Invertebrate Zoology: Domains of Life to Major Invertebrate Phyla

Comprehensive vocabulary flashcards covering the major concepts of Invertebrate Zoology, including biological domains, cytology, developmental body plans, Protozoa, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Mollusca, and Arthropoda.

Domain

The broadest taxonomic category into which all life forms are classified, containing one or more kingdoms.

Kingdom Archaebacteria

Ancient forms of bacteria referred to as extremophiles that thrive in Earth's most extreme environments, such as hot springs, highly saline water, swamps, and the intestines of cows.

Kingdom Eubacteria

Single-celled, prokaryotic organisms lacking a nucleus that are found everywhere on Earth except extreme environments and reproduce asexually.

Domain Eukarya

The taxonomic domain comprising all life forms built from eukaryotic cells containing a true membrane-bound nucleus, divided into the kingdoms Animalia, Plantae, Protista, and Fungi.

Kingdom Protista

The diverse 'odds and ends' or 'trash can' eukaryotic kingdom containing organisms that cannot be classified as an animal, plant, or fungus.

Kingdom Fungi

Eukaryotic, non-motile heterotrophs with cell walls made of chitin that absorb food by secreting digestive enzymes into dead or decaying organic matter.

Protoplasm

A historical term coined by J. Purkinje in 1840 to describe the living substance of a cell, known today to consist of cytoplasm and organized organelles.

Modern Cell Theory

The biological principle stating that all living things are composed of cells, the cell is the primary structural and functional unit of life, cells arise only from pre-existing cells via biogenesis, and hereditary information is passed on during division.

Somatic Cells

Diploid ($2n$) body cells that contain two complete sets of chromosomes and reproduce through mitosis to generate identical daughter cells.

Germ Cells

Haploid ($n$) gametes (sperm and eggs) that contain a single set of 23 unique chromosomes and are produced via meiosis.

Mitosis

A type of cell division occurring in somatic cells that yields genetically identical daughter cells for the purposes of growth and tissue repair.

Meiosis

A specialized cell division process that halves the chromosome number to produce haploid gametes for sexual reproduction.

Budding

An asexual reproduction mode common in yeasts and hydras in which a new individual grows as an unequal outgrowth on the parent body before detaching.

Parthenogenesis

A reproductive process involving the embryonic development of an organism directly from an unfertilized or un-united egg.

Gynogenesis

A reproductive process where sperm is required to activate egg development, but the male genetic material is discarded without fusing.

Radial Symmetry

A morphological body plan where any longitudinal plane passing through the central axis divides the organism into identical halves, commonly seen in tubular or vase-like aquatic animals like jellyfish.

Bilateral Symmetry

A body plan wherein a single sagittal plane divides the animal into mirrored right and left halves, strongly correlated with directional movement and cephalization.

Gastrulation

The post-blastula embryonic developmental phase where one side of the blastula invaginates to establish the primary germ layers and primitive gut.

Gastrocoel (Archenteron)

The primitive embryonic gut cavity formed by the inward depression of cells during gastrulation.

Blastopore

The external opening leading into the gastrocoel of an embryo, which typically develops into either the mouth or the anus.

Diploblastic

Organisms that develop from two embryonic germ layers—ectoderm and endoderm—separated by non-cellular mesoglea and lacking a true coelom.

Triploblastic

Organisms whose structural tissues develop from three primary embryonic germ layers: ectoderm, mesoderm, and endoderm.

Acoelomate

A triploblastic body plan lacking an internal body cavity between the gut and body wall, with the blastocoel space filled by mesodermal parenchyma.

Pseudocoelomate

An organism possessing a body cavity (pseudocoel) derived from the persistent blastocoel that is not lined with mesodermal peritoneum.

Eucoelomate

An animal possessing a true coelomic body cavity completely enclosed and lined by mesodermal peritoneum and mesenteries.

Metamerism

The serial repetition of homologous body units (metameres or somites) along the front-to-back longitudinal axis of an animal.

Contractile Vacuole

An osmoregulatory organelle in freshwater protozoans that collects and pumps out excess water and metabolic waste to prevent osmotic bursting.

Superclass Sarcodina

Protozoans that move and engulf food using fluid pseudopods, lack spore formation, possess a monomorphic nucleus, and reproduce sexually via syngamy.

Superclass Mastigophora

Flagellated protozoans that may be free-living in freshwater (such as Euglena) or parasitic in host blood (such as Trypanosoma, which causes sleeping sickness).

Subphylum Sporozoa

A group of parasitic, pathogenic protozoans lacking dedicated locomotory structures that reproduce through alternation of generations across two hosts (such as Plasmodium, the causative agent of malaria).

Subphylum Ciliophora

Protozoans propelled by hair-like cilia that display nuclear dimorphism with a reproductive micronucleus and a somatic macronucleus.

Phylum Porifera

Asymmetrical or radially symmetrical pore-bearing animals exhibiting a cellular grade of organization without true tissues or organs.

Choanocytes

Specialized flagellated collar cells lining the inner chambers of sponges that generate feeding water currents and trap food particles.

Spicules

Sharp structural rods made of silica or calcium carbonate that, along with spongin protein fibers, form the supportive endoskeleton of sponges.

Osculum

The large main excurrent pore in a sponge through which filtered water and sperm are expelled to the exterior environment.

Leuconoid Canal System

The most complex and efficient water-canal system in sponges, characterized by extensive outfoldings and branched flagellated chambers that allow for large body sizes.

Phylum Cnidaria (Coelenterata)

Diploblastic aquatic animals possessing radial symmetry, a tissue grade of construction, a gastrovascular cavity (coelenteron), and stinging nematocysts.

Nematocyst

A specialized coiled, stinging cell structure with a barbed projectile used by cnidarians to inject venom into prey or predators.

Polyp and Medusa

The two primary morphological stages in cnidarians: the polyp is a tubular, typically sessile asexual form, while the medusa is a motile, bell-shaped sexual form.

Planula

The ciliated, free-swimming larva produced by sexual reproduction in cnidarians that settles onto a substrate to develop into a polyp.

Class Anthozoa

A group of exclusively marine cnidarians (including sea anemones and corals) that exist entirely as polyps and completely lack a medusoid stage.

Phylum Platyhelminthes

Dorsoventrally flattened, triploblastic, bilaterally symmetrical, acoelomate, unsegmented worms with an incomplete gut.

Class Turbellaria

Mostly free-living, bottom-dwelling flatworms (such as planarians) renowned for their immense capacity to regenerate completely from small bodily fragments.

Class Cestoda

Endoparasitic flatworms (tapeworms) lacking a digestive tract whose bodies consist of an attachment scolex followed by a chain of reproductive proglottids.

Scolex

The anterior attachment organ of a tapeworm, typically equipped with suckers and a rostellum with hooks to anchor to host intestinal mucosa.

Proglottid

An individual segment of a tapeworm strobila that contains a complete set of both male and female reproductive organs.

Class Trematoda

Endoparasitic flukes possessing oral and ventral suckers that cycle through complex life stages, nearly always utilizing a mollusk as their primary host.

Neurocysticercosis

A severe brain infection that occurs when humans act as accidental hosts by ingesting eggs of the pork tapeworm (Taenia solium), forming cysticerci in cerebral tissue.

Phylum Nematoda

Thread-like, unsegmented roundworms that possess a complete two-opening digestive tract, a pseudocoelom, and a protective external cuticle.

Filariasis

A mosquito-borne parasitic disease caused by filarial nematodes that obstructs the lymphatic system, potentially resulting in chronic swelling, lymphedema, and elephantiasis.

Ascariasis

A widespread intestinal infection caused by the roundworm Ascaris lumbricoides, transmitted through contaminated food or water.

Trichinosis

A parasitic infection acquired from consuming raw or undercooked meat (especially pork) containing encysted larvae of the roundworm Trichinella.

Phylum Annelida

Triploblastic, coelomate segmented worms showing distinct metamerism, a complete digestive tract, and bilateral symmetry, including earthworms, leeches, and polychaetes.

Septa

Internal cross-walls separating individual body segments (metameres) within annelids.

Setae

Tiny chitinous bristles located on the body segments of annelids used to anchor the body and aid in crawling.

Crop and Gizzard

Specialized organs in the annelid digestive tract: the crop temporarily stores ingested food, and the muscular gizzard mechanically grinds it into smaller pieces.

Phylum Mollusca

Unsegmented, triploblastic, coelomate lophotrochozoan protostomes characterized by a three-part body plan consisting of a head, a muscular foot, and a visceral mass covered by a mantle.

Mantle

A fold of the dorsal body wall in mollusks that encloses the mantle cavity, carries out respiratory gas exchange, and secretes the protective shell.

Radula

A tongue-like rasping organ bearing rows of chitinous teeth found in the mouth of most mollusks (absent in bivalves), used to scrape up food.

Class Bivalvia

Aquatic mollusks, including clams and oysters, with bodies enclosed within a two-halved hinged shell (valves) that lack a radula or head and feed by filtration.

Class Cephalopoda

Marine predatory mollusks (such as squids and octopuses) featuring a closed circulatory system, image-forming eyes, prehensile tentacles, and a complex brain.

Phylum Arthropoda

The largest phylum of the animal kingdom, containing bilaterally symmetrical, segmented coelomates with jointed appendages and a hard chitinous exoskeleton.

Molting (Ecdysis)

The periodic shedding and renewal of the rigid arthropod exoskeleton necessary for the animal to grow larger.

Book Lungs

Respiratory structures in terrestrial arachnids composed of stacked tissue folds with alternating air pockets across which gas exchange occurs between blood and air.

Trachea

A system of internal branching tubules in terrestrial insects that takes in air through external spiracles and delivers oxygen directly to bodily tissues.

Metamorphosis

A biological process of post-embryonic development in many arthropods marked by marked structural transitions through larval, pupal, and adult forms.