Tuesday, February 24, 2009

Final Thoughts


Many of you have worked hard this semester and have learned a great deal of biology. You should be congratulated for that. You still have a long way to go, so I encourage you to keep working hard. If you are frustrated by your performance in the course thus far don't be disappointed. You have two more midterms, lab, and the final exam to raise your grade so keep at it.

Thanks for making this a great semester. I have enjoyed getting to know some of you a little bit this semester and I look forward to getting to know more of you in the future. I would like to say that I will miss you all, but I am ready for a break! Have a great semester and keep in touch.

See you at the final,

Mark McG

Answer Key for Second Midterm

The BAC will meet Wednesday at noon in room 204 in McClellan Hall. Please attend if you can, but don't miss a class to come to the BAC meeting.

Multiple Choice Answers

Form 1 and Form 2

1. a
2. b
3. b
4. a or e
5. d
6. c
7. d
8. b
9. a
10. b
11. d
12. a
13. d
14. b
15. b
16. c
17. d
18. a
19. b
20. e
21. b
22. c
23. a
24. d
25. d
26. a
27. d
28. c
29. b
30. a

Essay Questions

Photosynthesis Question

The rate of photosynthesis can be limited directly, or indirectly, by a variety of environmental factors. Agriculture provides us food and fiber and is a major component of the economy in many parts of the world. Farmers attempt to increase the production of their crops by fertilizing and irrigating.
Discuss how fertilization and irrigation can increase agricultural production by increasing rates of photosynthesis. An excellent answer will indicate how these activities affect the physiology of plants in a way that increases the rate of photosynthesis.

The rate of photosynthesis can be limited by a variety of environmental factors including temperature, light level, carbon dioxide, soil fertility, and water availability. Some of these factors (e.g., soil fertility and soil moisture level) can be manipulated by farmers in a way that can increase photosynthetic rates production whereas other factors (e.g., temperature and atmospheric carbon dioxide concentration) are harder to manipulate on a large scale. Thus, most large scale agriculture involves increasing soil nutrients by adding fertilizers and increasing soil moisture availability by irrigation.

Water can indirectly regulate the rate of photosynthesis. Irrigating crops increases the soil moisture content. When plants are water stressed they respond by closing their stomata which blocks carbon dioxide from entering the leaf by diffusion. Carbon dioxide is required in the light independent reactions of photosynthesis. The ultimate purpose of the light independent reactions is to use energy from ATP and NADPH to convert carbon dioxide to glucose which contains chemical energy stored in its chemical bonds. Specifically, carbon dioxide is involved in the following reaction-
CO2 + RuBP  PGA
Irrigating crops increases the soil moisture content which allows plants to keep their stomata open longer which allows them to take up carbon dioxide for a longer period of time which allows photosynthesis to occur longer.

Fertilizing can add a number of potentially limiting resources to the soil. An important nutrient in all fertilizers is nitrogen. Because nitrogen is an important element in amino acids, increasing soil nitrogen content can increase the rate of nitrogen uptake which allows plants to make more proteins. By far the most protein in plants is RuBP carboxylase, the enzyme that catalyzes the reaction between carbon dioxide and RuBP. Fertilizing with nitrogen increases the amount of RuBP carboxylase in the plant which speeds up carbon fixation and allows more carbon to be produced in the Calvin Cycle.

Life Cycle Question

Diagram the life cycle of a fern. Discuss the characteristics of ferns that makes them advanced relative to the mosses and primitive relative to the gymnosperms. Be sure to discuss the evolutionary advantage of the advanced traits relative to the primitive traits.
(I am sorry that this doesn't look right when it is posted)

zygote (2N) ==> sporophyte (2N) ==> sporangia (2n)
fertilization
meiosis
archegonia => (egg N) <== gametophyte <== spores
angtheridia=> (sperm N) mitosis


Ferns appeared at an intermediate step of the evolution of plants. Thus, they are advanced relative to the bryophytes but primitive relative to the gymnosperms. Ferns are considered to be advanced relative to the bryophytes because they are diploid dominant and have a vascular system and they are considered to be primitive to the gymnosperms because they are homosporous rather than heterosporous and they reproduce by spores rather than seeds.

Diploid dominance is advantageous relative to haploid dominance because individuals are not as adversely affected by lethal alleles. If an organism is haploid then they will die if they get a lethal mutation. However, if that lethal mutation is recessive, then that allele can be masked in the heterozygote state in a diploid organisms. Thus, dipoloid dominant species should have higher survival levels than homozygous dominant species.

The evolution of the vascular system (xylem, phloem, roots, stems, leaves) which occurred for the first time in ferns is a major adaptation for terrestrial plants. Plants with a vascular system produce true roots that can take up water and nutrients from the soil. They have xylem, the tissues that carry water and nutrients from the roots to the leaves, and phloem that carries sugar around the plant. Having a vascular system is a huge advantage because it allows plants to achieve a much larger size and allows them to inhabit more arid regions.

Heterospory, the production of two types of spores to produce two types of gametophytes, is an advantage over homospory, the production of one type of spore to produce one type of gametophyte because heterosporous plants no longer have to rely on swimming sperm. Thus, heterosporous plants have the potential to live in environments that are arid year around.

Reproducing by seeds is a major advantage relative to reproducing by spores because an individual seed has a much larger probability of survival. Seeds contain an embryo, seed coat and nutritive tissues. The resources held in the seed are used to nourish the germinating seedling until it is has established its roots and leaves well enough to collect its own food.

Thursday, February 19, 2009

Plant Diversity- The 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

Wednesday, February 18, 2009

Plant Diversity- Algae to 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

Tuesday, February 17, 2009

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 That Limit 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