EnvSci Sem 1 08-09: New reading

Xerox a copy of Broome, J. The ethics of climate change. Scientific American, June 2008, pp. 97-102. The issue is still on the display shelf in Lopez Library. This reading will be taken up on Aug 19. Note that this change is already reflected in the syllabus posted on this blog.

BioIT Sem 1 08-09. Counts for 23 June 2008

I counted these:
Group 4: 258/0.1
Grp 1: 55/0.4
Grp 2: 114 rods/0.1 (Ankistrodesmus is definitely a pretty thing!)
Grp 6: 166/0.1
Grp 3: 120/0.2
Grp 5 counted theirs. I think it's 176/0.1?

Scenedasmus and Ankistrodesmus are so unique that I think it will be a good idea to see the growth curves that result when we grow them in the same flask. Let's see if we have time.

I read an interesting article in the latest issue of Nature (vol. 453, no. 29, pp. 583-585) by N. Lane: "Origins of death". Apparently, certain unicellular organisms engage in apoptosis, i.e., programmed cell death. Also known as cell suicide, apoptosis is a regular feature of multicellular eukoryotes, that is, of plant and animal cells. It's what keeps your nose and other organs from growing too large; a defect in apoptosis is one feature of cancer. But it was unusual to find it in unicellular eukaryotes, because single celled organisms have usually been considered immortal: when they asexually multiply by splitting, the resulting daughter cells are considered "babies". They die only when there's a poison in the water, or it's too hot, etc. Now it seems some unicellular eukaryotes can initiate their own death under certain conditions, such as the presence of some virus in the culture. Mass suicide of a population containing infected algae might be a way of protecting neighboring populations from the virus.

Just in case your cultures suddenly crash, we will deep freeze them, then get in touch with some scientists who have the facilities to detect the tell-tale signals of apoptosis. A crashed culture will be a BIG thing; in fact, I'm almost hoping they do crash. This might get us published!

BioIT 08-09: Comparison of models

Here's a simpler comparison of three different growth models to describe algal growth.

1. Constant growth rate (A). The same number of algae are added to the population every time. That is, the rate at which N grows is the same at all times, or

dN/dt = rate

where "rate" is a constant.

2. Exponential growth (B). The rate at which N grows (dN/dt) is not constant, and depends at every time on the size of the population able to reproduce. The amount of new algae being added to the population represents, however, a constant proportion of the population. We call that constant proportion "rate", the equivalent of "interest rate" in banking.

That is,

dN/dt = N x rate

3. Sigmoid or density-dependent growth (C). As in the exponential model, the new population is a certain fraction of the old (dN/dt = N x rate). But now this proportion "rate" is not constant and depends on the N. That is, algae are reproducing maximally (rate = ratemax) when N is very low, and no longer reproducing (rate = 0) when the population reaches a certain size called the "carrying capacity", cc. (You might say the algae are "having the most fun when no one else is around" then become more and more "shy" as their neighbors increase. In reality, it has to do with less and less food and space as population grows: the culture has become too crowded for growth to be sustainable.) For simplicity, the relation between "rate" and N may be described by the linear curve in D.

Thus, as in the exponential

dN/dt = N x rate

but

rate = ratemax - (ratemax/cc) x N, the equation of the line in D.

Thus,

dN/dt = N x (ratemax - (ratemax/cc) x N), or factoring out

dN/dt = N x ratemax x (1 - N/cc)

What can make this confusing is the word "rate". In one context it refers to a proportion of the population (the variable "rate"), while in another context the same word refers to the number of new algae per unit time (dN/dt). Thus, if you are confused, change "rate" (proportion) into "interest" (as in banking), and use the word exclusively to refer to dN/dt.

Environmental Science Sem1 08-09 debates

Debate 1:
This house believes that order is not found in nature but is imposed on it by the human mind
Diaz-Hipolito-Asilo versus Sayo-Camello-Lim

Debate 2:
Earth's interconnectedness is evidence of intelligent design
Landong-Banalo-Aguila versus Siazon-Mindanao-Dona

Debate 3:
Man in his uncivilized state is inherently good
Verzosa-Abracosa versus Ortiz-Casilana

Debate 4:
To best protect its environment the Philippine government must impose socialist measures
Galang-Bendero versus Relucio-Laraya

Debate 5:
The state of knowledge today is sufficient to justify lifting all existing bans on the commercialization of genetically modified crops (or animals)
Valeroso-Gonzalez-Bato versus Perez-Toledo-Anastacio

Debate 6:
___ is the root of all environmental problems (Government defines ___)
Villafuerte-Benavidez-Calimlim versus Lee-Hiquiana-Marquez

FORMAT: Asian Parliamentary, modified to include audience participation

Environmental Science 1st sem 2008-09 syllabus

Topics

1. Harvey, Introduction to the circulation (June 13)
2. Descartes, Rules for the direction of (June 17)
3. (June 20)
4. Thomas, World’s biggest membrane (June 24)
5. Tansley, The ecosystem (June 27)
6. Vernadsky, The biosphere (July 1)
7. Leopold, Odyssey (July 4)
8. Commoner, The closing circle (July 8)
9. Lovelock, The recognition of Gaia (July 11)
10. Free cut (July 14)
11. Free cut (July 18)
12. LONG EXAM 1 (July 22)
13. Miller, Dimensions of deformity (July 25)
14. (July 29)
15. Clemens, The climax concept (Aug 1)
16. Boulding, Economics of spaceship (Aug 5)
17. Dillard, Intricacy (Aug 8)
18. Hardin, The tragedy of the commons (Aug 12)
19. Leopold, The land ethic (Aug 15)
20. Broome, The ethics of climate change (Aug 19)
21. Marsh, Man and nature (Aug 22)
22. (Aug 26)
23. LONG EXAM 2 (Aug 29)
24. McKibben, The end of nature (Sep 2)
25. (Sep 5)
26. Grumbine, The politics of wilderness (Sep 9)
27. (Sep 12)
28. DEBATE 1 (Sep 16)
29. DEBATE 2 (Sep 19)
30. DEBATE 3 (Sep 23)
31. DEBATE 4 (Sep 26)
32. DEBATE 5 (Sep 30)
33. DEBATE 6 (Oct 3)

Reference: Selections from Keeping Things Whole: Readings in Environmental Science, 2003. The Great Books Foundation, Chicago, 298 pp.