Estellvenia Sanders (CVHS, deaf
students) What is a cell?
Estellvenia introduced these key words: cell, cell wall, cell membrane, nucleus, vacuoles. The focus of the lesson was to identify parts of the cell (key words). As a model for the cell, she introduced a cucumber slice. The nucleus of the cell corresponded to the "seeds", the cytoplasm to the fruit , the "membrane: with the inner cucumber wall, and the "cell wall" with the outer skin of the cucumber. She mentioned that one could also use a transversely sliced hard-boiled egg (which is, in effect, a single cell) to visualize cellular structure.
Erma Lee (Williams School) -- Geochemistry: Movement of
Erma led us through an investigation of the movement of ground water through materials of various porosities. She added water to cups of equal size, filled with sand and marbles, respectively. To our surprise, each cup held about half of its volume in water. We had expected to be able to put less water in the cup filled with sand, because the grains of sand pack more tightly together, resulting in smaller interstitial spaces between the grains of sand than between marbles. However, the number of interstitial spaces between grains of sand is much greater than for marbles, so that total interstitial space is about the same for both. With an identical cup with fine (porous) sawdust, we were able to add one full cup of water. This we attributed to the absorbance (permeability) of the sawdust compared to near zero absorbance for sand grains and marbles.
At Ken's suggestion, we added a cup of sand to a cup half-filled with water (reverse order to that done above), to see if the results would be the same as our previous experiment with sand. They weren't, in that more sand could be mixed in when we added sand to water! (There was some concern as to whether these experiments were done with sufficient care the first time, since we might have been able to mix in "more sand" if we had tried.)
Ken Schug explained that, if both sand grains and marbles consist of spheres at the closest possible packing, the fraction of interstitial volume should be independent of the sizes of the spheres, as we observed in the first part. It seems quite reasonable for the sand grains to be essentially spherical. Fascinating, Erma!
Karlene Joseph (Lane Tech Biology) Facial features with a
Karlene passed out a handout concerning facial features for us to determine for our own faces by looking at ourselves with a hand mirror. We catalogued some of the following facial features:
|eye color||protrusion of lips||nostril shape||cleft chin?||ear point?|
|eyebrow texture||eyebrow color||eye separation||eye shape||hairy ears?|
|eyelash length||dimples?||ear size||hair body||freckles?|
|length of mouth||nose size||earlobes free or attached?||widow's peak?||face shape|
|thickness of lips||nose shape||chin shape||hair color||chin shape|
We made quantitative measurements -- wherever possible -- by using a ruler with the mirror and we resorted to descriptive answers only where necessary. In her handout, the "genotype" as well as the "phenotype" for each of these traits is given. [See http://plato.stanford.edu/entries/genotype-phenotype/ and http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/GP/Definition.html.] For example, the genotype [coded information] for "pointed nose" is "rr" and the "phenotype" is the physical characteristic of pointed features.
The distances between our eyes varied from 2.8 to 3.5 cm, and it was unclear as to how to separate "eyes close" and "eyes far apart" with our small sample. Also, it was unclear as to whether the distances should be normalized to overall body size, or taken as absolute indicators.
In a larger class, we could have pooled the data to see whether the "allele frequencies" for the class are consistent with the Hardy-Weinberg equilibrium equation, the basic equation for population genetics. [Hardy-Weinberg Equation: http://anthro.palomar.edu/synthetic/synth_2.htm] Attached or unattached earlobes would be a good trait for such a test. Good, Karlene!
Notes taken by Ben Stark