"Your
mother wears combat boots! "
"O yeah, well your ancestor was a protist!"
"Oh my gosh!!!."
Protists,
Single Cells That Do It All
An amazing world exists just beyond the naked eye. Pond water is one
place to investigate this landscape of single cells that behave as independent
organisms. Biologists have named this group the protists.
Stepping
Stones
Protist were around long before plants and animals appeared. Fossil
protists have been found in rocks dated at more than 1.8 billion years
old. In fact, your local pond is a very good place to find protists
very similar to those that started the lines of multicellular life — and
these organisms seem relatively unchanged from that ancient time. The
transition from single cell life to multicellular life is one of the
most fascinating questions of modern biology. This step is exemplified
by the colonial alga Volvox. All animal
life is now thought to have evolved from a simple colonial organism
that lived over 700 million years ago. To probe this topic further,
see our video/CD-Rom programs, The Domains
of Life. We have also posted a
annotated list of web links on this topic.
Ancient
Branching of the Tree Of Life
Protists represent some of the most diverse branches in the tree of
life. The evolutionary branch leading to Closterium,
the bright green alga cell seen in our gallery, may have split from
the yellow pigmented diatoms as far back as two billion years ago. The
line leading to ciliated protists such as Blepharisma or Stentor probably branched even earlier.
Although amoebas share the characteristics that their
cell membrane is flexible, there is even a great diversity among
this protist group. Evidence from molecular biology studies shows
that some amoebas are much more closely related to Euglena than they are to the classic
textbook amoeba, Amoeba proteus.
Compared to these diverse lines of protist life, we animals are actually
more closely related to our cousins, the fungi.
Have
a Look at How Life Works
Single-celled pond life gives us a unique chance to study the processes
of life right in the living cell! A close study of Paramecium with
a student microscope allows for the observation of phagocytosis, digestion,
water balance, ciliary action, cell excretion and a variety of responses
to stimuli. Paramecium
is easy to culture and can be studied without specialized laboratory
equipment. In our work developing teaching media for cell biology,
we regularly film and photograph live protists to demonstrate the biology
of the living cell. See our program series VISUALIZING
CELL PROCESSES and INSIDE
THE LIVING CELL where animations and live photo-microscopy
demonstrate how the cell function.
Why
Study Pond Microlife?
Right, what are all those little things really good for? Well, for one
thing, without bacteria no fish, no frogs, no birds, no pretty pond
lilies, cat tails, or sedges would survive. Bacteria are essential because
they break down dead organic material, allowing raw materials once locked
up in animal and plant bodies to recycle through the pond community.
The bacteria themselves, become food for protozoans such as Paramecium and Vorticella , and
these organisms, in turn, feed the insects, crustaceans, and baby fish,
building up food chains and creating a pond community. The green and
yellow algae (diatoms) seen in our gallery shots are examples of microscopic
producers that convert solar energy into complex molecules that can
be passed on to consumers. The same principles apply to a forest, grassland,
or ocean. The simple fact is that microorganisms create the ecological
foundation for life on planet earth — a foundation that supports humans
and all other living things.
For more
about single cell life see Guide
to Microlife, published by Franklin Watts, a division of Grolier
Publishing, ISBN 0-531-11266-7. This informative text includes color
photomicrographs by Bruce J. Russell. |
