ZOOLOGY.2

• Porifera Characteristics:

   Most primitive animal phylum

   No true tissues (sponges are at the “cellular level” of organization)

   Simple body plan with pores and water channels.
• CHARACTERISTICS OF CNIDARIA

   Two true tissue layers (germ layers (tissue level of organization)

   Alternation of generations: polyp and medusa; asexual and sexual reproduction

   Many colonial species

   Gastrovascular cavity with mouth, no anus

   Hydrostatic skeleton

   Nerve net and simple receptors
• CHARACTERISTICS OF PLATYHELMINTHES

   FLATWORMS

   Three true tissue layers (triploblastic)

   Bilateral symmetry

   No body cavity (acoelomate)

   Some simple organs & organ systems; no skeletal, circulatory or respiratory systems

   Simple excretory system of tubules with “flame cells”.  Incomplete or no digestive tract

   Most hermaphroditic

   Many highly specialized parasitic forms

   Most parasitic forms with complex life cycles including one or more intermediate hosts and one or more larval forms.
• CHARACTERISTICS OF NEMATODA


   Round, non-segmented, tubular body tapering at both ends

   No distinct head apparent characteristic "S" like movements as longitudinal muscles in body wall work against hydrostatic skeleton

   Presence of a body cavity and a complete digestive tract creates "tube within a tube" body design

   Strong muscular pharynx (tripartite in cross section) is not eversible.

   (A very large yet poorly known phylum in which the taxonomy has not been clearly worked out)
• Annelida

  • Cylindrical elongated segmented bodies; segments divided by septa
  • Well-developed true coelom
  • Closed circulatory system with one to several hearts and dorsal and ventral vessels
  • More efficient excretory system of nephridia
  • Well-developed muscular system with circular and longitudinal muscle layers around both the body wall and the GI tract
  • More efficient digestive system with typhlosole to improve absorption
  • Nervous system of paired ventral nerve cord with segmental ganglia
  • Cephalization with increased development of brain and anterior sense organs (this trait is only seen in the largest class of the phylum the Polychaetes, it has been lost in the other two classes)
  • Marine members with trochophore larva
• Mollusca

  • Triploblastic with true coelom
  • Bilateral symmetry; some with secondary assymetry
  • Soft, usually unsegmented body consisting of anterior head, ventral foot and dorsal visceral mass
  • Body usually enclosed by thin fleshy mantle
  • Mantle usually secretes hard external Shell
  • Complete digestive tract, many with a radula; a rasping or scraping feeding organ
  • Respiratory system consists of gills in aquatic forms or "lung"-like chamber in terrestrial forms
  • Most with open circulatory system; body cavity (coelom) a haemocoel
• Marine forms

  • Characteristic trochophore larva
• Freshwater bivalves

  • Glochidia larva
• CHARACTERISTICS OF Arthropoda (Subphylum Hexapoda)


   Body plan: head, thorax, abdomen

   Compound eyes

   Single pair of antennae

   Mandibles for feeding

   Three pairs of unbranched legs

   Two pairs of wings

   Respiration by tracheae

   Includes only invertebrates that can fly
• CHARACTERISTICS Arthropoda (Subphylum Myriopoda)

   Hardened chitinous exoskeleton

   Paired jointed appendages; anterior appendages modified into feeding structures

   Segmented body

   Reduced coelom is a haemocoel with dorsal heart  Complete digestive tract

   Well-developed nervous system with paired ventral ganglia and well developed sense organs

   Muscles in bundles rather than layers.

   Respiratory organs: gills, book gills, tracheae or book lungs

   Excretory organs: coxal glands ( antennal glands, maxillary glands, green glands)
• CHARACTERISTICS OF Arthropoda (Subphylum Myriopoda) 2.0

   Malpighian tubules

   Sense organs: ocelli, simple eyes, compound eyes, antennae, statocysts, tactile hairs,

   Chemoreceptors, tympanum respiratory organs: gills, book gills, tracheae or book lungs

   Excretory organs: coxal glands ( antennal glands, maxillary glands, green glands) or

   Malpighian tubules  Sense organs: ocelli, simple eyes, compound eyes, antennae, statocysts, tactile hairs,

   Chemoreceptors, tympanum
• CHARACTERISTICS OF Arthropoda (Subphylum Crustacea)


   Subphylum Crustacea: (crabs, shrimp, crayfish, barnacles, pill bugs, water fleas)

   Body plan: cephalothorax, abdomen, tail

   Compound eyes

   Two pairs of antennae

   Mandibles for feeding

   Branched (biramous) appendages

   Respiration by gills

   Only living subphylum that is mostly aquatic
• CHARACTERISTICS OF Echinodermata

   Radial (pentamerous) symmetry in adult; larva is bilaterally symmetrical

   Unique water vascular system

   All marine

   Endoskeleton of calcium carbonate ossicles

   Dioecious

   Free swimming bipinnaria larva

   Well-developed regenerative abilities (asexual reproduction)

   Extensive and diverse fossil record with many extinct classes
• Chordata I (Lower Chordates & Subphylum: Vertebrata – Class Agnatha)

   Dorsal, hollow, tubular nerve cord

   Notochord for support

   Paired gill (pharyngeal) slits

   Segmentation in some systems

   Most with postanal tail

   Deuterostome development
• Chordata I (Subphylum Vertebrata: Classes: Chondrichthyes & Osteichthyes)

   Alll chordate characteristics

   Enlarged brain enclosed in brain case

   Segmental spinal column enclosed in vertebrae

   Most with distinct head, neck, trunk, tail
• Chordata I (Subphylum Vertebrata: Class: Amphibia)

   Class: Aves (birds)

   Warmblooded; higher metabolic rate

   Pectoral appendaged modified into wings for flight

   Feathers replace scales over most of body surface

   Bones of skeleton reduced, hollow and fused to decrease weight while maintaining strength

   Respiratory system with extensively branching air sacs

   Oviparous; lay eggs
• Chordata I (Subphylum Vertebrata: Class: Mammalia)

   (mammals)

   Mammary glands

   Four chambered heart

   Muscular diaphragm

   Homeothermy

   Hair derived from epidermis

   With claws, nails or hoofs

   Viviparous with placental attachment to mother during development.