Thursday, January 22, 2009

Tonya's Comments on the Introduction and Chapters I-II

My turn :)

p5) As many more individuals of each species are born than can possibly survive, there is frequently a recurring struggle for existence

This idea of a struggle for existence can mean many things. For instance, it can be an aggressive struggle such as when a food supply diminishes, or it can be a passive struggle (e.g. individuals being killed off by a deadly virus).

Natural selection almost inevitably causes much Extinction of the less improved forms...

Does he really have to use the term 'less improved'? Yes, I agree in a certain context they are less improved because they went extinct in a certain situation, but perhaps if the situation would be different then they would be the improved form.

I'm not really liking the subchapter headings posted at the top of each chapter and not above the paragraphs associated with each topic. I guess I am supposed to guess which paragraph goes with each topic (not that it is hard, it is just annoying).

p7) [individuals of the same variety or sub-variety of older cultivated plants and animals] generally differ much more from each other than do individuals of any one species or variety in a state of nature.

What?! Maybe I am not understanding this correctly but this cannot be true, can it?

Darwin thinks it is absurd that some people thing that every race which breeds true has had a wild prototype (p19) :)
Darwin also believes it is always best to study some special group (p20). Yay beetles!

p26) it is difficult, perhaps impossible, to bring forward one case of the hybrid offspring of two animals clearly distinct being themselves perfectly fertile.

Can anyone please explain this sentence to me?????

p36) Interesting tidbit: the barbarians of Tierra del Fuego would rather eat their old women over their dogs in dismal times. Hmm.

p40) We know nothing about the origin or history of any of our domestic breeds.

Awe Darwin, if only you knew how far we have come.

p42) Facility in preventing crosses is an important element of success in the formation of new races

Prezygotic and postzygotic mating barriers!

Interesting tidbit #2: cats are valued by women and children, not by men.

p52) I was very impressed with Darwins understanding of incipient species and that not all must attain the rank of species but there are a multitude of situations that can occur.

Here, Darwin describes a species as: a set of individuals closely resembling each other

p54) What does he mean when he states "plants low in the scale of organization". This is an odd way of writing about a plant with uncomplicated morphology, if that's what he even means.

p56) ...where many species of a genus have been formed, on an average many are still forming...

Is this an active area of modern research? Very interesting!

p57) large genera the amount of difference between the species is often exceedingly small.

Yes, (with my very limited experience) I would agree with this statement as this is true in Nicrophorus (Silphidae: Coleoptera) which has many species; however, the opposite is not true because in Brychius (Haliplidae: Coleoptera), there are only three species and they are really hard to tell apart.


Dr. Fox said...

Re: Darwin's remarks on hybrid sterility on p. 26. What he's saying is that, if you breed a male of one species with a female of a quite different ("clearly distinct") species, the resulting hybrid offspring will not be fully fertile. This is probably correct, or if not, the exceptions are quite rare (I seem to recall somewhere that lions and tigers have been hybridized in zoos, but I don't know if the offspring are fertile...). Hybrid zones in biogeography occur where the ranges of two similar, closely-related species overlap. I don't know of examples of hybrid zones involving quite distinct, distantly-related species. Of course, this is in part because of prezygotic isolation rather than the postzygotic isolation Darwin is referring to, but that doesn't undermine Darwin's claim.

re: Darwin's remark on plants "low on the scale of organization" (p. 54): This sort of language was typical of the time.

Tonya said...

Yes of course, that makes sense now thanks.