Evolving Thoughts

The trashcan categorial

I’m introducing a new category – the Trashcan. This is a term used in systematics to identify a group that comprises “everything else” once you have done the identification of the real groups of some taxonomic grouping.

I will be using the Trashcan to group together all and only those links that have one common property – that they caught my eye. No other property is necessary or sufficient for inclusion. It has no rank, either.*

Under the fold is the Inaugural Trashcan.

Some work on the simplest vision system, of a marine worm, suggests how complex vision got started. Just two cells – a light sensitive cell, and a pigment cell above it.

Courtesy of the inestimable but all-too-infrequent Small Things Considered blog, a paper in Annual Reviews of Genetics that reviews the origins of multicellularity. I can’t access it easily today, as I’m officially on leave and at home (huh, like that’s making any difference).

Nature also has a summary of recent work that supports the idea that trace fossil tracks in the Precambrian might have been made by large single celled protists, not eukaryotes. I expect Chris Nedin to blog this in detail. Chris?

Finally, Siris has a quote that claims that the so-called “Modern” philosophers are squarely in the medieval tradition. I reckon this is true as late as Mill, Peirce and Jevons in the 19th century. The notion that critical thought began sometime in the 17th or 18th centuries is just revisionist. We owe so much to the revolution that began in the 10th century.

* Because ranks are purely arbitrary, unlike a trashcan… nevermind.

Evolution Species and systematics trashcan categorial

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Comments (6)

  3. so this is going to be kind of like Colubridae or Insectivora in that whatever you can’t fit elsewhere will be dumped here based upon some arbitrary characteristic of your choosing? (like in the case of Colubridae, I still don’t know what they use in this one; in the case of Insectivora, I hope people can figure that one out)

  4. so this is going to be kind of like Colubridae or Insectivora in that whatever you can’t fit elsewhere will be dumped here based upon some arbitrary characteristic of your choosing? (like in the case of Colubridae, I still don’t know what they use in this one; in the case of Insectivora, I hope people can figure that one out)

  5. On the simplest vision system, I think they missed Euglena, a protist. Euglena has chloroplasts and thus is interested in where the light comes from. At the anterior of the cell is the stigma, a red dot structure. Associated with the stigma is a light sensitive area of protoplasm. As the eugelena swims along, it rotates and can thus tell which way the light is by the stigma blocking, or not, the incoming light to the light sensitive area.
    The invisible man is blind because light comes into his eyes from all directions.

  6. On the simplest vision system, I think they missed Euglena, a protist. Euglena has chloroplasts and thus is interested in where the light comes from. At the anterior of the cell is the stigma, a red dot structure. Associated with the stigma is a light sensitive area of protoplasm. As the eugelena swims along, it rotates and can thus tell which way the light is by the stigma blocking, or not, the incoming light to the light sensitive area.
    The invisible man is blind because light comes into his eyes from all directions.

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