Of course, there were a few folks present at the volleyball Roosters and Hens 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

Rooster 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).

Hens 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).

Chick 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.

Beetle Sex 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.

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 105 Reproductive System
Information on the male and female reproductive systems
Bio 105 Conception, Prenatal Development, and Birth
Information on reproductive physiology, copulation, fertilization, embryonic and fetal development, birth, contraceptives, and STDs
Bio 105 Linked and Sex-Linked Genes
See discussion on “What is ‘Sex,’ Anyway?” that starts about half-way down the page.
Bio 104 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,
  2. If you choose an assisted reproduction technique,
  3. If you choose a sexually-transmitted disease,
  4. If you choose a genetic disorder that affects the reproductive system,
  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

Copyright © 2006 by J. Stein Carter. All rights reserved.
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