Basic Concepts
evolvingthoughts | January 23, 2007
Species: A term which everybody thinks they understand, but which nobody agrees upon, to denote the "basic units" of groups of biological organisms.
It is sometimes said, or has been said to me, that one ought not know too much about a topic if you are to define it clearly. This is because the expert knows all the many nuances that apply in different conditions, and writes not to the beginner but to the other experts. So I must note here that my thesis and continuing work is on species concepts, and things may get a bit rocky. You've been warned.
First of all I'd like to disagree with…
evolvingthoughts | January 22, 2007
Fitness. Of the many concepts of evolution, this is perhaps one of the more widely misunderstood. It comes from the unfortunate slogan written by Herbert Spencer and urged on Darwin by Wallace and others: survival of the fittest. People think it means the strongest, or the most aggressive, and that it means evolutionary theory is a tautology. We'll look at these in a bit. but first, what does it really mean in evolutionary biology?
Fitness is a property of a competing variant in a population. It means that X, whatever it might be biologically, is increasing in its frequency in a population…
evolvingthoughts | January 16, 2007A couple more Basic Concepts posts have been put up. Chaz Orzel at Uncertain Principles defines "Force" in physics. And PZ Myers at Pharyngula defines "Gene". However, PZ does this as a molecular biologist would, and ignores the phenotypic effects of genes, and some complications such as alternative splicing, which make the same stretch of DNA "code" for different products. John Hawks gives an example of this in human DNA. The complexity of the concept of a gene is well discussed here [PDF].
Larry Moran has a nice piece on ethics in science teaching. Not a "basic concepts" piece, but worth…
evolvingthoughts | January 15, 2007Mark Chu-Carroll has a good short discussion of the statistical concept of a "normal distribution" up.
evolvingthoughts | January 13, 2007Larry Moran has a Basic Concepts post on Evolution. It's not quite what I'd have written, but it's good anyway. Even if he isn't sufficiently selectionist and gene-centric...
I'm joking about the selectionism and gene-centrism.
evolvingthoughts | January 12, 2007
This is the first in an irregular series of basic concepts in science, that I suggested to the Seed Bloggers we might do from time to time. If anyone wants to suggest a revision, because I got it wrong or am unclear, make a comment - this will be revised to make sure it is OK.Clade: this term of art is a new one in biological systematics, or the science of classification, or taxonomy. The word has given its name to a new science of classification: cladistics, which is properly known as phylogenetic systematics.
A clade is, simply expressed, any branch (Greek: klados) of the evolutionary…