Re: Internal organs homologous across phyla?

On Wed, 25 Apr 2007 13:42:40 -0400 (EDT), dk@xxxxxxxxxxxxxxxxxxxxxxxxx
(DK) wrote:

In article <f0lgfe$1bat$1@xxxxxxxxxxxxxxxxxxx>, nospam@xxxxxxxxxx (Paul Ciszek) wrote:
I have occasionally read a reference to the heart, liver, etc. of
animals other than chordates. Are these organs merely analogous--
performing the same function as the similarly named organ in a
chordate--or are some of the homologous, arising from the same
aspect of fetal development, or the same HOX gene or something?
Do molluscs have kidneys? Or did chordates evolve all of their
internal organs from scratch?

Not 100% sure in terms of embrionic origins, but my answer would
be analogous rather than homologous. An eye is a classic example:
invertebrate photoreception is fundamentally different from vertebrate
one in almost every respect.

Although tissue types are widespread, organs are not. I can't think
of any organ that is homologous across phyla unless the phyla are
closely related -- a very unusual circumstance. Just think back to the
origins of phyla which, for most, are buried back in the early
Cambrian-preCambrian. What type of common ancestor would there have
been and what kinds of internal organs did it have?

The circulatory, the renal, the nervous, the respiratory, and the
digestive organs of, for example, the chordates (vertebrates), the
arthropods, the molluscs, and the echinoderms are completely
different.



.

Relevant Pages

  • Re: Internal organs homologous across phyla?
    ... Are these organs merely analogous-- ... performing the same function as the similarly named organ in a ... Or did chordates evolve all of their ...
    (sci.bio.evolution)
  • Internal organs homologous across phyla?
    ... animals other than chordates. ... Are these organs merely analogous-- ... performing the same function as the similarly named organ in a ... Or did chordates evolve all of their ...
    (sci.bio.evolution)