Thursday we discussed life as a member of the nekton - large, powerful swimmers that can overcome waves and currents. One of the things we did during our class meeting was consider factors that the nekton has to overcome in order to move as efficiently as possible through the water. How? Each student used plasticine clay to develop a form that would be most efficient for overcoming the following:
- Frictional resistance - a function of total surface area. So, frictional resistance is minimized as surface area is minimized.
- Form resistance - this is a function of the cross-sectional area of a body. So, form resistance as cross-sectional area is minimized.
- Induced drag - this is a function of the amount of turbulence produced as an object moves through the water. So, a matter of streamlining.
With frictional resistance the ideal shape is a sphere. The downside of a sphere is that there is still considerable form resistance and induced drag.
With form resistance the ideal shape is a thread, with minimal cross-sectional area. The downside of this shape is that there is considerable frictional resistance as the form has maximum surface area. But it's not bad when you consider induced drag.
With induced drag, the best shape is tapered front and back, especially the back of the object, so when water flows off of the back end, there is minimal turbulence.
There is no shape that is ideal for all three factors, but there is an optimal shape. Consider this, you want to have the smallest surface area possible AND the smallest cross-sectional area possible AND you want a tapered body. What's the ideal shape? Something like an elongate teardrop.
And do we see this in nature among larger aquatic organisms? We sure do!
Fishes (tuna, sharks), penguins, marine mammals (whales, seals, sea lions), etc.
Their body plans are examples of convergent evolution in which they have adapted their body form to move efficiently through the water. Now that's cool!
Then on Friday evening our group attended a public presentation featuring Steve Palumbi, Director of the Hopkins Marine Biological Station of Stanford University. He talked about extreme life in the sea. This took place at Southwest Oregon Community College (SWOCC) in Coos Bay. It was a real crowd pleaser.
His talk was based on a book he wrote recently, The Extreme Life of the Sea.
I was frankly quite impressed by the number of people who came out on a Friday evening to listen to a science talk. And it was informative and entertaining - the way good education should be.
And another week of the MBFE is in the books!
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