When grading your essays, the TAs and I strive to make the score that you receive on your essay accurately indicate how well you have answered the question. At times it is possible that the score that you received on your essay does not correlate with how well you answer the question so this essay resubmission policy is designed to correct those rare occurances.
Rules for Submitting Essays
1. Answers written in pencil can not be submitted for regrading.
2. Do not turn in essays until you have carefully examined the answer keys (provided below or on bulletin board). Take a look at the answer key and carefully compare your answer to the key. Ask the following questions. Did your answer actually answer the question that was asked? Did your answer include all of the details shown on the answer key? Was your answer as well organized as the answer key?
3. I only want to look at tests where you feel there is a severe difference between the score you earned and how well you answered the question (that means 3 or more poingt). I do NOT want to see any 19/20s!
4. To resubmit an essay please type out a brief paragraph describing why you think that your answer deserved more points that it was awarded. Staple the essay to this sheet (make sure you put your name on it) and leave the sheet in a box that is located outside of my office in McClellan Hall (room 215) by 5:00 PM on Monday March 26.
Answer Key For First Midterm
Essay
Exponential population growth is a model of population growth that only occurs when the per capita growth rate is constant. In populations experiencing exponential growth, the population size keeps increasing over time at ever increasing rates. Thus, populations growing exponentially would keep increasing in size forever. Obviously, we do not see this pattern of growth in nature, so this must not be a realistic model of population growth.
The problem with exponential growth is that the per capita growth rate is not constant. In fact, in most species we expect that the per capita growth rate should be negatively density dependent. The per capita growth rate (r) can be calculated by subtracting the per capita death rate (d) from the per capita birth rate (r). Because both per capita birth rates and per capita death rates are density dependent, it is not surprising that per capita growth rate is also density dependent and thus not a constant.
The per capita birth rate is negatively density dependent. As population sizes increase there are more individuals competing for the same amount of food, so each individual gets less food. Because the number of babies that a female produces is related to the amount of resources she has, as each female has less food, they should have fewer births resulting in a lower per capita birth rate.
The per capita death rate is positively density dependent. Per capita death rates increase with population size for three possible reasons. First, as population size increases competition causes each individual to get less food which increases their chance of dying of starvation. Second, predation rates could be higher in larger populations if predators were attracted to areas of high prey density or if prey were easier to catch when population sizes were high (maybe there are not enough hiding places to go around). Finally, mortality caused by disease could be higher in more dense populations because it is easier to spread disease throughout the population when individuals are in close contact.
Because per capita birth rates decrease and per capita death rates increase as population size increases, the per capita growth rate decreases as population sizes increases which results in a non-exponential pattern of growth.
Essay
The process of natural selection causes traits that increase the survival, reproduction, and mating ability of organisms. Thus, long tails in peacocks have been molded by this process.
If we assume that the long tails of peacocks can be explained by the handicap principle, then the reason that females choose to mate with the males with the longest tails is that the long tails are a “handicap” to effective survival in the peacocks natural environment. Thus, males that have managed to survive with large tails must have genes that code for phenotypic characteristics that make them especially good at surviving (finding food, escaping predation , etc.). Thus, by choosing to mate with a male with the most extreme tail, a female hopes to benefit by passing on those good survival genes to their offspring so both her sons and her daughters should have higher survival.
For the process of natural selection to occur there must be variation in phenotype within a population, the variation must be heritable, and variation in traits must affect fitness. Assume that tail length has a genetic component and that there is variation in tail length within a population of peacock ancestors. If females are choosing males with the most extreme trait because of the handicap principle then males with longest tails should be chosen to mate more often and the offspring of females that mate with long tails should survive better. Thus, there is a fitness benefit associated with mating with a male with the longest tail.
If this is true, then over time the frequency distribution of tail length in males should move to the right (directional selection) so we see increases in both the maximum, minimum, and mean tail length. The introduction of new mutations that allow males to produce even longer tails should allow directional selection to continue so that the mean tail length of males increases. We would expect directional selection to continue until the mating benefit of having the longest tail was offset by the survival disadvantage of having an extremely long tail and the fitness advantage of having the longest tail disappears. At this point stabilizing slection would kick in and direction selection would cease.
Answer Key for Retest
Posted on the wall where I posted MC answers.
Answer Key for Second Midterm
Graph A.
As light intensity increases the rate of photosynthesis increases until the rate of photosynthesis reaches a plateau. Initially, increases in light intensity greatly increase the rate of photosynthesis but as light intensity increases, the rate of increase in photosynthesis decreases until it equals zero.
Graph B.
As the concentration of carbon dioxide increases the rate of photosynthesis increases until the rate of photosynthesis reaches a plateau. Initially, increases in carbon dioxide concentration greatly increase the rate of photosynthesis but as carbon dioxide levels increase, the rate of increase of photosynthesis decreases until it equals zero.
Graph C
As temperature increases the rate of photosynthesis increases until it reaches a maximum and then decreases until the rate of photosynthesis is zero.
Essay
The rate of photosynthesis can be limited by a variety of environmental factors including light intensity, atmospheric carbon dioxide concentration, temperature, and soil nutrient content.
Increasing light intensity results in an increase in photosynthetic rates until photosynthetic rates reach a maximum suggesting that light intensity can limit the rate of photosynthesis. Light intensity limits the rate of photosynthesis by limiting the production of ATP and NADPH that are required to power the Calvin Cycle.
When further increases in light intensity fail to increase photosynthetic rates then other factors such as atmospheric carbon dioxide concentration or the amount of RuBP carboxylase have become the rate limiting step. The fact that the same increase in light intensity results in diminishing increases in photosynthetic rate as light intensity increases suggests that multiple factors can be limiting at the same time. When light levels are low light appears to be most limiting, but as light intensity increases other factors in addition to light levels appear to limit photosynthetic rates.
Increasing atmospheric carbon dioxide concentrations results in an increase in photosynthetic rates until photosynthetic rates reach a maximum suggesting that the atmospheric concentration of carbon dioxide can also limit the rate of photosynthesis. Carbon dioxide limits the rate of photosynthesis because carbon dioxide is used in the Calvin Cycle to produce glucose.
When further increases in atmospheric carbon dioxide concentration fail to increase photosynthetic rates then other factors such as light availability or the amount of RuBP carboxylase have become the rate limiting factors. The fact that the same increase in carbon dioxide content results in diminishing increases in photosynthetic rate as light intensity increases suggests that multiple factors can be limiting at the same time. When carbon dioxide concentrations are low carbon dioxide concentration appears to be most limiting factor, but as carbon dioxide concentration increases other factors in addition to light levels appear to limit photosynthetic rates.
Essay
Humans require energy to do biological work. The energy used to power biological work in humans come in the form of energy released by ATP. Energy in ATP is converted from energy stored in chemical bonds of glucose by the process of cellular respiration. Humans are capable of breaking down sugar to release ATP in both aerobic and anaerobic conditions so they use both aerobic and anaerobic respiration.
Aerobic respiration breaks down glucose in the presence of oxygen to release 38 ATP per glucose. Glycolysis, which occurs in the cytosol of the cell, breaks down glucose into two molecules of pyryuvate + H+ which requires the input of energy from 2 ATPs to release energy in 4 ATPs. Hydrogen ions are picked up by the hydrogen carrier NADH and then released to react with oxygen to form water. The pyruvate moves into the mitochondria where is is broken down to produce acetyl Co A and CO2. The Acetyl Co A enters the Krebs cycle where one molecule of ATP is release for each Acetyl CoA that enters the cycle. An excited electron undergoes electron transport which produces a large number of ATP. The ATPs are produced by chemiosmosis which is powered by a hydrogen ion concentration gradient that is produced when energy released by electron transport is used to actively transport H+. Aerobic respiration is a very effective way of converting glucose into ATP.
When oxygen is not available to remove the H+ from the system then organisms must use an anaerobic pathway. Glucose is still broken down by glycolysis with the same net gain of 2 ATP per glucose. In order to keep glycolysis going forward the pyruvate and H+ react to form acetaldehyde which is converted to ethanol (alcohol fementation). Alcohol fermentation is not as advantageous to the cells because alcohol can be poisonous to cells and potential energy in pyruvate can not be released. Humans need to use anaerobic respiration when they are so active that they are using oxygen faster than their system can supply it such that cells momentarily become anoxic environments.
Tuesday, March 9, 2010
Thursday, March 4, 2010
Multiple Choice Answers for Midterm #2 and BAC Report
Here are the final answers to the multiple choice portion of the second midterm. The original answers I posted contained several mistakes (sorry for the confusion and extra stress) so please compare your answers to these.
Form 1 (Blue Test)
1. b
2. c
3. d
4. a
5. e
6. all answers considered correct (BAC)
7. d
8. d
9. a
10. all answers considered correct (BAC)
11. e
12. a
13. b
14. c
15. d
16. b
17. a
18. a
19. b
20. a
21. e
22. b
23. a
24. e
25. d
26. a
27. e
28. d
29. b
30. c
Form 2 (Pink test)
1. a
2. e
3. b
4. c
5. b
6. c
7. d
8. a
9. e
10 all answers correct (BAC)
11. d
12. e
13. d
14. a
15. all answers correct (BAC)
16. e
17. a
18. b
19. c
20. d
21. b
22. a
23. a
24. b
25. a
26. e
27. b
28. d
29. a
30. d
BAC Report
Thanks to the members of the BAC (Brittany Luker, Isaac Perez, Sarah Qureshi, Brady Douglas, Patrick Thomas, Paulina Ramirez, Jordan Ardoin, Kadie Bowman, Ashlei Taylor, Kim Gorton, James Walls, Jonathan Hickey, Kendall Kennedy, Britney Williams, and Reid Smalley) for the work yesterday afternoon. I think they broke the record for the longest BAC meeting in history. They brought forward a number of questions for discussion.
DENIED
Most of the problems that students had with the questions appeared to arise because they were not answering the question that I asked.
9-pink, 5-blue
The question asks which species is most efficient at converting energy stored in glucose into ATP. The process that does this is cellular respiration. All three of the organisms listed as possible answers conduct aerobic respiration under the conditions described in the question so they are equally efficient at converting glucose into ATP. Thus, the correct answer is E.
13-pink, 8- blue
The question asks which human activities have increased the rate that carbon dioxide is ADDED to the atmosphere. Both burning coal and burning trees increases the rate that carbon dioxide is added to the atmosphere. Cutting down trees decreases the rate that carbon dioxide is removed from the atmosphere. Although it is true that decreasing the rate that carbon is removed from the atmosphere will result in an increase in atmospheric carbon dioxide content over time, this is not what the question asks. Correct answer D
20-pink, 15-blue
Chemiosmosis is the process that adds energy to ATP during both photosynthesis and aerobic respiration. Chemiosmosis is powered by the concentration gradient that is created when hydrogen ions are actively transported from the stroma inside the thylakoid space which occurs during electron flow. The process of chemiosmosis does not result in active transport of hydrogen ions, but depends on it. Correct answer D.
21-pink, 16-blue
This question asks when ATP is produced during LINEAR electron flow. Because the question asks about linear electron flow anything that happens during cyclic electroon flow is irrelevant! The only correct answer that refers to linear flow is B.
22-pink, 17-blue
This question asks about things that occur during the Calvin Cycle. Several students tried to artue that Carbon dioxide combines with RuBP to produce glyceraldehyde phosphate. The actual product produced during this reaction are an unstable 6-carbon intermediate which breaks down to PGA (either of those would have been correct answers if they were choices). Although it is true that glyceraldehyde phosphate is produced several steps down the line in the Calvin Cycle, you can't possibly think that any chemist would ever define the results of a chemical reaction in that way. Correct answer A
26-pink, 21-blue
This questions asks about the net gain of ATP during ALCOHOL FERMENTATION. Alcohol fermentation occurs as part of anaerobic respiration. All of the ATP released during anaerobic respiration comes from glycolysis. NO ATPS ARE PRODUCED BY ALCOHOL FERMENTATION. The only possible answer is E.
BAC recomendations accepted
10-pink, 6-blue
The seeds consumed by sparrows are angiosperms. These seeds are not dispersed by the birds they are consumed by the birds (seed predation). So I think the correct answe chould be D. However, in the book (PG. 625) is discusses seeds as "dispersable stage". While it is true that seeds are dispersable, the adaptations that allow seeds to be dispersed are produced by the fruit. However, I see that this statement could have been misleading and we didn't spend very much time discussing seed dispersal. Thus, all answers to this questions will be graded as correct.
15-pink, 10- blue
The statement in answer (a) is garbled enough that there is no best answer to this question. Thus, all answers will be considered to be correct.
Form 1 (Blue Test)
1. b
2. c
3. d
4. a
5. e
6. all answers considered correct (BAC)
7. d
8. d
9. a
10. all answers considered correct (BAC)
11. e
12. a
13. b
14. c
15. d
16. b
17. a
18. a
19. b
20. a
21. e
22. b
23. a
24. e
25. d
26. a
27. e
28. d
29. b
30. c
Form 2 (Pink test)
1. a
2. e
3. b
4. c
5. b
6. c
7. d
8. a
9. e
10 all answers correct (BAC)
11. d
12. e
13. d
14. a
15. all answers correct (BAC)
16. e
17. a
18. b
19. c
20. d
21. b
22. a
23. a
24. b
25. a
26. e
27. b
28. d
29. a
30. d
BAC Report
Thanks to the members of the BAC (Brittany Luker, Isaac Perez, Sarah Qureshi, Brady Douglas, Patrick Thomas, Paulina Ramirez, Jordan Ardoin, Kadie Bowman, Ashlei Taylor, Kim Gorton, James Walls, Jonathan Hickey, Kendall Kennedy, Britney Williams, and Reid Smalley) for the work yesterday afternoon. I think they broke the record for the longest BAC meeting in history. They brought forward a number of questions for discussion.
DENIED
Most of the problems that students had with the questions appeared to arise because they were not answering the question that I asked.
9-pink, 5-blue
The question asks which species is most efficient at converting energy stored in glucose into ATP. The process that does this is cellular respiration. All three of the organisms listed as possible answers conduct aerobic respiration under the conditions described in the question so they are equally efficient at converting glucose into ATP. Thus, the correct answer is E.
13-pink, 8- blue
The question asks which human activities have increased the rate that carbon dioxide is ADDED to the atmosphere. Both burning coal and burning trees increases the rate that carbon dioxide is added to the atmosphere. Cutting down trees decreases the rate that carbon dioxide is removed from the atmosphere. Although it is true that decreasing the rate that carbon is removed from the atmosphere will result in an increase in atmospheric carbon dioxide content over time, this is not what the question asks. Correct answer D
20-pink, 15-blue
Chemiosmosis is the process that adds energy to ATP during both photosynthesis and aerobic respiration. Chemiosmosis is powered by the concentration gradient that is created when hydrogen ions are actively transported from the stroma inside the thylakoid space which occurs during electron flow. The process of chemiosmosis does not result in active transport of hydrogen ions, but depends on it. Correct answer D.
21-pink, 16-blue
This question asks when ATP is produced during LINEAR electron flow. Because the question asks about linear electron flow anything that happens during cyclic electroon flow is irrelevant! The only correct answer that refers to linear flow is B.
22-pink, 17-blue
This question asks about things that occur during the Calvin Cycle. Several students tried to artue that Carbon dioxide combines with RuBP to produce glyceraldehyde phosphate. The actual product produced during this reaction are an unstable 6-carbon intermediate which breaks down to PGA (either of those would have been correct answers if they were choices). Although it is true that glyceraldehyde phosphate is produced several steps down the line in the Calvin Cycle, you can't possibly think that any chemist would ever define the results of a chemical reaction in that way. Correct answer A
26-pink, 21-blue
This questions asks about the net gain of ATP during ALCOHOL FERMENTATION. Alcohol fermentation occurs as part of anaerobic respiration. All of the ATP released during anaerobic respiration comes from glycolysis. NO ATPS ARE PRODUCED BY ALCOHOL FERMENTATION. The only possible answer is E.
BAC recomendations accepted
10-pink, 6-blue
The seeds consumed by sparrows are angiosperms. These seeds are not dispersed by the birds they are consumed by the birds (seed predation). So I think the correct answe chould be D. However, in the book (PG. 625) is discusses seeds as "dispersable stage". While it is true that seeds are dispersable, the adaptations that allow seeds to be dispersed are produced by the fruit. However, I see that this statement could have been misleading and we didn't spend very much time discussing seed dispersal. Thus, all answers to this questions will be graded as correct.
15-pink, 10- blue
The statement in answer (a) is garbled enough that there is no best answer to this question. Thus, all answers will be considered to be correct.
Sunday, February 28, 2010
Errors in Answer Key to Past Midterms
Several students have informed me that the answers provided in the back of the lab manual are not correct. I don't have access to the lab manual so I can't check this out.
I am sorry if I did not post the correct answer (no idea what went wrong). You can find the correct answers
http://biol1404.blogspot.com/2009/02/answer-key-for-second-midterm.html
Sorry for the inconvenience.
I am sorry if I did not post the correct answer (no idea what went wrong). You can find the correct answers
http://biol1404.blogspot.com/2009/02/answer-key-for-second-midterm.html
Sorry for the inconvenience.
Thursday, February 25, 2010
Plant Diversity- Gymnosperms and Angiosperms
Gymosperms and angiosperms are the "seed plants".
Gymnosperms
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- defne and contrast homospory and heterospory
- discuss the evolutionary advantage of heterosporty over homospory
- identify the parts of a seed and discuss why reproducing by seeds is an advantaged compared to reproducing by spores
- discuss the life cycle of a pine
- discuss the characteristics of pines that are advanced relative to the ferns and those that are primitive relative to the angiosperms
Angiosperms
Expected Learning Outcomes
At the end of the course a fully engaged student should be able to
- discuss the parts of a flower
- discuss the evolutionary advantage of reproducing by flowers rather than by cones
- discuss the life cycle of an angiosperm
- discuss the characteristics of angiosperms that are advanced relative to the pines and those that are primitive relative to the angiosperms
- discuss why angiosperms are the most successful of all plant groups
Plant Diversity- Ferns
Ferns are examples of the first vascular plants.
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- discuss the components of the vascular system
- discuss the advantage of a having a vascular system
- diagram the life cycle of a fern
- discuss the morphological and physiological characteristics of ferns
- discuss the characteristics of ferns that makes them considered to be advanced relative to mosses but primitive relative to the gumnosperms
- discuss how the morphological and life history characteristics limits their size and geographic distrubution
Plant Diversity- Algae and Mosses
As I mentioned in class, plants are interesting to me because the are so different than we are. At first these differences will cause unfamiliarity but eventually you will not be so bogged down by learning new vocabulary and you will hopefully come to realize that plants are more interesting than you might have thought (and besides, no plants means no dorritos, french fries, or beer?).
Further Viewing
1) Here is the slideshow that I will use in class for the final three lectures.
http://www.slideshare.net/secret/DBv71wnKTH1YBN
2) Here is a powerpoint presentation from a group called "world of teaching" that covers plant diversity? There are many "quiz questions" that should be helpful to look at.
http://www.worldofteaching.com/powerpoints/biology/Plant%20Divisions.ppt
Primitive Plants
Expected Learning Outcomes
A the end of this course a fully engaged student should be able to
- functionally define a plant
- discuss the characteristics of a primitive plant such as Chlamydomonas
- diagram a life cycle of a human
- diagram the life cycle of Chlamydomonas
- distinguish between oogamy and isogamy
- discuss the evolutionary advantage of multicellularity, diploid dominance, and oogamy
Transition to Land
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- discuss the problems plants face when moving to the land
- discuss the characteristics of the ancestor of land plants
- diagram the life cycle of a moss
- discuss the morphological and physiological characteristics of mosses
- discuss the characteristics of mosses that makes them considered to be advanced relative to primitive plants but primitive relative to the ferns
- discuss how the morphological and life history characteristics of mosses limits their growth and geographic distribution
Cellular Respiration
Cellular respiration converts chemical energy in glucos to chemical energy in ATP which is the ultimate source of energy used to do "biological work".
Glycolysis
1) Glycolysis animation
http://www.youtube.com/watch?v=7hiwSCUoSZY
2) Another Glycolysis animation- this one goes into a little more chemical detail so it might be useful if you are intersted in knowing more about the chemistry
http://www.youtube.com/watch?v=x-stLxqPt6E
Anaerobic Respiration
Alcohol Fermentation and Lactic Acid Fermentation
Further Reading
Alcohol Fermentation- http://www.tempeh.info/fermentation/alcohol-fermentation.php
Lactic Acid Fermentation- http://www.tempeh.info/fermentation/lactic-acid-fermentation.php
Further Viewing
http://www.youtube.com/watch?v=y_k8xLrBUfg
Aerobic Respiration
1) Aerobic Respiration
http://www.youtube.com/watch?v=iXmw3fR8fh0
2) Krebs Cycle
http://www.youtube.com/watch?v=aCypoN3X7KQ&feature=related
3) Electron Transfer Chain
http://www.teachertube.com/view_video.php?viewkey=a67b8fcdafb25c122359
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- discus glycolysis, anaerobic respiration, alcohol fermentation, lactic acid fermentation, aerobic respiration, the Kreb's Cycle, and electron transport
- compare and contrast aerobic respiration with anaerobic respiration
- discus why the breakdown of glucose to produce ATP is so much more efficient when oxygen is present
- describe where in the cell the different parts of cellular respiration take place
Factors Limiting the Rate of Photosynthesis
The rate of photosynthesis can be limited by a variety of environmental factors including
1) light
2) concentration of carbon dioxide
3) water
4) soil nutrients
Which factor most limits photosynthesis varies between environments.
Light- Can directly limit the rate of photosythesis by limiting the rate at which ATP and NADPH are produced
Carbon dioxide- can directly limit the rate of photosynthesis by limiting the rate at which the Calvin Cyle takes place
Water- can indirectly limit the rate of photosynthesis. When plants are water stressed they close their stomata (long before the concentration of water in the cell becomes too low for water to supply electrons to P680). Thus, the rate of photosynthesis is water stressed plants is directly limited by the amount of carbon dioxide in the leaf.
Soil Nutrients- Sometimes the rate limiting step in photosynthesis is the rate at which carbon dioxide + RuBP ==> PGA. This reaction is catalyzed by the enzyme RuBP carboxylase. Increasing the amount of RuBP carboxlyase in the cell can increase the rate at which this reaction occurs. Fertilizing plants with nitrogen will increase the amount of RuBP Carboxylase produced by the plant.
Expected Learning Outcomes
By the end of this class a fully engaged student should be able to
- discuss the factors that can directly or indirectly limit the rates of photosynthesis
- discuss how the most limiting factors should vary between environments
- discuss how the activities of farmers such as irrigation and fertilization can increase photosynthetic rates
- interpret the graph at the top of the post (irradiance measures light intensity and the three lines represent different concentrations of carbon dioxide)
- explain what why the graph shows that shape
Why Are Plants Green or Why Aren't Plants Black?
If I was hired as an engineer to design a machine whose job was to convert light energy into chemical energy I probably would not choose to use a green pigment. Instead, I would choose to use a black pigment because black pigments would absorb more energy because they would absorb all wavelengths of light. If you look at a field of plants you will notice that they are green (OK this doesn't work too well around Lubbock in the winter)and we have learned that chlorophyll, a green pigment, is the dominant photosynthetic pigment. What is going on?
Here is one theory about why chlorophyll is the dominant photosynthetic pigment in plants today. Early on there were photosynthetic bacteria with purple pigments (purple is a combination of red and violet). These aquatic bacteria had a very simple sort of cyclic electron flow that was able to convert light energy into energy in ATP (they didn't have non-cyclic flow or the Calvin Cycle).
Origin of chlorophyll- The purple pigment absorbed all wavelengths of light except for the reds and violets. Thus, any bacteria using purple pigments that lived deeper in the water than the purple bacteria on the surface would have no light to use because it had all been absorbed by the surface bacteris (exploitative competition). Because red and violet wavelengths pass through to deeper water, bacteria that contained a pigment that was able to absorb these wavelengths would be able to coexist with the purple bacteria. This was the origin of chlorophyll.
Competition purple and green photosynthetic pigments. Over time there was competition between organisms with purple photosynthetic pigments and green photosynthetic pigments. Obviously, the green photosynthetic pigments won this competition because chlorophyll is the dominant photosynthetic pigment today (there are still examples of photosynthetic bacteria with purple pigments, but they are limited to very harsh environments). Interestingly, chlorophyll came to dominate, not because it was a better at absorbing light energy, but rather because the cyclic flow machinery associated with chlorophyll was more efficient at producing ATP than the machinery associated with the purple pigment was. Thus, it is an evolutionary accident that modern plants are green.
Black Plants
It would be possible for modern plants to be black if they had enough accessory pigments to allow them to absorb all wavelengths of light. In fact, some red algae that live deep below the surface where light levels are low are basically black. Because the amount of light is not the factor that limits the rate of photosynthesis in most terrestrial plants, it is not worth the cost of producing extra accessory pigments. However, deep in the ocean where light levels are low, plants benefit from being able to absorb all wavelengths of light so deep marine algae have invested in extra accessory pigments.
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- discuss why terrestrial plants to not invest in the accessory pigments required to make them black
Carbon Fixation
Technically, arbon fixation is defined as the first chemical reaction that incorporates carbon dioxide into an organic molecule (a molecule with more than one carbon atom).
In C3 photosynthesis the following step is considered to be carbon fixation-
carbon dioxide + RuBP ==> PGA
In CAM photosynthesis the following is considered to be carbon fixation-
carbon dioxide ===> malate
Note: CAM plants also have the reaction- carbon dioxide + RuBP ===> PGA, but in this case this step is not considered to be carbon fixation.
Sometimes people will loosely use the term carbon fixation to mean the production of glucose by photosynthesis. Be sure that you are aware of how different authors are using the term and you should attempt to use the term as precisely as possible in your own work.
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- define carbon fixation
- identify carbon fixation in C3 and CAM photosynthesis
Leaf Structure
In most plants, leaves are the major sites of photosynthesis. Thus, we can think of leaves as "photosynthesis machines" and use our knowledge of natural selection to try to understand aspects of leaf structure.
Further Reading
http://micro.magnet.fsu.edu/cells/leaftissue/leaftissue.html
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- discuss important differences between animals and plants in gas uptake
- diagram the cross section of a leaf
- explain the adaptive basis of leaf structure
Photosynthesis - Summary
Once you understand the light dependent reactions, the light independent reactions, and how these two sets of interactions are linked together then you understand the basics of photosynthesis. The pattern of photosythesis that we have discussed so far is known as "C3 photosynthesis" (it is named this becasue the first stable product of the Calvin Cycle is a molecule that contains three carbon atoms). C3 photosynthesis is considered to be the basic mechanism of photosynthesis.
As I have mentioned in class the best way to assure that you understand what is going on is that you should be able to describe photosynthesis at different levels of detail.
1) the one sentence answer
2) the one paragraph answer
3) the full detail answer
In my experience, students quickly get lost by worrying about the details. Thus, I suggest that you start at the one sentence answer, then move to the one paragraph answer, and finally finish up with the full detail answer. You will find that by thinking about the one sentence and the one paragraph answers you will have already figured out how to organize your full detail answer.
I suggest that you try writing out the answers to these questions at the three levels.
1) What is photosynthesis?
2) What are the light dependent reactions of photosynthesis?
3) What are the light independent reactions of photosynthesis?
4) What is a photosystem?
I encourage you to post your answers here and then to provide critical feedback to your classmates about their answers.
Friday, February 19, 2010
Retest Answers and BAC
I met with the BAC on Wednesday afternoon. The results of the BAC are included on the answer key,
1. c
2. c
3. c
4. b
5. e
6. b
7. d
8. e
9. c
10. a
11. d
12. a
13. a
14. d
15. b
16. a
17. e
18. b
19. b
20. c
21. c
22. e
23. d and e
24. e
25. a
26. c
27. c
28. e
29. a
30. a
1. c
2. c
3. c
4. b
5. e
6. b
7. d
8. e
9. c
10. a
11. d
12. a
13. a
14. d
15. b
16. a
17. e
18. b
19. b
20. c
21. c
22. e
23. d and e
24. e
25. a
26. c
27. c
28. e
29. a
30. a
Wednesday, February 17, 2010
Photosynthesis- Light Independent Reactions- Calvin Cycle
In the light independent reactions the energy stored in ATP and NADPH is converted to energy stored in glucose. This invovles a chemical cycle known as the Calvin Cycle.
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- discuss what links the light dependent and light independent reactions of photosynthesis
- describe the initial step of the Calvin Cycle
- describe the chemical reaction catalyzed by the enzyme RuBP carboxylase
- discuss some interesting characteristics of RuBP carboxylase
- define "carbon fixation" and identify the carbon fixation step in the different modes of photosynthesis
- diagram the Calvin Cycle (at the level of detail that I talked about in class)
- discuss where and why ATP and NADPH are required in the Calvin Cycle
- disucus where in the cell that the Calvin Cycle takes place
Further Viewing
1) This is an excellent animation (narrated by a man with a perfect "announcer's voice"). This animation goes into the amount of detail you are required to know for this class. It even has its own quiz, so see how you do.
http://highered.mcgraw-hill.com/sites/0070960526/student_view0/chapter5/animation_quiz_1.html
2) I didn't know that photosynthesis was such a popular subject for musicians (I can't belive I gave up what would surely have been a lucrative career as a rock star to become a biologist- who knew I could have combined the two). The guy in the video is kind of a dufus, but the song is pretty cool, and I learned something from watchig it.
http://www.youtube.com/watch?v=OYSD1jOD1dQ
3)This is quite a good video (sorry, no song involved). Note, this video concludes that glyceraldehyde phosphate is the result of the Calvin Cycle. For our purposes in this class we are going to conclude that glucose is the end result of this cycle.
http://www.youtube.com/watch?v=mHU27qYJNU0
4) Maybe you will find this animation to be helpful
http://www.science.smith.edu/departments/Biology/Bio231/calvin.html
Tuesday, February 16, 2010
Photosynthesis- Light Dependent Reactions
Photosythesis takes place in two steps. In the first step, known as the light dependent reactions, light energy is converted into chemical energy held in the bonds of ATP and NADPH.
Expected Learning Outcomes
By the end of this course a fully engaged student should be able to
- list the parts of a photosystem
- discuss the function of a photosystem
- describe where the light dependent reactions of photosythesis occur and discuss why these reactions occur in this location
- describe cyclc electron flow, be able to explain both the energetic result and what chemcical changes occur
- describe non-cyclic electron flow, be able to explain both the energetic result and what chemical changes occur
- describe the cause and the result of chemiosmosis
- answer the question- "why doesn't photosynthesis stop after the production of ATP and NADPH in the light dependent reactions
Further Reading
Here is a link to some fairly detailed info about photosynthesis (it contains some very good diagrams).
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookPS.html
Further Viewing
These videos contain animations that might help you to understand what is happening in the light dependent reactions. I encourage you to watch each of these videos.
1) This video has some great animations of what is going on in the light dependent reactions.
http://www.youtube.com/watch?v=hj_WKgnL6MI
2) This short video is a good review of the light dependent reactions.
http://www.youtube.com/watch?v=eY1ReqiYwYs&feature=related
3) This is a video of a woman with a very southern accent talking about photosyntheis with some decent animations.
http://www.youtube.com/watch?v=RFl25vSElaE&feature=related
4) This one comes complete with a "Photosyntheis Song." I guarantee that you will be humming this as you walk around campus!
http://www.teachertube.com/view_video.php?viewkey=dc9810ac32b3c413fb29
Sunday, February 14, 2010
Introduction to Energetics
Energy is required to do work. In order to understand the two important energetic processes taking place in living organims (photosynthesis and cellular respiration) it is useful to understand some basics of energetics.
Expected Learning Outcomes
By the end of the course a fully engaged student should be able to
- give examples of biological work
- list different forms of energy, give examples of the different forms, and give examples of energy conversions
- define the First and Second Laws of Thermodynamics and discuss why these laws are important for biologists
- discuss electromagnetic energy, including the wavelengths associated with different forms of electromagnetic energy and the relationship between wavelength and energy
- define a photon
- discuss the three things that can happen when a photon of light hits a molecule
- define a pigment
- draw and interpret an absorption spectrum
Further Reading
Electromagnetic radiation- http://www.eoearth.org/article/Electromagnetic_radiation
Homework Assignment- Photosynthesis
The next homework assignment, photosynthesis, is currently available on Mastering Biology.
Due Date: 11:59 PM Monday February 22nd
Point Value: 15 points
Homework Format: In order to reduce the chance that students are able to exchange answers, we will not make the answers of the quiz avaialble until after the quiz is due. When we choose this option, the Mastering Biology website does not allow you to have multiple chances to answer each question. Thus, you will only be able to attempt each qustion one time.
We will begin talking about energetics and photosynthesis on Monday, Feb 15th. Hopefully, I will have covered all of the information that you need in order to answer these questions by Friday, but certainly we will have covered all of this material by next Monday. Thus, I suggest that you not try the homework until after we have completed talking about both the light dependent and light independent reactions of photosynthesis
Things Students Have Sent Me About Climate Change
Hello,
I appreciate the links that students have sent me about climate change including the cartoon posted above and the link to the newspaper article posted below. Keep them coming!!
Bill Nye the Science Guy: Climate Change Deniers are Unpatriotic
http://rawstory.com/2010/02/bill-nye-climate-change-deniers-unpatriotic/
Thursday, February 11, 2010
Intersesion Courses at Junction Campus
Texas Tech offers courses during Intersession (May 12 - May 27th, 2010) the period between the end of Spring Semester and the start of the First Summer Session at our field station in Junction, TX. http://www.depts.ttu.edu/hillcountry/junction/junction%20acad%
The Department of Biological Sciences offers a number of courses at Junction during Intersession-
BIOL 4301-180 - Herpetology (Reptiles and Amphibians) - Dr. Lou Densmore
BIOL 3301-180 - Field Ecology - Dr. Mark McGinley
ZOOL 4406-180 - Mammalogy - Dr. Robert Bradley
ZOOL 4408-180 - General Ornithology - Dr. Kent Rylander
Courses taught in Junction are intense so you can basically plan on being involved in class mornng, afternoon, and evenings virtually every day of intersession. Because the classes are hands-on and there is lots of interaction between faculty and students, most students think that taking classes during intersession is a great opportunity (and you can get three credit hours in less than three weeks).
If you are interested in learning more about any of these classes then contact the professor. Of course, Field Ecology is the absolute bestest class offered in Junction, so if any of you are interested in learning more please let me know.
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