General Zoology Final Term Notes

Phylum Cnidaria

• Radial or biradial symmetry.

• Aquatic.

• Sessile, free-floating, or weak swimming.

• Tissue-level organization.

• Primitive nervous system.

• Stinging cells.

Cnidarian Classes

• Cubozoa: Box jelly

• Scyphozoa: Moon jelly

• Anthozoa: Anemone

• Hydrozoa: Physalia

Cnidarian Forms

• Polyp: Mouth and Tentacle, Digestive cavity, Gastrodermis, Mesoglea, Epidermis

• Medusa: Mouth and Tentacle

General Organization

• Gastrovascular cavity for digestion.

• Two cell layers: gastrodermis and epidermis.

• Mesoglea: jelly between cell layers.

Reproduction

• Sexual: gametes shed into water.

• Asexual: budding or fission.

Stinging Tentacles

• Nematocysts discharge threads to entangle, penetrate, or poison prey.

• Cnidocytes contain nematocysts.

Feeding and Digestion

• Prey drawn into gastrovascular cavity.

• Gland cells discharge enzymes.

Class Hydrozoa

• Mostly marine.

• Alternation of polyp and medusa stages.

• Includes hydroids, fire corals, and Portugese man-of-war.

• Examples: Hydra viridissima, Tublariau indivisa, Physalia physalis, Eutonina indicans

Class Scyphozoa

• Dominant medusa stage.

• Polyp reduced or absent.

• Cup-shaped umbrellas.

• Includes true jellyfish.

• Examples: Aurelia aurita, Cyanea capillata

Class Cubozoa

• Cubical umbrellas.

• Fatal stings possible.

• Includes box jelly.

• Examples: Malo kingi, Tripedalia cystophora

Class Anthozoa

• Polyps with flowerlike appearance.

• No medusa stage.

• All marine.

• Includes sea anemones, corals, sea fans, and sea whips.

• Examples: Actinia equina, Entacmaea quadricolor

Phylum Ctenophora (Comb Jellies)

• Free-living marine.

• Diploblastic.

• Mesoglea present.

• Acoelomates.

• Radially symmetrical.

• Tissue level organization.

• Ciliated comb plates for locomotion.

Classes under Phylum Ctenophora

• Nuda: No Tentacles (Example: Beroe cucumis, Beroe abyssicola)

• Tentaculata: With Tentacles (Example: Cestum veneris, Thalassocalyce inconstans)

Phylum Platyhelminthes (Flatworms)

Characteristics

• Triploblastic, acoelomate, bilaterally symmetrical.

• Free-living or parasites.

• Soft body, may be ciliated.

• Dorsoventrally flattened.

• No anus or circulatory system, have a mouth.

• Respire by diffusion.

• Organ level organization.

• No digestive tract.

• Hermaphrodites.

• Sexual/asexual reproduction.

• Flame cells for excretion/osmoregulation.

• Ladder-like nervous system.

Platyhelminthes Classes

• Turbellaria: Example: Dugesia, Convoluta

• Trematoda: Example: Fasciola, Schistoma

• Cestoda: Example: Taenia, Echinococcus

Class Turbellaria

• Marine worms & planarians

• Free living

• Movement: cilia/muscle contractions

  • Digestive System:- Feeding: suction of pharynx

    • Gastrovascular cavity

  • No Respiratory/ Circulatory system: diffusion

  • Nervous System:- Ganglia

    • 2 Nerve cords.

    • Eyespot

  • Excretory System:- Flame cells- remove fluid waste

  • Reproduction:- Sexual-hermaphrodite, cross fertilize

    • Asexual- regeneration

Class Trematoda -flukes (parasitic)

• Leaf-shaped

• Sucks blood, cell fluids

• Sheep liver fluke:- 2 hosts: sheep, snail

• Blood fluke Schistosoma- causes Schistosomiasis

Class Cestoda

• Tapeworm

• Parasite

• Echinococcus granulosus

  Dog/Cat Tapeworm

• Body: absorbs nutrients

• Scolex- hooks and suckers to attach

• Proglottid- segment containing reproductive organs

Phylum Aschelminthes (Nematodes/Roundworms)

• Free-living or parasites.

• Bilaterally symmetrical and triploblastic.

• Unsegmented, slender.

• Dioecious.

• Pseudocoelom.

• Organ-system level.

Phylum Aschelminthes Classification

• Adenophorea

• Secerentea

ADENOPHOREA

• No phasmids.

• Mostly free-living

• Separate sexes

• Amphids behind the lips

• Adenophorea are commonly found in soil, water, and decaying matter.

• Trichinella spiralis Trichuris trichiura

SECERENTEA

• Has phasmids

• Simple amphids

• Mostly parasites

• Complete digestive system

• Ascaris lumbricoides Necator americanus