Hooke 1660s early "microscope" saw and named cells in cork
Schleiden & Schwann 1830s
first made the generalization that all plants and animal bodies are (mostly!) made of
Virchow 1858 "all cells from cells"
(the idea of the body as a colony of little growing dividing cells, each alive,
and each having been formed by division of a previous cell)
As opposed to spontaneous generation
(which had been "common sense" until mid 1800s)
Pasteur nutrient medium, bacteria, fungi, yeast etc.
public experiments demonstrating that boiled media will not rot or produce
bacteria, etc. if no microorganisms are permitted to get into it.
Related indirectly to the germ theory of disease
Pasteurization of milk, and also wine
Pasteur in France, and Koch in Germany
discovered which particular germs cause various different diseases.
Pasteur also invented the idea of weakening germs in culture, and using these to stimulate immunity = Vaccination
Taxonomy = Systematics
Linnaeus mid 1700s "Systema Naturae" Homo sapiens
species genus family order class phylum kingdom division
But why do the different kinds of plants and animals happen to be distributed in these kinds of sequential tree-like branching patterns?
Darwin / Wallace 1859
Evolution by natural selection
As compared with artificial selection:
production of different breeds of dogs, pigeons, rabbits, sheep = goats, etc.
Broccoli, cabbage. cauliflower, Brussels sprouts, etc.
carrots = Queen Anne's lace
Natural selection also includes sexual selection by female of species
Evolution as the cause of the branching pattern of taxonomy
Different kinds of evidence for evolutionary origins of each species:
* fossil record * homology * gene base sequences
Monophyletic groups versus polyphyletic groups "cladistics"
Sometimes lateral transfer of genes, as between bacterial species!
NOT inheritance of acquired characteristics (doesn't occur)
neither bigger muscles; nor cut off tails, nor longer necks, etc.
("Lamarckian evolution" was a mistaken alternative, proposed before Darwin)
Questions that you should be able to answer:
* questions with stars are either matters of opinion, or more difficult than most of the questions that will be on exams)
1) About what year (in history) did someone first see cells through a microscope?
2) Who proposed the idea that plant and animal bodies are mostly made out of cells? About what date? (+/- a decade)
3) How did Virchow extend this idea about cells? And about when did he do this?
4) What did almost everyone believe about the origin of maggots, molds, etc. in rotting materials ("common sense") before Pasteur?
5) How did Pasteur prove the real cause of rotting?
* 6) Do you think that this mistaken idea delayed correct understanding of the cause of most diseases? What about delaying improvements in beer and wine-making?
**7) Is Darwin's theory of evolution related in any way to what Pasteur proved about rotting, etc.?
8) How are cabbage, broccoli, cauliflower & Brussels sprouts related to each other? Evolutionarily? Historically? Genetically.
*9) Would you regard cabbage, etc. as "genetically modified" plants?
10) When did Linnaeus publish his work? What about Darwin? Was he before or after Linnaeus? About how long?
11) Rank the following taxonomic categories, in terms of which are subdivided into which others: class, genus, family, order, phylum, species.
12) Humans belong to which genus? Which species? Which order? Which class? Which phylum? * Which sub-phylum?
13) What is meant by a monophyletic group?
**14) If you hadn't learned otherwise, would you have guessed that cabbage belongs to a different genus or family than cauliflower, etc.?
15) Based on the fossil record, might you be persuaded to change the taxonomic classification of certain groups or animals, so as to avoid polyphyletic groups? (hint: absolutely!)
16) What is cladistics, more or less?
17) Is it an example of Darwinian evolution for humans or animals exposed to a disease to become gradually more resistant to them, over the years?
*18) Would a disease need to be fatal, at least sometimes, in order to produce such an evolutionary increase in resistance?
19) Should/could germs themselves evolve different properties, by means of natural selection? Would you expect them to become more lethal, or less lethal, to the organisms that they usually infect?
*20) Imagine that some kind of germ has previously infected only, say, fish; but somehow some of these germs have managed to infect humans for the first time! Figure out why they might be especially harmful, even lethal!! (Note that this really happens. Can you name any examples?)
*21) If you were writing science fiction, and had to invent some of the following, could you supply some details about how they would work? (Or would some of them be logically impossible? Why or why not?)
*a) Creatures that evolved by inheritance of acquired characteristics (= a planet where Lamarck was right, and Darwin wrong)?
*b) Life forms that were not made of cells?
*c) Cells that formed in some other way than by division of previous cells?
*d) A world where spontaneous generation, of the kind disproved by Pasteur, really did work!
*e) A universe in which the observed variations among minerals DID fit the pattern of Linnaeus' systematics. (Like plants and animals do)
*f) Groups of organisms in which most genetic change occurred by lateral transfer of genes from one organism to another, as does sometimes occur in bacteria, instead of by random mutations. (*What would their taxonomy be like?)
*g) Organisms which rarely fit the Linnaean pattern of classification?
*h) If Hooke had chosen the word "window" to refer to the little openings that he saw in cork?
**i) The development of the equivalent to modern medicine in a universe where microscopes were either never invented or for some reason impossible (no glass or comparable transparent materials, perhaps)?
**j) If smallpox and cowpox didn't happen to exist, could it have occurred to Pasteur to try to make vaccines against other germs?
***k) If diseases from the Aztecs had killed nine-tenths of the population of Europe, instead of the other way around?