Protista and Friends

By Taylor Courtney

Lab Procedure

Pond water was sampled and inspected under a microscope. Various pictures were taken of organisms found in the water and identified.
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Protista

Kingdom Protista is a very diverse group of eukaryotic organisms. Scientists usually classify protists as eukaryotic organisms that cannot fit into any of the other three eukaryotic kingdoms, plantae, animalia, and fungi. Protista are grouped into three categories, protozoans (animal-like protista), plant-like protista, and fungus-like protista, such as slime mold.

Discovering protista

Antony van Leeuwenhoek was born into a lower class family and had little money, but he didn't let that stop him from discovering blood cells, sperm cells, and most importantly in our case, protists. He began his scientific career by making some simple microscopes and grinding lenses. Later, his curiosity led him to create elaborate descriptions of various microorganisms, which today are almost always recognizable.


On December 25, 1702, Leeuwenhoek wrote a letter about finding a ciliate, which was the protist Vorticella.



"In structure these little animals were fashioned like a bell, and at the round opening they made such a stir, that the particles in the water thereabout were set in motion thereby. . ."


- Leeuwenhoek



Leeuwenhoek's discoveries just increased from there. Several other scientists, including Robert Hooke, also made important discoveries about protists.

Protista evolution

Protists are believed to be the descendants of prokaryotes. Scientists did not know much about the evolution of protists, mostly because the protist kingdom is extremely diverse. However, a recent discovery (November 2013) has shown us more about protists and their evolution.
In summary, scientist Matthew Brown and his research team discovered a new unicellular protist, Pygsuia biforma. This protist shares many of the same genes as multicellular organisms, so they believe this organism may be in a transitional stage. They also found genes in this protist that were previously believed to be animal-only genes.


This new discovery has led to more questions about protist evolution, but it also opened new doors about what protists may have gone through in history.

Protozoans

Protozoans are the most animal-like members of the protist kingdom. They are classified as being single-celled, heterotrophic, and most motile. Some examples are amoebas, trypanosomes, and giardia.

Discovered organisms

Below: Pediastrum (high power)

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Below: Vorticella (medium power)

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Below: rotifer (medium power)

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Below: active rotifer (medium power)

Rotifer

Below: Cyanobacteria (high power)

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Below: diatom (medium power)

Picture below may not be a diatom. Best guesses were made during the identification process.
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Below: Spirogyra (medium power)

This is a protist.
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Pond food web

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Lab questions

1. In my samples, rotifers and algae were the most common organisms. Vorticella was a close second, but the other two were definitely more prominent.


2. Finding, identifying, and taking a picture of protista was hard because they are extremely small and fast. Using a microscope on high power and trying to pinpoint a quickly moving organism was really difficult.


3. The Pediastrum was the most interesting organism that I found. It was interesting because it is in the algae genus, but it almost looked like it could be a protozoan. It didn't move, though, which was also intriguing.


4. The rotifer seemed to move by contorting its body into a compact shape and then shooting a pseudopod out in front to pull itself along.


5. Algae are the base of the food web in a pond. They photosynthesize, making food for themselves, but they also feed other organisms, including vorticella.

Sergio Martinez's "Hello, Rotifer!"

Hello, rotifer!

About the author

Taylor Courtney

2nd Period