A General Overview of the Animal Kingdom

Flashcards covering the classification, characteristics, and anatomical features of the nine major animal phyla and protozoa based on lecture notes.

Protozoa

A polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris.

Hierarchy of Classification

The taxonomic levels of classification: Kingdom, Phylum, Class, Order, Family, Genus, and Species.

Binomial/Trinomial System

The system of nomenclature or naming adopted by zoologists for living organisms.

Micromonas pusilla

A microscopic protozoan that has a size of about $0.001\,mm$.

Syringammina fragilissima

A protozoan that can reach sizes up to $20\,cm$.

Phylum Porifera

Commonly known as sponges or sea sponges, these are multicellular organisms with bodies full of pores and channels that lack true tissues and exhibit asymmetry.

Mesohyl

A gelatinous matrix filled in between the two thin layers of cells in the body of a sponge.

Coelenterata

A term encompassing the animal phyla Cnidaria and Ctenophora, which are aquatic invertebrate animals including jellyfishes, corals, and sea anemones.

Cnidocytes

Specialized cells in Coelenterates that contain tentacles bearing stinging organelles called Nematocysts.

Radiate Phyla

A term used to refer to phyla that exhibit radial symmetry, such as Cnidaria and Ctenophora.

Phylum Ctenophora

Commonly known as comb jellies, these are predators notable for using groups of cilia called "combs" for swimming.

Phylum Rotifera

Microscopic aquatic organisms (around $100\,\mu m$ to $30\,mm$) characterized by a corona, which is a rotating, wheel-like structure covered with cilia.

Phylum Platyhelminths

Commonly called flatworms; these are unsegmented, soft-bodied acoelomates with flattened shapes that allow for diffusion of oxygen and nutrients.

Acoelomates

Triploblastic animals that lack a body cavity altogether, such as flatworms.

Phylum Annelida

Segmented worms including earthworms and leeches; the smallest is Chetogaster ($1\,mm$) and the largest is Megascolides australis ($11\,feet$).

Phylum Nematoda

Commonly called roundworms; these are unsegmented animals that inhabit a broad range of environments and may possess anterior lateral organs called phasmids.

Phasmid

An anterior lateral organ in some nematodes used for receiving stimulus and helping the worm relocate to favorable environments.

Phylum Mollusca

The second largest animal phylum, including snails, clams, and octopuses, with sizes ranging from microscopic to the $21\,m$ giant squid.

Phylum Arthropoda

The largest phylum in the animal kingdom, characterized by jointed appendages and a skeletal covering composed of chitin bound to protein.

Chitin

A complex sugar bound to protein that makes up the nonliving exoskeleton of arthropods.

Phylum Echinodermata

Meaning "prickly skin," this phylum includes starfish and sea urchins, which are notable for their ability to regenerate tissues and limbs.

Phylum Chordata

The most advanced animal phylum, consisting of animals that have a vertebral column or notochord at some stage of their life cycle.

Symmetry

The repetition of parts in an animal in an orderly fashion, reflecting a correspondence in size, shape, and position on opposite sides of a dividing line.

Radial Symmetry

A body plan where parts are distributed around a central axis, with no front, back, left, or right sides; found in Cnidaria and adult Echinodermata.

Bilateral Symmetry

A body plan with two axes of orientation (front to back and top to bottom), resulting in dorsal, ventral, left, right, anterior, and posterior sides.

Cephalization

An evolutionary trend in bilateral animals involving the concentration of sensory equipment and a central nervous system at the anterior end.

Gastrulation

An early developmental process in which a blastula reorganizes into a multilayered structure called the gastrula.

Diploblastic

Animals that have only two germ layers: the ectoderm and the endoderm.

Triploblastic

Animals that have three germ layers: the ectoderm, the endoderm, and the mesoderm.

Coelom

A fluid- or air-filled space located between the digestive tract and the outer body wall; also known as a body cavity.

Coelomates

Animals possessing a "true" coelom formed from tissue derived from the mesoderm, including Annelida, Mollusca, Arthropoda, Echinodermata, and Chordata.

Pseudo coelomates

Animals with a body cavity formed from both mesoderm and endoderm, such as Rotifera and Nematoda.