I shall respond to both these messages together.
First, I agree that life cycles should not be the primary thrust for an
introductory botany course. I abandoned that immediately and teach only
an angiosperm and bryophyte life cycle (partly out of bias, but mostly
because the students get to practice sterile culture techniques with a
protonema - the only place in our curriculum to do this sort of plant
culturing.) We do all the divisions in the plant morphology course, so
those who really need that background can get it there.
Now for Fucus, it is pretty well accepted that it is not truly gametic
meiosis in Fucus. Instead, it appears that meiosis occurs first to
produce 4 male or 4 female meiospores, then mitosis to produce 8 eggs or
64 sperm. My information is old, based on Bold, Alexopoulos, and
Delevoryas, Morphology of Plants. Even if it is gametic, this reduction
of the gametophyte in algae, and the presence of vessels in Fucus, is a
good example of evolution occurring in algae that in many ways parallels
that of flowering plants, but lacking true lignin and a vascular "system"
and flowers, it developed in other directions instead.
Then there are diatoms! Gametic meiosis in these one-celled things.
Janice
***********************************
Janice M. Glime, Professor
Department of Biological Sciences
Michigan Technological University
Houghton, MI 49931-1295
jmglime at mtu.edu
906-487-2546
FAX 906-487-3167
***********************************
>
> >My botany class has reached the point in the semester where we talk about
> >plant life cycles. I begin with a generalized diagram of a plant life
> >cylcle with alternation of generations and tell them that the different
> >plant divisions tend to follow this pattern, but the relative prominence of
> >the gametophyte and sporophyte generations differ for the major groups.
> >Soon afterward we hit the brown algae and most textbooks describe the life
> >cycle of Fucus which has gametic meiosis and does NOT seem to follow the
> >general pattern of sporic meiosis. Is this aberrant among the Phaeophyta?
> >If it is why do textbooks concentrate on Fucus rather than Laminaria or the
> >giant kelps that alternate between huge sporophytes and tiny gametophytes?
> >
> > I would appreciate advice on how to convey these topics to a class
> >without confusing students (or the professor).
> >
>> I am nearing the same point in the semester - diversity (gymnos "through"
> algae) - and often feel as though I should be wrestling with the same
> issues. But I'm not. I dropped all life cycles but angios, gymnos,
> seedless vascular plants (a fern) bryophytes (moss), and a generalized life
> cycle. Why? Because what I remember from my introductory botany class in
> college (and I was a "budding" [sorry] plant geek) was that these were
> boring and confusing. This is not intended as a criticism of those who
> cover these topics. I suspect there is a way to convey these topics with
> enthusiasm and interest - I have just never seen such a treatment nor have
> produced such. Maybe this is more of a public confession (mea culpa, mea
> culpa . . .) and request for support/forgiveness??? I must add that I have
> additional concerns related to what I replace those topics with (another
> topic). I guess I also want ideas on how to best treat those diversity
> topics that have survived my curricular axe.
>> A real can of worms, maybe.
>> Wil Taylor
> ********************************************************************************
>> Wilson A. Taylor
> Department of Biology
> University of Wisconsin-Eau Claire
> Eau Claire, WI 54701
>taylorwa at uwec.edu>> ********************************************************************************
>>
