13 characteristics

Symmetry

The balanced distribution of duplicate body parts or shapes. There are several types of symmetry, including asymmetry (lack of symmetry), radial symmetry (arrangement around a central axis), and bilateral symmetry (having a left and right side).

Body cavity

A fluid-filled space inside the body that houses the internal organs. A true body cavity is called a coelom and is lined with tissue derived from the mesoderm. Some animals have a pseudocoelom, which is not completely lined with mesoderm, while others lack a body cavity altogether (acoelomate).

Circulatory system

The system responsible for circulating fluids, nutrients, gases, and other materials throughout the body. It can be open (where hemolymph bathes the organs directly) or closed (where blood is confined to vessels).

Tissue organization

The arrangement and specialization of tissues in the body. Animals can be diploblastic (having two germ layers: ectoderm and endoderm) or triploblastic (having three germ layers: ectoderm, mesoderm, and endoderm).

Openings into digestive tract

The number of openings into the digestive system. Animals can have one opening (incomplete digestive system) or two openings: a mouth and an anus (complete digestive system).

Habitat

The natural environment where an organism lives, including all biotic and abiotic factors.

Gas exchange

The process by which oxygen is taken in from the environment and carbon dioxide is released. This can occur through various structures such as gills, lungs, or the body surface.

Excretory system

The system responsible for removing metabolic wastes from the body. Different animals have different structures for excretion, such as kidneys, nephridia, or Malpighian tubules.

Types of locomotion

The various ways animals move, such as walking, swimming, flying, crawling, or burrowing. Locomotion depends on the animal's body plan, appendages, and environment.

Support systems

The structures that provide support and shape to the body. This can include internal skeletons (endoskeletons), external skeletons (exoskeletons), or hydrostatic skeletons (fluid-filled cavities).

Segmentations

The division of the body into repeated segments. Segmentation allows for specialization of body regions and increased flexibility and mobility.

Appendages

Structures that extend from the body, such as legs, arms, wings, or antennae. Appendages are used for locomotion, feeding, sensory perception, and other functions.

Types of nervous system

The organization of the nervous system, which can range from a simple nerve net (as in cnidarians) to a complex brain and nerve cords (as in vertebrates). The nervous system coordinates and controls the body's functions.