0 a main division in a taxonomic (= scientific naming and organization system) relating to animals:
1 one of the groups into which animals are divided, mainly based on the shape of the animal's body and the way that the body is arranged
Origin of the metazoan phyla: molecular clocks confirm palaeontological estimates.
Whereas they are consistent in the classification of lower level taxa, the major divisions of the phylum differ according to the characters used.
However, while there are many universal themes underlying fertilisation biology, there are also interesting differences between phyla and even between species.
The editors studiously avoid any further mention of ' stocks ', ' phyla ', or ' superfamilies ' of any kind.
Operant processes are known to occur in several phyla, suggesting that their origin reaches deeply into the history of life on earth.
What it conspicuously doesn't do, however, is say anything too explicit about the origin of phyla.
One area of particular interest at the moment in metazoan phylogeny is the status of a number of so-called minor phyla.
The free-living planaria tissue section was used as a negative control, because this organism belonged to the same phylum.
