ALTERNATING GENERATIONS IN
PLANTS SIMPLIFIED (USING BRAD
PITT, PARIS HILTON AND THE
SMURFS)
Borrowed from Dr. Krempels’ plant lecture.
http://www.bio.miami.edu/dana/dox/altgen_new.html
NOTE: This is an analogy, it is NOT what actually
happens
ALTERNATION OF GENERATIONS

Alternation of Generations. This term reflects
the fact that the generations change ploidy, with
a diploid generation (the sporophyte) giving
"birth" to a haploid generation (gametophte), and
that haploid generation giving "birth" to the next
diploid (sporophyte) generation, and so on.
ALTERNATION OF GENERATIONS: AN
ANALOGY

The typical human is diploid. Here are Diploid
Brad and Diploid Paris.
ALTERNATING GENERATIONS ANALOGY
But these are not typical humans. Having
evolved from vegetables to mimic humans, they
still undergo alternation of generations as they
reproduce. Here's how it works.
 In the springtime, Diploid Brad and Diploid Paris
begin to feel frisky. Lesions known as sporangia
begin to develop on specialized areas of their
"skin", and inside the sporangia, diploid cells
undergo meiosis to produce haploid cells called
spores.

SPORES!

After a certain period of maturation, the spores are ready
for distribution into the environment. The sporangia
rupture, releasing the tiny, blue spores into the air, where
they are carried to new and exciting environments.
GAMETOPHYTES!
The tiny spores swirl out into the night, diaspora
of the human vegetable mimics.
 Wind carries them everywhere. Some land on the
tops of buildings, and there remain until the
elements dry and kill them.
 Some end up in Fido's food bowl, and are ingested
along with the Alpo.
 But a few lucky individuals are carried far away,
and land on a suitable patch of moist soil.
 And here the spores germinate and grow via
mitosis to become the haploid gametophyte of
the species.

GAMETOPHYTES CONT!
Lacking the charisma and good press of its
parent sporophyte, the gametophyte looks
nothing like its sporophyte parent.
 Brad's male microspores will develop into
males...

GAMETOPHYTES YET AGAIN

and Paris's female megaspores will develop into
females.
GETTING FRISKY PLANT STYLE
The male Smurf gametophytes have male sex
organs known as antheridia that produce
sperm.
The female Smurfette gametophytes have female
sex organs known as archegonia that produce
ova.
 In their damp little glade, the small forest of
Smurfs and Smurfettes wait for that fateful
event they need to reproduce: a good rainstorm.

And then it rained! (use your imagination)
Fortunately, the picture is blurry. Because with the rain, the
males release their sperm into the wild storm, where they
swim wildly, searching for the females. The sperm travel up
the legs of the Smurfettes, and find the archegonia, wherein
lie the waiting ova.
FERTILIZATION!

Fertilization takes place inside the Smurfette's
archegonium, and a new zygote is born.
CONGRATULATIONS – A NEW SPOROPHYTE!


Sadly, Smurfette cannot give birth to her developing
zygote, and as it grows, it gradually crushes her out of
existence, erupts from her quivering shell as a new,
diploid sporophyte.
Once (the diploid sporophyte) has grown to its adult
size and is sexually mature, sporangia will erupt
along the new sporophtyes body again, and the cycle
will continue.