Feb. 12, 2009
Today, we covered a few smaller topics, and began our study
INDIVIDUAL CELL MOVEMENT
Individual eukaryotic cells generally move (or
are motile) in one of two ways:
1 amoeboid movement (=
like an amoeba, by deforming the cell
2 by means of flagella (singular = flagellum).
Eukaryotic flagella typically have a 9+2 microtubule arrangement, and are is
linked to a centriole in the cell. When flagella are small and short, they
often are called cilia. There are two main types of eukaryotic
flagella: whiplash and tinsel. (See p.309 in the textbook.) It
is remarkable that eukaryotic flagella all have a similar structure -- it
strongly implies that flagella were acquired very early in the evoluaiton of
eukaryotic cells. Obviously, flagella give cells advantages in covering
territory, encountering prey, mating, moving from inhospitable environments to
more favorable environments, etc.
Depending on whether the environment is aquatic or just
moist, motile cells of many organisms can convert from flagellated to amoeboid
(by withdrawing the flagellum into the cell), or vice versa.
Why do we
bring this up now? -- because algae and fungi are on the horizon,
and often have motile cells.
THEORY OF SERIAL
THIS IS A SIGNIFICANT
BIOLOGICAL THEORY THAT YOU SHOULD KNOW ABOUT.
The ramifications of
this idea are quite far-reaching.
Ancient prokaryotes were
captured by other cells and, in time,
became integral parts of the
cells that had captured them.
Why? - because having the "captives" gave the
larger cells great advantages.
Endosymbiosis was the probable origin
of mitochondria, plastids, possibly flagella
or, in other
words, serial endosymbiosis produced the first eukaryotic
is similar to prokaryotic DNA, ribosomes are similar to prokaryotic
is similar to prokaryotic cells, reproduction is independent of the cell in
they "reside". Endosymbionts even exist today (algal cells inside the
cells of coral polyps = zooxanthellae)
This theory was first developed by Mereschkowsky (1905),
and later fleshed out by Margulis in the 1980s. For additional reliable details
and evidence, you can follow this link .
TYPES OF SEXUAL
Check out a summary of this at the
bottom of p. 309 in your textbook, and consult the handout distributed in
class [on Tues. Feb. 17].
The Algae =
anything photosynthetic thats less complex than a plant . . .
-- basically aquatic
(some are terrestrial in moist habitats)
-- organization is simple (usually) to
(old name for non-embryo-forming organisms with cell walls =
-- asexual reproduction by
fragmentation and/or zoospores [= spores that swim with flagella] is
-- ecologically, algae =
The algae are a very diverse group of
organisms, some of which are very distantly related to each other, but the term
algae is useful from a functional and ecological
Alga is the singular of
SIGNIFICANCE OF ALGAE -- is coming next . . . and a bunch of algal
See pp. 298-299 in your textbook.
notes for Feb. 12