BIOS10119 Lecture Notes - Lecture 1: Moralistic Fallacy, Class Discrimination, Fallacy

Andrea Smith was taking notes for her biology exam. Her professor has told her that the exam would cover, in part, the di erences between sexual and asexual reproduction. As she reviewed her notes and prepared for today’s class, she was thinking about her own reproductive dilemma. If only asexual reproduction were the case for humans, maybe she wouldn’t be in this mess. Or at least there wouldn’t be questions about who was the father of her twins. “Dwelling on it isn’t going to help me prepare for class, and right now I have got to nish this chapter on animal reproduction,” she thought. She tried to concentrate and forget about her current dilemma as she feverishly typed on her notepad:

Asexual or sexual reproduction: 3 types of asexual reproduction: (1) ssion: separation of a parent organism into two or more individuals of equal size, (2) budding: growth of new individuals from outgrowths of existing organisms, and (3) fragmentation accompanied by regeneration: the breaking of the body into several pieces, some or all of which develop into new complete individuals through the regrowth of lost body parts. NOTE: Be able to explain the di erences between sexual and asexual reproduction!

She suddenly let out a long sigh. “It’ll be ne,” she thought. “I just hope that none of my family or friends watches the show. What was I thinking when I agreed to this? But that’s what Xavier wanted, and I will do whatever it takes to prove he is the father. Besides I am going to need the money if I have to take care of these babies on my own!”

e next day in class she was feeling even more nervous and was becoming increasingly angry as she thought about her current situation. Her thoughts were interrupted by the sound of her professor’s voice:

“OK, class,” her teacher was saying, “that wraps up asexual reproduction. Let’s move on to reproductive cycles
and patterns. Most animals exhibit cycles in their reproductive activity. Reproductive cycles are often controlled
by hormonal and environmental cues. Animals may reproduce either exclusively asexually or sexually while other animals alternate between the two methods. For example, some animals can lay eggs of two types, depending on
the environment and/or season. One egg type matures only if it is fertilized while the other type does not require fertilization for development, a process called parthenogenesis. Some animals, and in rare cases humans, have both male and female reproductive systems. Some hermaphrodites can fertilize themselves, but most must mate with a member of the same species. Please look over these handouts and answer the questions that follow.”

As the other students read through the assignment, Andrea was thinking: “I’m dealing with a case of sexual reproduction that no doubt started with the fertilization of my egg with, hopefully, Xavier’s sperm. at reminds me, I need to make sure I go over internal and external fertilization again in my notes. I’m not sure I completely understand it.”

All this started the night Xavier had come came over to talk to Andrea about their break-up. He had smelled and looked so good that evening. e events of that night had left Andrea wondering if there was really some truth to that stu about pheromones, which Andrea has learned in her class were chemical signals released by one organism that in uence the behavior of another individual of the same species. Even though Andrea had met someone else and had

“An Unusual Case of Animal Reproduction” by Powell and Tillman Page 1

been seeing Neo for a while, she hadn’t been able to resist Xavier. Neither she nor Xavier had behaved like themselves that night. It was unlike them not to use some barrier method of contraception. As the class wrapped up, Andrea’s mind was still on her upcoming appearance on a daytime talk show. In some ways she was dreading it; but she was determined to prove what she believed she had known all along: at Xavier was the father of her twins.

Questions

1. What is the di erence between asexual and sexual reproduction?
2. List and de ne some types of asexual reproduction. Give one example of each. 3. What is the di erence between parthenogenesis and hermaphroditism?
4. What is the di erence between internal and external fertilization?
5. What is the function of pheromones?

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“An Unusual Case of Animal Reproduction” by Powell and Tillman

Page 2

Part II – The Pregnancy

“I can’t believe it has come to this! Airing our dirty laundry on national television. I never thought Xavier would let things get so out of hand.”

It was late and Andrea was so upset she couldn’t sleep. She tried studying for the upcoming exam, but she couldn’t concentrate. She decided to get an early start on packing. She was so angry with Xavier. How could he have left her pregnant and alone, she thought, as she neatly added her new dress to the bag? How could he think that their babies might belong to someone else? She grabbed her journal, about to add it to the bag, but instead sat in her cozy corner chair and began to read:

January 12, 2007

I’m pregnant with twins! Sometimes it’s still hard to believe because it was so unexpected. I feel like I am about to pop! I know that Xavier is the father of my babies and I can’t wait for us to be a family. But he has doubts about it all because he knows that I met someone else during the brief time that we split up. And he wants to be sure that he is the father before we can move on. But what if it is Neo, the new guy I met? ere’s a slight chance but I doubt it. I know the exact time of conception. It was the night Xavier came over to talk about our relationship. It was a little over a week after that night that the pregnancy test detected the increase in HCG. I guess I just missed him so much.

I do regret that Xavier hasn’t been around much during the pregnancy. He has missed the development of our babies. In the past months, I have heard the babies’ heartbeats and felt them moving around. I wish he would come back because it’s obvious that I am pregnant now. Hopefully we can talk through our di erences and get back together before the pregnancy gets di cult—the frequent urination and back pain my OB/GYN keeps warning me about. I know there is no way he will ever let me go through labor alone. I only pray the contractions are not more than I can bear. Xavier seems committed to the idea of a paternity test. Hopefully it won’t come to that, but if it does, we’re going to a daytime show to gure all this out.”

“Wow! at seems like a lifetime ago,” she thought. “Now we have these beautiful twins and we don’t seem any closer to becoming the real family I dreamed about. Well this will all be over in a couple of days. I am 110% con dent that the twins belong to Xavier, not Neo. I can’t wait to see the look on Xavier’s face and hear him apologize once he sees the results of the paternity test!”

Questions

1. What does Andrea mean by time of conception?
2. How is HCG used to determine pregnancy?
3. List some changes that occur with the fetus/mother during the 1st, 2nd, and 3rd trimesters. 4. What hormones are responsible for inducing and regulating labor?
5. What trimester is Andrea in during this journal entry?

NATIONAL CENTER FOR CASE STUDY TEACHING IN SCIENCE

“An Unusual Case of Animal Reproduction” by Powell and Tillman

Page 3

Part III – The Results

Andrea replayed the words over and over again in her mind: “Xavier, you ARE the father!” She was ecstatic. Finally, she could breathe, knowing that Xavier was the father of her babies. en she heard what the host had to say next...

“Neo...YOU ARE the father!”
Andrea looked around in disbelief. She heard herself saying, “What do you mean? You just said Xavier was the father!

If Xavier is the father, how can he be the father?” she asked as she pointed toward Neo.

“Well, this is a rst, even for our show. But it appears that your twins were fathered by both of these men.”

“I can’t believe it. e rst time I do something like this and I end up with twins and two fathers! Not only did I expose myself to potentially deadly STDs, but now I have two children, whom I have no doubt that I will be raising alone, and I have put my school career in jeopardy,” Andrea thought.

She still couldn’t believe this was really happening to her. How was it possible that her TWINS have di erent fathers? What were the events that must have happened within her body that could lead to these circumstances? She grabbed her

journal from her bag and ipped back to the entry describing her feelings the day she found out she was having twins:

August 23, 2006

I just came back from another Dr’s appointment. Dr. Blossom informed me that I am having two babies— twins—fraternal. I don’t know if they are boys or girls yet. One could be a boy and the other a girl. I still can’t believe this has happened. Xavier has to be the father. He has to be! I will have to just play the hand I have dealt myself. How stupid was I? I was going to practice abstinence after Xavier and I broke up...and I certainly wasn’t planning on meeting and getting involved with Neo! I can’t believe that Neo and I didn’t use a condom either. And it’s no excuse that we had been drinking. I just got caught up in the moment with Xavier—going down memory lane and things got all sentimental. I could have at least thought to use the rhythm method and kept track of when ovulation may occur. is has to be the most irresponsible thing I have ever done! Why did I stop taking my birth control pills anyway? And I have no idea where I put that diaphragm. Undoubtedly, some people will judge me as the type of woman who should have a tubal ligation that would permanently prevent any pregnancy.

Everything hit her at that very second. She closed her journal and just sat there for a moment. Andrea was reminded that she had stopped taking the pill the month before she became pregnant. She remembered that physicians recommend that a woman wait at least one cycle after she stops taking the pill before becoming pregnant because there is a chance that multiple ovulations may occur. Did it have something to with oogenesis? Andrea was so confused she just couldn’t keep things straight in her mind. She thought about it for a minute to let it all sink in.

Andrea sat back and thought about the lecture on animal reproduction the week before. She pulled out her lecture notes on the menstrual cycle, the basic foundation of everything that she was going through.

Questions

1. Describe the two types of cycles that occur in female mammals (menstrual vs. estrous).

2. Compare and contrast the sterilization techniques (vasectomy and tubal ligation) and the temporary and reversible methods discussed in the case.

3. What are the functions of GnRH, FSH, LH, estrogen, and progesterone?

4. How can the paternity results be explained? Your answer should consider the amount of time before and after ovulation a woman is at risk for pregnancy and how long sperm can survive in the reproductive tract. Your discussion may include the following terms: ova, oogenesis, and fertilization, etc.

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“An Unusual Case of Animal Reproduction” by Powell and Tillman Page 4

Andrea’s Lecture Notes: The Female Reproductive Cycle

(I) e female reproductive cycle involves both the uterus and the ovaries:

Menstrual cycle = uterine cycle
• Refers to the speci c changes that occur in the uterus

Ovarian cycle
• Cyclic events in the ovaries that regulate the menstrual/uterine cycle

(II) Hypothalamus secretes gonadotrophin-releasing hormone (GnRH) which stimulates the anterior pituitary to secretefollicle stimulating hormone (FSH) and luteinizing hormone (LH) into the blood. FSH and LH regulate the ovarian cycle.

~OVARIAN CYCLE:

Folicular Phase

FSH and LH stimulate a follicle to grow

e growing follicle releases estrogen

Ovulation

• An LH surge triggers ovulation

Luteal Phase

LH stimulates ruptured follicle to become corpus luteum

Corpus luteum secretes estrogen and progesterone, which inhibits LH and FSH secretion from the pituitary

Corpus luteum disintegrates

Estrogen and progesterone levels decrease, releasing the inhibitory e ect on the hypothalamus and the

pituitary

FSH and LH are released and a new cycle begins

(III) Ovarian hormones, estrogen and progesterone, regulate the uterine (menstrual) cycle ~UTERINE CYCLE:

Proliferative Phase

• increasing estrogen levels causes the uterine lining (endometrium) to thicken: prepares the uterus for

implantation of the blastocyst

Secretory Phase
• increased levels of estrogen and progesterone following ovulation maintains the endometrium by increasing

blood supply and growth of endometrial glands that secretes nutrients

Menstrual Flow Phase
• decreased levels of estrogen and progesterone cause the uterine arteries to spasm, depriving the endometrium

of blood: endometrium disintegrates, resulting in menstruation

Based on the information in the case study, Animal Reproduction, please answer the following questions.

Andrea is pregnant and is trying to calculate the time of conception.What is time of conception and how is it determined?

What are the functions of GnRH, FSH LH, estrogen and progesterone in pregnancy?

Andrea is having twins but the babies have two different fathers.Explain the difference between fraternal and identical twins.Which are these?How could the babies have different fathers?

Check the Course Announcements at the beginning of the week following the deadline for Part 1 to discover exactly what happened to the deer population on the Kaibab plateau. This information is essential for completion of Part 2.

The second part of your project is to take what you've learned about the Kaibab forest ecosystem and write an accurate description of the boom and bust of this deer population, using correct ecological language. Consider as many of the aspects of these events as you can. Be sure to consider the effects on the other species in the ecosystem as well.

Refer to your on-line materials and the appropriate sections of your textbook. Your discussion should include (but not be confined to) consideration of all of the following concepts: carrying capacity, predator/prey relationships, population cycling, resource partitioning, competitive exclusion, fundamental and realized niches, food chains, food webs and trophic pyramids.

Note that the purpose of this exercise is for you to demonstrate to me that you understand these important concepts of ecology by utilizing them accurately and appropriately in the description of the disaster in the Kaibab forest. Your essay must include both clear indications that you understand the meanings of these principles and clear indication that you understand how these principles can be used to describe what happened to the ecosystem on the Kaibab plateau.

information given of part one: On the north rim of the Grand Canyon, an area called the Kaibab plateau, there is a conifer forest called the Kaibab forest. The forest's trees include pine, fir and spruce. Shrubbery includes a variety of willows, raspberries, etc. A hundred years ago, this forest was a stable ecosystem, housing, among other species, a population of about four thousand mule deer.

These deer were hunted by local Native Americans, who used them for food and other materials. They were also hunted by predators like pumas, wolves and coyotes.

In 1906, the US made this region into a National Game Preserve. With the intent of protecting the deer, hunting was forbidden. Bounties were paid for killing the pumas, wolves and other large animals that preyed on the deer. By 1925, more than 6000 predators had been killed, virtually wiping out the ecosystem's large predators.

*Read the instructions* for Part 2, then consider this additional information about the Kaibab forest.
There are some hints in here to suggest the *minimum* range of the subjects you need to discuss to explain this; You will need to read the chapters and the course materials to understand the meanings of these concepts, and to be able to use them to explain the Kaibab disaster. There are other important concepts as well--so keep your eyes open as you read. It wouldn't hurt to go back and read the original description in Part 1, either. And you may find it necessary to do some quick browsing in areas of your book not directly related to ecology. (For instance, you might just want to do some looking into the nature and importance of the bark and twig ends on a tree.) Do not neglect the on-line essays which are provided for you in this Unit. What you should *not* do is Google the Kaibab, or look it up on a source like Wikipedia. This is not about what you can *discover* about the Kaibab forest.
Your grade will depend upon how completely you convince me you understand the concepts involved in this description. This is your test on ecology--your goal is to convince me that you understand the concepts and terminology of the subject, and can apply them to a real life situation.
Before we go on to the new information, there are a few things that came up as I was grading the Part 1 submissions which I think I should mention, just to keep you from straying in some incorrect directions.
First, remember that your concern is the fate of the Kaibab forest in the *immediate* sense--over tens of years, not thousands. There are no evolutionary issues here, at least in the short term (and that's your concern right now). So we won't be talking about adaptive radiation.
Also, keep your focus on the *Kaibab forest*, not on other ecosystems. Oh, and remember that the Kaibab is pretty isolated--emigration really isn't a reasonable alternative for the species living in this forest.
And finally, until we get to Part 3, the only human interaction we are considering is the initial decision to put bounties on those large predators, which led to their near-extinction in the area. You will be thinking a bit about human hunters trying to control the deer population toward the end, but the rest of the time you're just concerned with the natural processes going on in the ecosystem.
Okay, now on to the actual description of what happened in the Kaibab Forest as a result of killing almost all of the large predators. Remember, your task in Part 2 is going to be to describe and explain all of this using the concepts of ecology which you are learning in Unit 2 of the course.
*****
The primary, most immediate outcome of the removal of the predators from the ecosystem was that the deer population exploded, because the loss of the normal predator populations removed a primary source of population control. And the expanding deer population ate a *lot.* [Hint: explaining this requires discussion of population cycling, predator prey relationships and carrying capacities.]
As the deer population got larger and larger, their impact upon their favored food plants became extreme. They ate a much larger percentage of each year's plant populations, and they ate a larger portion of each individual plant. They also began to eat more from the plants which they didn't like so well--plants normally consumed by other herbivores in the ecosystem. In the winter, the starving deer ate about anything remotely resembling food, including twigs and bark from trees. As a result of the destruction of many of the twig ends of the trees, the spring tree growth was inhibited (why?). The stripping of the bark caused the death of some of the trees (why?). The extreme browsing on the herbaceous plants caused shifts in the plant population diversity, as the deer drove many of their favored plants into extinction within the ecosystem. [Hint: Explanation here will need to include discussion of resource partitioning, competitive exclusion, and realized vs. fundamental niches.]
All of this also impacted upon the rest of the animals in the ecosystem, since many of them depended upon the same kinds of food the deer ate, or depended upon the foods that the deer were eating because they could no longer get the food they favored. Then of course, the smaller predatory species (like foxes and owls) depended upon the health of those populations of small herbivores (like rabbits and mice). [Hint: sounds like food chains, food webs and trophic pyramids come into this part.]
After a couple of decades, the ecosystem was quite altered. The plant community was very different from what it had been before, and the deer herd, though not extinct, was composed of significantly smaller and weaker deer than the herd from the 1890s. (This was partially due to their straightened circumstances re. food, but also partially due to the absence of predators. Why would the removal of the natural predators cause this change in the general vigor of the deer in the herd (and why would the substitution of *human* hunting not exert the same positive influence)?)
Okay, the next phase of your assignment is to describe all the things going on in this ecosystem using the proper terminology that you should be learning from studying this unit of the course. Note that your use of terms like, for instance, "resource partitioning" needs to show that you understand not just what the concept means, but how it is reflected in this specific ecological disaster. Feel free to discuss this as much as you want to on your Discussion Board. Don't ignore the little questions tucked into the above description, and pay attention to those hints. Your response must demonstrate proper understanding of these concepts and how they are demonstrated by the disaster in the Kaibab forest.
This is the largest part of your exam project; your response should reflect the fact that this is a 50 point "essay" question. You are given a lot of organizational clues and hints about what issues you need to include in the information above. Make use of those things.

Tasmanian devils (Sarcophilus harrisii), the world’s largest carnivorous marsupials, are facing extinction. Not from hunting, or habitat loss, but from within; a transmissible cancerous derivative of Schwann cells, responsible for devil facial tumour disease (DFTD). First seen in 1996, the disease has spread widely though the population, and is now estimated to be present in 80% of the population. With the grim prognosis of ~100% mortality in 12-18 months, animals that once went through multiple breeding cycles are now lucky to reproduce once before death, resulting in a 70% decline in their population over the past decade. The cancer is transmitted by biting (a common ritual used by these animals to establish and maintain social position), with cancer cells from one animal (the biter) being implanted in the wound inflicted on the other animal. Equally common in both sexes, the disease itself is more prevalent in animals higher on the social scale, presumably reflecting higher levels of social interaction (biting). The cancer is usually first evident as facial tumors, from which metastasis to cervical lymph nodes occurs, often followed by dissemination to other organ systems. Cause of death is by organ failure or by malnutrition in those with facial tumors large enough to prevent feeding. Based on what we have covered regarding the Major Histocompatibility Complex, you would expect the passage of a cancer from one individual to another* to be a rare event (to see just how rare, read the accompanying popular press piece from the New York Times). Here are some things that you already know: *Yes, some viruses can cause cancer (example: Hepatitis B virus and liver cancer), and you can transmit a virus from one individual to another; but that is not the same thing as passing the cancer itself. v Almost all nucleated cells express high levels of class I MHC proteins on their surface. v Class I MHC proteins collect peptides produced from endogenous proteins and display them at the cell surface. v Different Class I MHC proteins bind and display different peptides. v Developing cytotoxic T-cells that recognize self-antigens are eliminated. v Mature cytotoxic T-cells conduct surveillance by scanning the peptides displayed by class I MHC proteins. v Mature cytotoxic T-cells that recognize an antigen on a cell will kill that cell (recall that cytotoxic T cell activity is important in rejection of tissue transplants).

Before the questions:
v Tasmanian Devils are not immunosuppressed.
v Tasmanian Devil cytotoxic T-cells are not broken, they can kill cells.
So neither of those should be part of your answers.
This is an ongoing research topic with large gaps in our knowledge; we really don’t fully understand how this works
and so there is no “correct” answer. Your job is to provide a logical argument, with some research and details to
support your contention. Note that in questions 1 & 2 class I MHC should be part of your answer, but not in
question 3.

Questions:
1.) Acquiring DFTD is basically like receiving a transplant that is not rejected. How can that be? Suggest a possible
way this could occur. Be sure to explain why you think this would work, and then explain how you would test
that model to determine if it were correct. (10 point question).
2.) Canine Transmissible Venereal Tumor (CTVT) is the other know transmissible cancer in mammals. Unlike
DFTD, CTVT does not usually result in death. Do a little research on this disease and summarize how it is
different from DFTD. Provide an explanation as to why one is lethal and the other is generally not. (10 point
question).
3.) Recently, researchers at Washington State University determined that some Tasmanian devils had developed
resistance to this cancer. By scanning partial genome sequences of resistant and susceptible animals (a
complete devil genome has yet to be assembled) they identified a set of genes where mutations appeared to
enhance resistance. Speculate as to the function of the proteins these genes encode, and explain why that
might provide for resistance (note: they were NOT MHC genes).

Mainly need guidance/ideas for #1's 1 and 3!