A Fish Anatomy Lesson

cc-red-snapper-0357 — Proper respect for other living things requires us to minimize the waste we produce, and learn from the creatures we eat.

First off, three cheers for Viet Hoa, the Vietnamese food market on Cleveland Ave in Memphis. I’ve been searching for a source of fresh, uneviscerated, marine fish in this mid-continental city for quite a while, and I’ve finally found them. The market was the source of the subjects of an excellent anatomy lesson, and a delicious dinner.

I’d grabbed three fish, and a few goodies, and packed them on ice on the day before our trip. The large red snapper was a little pricey because it was fairly big, but I knew it would be quite tasty and I was hoping the internal organs would be big and clearly visible. The milk fish was an unknown, but it was big and cheap so worth experimenting on. The last fish was the smallest, and I’m not quite sure what kind it is, except that it’s marine. I’d tried one at home the previous week and found that while it had an excellent taste, the internal bits were on the small side.

Red Snapper

On the first night of the immersion I started with the biggest fish, the red snapper, with everyone around the table. I’m happy to say that all my students were there for the lesson, facing the table, even the more vegetarian minded. I’ve always believed that there is a certain, necessary, ethic to knowing where your food comes from, and what went into preparing it for you. If you’re going to eat meat, you should be able to spare a moment to think about the animal.

fish-intestines_0704 — Small intestines are very long (and stretchy).

The digestive system was the easiest to identify and trace. The mouth and anus are pretty obvious on the outside. After cutting through the skin of the belly, you can follow the intestines from the anus all the way to the stomach. The intestines are quite long.

fish-stomach-contents-0364 — Shrimp-like stomach contents.

We found two partially digested, shrimp-like creatures in the stomach of the red snapper.

From the other end of the digestive system, once you get all the contents out of the body cavity, you can stick a probe through the mouth (watch out for sharp teeth) down through the esophagus to the stomach.

Pulling back the gills, you can see all the way through to the mouth. One student noticed how bright red the gills were, so we talked about oxygenation of blood and compared the fish’s gills to the human respiratory system.

fish-mouth-0350 — The fish's respiratory system.

Judging from the fish anatomy diagram on the La Crosse Fish Health Center website, we found the air bladder (tucked in the center right next to the spine), the liver, the kidneys, and probably the heart. We pulled them out and photographed them.

fish-organs-0360 — Organs from the red snapper.

Baked Fish Recipe

Finally, I laid the fish on a bed of thinly sliced onions, surrounded it with wedges of tomato (seeded), covered it with lemon slices, dribbled a tablespoon of olive oil on top, and forgot to add the cup of white wine (which we did not seem to have on hand for some reason) and the bay leaf. It was a big fish so we ended up baking it for about 40 minutes at 400 degrees Fahrenheit.

Then we ate it. I say we, but it really was just a couple of students and myself who did most of the eating, although I believe I convinced everyone to at least try it. Of the more serious students of anatomy, the eyeballs were highly prized; with only three fish we did not have enough to go around.

By the time we were done with dinner the skeletal system was very nicely exposed.

The Other Fish

fish-milk_0715 — Opening the body cavity of the Milk fish.

A couple of my students did the honors of cleaning the other two fish. With its large organs, the milk fish was an excellent subject for dissection, but it was not particularly palatable. We did however find the gall bladder.

fish-gall-bladder_0717 — The breached gall bladder is on the lower right of the picture.

Even the smallest fish proved a worthwhile subject for the more patient student.

fish-knuckles_0720 — Up to the knuckles in fish.

Instead of eating the rather unappetizing, baked milk fish I combined it in a soup with some clams I’d picked up from Viet Hoa. I’d grabbed the clams so we compare modern bivalve shells to the cretaceous ones we’d find at Coon Creek. A bit of boiling with a few herbs, made for an excellent broth the following night.

In Summary

Cleaning fish for an anatomy lesson worked very well. As we excavated each internal organ, we could talk about what it did, why the fish needed it, and what was its analogue in humans. And, in the end, they made for a couple excellent meals.

P.S. – From the Gulf Coast Research Lab’s Marine Education Center, here’s a reference image for a perch dissection.

sc-perch-1399 — Perch dissection reference.

The Challenge of Assessing Good Language

Middle school is where you learn the conventions of language: comma placement; who versus whom; and things like that. But language, and even its conventions, are ever evolving. Stephen Fry makes the case that we should be a little less pedantic.

Global Atmospheric Circulation and Biomes

We’re studying biomes and I don’t know a better way to consider how they’re distributed around the world than by talking about the global atmospheric circulation system. After all, the primary determinants of a biome are the precipitation and temperature of an area.

It’s a fairly complicated diagram, but it’s fairly easy to reproduce if you remember a few fairly simple rules: hot air rises; the equator is hotter than the poles; and the Earth rotates out from under the atmosphere.

Hot air rises

Atm-circ-01 — Light from the Sun hits the equator directly but hits the poles at a glancing angle, so the equator is warmer than the poles. Warm air at the equator rises while cold air at the poles sinks.

The equator receives more direct radiation from the Sun. A ray of light from the Sun hits the ground at an angle near the poles so it’s spread out more. More radiation at the equator means the ground (or ocean) is warmer, so it warms up the air, which rises.

The warm air can’t rise forever, gravity puts a stop to that. If we did not have gravity the atmosphere would float off into space (and the universe would be a fundamentally different place). Instead, when the air reaches the upper atmosphere at the equator it diverges, heading either north or south toward the poles.

From all around the hemisphere the air converges on the poles. The air is cooling as it moves away from the equator, and when it gets to the pole it sinks to ground level and then makes the journey back to the equator. It’s a cycle, aka a circulation cell.

Atm-circ-02 — Hot air rising near the equator and sinking near the poles creates a cycle, a circulation cell, in each hemisphere. In this picture, the winds at ground level (dashed blue lines) would always be blowing from the poles toward the equator. This is what the world might be like without the coriolis effect.

Standing on the ground, the wind would always be blowing towards the equator from the poles. If you were in the northern hemisphere, in say Memphis, you would always be getting northerly winds.

The ITCZ and the Polar High

At the equator the rising air also takes with it water vapor that was evaporated from the oceans or from the land (evaporation and transpiration, which are together called evapotranspiration). The warm air cools as it moves up in the atmosphere and the water vapor forms clouds.

You get a lot of clouds and rainfall anywhere there is a lot of rising air.

Because air is coming together, converging, from north and south at the equator, and the equator is in the middle of the tropics, the zone where you get all this rising air is called the Inter-Tropical Convergence Zone or ITCZ for short (that’s an acronym by the way). The ITCZ is pretty easy to identify from space.

IDL TIFF file — The line of clouds near the equator shows where air is converging at ground level and rising to create clouds. It's called the ITCZ. (Image via NOAA, which also hosts real-time images of the Tropical Atlantic that show the ITCZ very well).

All the rain from the ITCZ, and the warmth of the equator means that when you go looking for tropical rain forests, like the Amazon and the Congo, you’ll find them near the equator.

Now at the pole, the air is sinking downward from the upper atmosphere. Sinking air tends to be very dry, and places with sinking air also tend to be dry (it’s not a coincidence). So although the poles are covered with ice, they actually tend to get very little snowfall. What little snow they get tends to accumulate over tens, hundreds and thousands of years but the poles are deserts, arctic deserts, but deserts all the same.

The region of sinking air near the poles is called the polar high because of the high pressure generated by all that descending air.

We’ll complicate the picture of atmospheric circulation now, but the ITCZ and the polar high don’t change.

The Earth Rotates

The complication is the coriolis effect. You see, as the Earth rotates it kind-of drags the atmosphere with it. After all, the atmosphere isn’t nailed down. It’s got it’s own motion and intertia, and doesn’t necessarily want to rotate with the Earth.

Coriolis4bw — Deflection of the wind, represented by a ball, because of the movement of the Earth beneath it. The ball here moves in a straight line but it appears to curve because the Earth is rotating out from under it. Click the image for a bigger, better version.

So a wind blowing from the North pole to the equator gets deflected to it’s right; the northerly wind becomes an easterly.

I could write an entire post about coriolis (and I will) but for now it shall suffice to say that the low-level wind from the pole gets deflected so much that it never reaches the equator. The high-level wind from the equator never reaches the pole, either. Instead of the one, single, circulation cell in each hemisphere, three develop, and you end up with the picture at the top of this post.

Note also that the winds in the region just north of the equator (where the label says “Tropical Air”, come from the northeast. These are the northeast trade winds that were vital to the transatlantic trade in the days of sailing ships. Know about them help a lot in the Triangular Trade game.

The Sub-Tropical High and the Sub-Polar Low

With three circulation cells you add the sub-tropical high, and the sub-polar low to the ITCZ and polar high as major features that affect the biomes.

Remember, rising air equals lots of rain, while descending air is dry.

So the sub-tropical high, with its descending air, makes for deserts. Since it’s in the sub-tropics these are hot deserts, the type you typically think about with sand-dunes, camels and dingos.

deserts-id — Sub-tropical deserts from around the world. They're located in the zones 30 degrees north and south of the equator at the sub-tropical high. Base map by Vzb83 via Wikimedia Commons.

The USGS also has a great map that names the major deserts.

Biomes

So if we now look at the map of biomes and climates from around the world we can see the pattern: tropical rainforests near the equator, deserts at 30 degrees north and south, temperate rainforests between 40 and 50 degrees latitude, and arctic deserts at the poles.

Power Down and Disconnected

Like addicts racing to get their overdue fix, my students raced to the computers this afternoon after having had to survive all day without power and without the internet. I’ll confess that I felt the same urge, but was able to restrain it. Until now.

We usually don’t have internet access during our immersions, but then it’s expected and students are not inside needing to refer to the study guides to figure out their assignments. At the beginning of the year I gave everyone paper copies of the study guides, but now there are just a core few who request them.

Fortunately, we had a couple of smart-phones so one student would look up the reading assignment and post the page numbers on the whiteboard. Fortunately, the reading assignments were out of the book.

We weren’t quite surviving without technology, but it was close, and students were getting innovative.

We’ve had storms every few days for the last couple of weeks, which is typical for Memphis at this time of year. Over the last few days a frontal system has just been pushing back and forth over us. When it pushes south we get a cold front with thunderstorms and rain, but clear skies afterward. When the front pushes north it gets warm and humid, and the sky goes overcast for most of the day.

weather-Apr20-2011-5pm — Weather map for Wednesday, April 20th. The blue and red line passing through the southeastern U.S. show the mixed warm and cold fronts that have been oscillating past Memphis for days. Image from the National Weather Service.

This line of fronts marks the general location of the sub-polar low, which is moving north with the spring. But more on that tomorrow.

Why go to College? Not for the Money.

If learning is not for its own sake, it isn’t liberal learning. It’s a utilitarian calculus for material self-advancement. The important things are not worth knowing because they are useful. They are worth knowing because they are true. [my italics]

–Andrew Sullivan (2011): Education For Its Own Sake

This quote, feeds off a plea by Freddie DeBoer against our constantly putting things in terms of dollars, cents and economic value. It argues against much of the premise of behavioral economics (and much of environmental economics too), which tries to better understand human nature by translating everything into money.

The economists themselves will tell you that this remains just one part of the story, and the work brings us to a better understanding of how humans behave and what they really value, but, living in a very capitalist society, it’s easy to lose track.

Epic Rain-Garden

flowerbed-angels — They're making dirt-angels, actually.

Talk about a long day! (“What an understatement,” she says.)

flowerbed-before — The 'before' picture.

We moved about 45 tons of sand, gravel and compost today, filling in the moat we dug last week. We were lucky enough to have the help of a backhoe for the digging, but all the filling in today was done by hand, with shovels and wheelbarrows.

flowerbed-night-backhoe — Digging the moat.

Despite rumors about it being a first line of defense against the Cordovan barbarian hordes, the moat was actually intended to become a rain garden, which was designed by the Rhodes College Hydrogeology class to intercept some of the runoff slope that funnels water directly down toward the school during the intense rainfall that we get with our spring and fall mid-latitude cyclones.

So we had to get rid of the heavy, dense, silty-loam soil that is really slow to let water seep through, and makes it hard to grow anything on the Memphis side of the Mississippi River. The fine grained silt was blown over from the Mississippi River floodplain about 20,000 years ago when the ice-age glaciers were melting and all their ground up rock flour was being washed down the Mississippi. This type of wind-blown sediment is called loess. I like the sound of the word because if you stretch out the “oe” properly it does something to the back of your throat that feels distinctly German; however, if you ask someone from the deep south to pronounce it, you’ll hear the name of Clark Kent’s girlfriend.

flowerbed-sh-oil — Middleschooler pushing a wheelbarrow full of silty-loam.

The backhoe dug two trenches, each about 2 m wide, 6 m long, and about 60 cm deep, and piled the soil up next to the holes. Moving this stuff is not trivial. My middle-school students gave it a try on Friday afternoon and though they made a small dent, there is an awful lot more to do (my students also helped figure out how long it would take to finish pumping out Friday morning’s collected rainwater from the trenches).

flowerbed-pea-gravel-delivery — Five cubic yards of pea gravel.

Then, on Saturday, with large piles of the old soil still sitting there, we replaced the impermeable loam with a fifty-fifty mix of sand and compost, underlain by five centimeters of pea-sized gravel on top of five centimeters of crushed limestone. This material was delivered by dump truck on Friday afternoon, while school was still in session. It was loud, exciting, and according to one member of the pre-school aged audience, “the best day ever!”

flowerbed-best-day-ever-oil — Enjoying the 'best day ever.'

I have to agree. It was kind-of exciting. Although for me, the bright, brown pile of pea gravel evoked fond memories of pyramids of powdered curry, saffron and tummeric sitting on the spice-seller’s stall in a market in Morocco .

flowerbed-pea-gravel-therapy-1 — Rhodes students slacking off (after lugging soil and gravel all day).

For others the pea gravel was a more tactile experience: snuggling into it, after a hard day’s work, appeared to be quite therapeutic.

flowerbed-pea-gravel-therapy-2-oil — Girl Scouts taking a well earned break.

flowerbed-pea-gravel-therapy-3 — Middle school students slacking off (after ...?).

flowerbed-hauling-dirt — Hauling silty clay.

flowerbed-wading — Dr. Jen raking in the first of the gravel in the not yet drained pit.

flowerbed-team-ziebarth — Team Z. on the top of the mound.

flowerbed-gravel-tossing — Gravel tossing.

flowerbed-job-well-done — The last of the pile. Job well done.

To be continued…

It’s 10 PM and the Moat is Empty

My students and I had a great chance to use the our recent geometry work when we figured out how long it would take to drain the new moat in front of the school.

It’s not really a moat, it’s going to be a flower bed that will soak up some of the runoff that tries to seep into the school’s doors every time a spring or fall thunderstorm sweeps through.

The hole was dug on Thursday evening and filled with rainwater with water, half a meter deep, by Friday morning’s rain. At least we know now that the new beds are in the right place to attract runoff.

But to fill the trenches with gravel, sand and soil, we needed to drain the water. With a small electrical pump it seemed like it would take forever; except that we could do the math.

The pump emptied water through a long hose that runs around the back of the building where the topography is lower. I sent two students with a pitcher and a timer (an iPod Touch actually) to get the flow rate.

They came back with a time of 18.9 seconds to fill 4 liters. I sent them back to take another measurement, and had them average the to numbers to get the more reliable value of 18.65 seconds.

Then one of the students got out the meter-stick and measured the depth of the moat at a few locations. The measurements ranged from 46 cm to about 36 cm and we guesstimated that we could model the moat as having two parts, both sloping. After measuring the length (~6 m) and width (2 m), we went inside to do the math.

moat-volume — Rough sketch of the volume of water in the moat.

With the help of two of my students who tend to take the advanced math option every cycle, we calculated the volume of water (in cm³) and the flow rate of the pumped water (0.2145 cm³/s). Then we could work out the time it would take to drain the water, which turned out to be a pretty large number of seconds. We converted to minutes and then hours. The final result was about 7 hours, which would mean that the pump would need to run until 10 pm.

And it did.