Zoology

Multicellularity

The state of being composed of many cells that form specialized structures and functions.

Choanoflagellates

Single-celled protists with a flagellum and microvilli, considered the closest living relatives of animals.

Metazoans

Multicellular animals that possess tissues and organs.

Phylum Porifera

A phylum consisting of sponges, characterized by being sessile and filter-feeding.

Ctenophores

Soft-bodied, gelatinous marine animals known as comb jellies, potentially the first multicellular animals.

Spongocoel

The central cavity of a sponge where water is filtered and circulated.

Choanocytes

Specialized cells in sponges that filter feed and create water currents.

Pinacocyte

Epithelial cells of sponges that control the size of ostia and form the outer protective layer.

Archaeocytes

Totipotent cells in sponges responsible for nutrient transport, digestion, repair, and reproduction.

Mesohyl

The gelatinous non-cellular layer found between the two main cell layers of sponges.

Spicules

Rigid needle-like structures that form the skeleton of sponges, made of silica or calcium carbonate.

Spongin

A flexible fibrous protein found in some sponges that forms a flexible skeleton.

Asexual reproduction

A type of reproduction that does not involve the fusion of gametes, seen in processes like budding and fragmentation.

Hermaphrodites

Organisms that have both male and female reproductive organs and can produce both sperm and eggs.

Filter feeding

A feeding strategy where organisms remove particles from water, commonly used by sponges and bivalves.

Asconoid

The simplest body structure of sponges, consisting of a simple sac-like shape.

Syconoid

A more complex sponge body plan with folded walls, allowing for greater surface area for filtering.

Leuconoid

The most complex sponge body plan with numerous choanocyte chambers and efficient water flow.

Hexactinellida

Glass sponges characterized by six-rayed silica spicules, mostly found in deep marine environments.

Demospongiae

A class of sponges known as bath sponges, with spongin and/or silica spicules and leuconoid body plan.

Calcarea

Class of calcareous sponges that have calcium carbonate spicules and can exhibit multiple body plans.

Homoscleromorpha

A class of sponges with reduced or absent spicules and a distinct epithelial layer.

Placozoa

Simple marine invertebrates with a flat body and three epithelial layers that feed by phagocytosis. Cilia

Cnidaria

A phylum of aquatic animals characterized by radial symmetry, including jellyfish, corals, and sea anemones.

Ectoderm

The outer germ layer in animals that develops into the skin and nervous system.

Endoderm

The inner germ layer that develops into the digestive tract and organs.

Polyp

The sessile life stage of cnidarians characterized by a cylindrical body with tentacles.

Medusa

The motile life stage of cnidarians, typically umbrella-shaped and free-swimming.

Scyphozoa

Class of jellyfish in which the medusa stage is dominant.

Hydrozoa

Class of cnidarians that can exist in both polyp and medusa forms, often colonial.

Cubozoa

Class of box jellyfish known for their cube-shaped medusa and potent venom.

Anthozoa

Class of cnidarians that includes corals and sea anemones, which are only found in the polyp stage.

Rhopalia

Sensory structures in some cnidarians that contain ocelli and statocysts.

Cnidocytes

Specialized stinging cells found in cnidarians that contain nematocysts.

Nematocysts

Harpoon-like organelles in cnidocytes that discharge venom to capture prey.

Gastrovascular cavity

The digestive cavity in cnidarians that serves as both mouth and anus.

Mutualism

A symbiotic relationship where both organisms benefit, such as clownfish and sea anemones.

Colloblasts

Specialized sticky cells in ctenophores used for capturing prey.

Platyhelminthes

A phylum of flatworms characterized by bilateral symmetry and acoelomate body structure.

Cephalization

The concentration of sensory organs and nervous tissue at the anterior end of an animal.

Acoelomate

An organism that lacks a coelom and has solid mesoderm.

Neodermata

A clade of parasitic flatworms with a specialized outer body covering.

Turbellaria

Class of free-living flatworms that includes planarians.

Cestoda

Class of tapeworms that are endoparasites of vertebrates, lacking a digestive system.

Trematoda

Class of flukes that are endoparasites with complex life cycles.

Lophotrochozoa

A clade of protostomes characterized by the presence of lophophores or trochophore larvae.

Mollusca

A diverse phylum of invertebrates that includes snails, clams, and cephalopods, known for their shells.

Radula

A rasping organ used by mollusks for feeding, absent in bivalves.

Mantle

A layer of tissue in mollusks that secretes the shell.

Cephalopoda

Class of mollusks known for their advanced nervous systems and complex behaviors.

Annelida

A phylum of segmented worms that exhibit metamerism and have a coelom.

Polychaeta

Class of annelids primarily inhabit marine environments, characterized by parapodia and well-developed sensory organs.

Clitellata

Class of annelids that includes earthworms and leeches, characterized by a clitellum for reproduction.

Clitellum

A thickened, glandular section of the body wall in annelids, involved in reproduction by secreting a cocoon for fertilized eggs.

Statocyst

A sensory structure in some invertebrates, often involved in balance and orientation in the water.

Lophotrochozoa

A clade of protostomes characterized by the presence of lophophores or trochophore larvae, including the phyla Platyhelminthes (flatworms), Annelida (segmented worms), and Mollusca (snails, clams, cephalopods).

Flatworms nerve system

Flatworms have a simple nervous system with a pair of cerebral ganglia acting as a 'brain' and two nerve cords running along the body, allowing for basic sensory processing and movement coordination.