#1) " Protist" means approximately "lower eucaryotes",
most of which are unicellular, but brown algae include kelp - which can be very big.
And many green algae and almost all red algae are multicellular.

Protists are "everything else", besides fungi, multicellular animals, and higher plants.

Protists are thus not a natural group that would belong together on the evolutionary tree; and they differ VERY widely! They are not a monophyletic group, but polyphyletic.

Protists include protozoa (e.g. amoebae & ciliates like Paramecia, slime molds, dinoflagellates, Euglena, etc. etc. etc.

#2) Gene sequencing, and other cell-level differences between these different groups indicates that they differ from each other much more fundamentally than, say, humans vs. trees!

Multicellular animals seem to be closer to fungi, while higher plants are closer to green algae. (in terms of evolutionary branch points)

#3) Each of the following are fundamentally very different
Green Algae - more closely related to higher plants
Red Algae - some of which secrete coral-like deposits
Brown Algae - kelp, etc.

#4) Euglena were thought to be green algae; but turn out to be trypanosomes
(protozoa, like those that cause Sleeping Sickness!) whose "chloroplasts" were symbiotic green algae.

Many other groups that were thought to be green algae, but their "chloroplasts" turned out to be green algae, and sometimes to be animals with symbiotic algae. (like "Russian dolls")

#5) Giardia have no mitochondria, two nuclei per cell, cause very bad diarrhea, are hard to kill, and contaminate most springs in National Parks, and city tap water in St. Petersburg ("Leningrad")

#6) Malaria is caused by a kind of "protozoa", that invade human blood cells, are spread by mosquito bites, now only in tropical countries, but previously as far north as Philadelphia.
Until almost 1900, it was believed to be caused by "bad air"
Malaria still kills a little more than one million people per year.

#7) Paramecia (and other "ciliates") are unicellular, but often bigger than small multicellular animals (1/5 micrometer long)
The have "micronuclei" with one set of chromosomes
and also "macronuclei" with 100s of copies of their DNA.
If you imagine a multinucleate animal, without boundaries between cells,
but with 100s nuclei worth of DNA concentrated in one place,
that would be sort of like what ciliates are.

#8) Diatoms are one-celled algae, that live in box-like shells.
Many species of diatom crawl by exerting forces along grooves in these shells.
(But the round ones have no locomotion)

#9) "Amoeboid locomotion" occurs differently in many species,
including individual cells of humans & other multicellular animals.
Such cell locomotion is very important in embryonic development.
Muscle and pigment cells crawl to their eventual locations, for example

#10) Philosophy of Science writings of Thomas Kuhn.
He stressed that new discoveries require radical rethinking of concepts and analysed the historical pattern of such "Scientific Revolutions", which he contrasted to "paradigm science"

His best book was 'The Structure of Scientific Revolutions".
One of his claims was that most textbooks fictionalize the history of each subject, to make progress seem more like a straight line.

On page 537, our textbook proves Kuhn right by oversimplifying what Kuhn himself claimed, to make it seem to apply to the endosymbiotic origin of chloroplasts, phylogenetic taxonomy,
and the old "5-kingdom" classification system of classification. (which only elementary textbooks ever took seriously, anyway!)
Better examples of scientific revolutions would be chemiosmotic coupling, Darwinism, and especially the clonal selection theory of antibody formation, which we will get to later in this course.

-------

Questions that might be on an exam:

b) What are some of the kinds of organisms that are classified as protists?

c) What are three major groups of eucaryotes that are not included among the protists? Is this because their evolutionary origin is different from the protists?

*d) It used to be supposed that the one-celled "plant" called Euglena was similar to the common evolutionary ancestors or both plants and animals. What is now believed about their evolution?

e) In what sense are Euglena partly plants and partly animals, after all?!

f) Why does the textbook say that the word "protist" may soon be abandoned? Will some new word replace it, with a synonymous meaning? Why not?

g) Why was it somewhat misguided to think about protozoa as just one-celled equivalents of animals?

h) Is it closer to the truth to regard green algae as simpler relatives to higher plants? (hint: yes)

i) What about Red Algae and Brown Algae: are they closely related to Green Algae, or what? (hint: no)

j) Because of what weird nasty protist with 2 nuclei will you get sick if you drink water from an appalachian spring?

k) What else is weird about the cell structure of these organisms?

l) What sort of organism causes malaria? How are they spread?

*m) The name "malaria" comes from what mistaken belief about the causes of diseases spread by mosquitoes? Until about when did medical science still believe this false theory? (1900)

n) How big can Paramecia and other ciliates become, more or less?

o) How can ciliates be so much bigger than the individual cells of humans and other multicellular animals (and plants)?

p) The shape of diatoms is caused by the shape of what part of them?

q) Is there more than one form of "amoeboid locomotion"? (hint: doggone right, there are!)

*r) Can you describe some of the different types of amoeboid locomotion that you saw in my time-lapse videos?

s) What did Thomas Kuhn mean by paradigm science?
As contrasted with what other category of scientific progress?

**t) Can you suggest some areas of science that are ripe for scientific revolutions, in Kuhn's sense?

u) What philosopher of science wrote "The Structure of Scientific Revolutions".

*v) Kuhn wrote that the biggest new discoveries are usually made by researchers who are either quite young (in their 20s)
or who are switching from one field to another field?
(like many of the first molecular geneticists were switching into Biology from Physics!) Can you guess why this is true?

**w) Do you think maybe the word "paradigm" is getting a little over-used in science, politics, newspapers, The Simpsons, etc.

*x) Was it paradigm science to show that mosquitoes cause malaria?

**y) Which was the weirdest kind of organism you have heard of?

**z) In Star Trek, why do all the different intelligent life forms differ mostly in the shapes of their foreheads? Compare this to the magnitudes of the differences among "Protists"!