Animal Biodiversity: Body Taxonomy

Radial symmetry

When body parts are arranged around a central axis.

Bilateral symmetry

When the body is divided into 2 equal halves along the sagittal plane, with mirrored left and right sides.

Cephalization

The concentration of sensing & feeding organs at the anterior (front) end of an organism. This is associated with bilateral symmetry.

Segmentation

The division of an organism's body into repetitive structures that result from mesodermal somites.

Modular organisms

Grow by adding genetically identical units, or modules. (only sponges).

Colonial organisms

Grow by adding genetically identical ramets that are usually interconnected. These ramets are known as zooids in phyla Bryozoa and Hydrozoa and polyps in corals.

Pseudocoelom

A body cavity that is not completely lined by mesoderm, unlike a true coelom.

Coelom

A body cavity that forms within the mesoderm and allows for separation and specialization of the organs. Formed by either enterocoely or schizocoely.

Enterocoely

When the coelom develops from pouches that bud off the gut.

Schizocoely

When the coelom develops by splitting a solid mass of mesodermal tissue.

Endotherms

Organisms that can regulate their body temperature through internal processes ("warm-blooded”). These organisms minimize their surface/volume ratio.

Ectotherms

Organisms that depend on external sources to regulate their body temperature (“cold-blooded”). These organisms maximize their surface/volume ratio.

Homologous structures

Features in different species that share a common ancestry, but that have different functions.

Analogous structures

Features in different species that serve similar functions but do not necessarily share a common ancestry.

Body plan constraints

Features (like an exoskeleton) that limit the growth of an organism. Highly constrained = nematodes & annelids. Moderately constrained = arthropods. Unconstrained = Molluscs & Chordates.

What 2 details follow a binomial species name in scientific literature?

The name of the person who first described that species (authority) and the date of publication of that species in the scientific literature.

The biological species concept

A species is a group of interbreeding individuals of common ancestry that are reproductively isolated from all other groups.

Synapomorphy

A shared, derived character of a biological clade.

Gross morphology (visual evidence)

The original basis for animal taxonomy/classification.

The current consensus of the relationships between major animal groups relies on…..

Genetic sequence data, which confirms many patterns from embryology.