Please enlighten my ignorance 8-)

Zebitty zebitty at australis.aunz.com
Wed Jan 10 04:58:21 EST 2001


Hi, I'm back from my sojourn to Northern Australia and am a bit more prepared 
now. Thanks for your replies.....and yes I did mean Solanum. 
Now to address a few issues.....I trained in comparitive and human physiology 
so largely animal taxonomy is not an issue as I am aware of the kingdom 
structure.......I am however, a botanical taxonomy virgin....so please be 
gentle 8-)

>Yes living creatures in the same species/genus/family usually look
>alike, but not always. The Australian Platypus and Echidna are closely
>related (ie they are both monotremes) however, superficially, they look
>quite different, and inhabit different environments. 

Monotremata is a famililial relationship.....based on the fact that they only 
have one opening for intestinal and reproductive systems. However, can one be 
sure that they are truly closely genetically related (I'm not aware of any 
studies though I'm sure they exist) or could they both just grouped together on 
that one basic morphological similarity which may or may not be the result of 
convergent evolution - perhaps all proto-mammals had this arrangement. To use 
another example. The visual pathway of Megachiroptera (flying foxes) is very 
similar to primates (the only other animal that is!!!) so do we conclude that 
primates and megachiroptera are related or is it the result of convergent 
evolution? 

On a familial level I find much of plant taxonomy perplexing....I was finding 
genus relationships in plants difficult enough to grasp as (this was the 
original example that I had in mind) Euphorbia millii and Euphorbia pulcherrima 
seem (as far as my limited ability can tell) to have little in common apart 
from the fact that they both have a hydrophobic milky sap. But quite obviously 
a milky sap is a poor commonality as many quite obviously unrelated species 
(ie. Ficus elastica) have milky sap.

Yet an anteater may
>superficially look like an Echidna, but it is not closely related . 

Personally I don't think they look anything like one another. But that could be 
because I am familiar with animal but not with plant morphology.

>Taxonomy is based on features which are often, but not always, based on
>genetic chromosomes. 

Given that much of the taxonomic record was developed before the discovery of 
the double helix, I would question that assertion!! But if you can convince me 
otherwise I'd be happy to listen.

>Are you getting confused between genetics, and what are living creature
>looks like?

No, I don't think so. Physiology and morphology can be similar or even the same 
and be unrelated as a result of convergent evolution. And this is my 
point.....how much of plant taxonomy is actually genetic and how much is merely 
based on strong similarities in certain structures and systems?

>
>Cereoid wrote in message
><91mb9o$n26o$1 at newssvr06-en0.news.prodigy.com>... 
>>Dear Zebitty,
>>
>>Which species in particular that are in the same genus but look
>>radically different is it to which you allude?
>>
>>Species in the same genus typically share certain floral features but
>differ
>>vegetatively. It may also be true that vegetatively similar plants are
>>in different genera.
>>
>>Then there is the possibility that the plants you have seen are
>>misidentified or no longer in the same genus.
>>
>>
>>"Zebitty" <zebitty at australis.aunz.com> wrote in message
>>news:91m7hc$e88$1 at gnamma.connect.com.au...
>>> Hi,
>>> I have recently started to learn a bit more about plants for my own
>>> purposes, and have noticed something that I haven't been able to
>>> answer. 
>>Is
>>> plant taxonomy based purely on genetic relationships (much like
>>> animals) 
>>or
>>> on something else. I ask because I notice several species of plants
>>> that look radically different in their adaptations to their
>>> environments and 
>>yet
>>> have the same genus. Now generally animals of the same genus tend to
>>> look fairly similar. This does not seem to be the case with many
>>> plants. Why 
>is
>>> this? Or is it just my lack of understanding of plant morphology?
>>>
>>> Thanks to anyone who helps
>>>
>>> Zebitty
>>>
>>> "If I have seen further, it is because I have stood on the shoulders
>>> of giants"
>>> Sir Isaac Newton
>>>
>>>
>>
>>
>
>
>


-- 
"Life wasn't meant to be easy....otherwise everbody would do it"
Rhys Parry






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