Comments on: On the Origin of Animals

By: New family tree of worms has roots in the 19th century « Thoughtomics

New family tree of worms has roots in the 19th century « Thoughtomics — Thu, 03 Mar 2011 14:13:30 +0000

[...] The marine ragworm, or Platynereis dumerilii, has recently come in vogue for studying how eyes and organs evolved in animals. Many of its characteristics, like its large antennae and sensory palps, seem to [...]

By: DDeden

DDeden — Sat, 11 Dec 2010 19:51:10 +0000

6 Elements (CHONSP) synergise to form the biological core of life, 6 elements (ROYGBIV) prismatically synergise to form the electromagnetic core of light, 6 hoop elements synergise triaxially to weave a paper (truncated icosa) sphere.

I was just reading about some flat square archaebacteria from Sinai
living in hypersaline conditions which have peripheral vacuoles/
bubbles/vesicles, thought either for buoyancy (see air sacs) or
osmosis/sunlight/respiration. There Magnesium is unusually abundant. Also noted triangle flat ones (japonica) which become spheres when salt is reduced.

http://skepticwonder.fieldofscience.com/2010/12/walsbys-square-archae...

note

Human stem cells become either fat cells or bone cells depending solely on their exterior environment (epigenetics)
http://www.eurekalert.org/pub_releases/2004-04/jhmi-csc041604.php

In the April issue of Developmental Cell, the Hopkins researchers
report that mesenchymal (pronounced mez-EHN-kih-mal) stem cells forced
to be spherical efficiently transform into precursors to fat cells,
while those allowed to stretch and flatten move closer to becoming
bone cells.

By: A System of Developmental Robustness « From C to Carnivore

A System of Developmental Robustness « From C to Carnivore — Thu, 24 Jun 2010 18:56:47 +0000

[...] of tissue identity and offer some clues as to what the Urbilaterian was like. Lucas bloged about this a while ago in [...]

By: Giving credit where credit is due – what’s out there in the blogosphere « From C to Carnivore

Sat, 17 Apr 2010 00:16:34 +0000

[...] On the Origin of Animals – by Lucas Brouwers [...]

By: Carnival of Evolution #22 « Beetles In The Bush

Carnival of Evolution #22 « Beetles In The Bush — Fri, 02 Apr 2010 05:07:51 +0000

[...] at Thoughtomics admits he is an animal. In his post, On the Origin of Animals, he discusses a Nature paper published last month by a team of researchers that used the conserved [...]

By: DDeden

DDeden — Sun, 21 Mar 2010 22:20:07 +0000

I don’t know of any of these which do not go through a spherical stage sometime during the reproductive cycle:
http://1.bp.blogspot.com/_FeaU01D-3wI/S5S_3YilMYI/AAAAAAAABT4/CDcD-oasX30/s1600-h/ToE+2010+v1-2+PsiW.jpg

Like a pin pricking a bubble, conception induces polarization (asymmetry), followed by subdivision into blastula & growth into ‘all sorts of weird shapes’.

Before that, the pre-fertile egg cell external membrane has localized spherical symmetry (simplest, max. volume with min. surface area, max. packing density) where no axis is predominant; the only membrane “polarities” are inside/outside (osmotic) and structural (geodesic) which are in isotopic equilibrium until conception induces nonspherical (complex) symmetry.

By: Dunbar

Dunbar — Sun, 21 Mar 2010 05:05:23 +0000

To be a pedant, technically not all blastulae are perfect spheres. I believe, for instance, chicken blastulae are discs (or flattened spheres).

I’m a bit confused about DDeden’s comment– does he/she mean to say that an apolar nature precedes, historically and ontogenetically, a polar nature to animal life? If so, I find that odd because as all cell biologists know, asymmetrical cell division and therefore polarisation is immensely important to all cellular life. An egg, for instance, is instantly polarised upon fertilisation. Yeasts have been shown to differentially pass on proteins to daughter cells– bacteria I think do something similar. Heck, tons of cells (and viruses) come in all sorts of weird shapes. There’s no validity in saying that spherical geometry was important for ancestral forms without more convincing arguments, especially when life seems to like polarity.

By: Lucas

Lucas — Thu, 18 Mar 2010 21:44:58 +0000

Thanks for your comment! Considering spherical organisms more ancestral is a view I didn't come across before. It's certainly true that all bilaterals go through a spherical blastula stage. But as soon as the mouth and anus develop, directionality is introduced in the embryo, in the form of the anteroposterior axis. Being able to discriminate up from down is also a major advantage, perhaps explaining the origin of the dorsoventral axis. The fact that all radial organisms go through a bilateral larval stage also seems to suggest that the bilaterian ancestor was a bilateral as well. Many of the earliest metazoan fossils from the Ediacaran biota also show segmented body plans, instead of radial ones. Maybe if we go further back, to the origins of multicellularity, that we will find our radial ancestor? And funny that you should mention serotonin and melatonin, I recently came across the example you write while working with the kegg pathway database! And you're of course right in stating that parts (biochemical or genetical) get re-used, mixed and matched all the time. My short introduction to microRNAs is wholly inadequate of course, as it is a subject that deserves an entire blog itself! (after writing this down, I looked it up whether one existed.. and there we go! Seems more focussed on diseases though..)

By: DDeden

DDeden — Thu, 18 Mar 2010 06:42:56 +0000

I’ve gotten some flack for this, but I think spherical geometry is useful in determining the deep ancestral life forms, such as the icosahedral viruses and primitive pentadactyle/pentameric traits common to so many taxa. Rather than seeing simple bilaterals and radial segmented worms as very early, I view them as very derived, just as “simple” snakes are derived from lizard-like ancestors, not vice versa. AFAIK all life goes through a reproductive spherical stage, egg/spore/seed, no matter what external form the egg case, larvae & adults eventually become. A sphere must have certain chemical/physical properties, whether at the nano-scale micro-scale or macro scale, otherwise it dissipates/breaks at the wrong time, and this preceded more advanced development of polarization, protein & lipid layers, later mineral shells, locomotion, complex feeding etc.

“some genes that play a central role in neuronal cells, are useless for cells that make up the gut.”

If you google ‘serotonin’, you’ll find that while it is a brain precursor to melatonin (sleep), most is produced in the gut, where it is sent via platelets to transform bone, which is just a mineral reservoir. Animals are complicated, tending to re-use systems in new ways when advantageous.