Exploring the Diversity of Protists: Meet the Fascinating Microorganisms

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In summary, protists are a diverse group of organisms that are defined by what they are not rather than what they are. They do not belong to other eukaryotic kingdoms and do not form monophyletic clades. They can exist in various forms such as algae, protozoans, and absorptive forms and can exhibit different types of nutrition and reproduction. The main distinguishing trait of protists is their classification of convenience, as they do not fit neatly into other categories and are considered a taxonomic trashbin. There is no solid definition for protists, and their classification is largely based on observation and personal interpretation. This often leads to conflicting definitions and classifications, as some species do not fit into any category. Overall, prot
  • #1
TECHXHEAD
Protists are generally defined by what they are not than by what they ARE. They are not monophyletic clades, they do not belong in other eukaryotic kingdoms, they contain much more diversity.

They can exist as algae, protozoan, absorptive, forms. As well as photoautotrophs, chemoheterotrophs, and mixotrophs. They are extremely diverse in terms of form, nutrition, and asexual reproduction.

So what is their distinguishing trait? What differentiates them and why are they defined in this matter? It is somewhat vague that they are described by what they are not than by what they are.
 
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You missed the point, I believe. They are a classification of convenience. Everybody knows they do not fit together any which way. When I used to teach this I got questions like this. There is no solid defensible postion other than to say Ernst Haeckel created the protista and now we put clearly unrelated oddballs in there. It is a taxonomic trashbin.

Otherwise, some species/groups in there would be in their own kingdom all by themselves. Would you like to learn that there are ~67 kingdoms and here are there names? I do not see what purpose that would serve. As long as you mention that Protista are truly a dumping ground because we cannot deal with them, what harm?

My personal take is that many are sole survivors of unique phyla the evolved in pre-Cambrian times. We lost all of their antecendents 500 MYA. Blame it on 'white earth'. :)
 
  • #3
I'd like to hijack this thread with a related question:

I also recently learned about protists being the "default" organisms in my General Bio 2 class last semester. We aso learned very specific definitions for an animal and a plant. For example: An animal is a sexual organism that reproduces with numerous small motile, sperm and larger, less numerous non motile eggs. Animals also develop from zygotes which divide to form a blastula which develops into a gastrula.

But this semester in general microbiology my professor referred to algae as plants and amoebas as animals, throwing all my painstakingly learned definitions out the window! I briefly asked him to clarify this after class and he reaffirmed what he said in lecture. This guy has a phd and is head graduate student advisor.

Could anybody offer any clarification on this?
 
  • #4
You know in Math there are axioms - statements you assume to be true, and that you choose as a starting point to prove theorems.

In Biology there are almost-axioms are called definitions. These are largely observationally derived. Math axioms are not derived by observation AFAIK. Definitions like these are part of so-called alpha science - the science of describing everything out there so we can make sense of it all.

While there are excellent definitions of 'species', 'taxonomy', 'plant', and 'animal', not everyone uses exactly the same one. When that happens you get slightly different results downstream.

Why is this? Simply because for every definition there exists at least one or more species that break any definition of a phylum or a species you choose. These species that don't follow the axioms we used to decide. So you pick a definition that works for you.

There is no perfect definition. Some species break all rules. Example: switchgrass (Panicum virgatum). It ain't a species, at least not by any definition of a species I have seen. But we still call it a species. Because that is how we deal with everything else.
Square peg in round hole problem. This happens a lot in Biology.

Your prof is using the animals='eurokaryotes that do not do photsynthesis' definition. And
plants='eukaryotes that do pefrform photosynthesis''

This is common in Science, and as long as you are upfront about it nobody will complain - unless of course you violate your own definitions.

And the things you cited - amoebas and single cell algae like Chlorella really mess up our nicely man-man contrived taxonomic cubby-hole system. So we either call them plant and animal (old-fashioned) or protists (new-fangled). You pick.
 

1. What are protists and why are they considered microorganisms?

Protists are a diverse group of unicellular or multicellular eukaryotic organisms that are not classified as plants, animals, or fungi. They are typically microscopic in size, ranging from about 1 to 100 micrometers. They are considered microorganisms because they are too small to be seen with the naked eye.

2. What are some examples of protists?

Some examples of protists include amoebas, paramecia, diatoms, euglenas, and dinoflagellates. They can also include algae, slime molds, and water molds.

3. How do protists reproduce?

Protists can reproduce through both asexual and sexual reproduction. Asexual reproduction can occur through binary fission, where the organism splits into two identical cells, or through budding, where a smaller cell forms from a larger parent cell. Sexual reproduction involves the fusion of two cells and the exchange of genetic material.

4. What is the ecological importance of protists?

Protists play a vital role in many ecosystems. They are important producers in aquatic environments, providing food for other organisms through photosynthesis. They also serve as decomposers, breaking down organic material and recycling nutrients. Some protists also have symbiotic relationships with other organisms, such as corals and algae.

5. How do protists impact human health?

While some protists can be beneficial, others can be harmful to human health. For example, some protists can cause diseases such as malaria, sleeping sickness, and dysentery. However, protists can also be used in medical research and have potential in biotechnology, such as in the production of antibiotics and other pharmaceuticals.

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