Systematists use several fundamental criteria to assign animals to phyla. Check all of the criteria that systematists would use to classify animals under specific phyla. Check All That Apply Feeding behaviorFeeding behavior Adult body symmetryAdult body symmetry Ultimate adult body sizeUltimate adult body size The embryological formation of body cavitiesThe embryological formation of body cavities Biogeographic distributionBiogeographic distribution Gene sequencesGene sequences The number of tissue layersThe number of tissue layers

Scientists and taxonomists use different criteria to assign different animals to particular phyla. The various systematic criteria that are used more frequently by systematists are as follows:

1. Adult body symmetry

Body symmetry is one of the criteria used to assign an organism or animal to a particular phylum. There is two symmetry found in animals radial and bilateral. If any plane passes through the middle axis and divides into two identical segments called radial symmetry and Bilateral symmetry is where only a single plane divides the body into halves. However, there are many animals that do not have any symmetry and called assymetrical.

2. The embryological formation of body cavities

Other than layers body cavities also helps in assigning the animals that depend on coelom - body cavity between the body wall and gut wall

Animals could be - coelomate(coelom present), pseudocoelomate -(not lined with mesoderm) and acoelomate(coelom absent).

Gene sequences

Genetic similarities also consider and how close an organism to their organism of the phylum or species.

The number of tissue layers

Different body parts, tissues, muscles, and organs developed from the different cell layers that are formed during embryo, therefore, called embryonic layers.

Animals on the basis of these embryonic layers could be diploblastic or triploblastic. Diploblastic animals form 2 embryonic layers the outer and inner layers called the ectoderm and the endoderm respectively. Triploblastic animals have an extra middle layer known mesoderm.