Let's get the ball rolling.....Some questions for Dr. Ron

[Anonymous]

OK, I'l break the ice. Here's a couple of questions:

1) "Any group of organisms can be called a taxon...". Does this mean any group of LIKE organisms, or can they be widly diverse and you are just denoting a set of organisms?

2) "Primative means 'near the ancestral condition'". Please define ancestral condition in terms of time or evolutionary stages. In other words at what point does A become the ancestral condition to B? Or how much change is required in an organism to be considered an evolutionary step?

3)"Unicellular Algae- Mostly photosynthetic". Searching the web for Pfiesteria piscicida yields multiple instances of a Dinoflagellates that feed on external organic matter. If photosynthesis is not required for the definition of Algae please provide one.

4)"Requires AA, Vitamines B12....". AA=Amino Acids?

5) Does zooxanthellae contain chlorophyl? If not does the pigment react and funtion the same way? Also, if not chlorophyl are there terrestrial occurances?

Fun lecture Dr. Ron. It's been years since school.

-Greg

 

[ATJ]

Greg,
I could probably have a stab at questions 1-4 but I'll defer to Dr Ron. For question 5, Borneman (2001) states that zooxanthellae can contain both chlorphyll a and chlorophyll c<SUB>2</SUB>, peridinin, and a number of accessory pigments.

 

[jamesw]

I emailed Dr. Ron letting him know he has some questions waiting in this forum. We should hear from him soon.

Cheers
James

 

[rshimek]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote

Originally posted by GDawson:

Hi Greg,

1) "Any group of organisms can be called a taxon...". Does this mean any group of LIKE organisms, or can they be widly diverse and you are just denoting a set of organisms?

It can be any group of organisms. A taxon is an arbitrary grouping. There is a danger here of bogging down with terms and of semantic problems.

Strictly speaking a taxon can be any group. So for example, for the purposes of some research I may define any particular group in any manner I choose.

However, when one starts to put such groups within the formal taxonomic hierarchy for animals, the type of group, and what animals may be placed in it, is goverened by a significant set of rules- "The International Code of Zoological Nomeclature" as well as by the peer review process. Do a web search on the ICZN and see what you find...

2) "Primative means 'near the ancestral condition'". Please define ancestral condition in terms of time or evolutionary stages. In other words at what point does A become the ancestral condition to B? Or how much change is required in an organism to be considered an evolutionary step?

There is no specific overall level, time, or condition that serves to answer this. Ancestral and derived are relative conditions. For example, the immediate ancestor of modern humans was another human species, Homo ergaster (=H. erectus[). However this species was very advanced when compared with the first vertebrates.

The point at which one species changes into another, more derived, one is a question of some difficulty and has to answered in the context of each particular taxon that is being discussed. Probably the best tool for attacking this is cladistics, which tries to unambiguously separate and define taxa on the basis of objective characteristics.

3)"Unicellular Algae- Mostly photosynthetic". Searching the web for Pfiesteria piscicida yields multiple instances of a Dinoflagellates that feed on external organic matter. If photosynthesis is not required for the definition of Algae please provide one.

Many so-called algal groups have members that are not photosynthetic. That's the breaks.

There is NO formal definition of an alga. Organisms called algae occur in at least 4 kingdoms and probably close to 10 phyla. So... We all have some sort of "warm fuzzy" or "cold slimy" feeling of what an alga is, but you can't really erect an inclusive definition. As Sen. Jesse Helms once said about pornography, "I may not know how to define it, but I can sure tell what it when I see it."

4)"Requires AA, Vitamines B12....". AA=Amino Acids?

Yup.

5) Does zooxanthellae contain chlorophyl? If not does the pigment react and funtion the same way? Also, if not chlorophyl are there terrestrial occurances?

Zooxanthellae are dinoflagellates. Check R&B and see what they say about chlorophyll and other pigments. All photosynthetic organisms have chlorophyll.

[ November 07, 2001: Message edited by: rshimek ]</p>

 

[ATJ]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by rshimek:
<strong>The point at which one species changes into another, more derived, one is a question of some difficulty and has to answered in the context of each particular taxon that is being discussed. Probably the best tool for attacking this is cladistics, which tries to unambiguously separate and define taxa on the basis of objective characteristics.</strong><hr></blockquote>

And if the particular group you are talking about is Scleractinia (stony corals)... oh boy.

Charlie Veron's Corals in Space and Time is specifically about speciation in stony corals. He asks the question "What is a species?" and spends over 200 pages discussing it. It is a very interesting and thought provoking read.

Of course, there will be other taxa that may be as difficult or even worse.