Real tough guys - lichens

Having dodged the worst parts of an ice storm, a few days of warmer weather are predicted where the daytime temps will be above freezing. Along with this comes rain, but with the ground still frozen, a lot of runoff is expected.  Here and there a few sprouts of early bulbs are peeking out.  However if you want to see some happily green organisms, start looking at tree bark and branches.  Without the crown of leaves, more sunlight will fall on tree trunks than you might expect, and lichens take advantage of this. These are really tough organisms. Tree bark, stones, cement, these are really hard substrates; organisms growing there are highly exposed, subject to desiccation and temperature extremes, and yet in places the lichens are almost luxuriant.  Locally common lichens grow as a crust and so don't look as lush as the larger, more branched or leafier types (fruticose or foliose).  Although TPP is not adept at identifying lichens, he loves the Lichens of North America; a wonderfully illustrated atlas of lichens (just the ID keys and other field guides are also available).  Should you decide to give it a go, you'll run into a bit of a terminological learning curve and the need of come magnification.  Maybe a kind reader will offer some suggestions about the lichens shown here.

If you don't already know this, lichens are symbiotic organisms, basically a fungal body housing symbiotic algae. The algae can still be free-living, and so to the fungus, but neither one alone looks like the lichen.



Algal designs for money!

Happy Birthday to M. C. Escher. Everybody TPP knew in college had an Escher print, or two, hanging in their rooms; they were so clever, so well designed, so much fun, but who knew he tried designing money?  The designs on this bank note are algae: a diatom, Pediastrum, Spirogyra, a volvocalean colony, and more. This is the real green stuff, of course, it's only in the USA where all the bank notes are the same boring algal-colored green. 

KILLER ALGA EATS PEOPLE!

In the category of outrageous "news" stories about plants, can TPP play?  Just a couple of days after seeing the blooming of a spiny pineapple touted as a "sheep-eating" plant, another image comes to the fore that shows something even more stunning.  After all, there were no pictures of dead sheep hung up on these spiny pineapples, but this image is quite clear.  This alga can and will consume humans!  This poor kid is just about toast as he is dragged under by a bloom of green algae (probably Cladophora).  What happens next is just too gruesome to relate.  Algal blooms happen almost every summer and you would think people would learn to be more careful.  This can happen at your swiming hole too, so let's watch that nitrogen pollution people.  Don't feed those killer algae, or they will feed on you! 

Today's Laboratory - Survey of algae

Surveys, breadth without depth, are hardly ideal, but watcha gonna do?  TPP's classroom is over 800 miles from seawater at a public university that cannot afford stools for students to sit on let alone paying for a nice shipment of seaweeds from a coastal area.  So you have to make do with small ones, immature ones, pickled and dried specimens, and prepared slides.  Lots of other green beasties get covered in this survey too: cyanobacteria (formerly called blue-green algae), diatoms, dinoflagellates, and euglenoids.  No chloroarachniophytes though.  Too bad.  Little green spidery organisms are kinda cute.  This survey is an observational challenge for students because many of these organisms are small, very small.  Some are motile and more agile than are students at the controls of a microscope.  Too often students get too much material on a slide for observation; if you can see it with the naked eye, you don't need a microscope.  Less is often better.  Patience helps because you have to look around, a lot to see what you can see, and students today are not practiced observers, and they aren't very patient.  Instant gratification is more the norm.  It doesn't help that their instructor can usually observe more in a glance than they have in several minutes.  You can make it look too easy, but then again, you're dealing with a dozen and a half students, so you can't tarry long to pretend it takes you a lot of time.  Still a few will observe some nifty things, and others will be motivated to shop for more images on line, and slowly mental constructs of these organisms begin to form.  Rome wasn't taught botany in a day.

Mostly Unicellular

"Unicellular organisms are so successful, so numerous, and so diverse that an unbiased description of life on Earth could be summed up with just two words: mostly unicellular." This is the 1st sentence from the 3d chapter of the book the Phactor is supposed to be finishing, soon. This of course paraphrases the Hitchhiker's Guide to the Universe's description of Earth: mostly harmless. As a big conspicuous organism living at a macroscopic level, it's very hard to understand just how many unicellular organisms there are, but just as a hint, your body harbors more unicellular organisms than you have cells making up your body, and both are really big numbers. The other thing about this is that organisms seem to have become big, and this happened because lots of small cells teamed up to produce big organisms, rather quickly, at least in geological terms, which means over millions of years. Recent research has shown that under selection pressure, yeast, usually a unicellular organism, becomes multicellular rather quickly. Although this seems to be getting a lot of attention, it doesn't actually surprise the Phactor very much for two reasons. One yeast undoubtably has a multicellular ancestry among filamentous fungi, in other words, it was reduced to unicellularity and it isn't unreasonable to think that some of its multicellular genetic heritage still resides within. When dividing quickly, yeast cells divide by budding, an asymmetrical division, that can produce short chains of cells although evetually they separate. Second, research with other unicellular organisms, in this instance a unicellular algae called Chlorella that lives free-floating in its aquatic environment, has shown similar tendencies. If predators are in the environment, the selection pressure upon unicells (getting eaten), selects for larger multicellular organisms where several cells hang together after division rather than separating. This makes them larger and not so prone to predation, and therefore more successful in reproducing. This is just what evolution is about, non-random reproduction. If anyone says they don't understand how random processes can produce biological diversity they have demonstrated that they have no idea at all of what they speak. What is being altered by the selection is developmental timing, the onset of cell wall synthesis, which if it begins prior to cell separation effectively "glues" the two daughter cells together. Note that no new genes were needed, no new genetic information, just a bit of inheritable variation in developmental timing. In the absence of predators, the selection pressure shifts back and unicellular types again dominate because the bigger multicelled algae have a faster sinking rate and aren't as successful as free-floating algae under these conditions. No big surprises here although certainly a very nice piece of research, and when the actual publication is released, we shall see if the algae work is cited in their literature or not.

When did life get big?

Macroscopic fossils, fossils big enough to be seen with the naked eye, appear in the late precambrian, and they come in a surprising variety, but if the Phactor remembers correctly, and with a check in the literature indicates he does, actually the oldest macroscopic fossil is a seaweed similar to red algae that dates to 2.1 billion years ago, not some 600 million years ago. Now this was not actually very spectacular at only about 2 cm tall, and since red algae are basically filamentous, it makes sense that they were among the first large organisms. Even at such a size, such a tiny seaweed would tower over a microbial mat community like a redwood towers over a moss. So actually life got bigger a lot eariler than many people suggest. This was the second of two big episodes of size increase in the history of life, the first being when eukaryotic organisms appeared allowing cells to be considerably larger than prokaryotic cells. Multicellularity allowed organisms to be even larger resulting ultimately in blue whales and redwoods.

Massive simultaneous algal orgy

Sex is always a good topic although mostly people have the wrong idea. From the biological perspective sex is production of genetically diverse offspring via mating. Most organisms, which are mostly unicellular, reproduce asexually, so all their offspring are genetically identical, a clone. And this works so well and so efficiently that sex among some organisms is a rare event in nature, so when biologists witness one, they get excited, intellectually.
In this instance the organisms are two species of diatoms, unicellular algae that are phytoplankton, the grass of the oceans. Diatoms are pretty nifty because their cell wall is made of glass, in two halves that overlap each other rather like a petri dish. This poses a bit a biological problem because a cell cannot bend or stretch a glass cell wall so when the cell reaches a certain maximum size for its cell wall the cell divides, which is how it reproduces asexually. The two daughter cells each inherit one-half of their progenator's cell wall, and synthesizes a new inner half. This means one of the two can grow as large as the original cell, but the other having inherited the slightly smaller inner half, so it's maximum size is constrained and it becomes a bit smaller.
Now think forward. When each of these two cells divide, the larger of the two produces two daughter cells just like the two described. But when the other daughter cell divides the biggest one daughter can get is the slightly reduced size of the maternal cell, but the other receiving the inner half of the cell wall is smaller yet. Now let's do this thousands of times. Some diatoms will still be as big as the original cell, but lots of lineages were getting smaller and smaller. At some point the smaller cell size triggers sexual reproduction where the smaller cells divide into gametes, sex cells, which escape their glass prison, fuse with a suitable mate, forming a new cell that enlarges to an optimal maximum size for a diatom, synthesizes a new cell wall and starts the whole process all over again.
The environment plays a role in such events because you don't want to be the only organism at an orgy to release your gametes into the big broad ocean. So what happened here was some environmental event triggered sexual reproduction in two species of diatom simultaneously, and someone was there to watch (record some data).
Whew! Sort of gets you all sweaty just thinking about it.