f course, there were a few folks present at the volleyball picnic who were more interested in the opposite sex than in playing volleyball. Farmer Melanie’s roosters were definitely interested in showing off for the hens and in chasing each other away from the hens. Hens and roosters have pretty-much all the same parts in their reproductive systems as humans do, and those parts work pretty-much the same as they do in humans.

Reproductive System

Just like human males, roosters have testes in which sperm are produced. Also like human males, roosters’ testes produce lots of testosterone, and that, in turn, stimulates development of their secondary sexual traits. In the case of roosters, that typically includes the comb on top of their heads, the red wattles that hang down under their chins, big, arching tail feathers, and spurs on the inside edges of their feet. One big difference between roosters and human males is that roosters do not have an organ analogous to a man’s penis. In both roosters and hens, there is only one external opening called a cloaca, and the “ends” of the reproductive, excretory, and digestive systems all empty into the cloaca. Thus, when roosters mate with hens, they match up their cloaca with the hen’s cloaca for the few seconds they’re able to maintain that close of contact. More detailed information on the human reproductive system can be found on the Biol. 105 Reproductive System Web page (see link below).

Just like human females, hens have ovaries in which eggs are produced. Well, actully, if we’re going to be picky about details, we need to modify that a bit. . . it turns out that as little hens grow up, typically only the left ovary develops and eventually makes eggs. When a hen’s ovary makes eggs, they don’t start out like the chicken eggs you’re used to seeing. Initially, the egg is made of only the actual egg cell and the yolk. In humans, when a couple has sexual intercourse, the man’s sperm swim up her uterus and fallopian tubes to fertilize her egg near the far end of the fallopian tube. Similarly, in chickens, the rooster’s sperm must swim up her reproductive tract and fertilize the egg cell before her body adds all the other “stuff” around the outside. Then, her body adds the egg white (albumin) which is similar in function and chemical make-up to amniotic fluid in humans, and then, finally adds an egg shell around the outside. Human females don’t need and so don’t make an egg shell because in humans, the embryo will be implanted and retained in the uterus as it develops.
However, many people are surprised to find out that the chicken eggs they buy at the grocery store are not fertilized – the hens that laid those eggs never even saw a rooster. Again, this is very similar to what happens in human females. In a human female, approximately every 28 to 29 days or so (that’s a rough average, and individual women’s bodies vary a lot from that), an egg matures and bursts out of one of her ovaries, then starts to travel down that fallopian tube. That process will happen regardless of if that egg gets fertilized or not, and if it is not fertilized, she’ll have her period. Similar to that, but much more frequently (about every day or two), an egg is produced in a hen’s body, and her reproductive tract coats that egg with albumin and an egg shell, then passes it out, regardless of if it was ever fertilized or not. Thus, humans who “raise” eggs for profit have realized they don’t need to keep roosters around and pay to feed them (which, of course, eats into their profit margin).

In humans, if an egg is fertilized and successfully implants in the woman’s uterus a week later, the week-old new baby will continue to grow and develop, until nine months later, (s)he is born. Similarly, if a rooster’s sperm fertilize a hen’s eggs, and if she broods the eggs to keep them warm, in 21 days, little chicks will hatch out and continue to grow and develop.

In insects, too, the whole process is fairly similar: males and females mate, females lay fertilized eggs, and the eggs hatch into young. However, there are more species of insects in the world than all the rest of the plants and animals put together, so there is a wide variety of “details” involved.

• Males of most beetles have an intromittent (meaning, it goes inside) organ that fits into the female’s reproductive tract, while male grasshoppers, katydids, and butterflies have claspers that grab onto the entrance of the female’s reproductive system. In some insects, the male’s intromittent organ is specially modified to clean out or kill any sperm from a previous mating that might be present in the female’s reproductive system before depositing that male’s sperm.
• Male katydids and crickets transfer their sperm in an external sack, and the sperm must swim from there into the female’s reproductive tract (before she turns around and eats the sack).
• Females of most insects have an organ called a seminal receptacle that’s part of their reproductive tract, and this organ is used to store sperm until needed to fertilize eggs. For example, a queen honeybee (the one in the upper left corner of this photo is marked with red on her back) mates only once in her life, and from that one mating she stores enough sperm to fertilize all the eggs she’ll lay for the rest of her life (about another 3 to 4 years). If you’ve ever seen the inside of a bee hive, that’s a lot of worker bees!
• Females of some insects, such as Madagascar Hissing Cockroaches, hold the fertilized eggs within their body while the eggs develop, and then the eggs are laid as they hatch (or hatch as they’re laid?), so that the female gives birth to live young. Insects aren’t the only animals in which this occurs: guppies, for example, do this, too.
• The eggs of certain kinds of parasitic wasps can hatch into hundreds or thousands of young! That way, when a female has “one shot” at laying an egg in a host (most of these are parasites on other insects like caterpillars, not on humans), that egg can produce many offspring.
• Some kinds of walkingsticks and other insects can produce eggs by parthenogenesis, the ability of an unfertilized egg to develop and hatch. Often, those insects live in environments where there aren’t many mates around and they’re pretty spread out, so the chances of mating are slim. In that case, parthenogenesis allows the species to keep going even if a mate can’t be found.
• Interestingly, in honeybees, fertilized eggs hatch into females (workers and queens), while unfertilized eggs hatch into males (drones).

Background Information

Links to Related Information on Our Web Server

The following Web pages contain information related to male and female reproductive systems, birth control, and sexually-transmitted diseases.

Bio Lecture Reproductive System

Information on the male and female reproductive systems

Bio Lecture Conception, Prenatal Development, and Birth

Information on reproductive physiology, copulation, fertilization, embryonic and fetal development, birth, contraceptives, and STDs

Bio Lecture Linked and Sex-Linked Genes

See discussion on “What is ‘Sex,’ Anyway?” that starts about half-way down the page.

Bio Lecture Meiosis

Review the process of meiosis (covered in an earlier topic) by which egg and sperm cells are produced.

Your Assignment
Reproductive System

There will be one, combined assignment for the Reproductive System and Prenatal Development topics. Thus, even though this will appear on each of those pages to remind you, you only need to do it once. You are asked to pick either a contraceptive or an assisted reproduction technique or a sexually-transmitted disease (STD) or a genetic disorder that affects the reproductive system, and do further “research” to learn more about your chosen topic. The grading criteria for this assignment are given below, and you should also refer to those as you work on the assignment. A total of xx points is possible.

1. If you choose a contraceptive,
   • Background: Find out and explain how it is made (for example, one kind of contraceptive is a hormone extracted from the urine of pregnant mares). Are there any ethical concerns with the way it is made?
   • Description: What is its mode of action (how does it work)? Does it prevent ovulation, or does it kill sperm, or does it prevent a week-old embryo from implanting in the uterus (which. by the way, technically, makes it an abortifacient), etc. Is it done to or by the man or the woman or the two of them, together? Are there any ethical concerns with the way it works? What is its “failure” (is a baby really a “failure”...) rate?
   • Side-Effects: What are its side effects and/or effects on other body organs and systems?
2. If you choose an assisted reproduction technique,
   • Background: Find out and explain what kind of pre-testing and diagnostics are done before this technique can be or is used. When is it considered appropriate to use this particular technique? Are there any ethical concerns with any of this pre-testing or the recommendation to use this technique?
   • Description: Describe how this technique works or is applied. What is done? Is it done to or by the man or the woman or the two of them, together? How dangerous or invasive is this technique? What is the success rate? Are there any ethical concerns associated with this technique?
   • Side-Effects: What are the side effects (increased mental stress?) and/or effects on other body organs or systems?
3. If you choose a sexually-transmitted disease,
   • Background: When was this disease first “discovered” (recognized, described), and by whom? What are its signs and symptoms? How is it diagnosed, and are there any ethical issues related to its diagnosis?
   • Description: How is this disease typically treated? What is the success or cure rate? For how long after the treatment is a person considered still “contagious,” and when is (s)he considered “cured?” Are there any ethical issues related to how this disease is treated?
   • Side-Effects: What are the side effects of this disease or its treatment? How does it affect other body organs and systems (for example, human papilloma virus increases the chances of cervical cancer)?
4. If you choose a genetic disorder that affects the reproductive system,
   • Background: When was this condition first “discovered” (recognized, described), and by whom? What are its signs and symptoms? How is it diagnosed, and are there any ethical issues related to its diagnosis? Does having this trait affect the person’s fertility?
   • Description: Does this condition need to be treated medically in any way? Does any kind of treatment improve the condition or the person’s quality of life? What are the goals/objectives of treatment? What is the “success” rate of treatment (and what is considered to be “success”)?
   • Side-Effects: What are the side effects of this disorder — how does it affect other body organs and systems?
5. At this point, if you are a registered student, you should submit your work.

Grading Criteria

1.   Background Information:
2	—	The background information was very thorough and detailed
1	—	The background information was OK
0	—	The background information was skimpy or lacking
2	—	The background information was correct
1	—	The background information was mostly correct, but had a few mistakes
0	—	The background information was mostly incorrect
2.   Description:
2	—	The description for the chosen topic was very thorough and detailed
1	—	The description for the chosen topic was OK
0	—	The description for the chosen topic was skimpy or lacking
2	—	The description information was correct
1	—	The description information was mostly correct, but had a few mistakes
0	—	The description information was mostly incorrect
3.   Side Effects:
2	—	The side-effects information was very thorough and detailed
2	—	The side-effects information was OK
0	—	The side-effects information was skimpy or lacking
2	—	The side-effects information information was correct
1	—	The side-effects information information was mostly correct, but had a few mistakes
0	—	The side-effects information information was mostly incorrect
4.   Overall::
2	—	The grammar, English usage, punctuation, and spelling were very good
1	—	The grammar, etc. were OK
0	—	The grammar, etc. were poor
2	—	The student, obviously, went beyond the minimum requirements of the assignment
1	—	The student adequately completed the assignment
0	—	The student completed considerably less of the assignment than what was required
2	—	It is evident that the student used much insight, thoughtfulness, and critical thinking when completing this assignment
1	—	The student adequately thought about the assignment – there was, perhaps, a bit of “fuzzy thinking” in a couple places
0	—	The assignment gives the appearance of being “slapped together” just to get it done, with little evidence of thoughtfulness
Total Possible:
18	—	total points