Today is Darwin Day, or to put it another way, the 203rd anniversary of Darwin’s birth. You can find various posts around the web, as well as various activities to participate in, by searching on “Darwin Day.” My own contribution is below. Continue reading
Falcon-Lang’s find was a collection of 314 slides of specimens collected by Darwin and other members of his inner circle, including John Hooker — a botanist and dear friend of Darwin — and the Rev. John Henslow, Darwin’s mentor at Cambridge, whose daughter later married Hooker.
The first slide pulled out of the dusty corner at the British Geological Survey turned out to be one of the specimens collected by Darwin during his famous expedition on the HMS Beagle, which changed the young Cambridge graduate’s career and laid the foundation for his subsequent work on evolution.
More info can be found here. Apparently, there is also a more formal writeup in Geology Today, but I haven’t been able to track that down yet.
Darwin was quite experienced with the microscope. In this experiment we see another aspect of the “experimental Darwin”. Here Darwin is examining the effect of ammonia on plants (this is part of his research in insectivorous plants) Continue reading
It’s a profoundly interesting question and Charles Darwin experimented to find the answer. I bet you all thought I had forgotten about my series on Darwin’s experiments! Darwin came up with a couple of different methods for answering the question. This is one (In this one Darwin also notices a phenomena familiar to archaeologists – but you will have to figure that one out on your own):
Okay, it was really about mold formation, but the experiment itself sounds like something that would make Michael Schiffer (for those of you unfamiliar with him, Schiffer’s work primarily centers around the processes – natural or manmade – that go into the creation of an archaeological site.) proud. In this experiment Darwin takes advantage of some natural and manmade processes to examine mold formation. The experiment concerns three fields belonging to his father-in-law, Josiah Wedgwood II, that had been treated in three different fashions – it also involves one of Darwin’s favorites (earthworms):
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Intelligent Design proponents are fond of saying that Darwin considered the cell to be just a formless blob of protoplasm. Behe’s Darwin’s Black Box is a good example of this kind of silliness. Few IDiots realize that Darwin was, in fact, a first rate microscopist. In this experiment we see Darwin at the microscope. We also see that he was aware that cells were more than just vague bits of protoplasm.
One of the key aspects of science controversy – that is people disagree with you and say so. Liu-Ochman flagellum evolution paper paper is a good example. Disagreements are a crucial aspect of how science progresses. In this example Darwin is defending one of his statements about barnacles (the discussion is taking place in the pages of Nature):
I BEG permission to make a few remarks bearing on Prof. Wyville Thomson’s interesting account of the rudimentary males of Scalpellum regium, in your number of August 28th. Since I described in 1851, the males and complemental males of certain cirripedes, I have been most anxious that some competent naturalist should re-examine them; more especially as a German, without apparently having taken the trouble to look at any specimens, has spoken of my description as a fantastic dream. That the males of an animal should be attached to the female, should be very much smaller than, and differ greatly in structure from her, is nothing new or strange.
It is a truism in science that experiments raise more questions than they answer. Darwin encountered this phenomena during his experimental career as well. Case in point, in The effects of cross and self fertilisation in the vegetable kingdom Darwin relates how he started the experiments for the book:
I was at last led to make the experiments recorded in the present volume from the following circumstance. For the sake of determining certain points with respect to inheritance, and without any thought of the effects of close interbreeding, I raised close together two large beds of self-fertilised and crossed seedlings from the same plant of Linaria vulgaris. To my surprise, the crossed plants when fully grown were plainly taller and more vigorous than the self-fertilised ones. Bees incessantly visit the flowers of this Linaria and carry pollen from one to the other; and if insects are excluded, the flowers produce extremely few seeds; so that the wild plants from which my seedlings were raised must have been intercrossed during all previous generations. It seemed therefore quite incredible that the difference between the two beds of seedlings could have been due to a single act of self-fertilisation; and I attributed the result to the self-fertilised seeds not having been well ripened, improbable as it was that all should have been in this state, or to some other accidental and inexplicable cause. During the next year, I raised for the same purpose as before two large beds close together of self-fertilised and crossed seedlings from the carnation, Dianthus caryophyllus. This plant, like the Linaria, is almost sterile if insects are excluded; and we may draw the same inference as before, namely, that the parent-plants must have been intercrossed during every or almost every previous generation. Nevertheless, the self-fertilised seedlings were plainly inferior in height and vigour to the crossed.
My attention was now thoroughly aroused, for I could hardly doubt that the difference between the two beds was due to the one set being the offspring of crossed, and the other of self-fertilised flowers.
Darwin designed this first experiment to test height and fertility of crossed and self-fertilized plants of the species Ipomoea purpurea .
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In addition to being a great example of Darwin exploring a problem and performing experiments based on those explorations, this next example has one added point of interest. Darwin admits to making an error in a previous work. The admission is based on the collection of further data – a hallmark of good science! This example comes from The power of movement in plants: