Animal Evolution & Diversity: Invertebrates Part I

Vocabulary flashcards covering the characteristics, classification, and major evolutionary trends of invertebrates, as well as specific details on Ctenophores, Porifera, and Cnidaria.

General animal characteristics

Multicellular, heterotrophic, internal digestion, and motile (possessing nervous and muscle tissue).

Structural proteins

Proteins like collagen found in connective tissues that support animal cells in the absence of cell walls.

Extracellular matrix (ECM)

The substance that supports animal cells, joined by cell junctions for adhesion and communication.

Hox genes

A group of genes possessed by most animals that functions in patterning the body axis.

Choanoflagellate

A flagellated protist believed to be the closest living relative of animals.

Receptor tyrosine kinases (RTKs)

A category of enzyme-linked receptor used in cell communication found in all animals and choanoflagellates.

Kingdom Animalia

A monophyletic group that is the most species-rich kingdom, with invertebrates accounting for approximately $95\%$ of species.

Radial symmetry

A circular arrangement of body parts around a central axis where any plane through the main axis divides the animal into similar halves.

Bilateral symmetry

A body plan that can be divided into right and left mirror images on only one plane through the anterior-posterior midline.

Cephalization

The concentration of sensory organs and nerve tissues at the anterior end (head), associated with bilateral symmetry.

Diploblastic

Animals having two cell layers: the ectoderm and endoderm.

Triploblastic

Animals having three cell layers: the ectoderm, mesoderm, and endoderm.

Protostomes

Organisms where the blastopore develops into the mouth; they typically exhibit spiral and determinate cleavage.

Deuterostomes

Organisms where the blastopore develops into the anus; they typically exhibit radial and indeterminate cleavage.

Indeterminate cleavage

A cleavage pattern where cells are totipotent, meaning identical twins are possible.

Acoelomate

An animal that lacks a fluid-filled body cavity; the space between the gut and body wall is filled with cells.

Pseudocoelomate

An animal with a body cavity lined by mesoderm on only one side, in which internal organs are suspended.

Coelomate (eucoelomate)

An animal with a body cavity lined on both sides by mesoderm.

Peritoneum

A layer of muscular tissue derived from mesoderm that lines the coelom and surrounds internal organs.

Open circulatory system

A system where blood (hemolymph) flows through vessels and open spaces, bathing internal organs directly.

Closed circulatory system

A system where blood is confined entirely to vessels, with capillaries serving as sites of exchange.

Ctenophores (comb jellies)

The earliest-diverging animal lineage; they are marine, use cilia for locomotion, and lack Hox genes.

Porifera (Sponges)

Simple animals that lack true tissues and a nervous system, utilize intracellular digestion, and are usually asymmetric.

Choanocytes

Specialized sponge cells that trap small food particles.

Amoebocytes

Mobile cells in sponges that absorb and digest food from choanocytes and carry nutrients to other cells.

Spicules

Structural elements found in sponges for support and defense.

Cnidaria

A phylum of radially symmetric, diploblastic animals including jellyfish, hydra, and coral.

Mesoglea

A gelatinous layer that connects the endoderm and ectoderm in cnidarians.

Polyp

The sessile body form of a cnidarian.

Medusa

The motile body form of a cnidarian.

Gastrovascular cavity

A central digestive compartment with a single opening that functions as both mouth and anus.

Cnidocytes

Specialized stinging cells in cnidarians used for defense or capturing prey.

Nematocysts

Stinging structures contained within cnidocytes.