BIOLOGY 103 FALL, 2000 FORUM, WEEK 3

We collected four different plant organisms, ranging in size from 35'+ to 3" tall. The samples consisted of a leaf from a maple tree, a leaf from a 6' tall bush, a blade of grass measuring 5", and a little three leaf clover measuring in at 3".

After converting our samples into slides where we could observe the size and structure of the cell, we collected the following data: Tree cells averaged in size 41.6 micrometers; Bush cells 23.4 micrometers; Grass cells 55.9 mircrometers; Clover cells 26.87 micrometers.

Due to the variety of sizes ranging, there is no solid evidence present to proove that cell size determines organizm size. First off, the largest organism obviously did not display the largest cell size, the organism which did so measured only 5", the second smallest organism in the sample series. The Bush and Clover, two organisms varying greatly in size did not do so with their cell size, since at average measurements of 23.4 and 26.87, the sizes were relatively close.

From our general observations, we noted that the structure and shape of the cell was relatively similar to the overall structure of the organism or the large sample we collected. The cells which came from leaves which were jagged and pointy around the edges had cells with ridged and pointy edges; the grass had long, retangular shaped cells and the clover had small, round cells.

Even though our evidence somewhat disproves that cell size is not relative to organism size, we cannot make a general conclusion that it definitely does not determine size, since we feel that for the larger organisms our samples were not fully adequate. It is possible that the cell structure in the bark, branches, trunks, roots, etc. differ. So it seems this experiment of ours has left us hanging at a cross road.

Jeff's hypothesis: the larger the organism, the larger the cell's size would be. Basically, it consisted of the concept that an organism's size is directly related to its cell size. We found this hypothesis to be wrong: we picked three different plants that grew on the ground as samples to be used in observation in trying to prove the hypothesis wrong.

We went to the courtyard and gathered three sample plants. All three plants that we collected were from the ground. The largest leaf that we collected measured 7cm x 4 cm, the second largest leaf measured 4.5 com x 5.0 cm and the third leaf, the smallest one, measured 2.5cm x 2.2 cm.

We scraped off cell-layer samples off the surface of the leaves onto the slides. For each leaf, we took three samples as we thought getting the average sizes would be more accurate.

The largest plant's cells averaged 39 micrometers; The second plant's cells averaged 19 micrometers and the smallest plant's cells averaged 32 x 83.2 micrometers (it was rectangular in shape unlike the other two which were circular-shaped cells).

We observed the cells to be similar in shape although the third plant's cells were slightly more rectangular. Also, we noted that the sizes of the plants themselves measure as a ratio of 2:1, as in the largest plant was almost double in length to the second plant's size while the second plant's length was double that of the smallest plant.

Results: The first two plants did provide evidence that plant size determined the cell sizes. But the third and smallest plant's result went against the hypothesis since its' cell size averaged to be greater than those of the largest plant's cells.

Problems:

· Are three samples enough to determine the size or average size of the plant's cells?

· We only observed tiny parts of a huge organism. It might not have been enough just to pick up one or two leaves and then scrape samples off of the surfaces. Maybe further sampling would be more accurate.

Overall Conclusions:

Although our evidence seems to challenge the hypothesis, the problems mentioned above could be a factor toward invalidating the observations we have made.

Just to toss in my skeptical view point of the day (it's starting to become a trend for me):

In class we talked about diversity falling into "natural" divisions, clusters. And though I'll agree that it seems that the vast majority of creatures do follow this structure there are always exceptions, admittedly few and far between, but they drill holes in our clusters. We said plants don't move, that isn't necessarily true. There are documented cases in the rainforests of entire groves of trees that move through out the forest in search of nutrients. They do not move quick enough for the human eye to notice at a glance but they ARE moving at a rate that can be observed over the span of a day or two. The reason I brought up the duckbill platuspus however you spell it in class is because it is an example of another creature which crosses boundaries, a mammal that lays eggs. Our text book talked about the arguments people have about classifcations of bacteria and single cell organisms. So what I would say overall I guess is that life may cluster, but it doesn't cluster neatly. There are always exceptions to the rule.

But, in thinking of the differences between the earth and galaxies, I had an interesting idea. Rachel pointed out that galaxies can reproduce. As far as we can see, galaxies don't reproduce other galaxies. However, this must be possible, especially if we look over extremely long time periods. Then, to the extent that galaxies can reproduce, it must also be possible that they are living. Also, galaxies reproduce parts of what make up their own galaxy. Just as animals and plants can grow and make new cells for themselves, so too can galaxies.

In the morning we looked at the vastness of the space between objects that make up solar systems and galaxies and saw no patterns in the emptiness. And then by gaining enough perspective, by allowing more units (planets, stars, clusters of stars, galaxies) into view we could see pieces, i.e. the galaxies that make up the entire universe. And as was also discussed, new galaxies do in fact form. Then in the lab we looked at cells under the microscope. Clearly, we knew, as we looked at those cells that they had been living parts of a more complex living thing (tree, bush, person, etc). And of course one of the reasons that we could not “verify” Jeff’s hypothesis was that even if there was some correlation between cell size and organism size, we needed only to remind ourselves that we were looking at only one example of a cell, among layers and types of cells that came from only one part from an organism with many parts, layers and types of cells.

Perhaps, we have trouble with the concept of the Earth as alive because we cannot understand the pattern. Even though we can see pretty far, we cannot yet see far with much clarity. We don’t know that the Earth is not an organism, a cluster of organisms, or a part in a much larger organism with vast empty spaces between its cells. The spaces between or inside of our cells do not, from our vantage point, appear to be vast. But it made me realize that scale, orders of magnitude and perspective, may be the most important concepts that science can use to become less wrong?

As human beings, we are on dependent on each other. For example, women are dependent on men to reproduce. If it be through sexual intercourse or through artificial insemination, there is a dependency on the ,male species.

Again, I question, how can something depend on nothing?

More food for "firsts" thought: The Vendian (first) Animals section in the Eukaryotes vs Prokaryotes link in class notes...

In that context, I am intrigued/bemused by Gloria's question, which seems to me another version of the "was there a first living organism?" question. If our experience is always of a diverse collection of interacting things, is it possible that that is actually a fundamental starting point (both for biology and for physics/cosmology), and that our "intuitions" (themselves the product of observations) are misleading us when we believe there must have been a first organism AND a starting point, out of "nothingness", for the universe? Can we instead get ourselves to think of an always changing but also always existing interactive collection of diverse things? What would that "look" like? And what different questions would arise (what different observations would it be worth making?) if we took that starting point seriously?