We are now closed for the season (until august 2014). However, there are still some limited opportunities for private visits by appointment only, at a few specific "slot" times. You should arrive at the agreed upon slot start time and leave before its end (1 1/2 hour maximum duration). There are 2 slots available this weekend, both in the afternoon: saturday 3-4.30 and sunday 3-4.30. If you would like to visit this weekend, please email me your choice of slot time, with the number of visitors you plan to bring, your walking abilities, and your car plate number. If I respond positively, I will meet you in the parking area at the start of the slot time to welcome you, receive your waivers and direct you over the woodland path. Absolutely no visiting outside pre-arranged appointment times.
I wrote in my last post that the key to emergence of complex life from simple life forms was the appearance (by evolution) of sexual reproduction (basically Daddy's sperm combines with Mommie's eggs to make a new individual). But before explaining why sex was so crucial, I must better explain the difference between simple and complex life. There are actually 2 types of difference, though they are related. The first is the difference between simple and complex cells. The former (basically bacteria, but also another type of recently discovered, rather obscure cells called "archaea"; the technical term is "prokaryotes") have no cell nucleus, and lack many other internal structures that are found in complex cells. These cells have been around for about 4 billion years, and emerged quite quickly after the earth formed. They reproduce asexually (though they can swap genes). Complex cells are bigger, have sex, nuclei and various other things like mitochondria (which provide increased levels of energy). They are known scientifically as "eukaryotes".
The second type of simple/complex difference is between single celled organisms and multicellular organisms (like us: we are made of about one hundred trillion complex cells, excluding the quadrillion bacterial simple cells in our gut; a blue whale might have a hundred quadrillion cells). All multicellular organisms are made of complex cells, but there are many single-celled complex organisms (such as amoebas).
It seems as if sex is necessary to make complex cells and even more necessary to make multicellular assemblies of complex cells (like us). In my next posts I will explain (1) why asexual (e.g. vegetative) reproduction cannot generate either type of complexity (2) why sex does the trick. After explaining why sex is necessary, I will explain why it's difficult to do properly.
The image, showing a bird pollinating a rosebud sage, is by Keith Bittner. A hummingbird has "only" about 100 billion cells.
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