Phylum Cnidaria Flashcards

Study Notes

Phylum Cnidaria Overview

Characterized by being diploblastic, consisting of endoderm and ectoderm layers.
Possess cnidocytes, specialized cells for capturing prey.
Most species display planula larvae, facilitating dispersal.

Cnidocyte and Cnida

Cnidocytes are stinging cells used for defense and prey capture.
Cnida refers to the coiled filament within an inverted tube that can be expelled to deliver sting.

Nematocysts

A type of cnida, nematocysts are venomous harpoons enabling predation.

Tissue Organization

Exhibits three tissue types: digestive, nervous, and muscular, allowing for complex functions.

Epidermis and Gastrodermis

Epidermis has epitheliomuscular cells with longitudinal muscle fibers for contraction.
Gastrodermis contains nutritive-muscle cells with contractile circular muscle fibers aiding in digestion.

Mesoglea

A gelatinous layer composed of water and collagen, situated between the endoderm and ectoderm.

Class Hydrozoa Characteristics

Dominantly polyp form with cnidocytes primarily located in the epidermis.
Typically very small, with medusa stage having a velum present and no gastric pouches or oral arms.

Hydrozoa Feeding and Digestion

Hydra utilize gland cells to secrete enzymes for digestion, and nutrients are absorbed by surrounding cells via diffusion.

Hydra Reproduction

Can reproduce sexually (dioecious with distinct male and female) or asexually through budding, with embryos encysting until favorable conditions arise.

Specimen Obelia in Hydrozoa

Colonial organism alternating between polyp (hydranth for feeding, gonangium for reproduction) and medusa forms, with both sexual and asexual reproduction.

Specimen Gonionemus

Medusa form is predominant with distinct gastric canals and sensory capabilities via statocysts and ocelli.

Specimen Physalis

Portuguese man o' war is a colonial organism comprised of numerous polyps functioning together, featuring structures for floating (pneumatophore) and feeding (gastrozooids).

Class Scyphozoa Characteristics

Known as true jellyfish, with a dominant medusa form and cnidocytes in both epidermis and gastrodermis.
Lacks a velum and has amoeboid cells within the mesoglea.

Scyphozoa Specimen Aurelia

Features four oral arms and a gastrovascular cavity with four folded pouches.
Exhibits a complete canal network with scalloped bell margin containing sensory rhopalia.

Scyphozoa Reproduction Cycle

Life cycle includes stages from medusa to zygote, planula larva, scyphistoma, strobila, ephyla, and back to medusa.

Class Anthozoa Characteristics

Known as "flowers of the ocean," consists solely of polyp forms with septa in the gastrodermis bearing nematocysts.
Tentacle structures can be either hexamerous or octamerous.

Anthozoa Corals

Colonial polyps that secrete calcium carbonate skeletons; hard corals are hexamerous while soft corals are octamerous.

Importance of Cnidarians

Serve as critical habitat for marine biodiversity while also playing a role in food chains, such as turtles and crabs consuming jellyfish.

Description

Test your knowledge on the characteristics and definitions related to Phylum Cnidaria with these flashcards. This quiz covers important terms such as cnidocytes, nematocysts, and tissue layers. Ideal for students studying marine biology or zoology.