The primary sexual organs in males are the testes which are suspended within the scrotum. Sperm are produced in the testes but mature within the epididymis. After maturation, sperm are stored in the vas deferens which consists of two long tubes leading to the ejaculatory duct which leads to the urethra. Ejaculate and urine both exit the penis through the urethra. The seminal vesicles, the prostrate gland, and bulbourethral glands all add secretions to semen which is the fluid that sperm is ejaculated in. Sperm require a particular environment to be more viable and components added by the seminal vesicles and the glands help create this environment. At birth all males have a foreskin over the penis which is usually removed by circumcision.

The penis is the male sexual organ. To facilitate erection, throughout the penis there is spongy tissue with expandable blood spaces. During sexual arousal these spaces fill with blood, causing erection. The sphincter closes off the the bladder so no urine enters the urethra during erection. Sperm enter the urethra via the vas deferens and muscle contractions trigger ejaculation. There are over 400 million sperm expelled during ejaculation.

Graphic of the male reproductive system taken from http://www.riversideonline.com/health_reference/Mens-Health/MC00023.cfm

As stated before, sperm and male sex hormones are produced in the testes. Testosterone is the main male sex hormone and is important for normal development and functioning of the male sexual organs. Testosterone also contributes to male physical characteristics like larger muscles and a deeper voice. The hypothalamus controls the functioning of the testes by secreting a hormone called gonadotropin-releasing hormone, GnRH.

Inside the testes are compartments called lobules which contain seminiferous tubules. This is where the production of sperm takes place. The process is known as spermatogenesis. Spermatogonia divide to produce spermatocytes which undergo meiosis I to become secondary spermatocytes which contain 23 chromosomes. These secondary spermatocytes will then go through meiosis II yielding 4 spermatids which become sperm. Throughout this process, sertoli cells provide support and nourishment. Spermatogenesis is a 74 day process.

A graphic from the text showing testis, sperm, and spermatogenesis. Taken from Human Biology page 323, Sylvia S. Mader

Female Reproductive System

Eggs and the sex hormones, estrogen and progesterone are produced in the ovaries, the female gonads. Oocytes within ovarian follicles mature during the ovarian cycle. Females are born with more then two million follicles but only a few, (400) mature. Usually women only produce one egg per month while they are reproductive.

Meiosis in females is known as oogenesis. An egg bursts from the ovaries during ovulation and is swept into the fallopian tubes, AKA oviducts, by finger-like projections called fimbriae. The egg then travels down the fallopian tubes to the uterus. Fertilization of the egg by a sperm usually takes place in the fallopian tubes. After fertilization, the egg implants on the endometrium of the uterus. If an egg implants in the fallopian tubes it is know as an ectopic pregnancy. The fallopian tubes can not support an embryo and do not expand like the uterus. The uterus is the organ where development of the fetus occurs. The cervix, the opening of the uterus is found at the back of the vagina. During intercourse sperm enter the uterus via the cervix and travel into the fallopian tubes in search of an egg. cervical cancer used to be the leading cause of cancer deaths in women but its incidence has been greatly reduced by the pap smear, a test for changes in cervical cells.

A graphic of the female reproductive system taken from www.northstar.k12.ak.us/.../markey/webpage.html

Ovarian Cycle

The female sex hormones estrogen and progesterone are responsible for female characteristics like breast development and body hair. These hormones also play an important role in the ovarian cycle. The average ovarian cycle lasts about 28 days. The cycle begins when lower levels of estrogen and progesterone cause the endometriun to disintegrate and pass out of the vagina, this is called menstruation. Menstruation is usually a sign that a women is not pregnant. Day one of an ovarian cycle is the first day of menstruation. Around 6-13 days later estrogen is increased by a new follicle and the endometrium begins to thicken in preparation for implantation in the event of a pregnancy. This is known as the proliferative phase. Ovulation usually occurs around day 14. During days 15-28 of the cycle, the corpus luteum increases production of progesterone causing the endometrium to thicken even further. This is the secretory phase and the body is now ready to receive a developing embryo.

A chart showing female hormone levels from Human Biology page 329, Sylvia S. Mader.

During pregnancy the embryo implants on the uterine wall and menstruation does not occur. The corpus luteum will increase the amounts of progesterone because of a hormone secreted by the placenta, human chorionic gonadotropin (HCG). HCG is the hormone detected in a pregnancy test. Later on the placenta will produce its own progesterone and some estrogen.

Hormones during pregnancy, Human Biology page 330, Sylvia S. Mader

Birth Control

There are many different methods available to women wanting to prevent pregnancy. The only sure way is abstinence, abstaining from sexual intercourse. However, contraceptives like birth conrol pills or Depo-provera can be about 98%-99% effective when used correctly. This methods use synthetic hormones (estrogen and/or progesterone) to inhibit ovulation. There are some side effects or risks like menstrual changes, weight gain, headaches, and blood clots that may occur with these methods. Hormonal methods do not provide protection from STDs.

The intrauterine device (IUD) is a piece of plastic, in some cases with copper or hormones, that is placed inside the uterus. It changes the environment of the uterus so that the egg does not implant on the uterine wall. Some women experience heavy cramping and bleeding with the IUD. Infections can also occur and it is recommended to be in a monogamous relationship while using the IUD.

Tubal Ligation and Vasectomy are surgical methods that bring about sterilization. In males the vas deferens is cut. Ejaculation still occurs but the semen is without sperm. In a tubal ligation the oviducts are cut, preventing the sperm and egg from reaching each other.

Barrier methods include the diaphragm and the male and female condoms. The diaphragm is used with a spermicide and is fitted by a clinician. Barrier methods, particularly the male and female condom, offer some protection against STDs but must be used correctly the whole time there is sexual contact. Even when used correctly, barrier methods are not 100% protection against STDs.

Photographs depicting different birth control methods, form Human Biology, page 331, Sylvia S. Mader

STDs

There are many different sexually transmitted diseases that people should be aware of. Some are bacterial, some are viral. Chlamydia and Gonorrhea are examples of bacteria and can be treated by antibiotics. Years ago, when I first started in women's health, Chlamydia was the most common STD. Things have either changed or we just know more. Human Papillomaviruses, AKA HPVs are the most common STDs today. HPVs may cause warts, but not always. What is really scary about HPVs is that some strains are linked to cervical cancer. There is no known cure for HPV but a new vaccine can protect women from some dangerous strains. Unless a woman has regular pap smears she may never know she has the virus. So get your pap smears ladies! By the way, condoms do not necessarily protect from HPV because they may not cover the entire area affected.

Other viruses include HIV and Hepatitis B and C. Hep A is not sexually transmitted. There is a vaccine for Hep B. Hepatitis affects the liver and is actually a more hearty virus than HIV, it just doesn't get the press, go figure.

Some infections like Bacterial vaginosis or yeast are not necessarily sexually transmitted and are fairly common. Yeast is a fungal infection.

Stages of Development

When a sperm meets an egg and a zygote is formed the event is called fertilization. Fertilization usually occurs in the oviducts. Only one sperm fertilizes an egg. The nucleus from the sperm head fuses with the nucleus of the egg. The newly formed zygote has 46 chromosomes. After fertilization the zygote begins to divide, this is called cleavage.

These images show human embryos at various stages of development. Taken from hesc.stanford.edu/research/programs/human.html

Pre-Embryonic Development

The pre-embryonic stage consists of the first week of development. After the zygote has begun to divide it becomes a morula, a complex Ball of embryonic cells. The morula becomes a blastocyst. The cells of the blastocyst will arrange themselves into am inner cell mass with an outer cell layer.

A graphic of pre-embryonic development taken from Human Biology page 356, Sylvia S. Mader

Embryonic Development

The embryonic development stage begins the second week and continues through the second month. Implantation occurs in the second week. HCG is secreted by the chorion which helps maintain the corpus luteum. The inner cell mass becomes the embryonic disk. The amniotic cavity surrounds the embryo and the yolk sac is a site for blood formation.

Gastrulation is morphogenesis in which cell move to form tissue layers called primary germ layers. At the end of gastrulation the embryonic disk becomes the embryo with the ectoderm, mesoderm, and endoderm. Each of these layers is associated with different parts of the body as illustrated below.

Illustration showing the three germ layers and their significance. Taken from Human Biology page 358, Sylvia S. Mader

Development of the heart and nervous system begins in the third week. In the fourth and fifth weeks a body stalk appears, this is the future umbilical cord. Little buds appear that will be future arms and legs. During weeks six through eight the embryo begins to look human. This is an important stage, drugs and alcohol can affect a developing embryo before the mother even knows she is pregnant.

Fetal Development

By the third month it is possible to determine the gender by ultrasound. The placenta is functioning and provides nourishment for the fetus. The placenta also secretes progesterone and estrogen. Cartilage begins to be replaced by bone during the third and fourth months. The skull has six areas where the bone is not fully formed. These are called fontanels. The fontanels provide the skull flexibility during birth.

The mother will usually feel movement around the fifth month. If the child is born at this time it is possible for it to survive, albiet there can be many problems for a premature child. During weeks eight and nine the fetus grows bigger. It positions itself in a head down position in preparation for birth. If a child does not come out head first it is called a breech birth. Because of the dangers in delivering a child in this position many women will have a cesarean section.

Birth

There are three stages to parturition, the process of giving birth. During Stage one uterine contractions cause the cervical canal to thin, a process called effacement. The amniotic membrane often ruptures during this stage, an event that is often referred to as one's "water breaking." Contractions are regular, unlike Braxton Hicks contractions, but they may be relatively far between for some time. Once the cervix is fully dilated, stage one is over.

During stage two, contractions are closer together, about every 1-2 minutes. The woman will feel a desire to push at this point. The baby is delivered during stage two. Sometimes a doctor may have to make a small incision called an episiotomy to enlarge the opening of the vaginal orifice.

Stage three is the delivery of the afterbirth, the placenta and membranes. This can occur as many as fifteen minutes after the baby is born.

The different stages of birth, taken from Human Biology page 370, Sylviia S. Mader.

Aging

There are different stages of life, infancy, childhood, adolescence, and adulthood. development does not end at birth, chidren continue to grow and age. Gerontology is the study of aging. This field, is increasing in interest because it is estimated that by the year 2030 over 20% of our population will be over the age of 65. You should know that Yavapai County is of particular interest because currently 25% of our population is over age 60! You can find this information through the census website, link below.

Aging has an effect on many of our body systems. Bone density decreases and in some cases can lead to osteoporosis. Skin becomes thinner and less elastic causing wrinkles to form.

Women reach menopause somewhere between 45 and 55. Men go through andropause but some sperm continue to be produced until death. It is a myth that older adults are not sexually active. In fact, incidence in STDs in adults over 45 is increasing. This is a particular problem in assisted living communities. There is lots of infomation on this at the CDC website and the Center for Healthy Aging, link below.

I think it is important to point out that there is much wisdom and life experience to be found in older adults. It grieves me that the US is an ageist society that almost worships youth. Many other cultures revere their oldest members. Aging does not mean that we have to become weak and sick. People can stay healthy longer by staying active and eating right. The adults I work with here in town are mostly very active and some are in their nineties. I am a richer person for knowing them.

I got this image from MSN office clipart. I like it because these ladies look like they are having a good time. Good for them!

Conclusion

Reproduction is a fascinating subject. It is even more interesting given the fact that I have had two children and have experienced it firsthand. It is easy for me to get on my soapbox about the aging issue as I live and breathe it every day.

Works Cited

Human Biology, Sylvia S. Mader

Professor Frolich's Power Point

www.sciencemuseum.org

hesc.stanford.edu/research/programs/human.html (this will not go live but you can find it under the photo)

www.northstar.k12.ak.us

www.riversideonline.com

http://www.healthyagingprograms.org/

http://quickfacts.census.gov/qfd/states/04/04025.html