Subkingdom PARAZOA: Cellular level of functional animal organization.

Phylum: Porifera - [pore bearer] sponges.
1. mostly marine, one freshwater family in streams of Kentucky.
2. radial symmetry to none.
3. two body layers; outer ectodermis and inner endodermis - middle acellular layer of jelly mesophyl.
4. primitive tissue development, no organs, or moveable parts.
5. digestion intracellular.
6. usually with skeleton of spicules and fibers.
7. dioecious and monoecious; forms reproduce sexually and asexually. Free swimming sexually produced larva, amphiblastula.

Specialized cells present: choanocytes, amoebocytes, porocytes.
Feed by drawing microorganisms through pores.

EUMETAZOA: Organ level of functional animal organization Acoelomate, Radial Symmetry.

Phylum: Coelenterate [hollow intestine] = Cnidaria [nettle-like]; corals, jellyfishes, anemones.

1. symmetry radial about an oral-aboral axis; no head.
2. two body layers: outer ectodermis and inner endodermis - middle layer of mesoglea.
3. mouth surrounded by soft tentacles; sac-like digestive cavity, no anus.
4. nervous system in form of branching nerve-net. Impulses may travel in either direction.
5. contractile fibers that function as muscle cells provide for movement.
6. reproduction asexual and/or sexual; alternation of generations in some - hydroid (asexual) and medusa (sexual) stages. Monoecious or dioecious (Scyphozoa). Planula larva.
7. Skin provided with specialized cells - Cnidoblasts: stinging cells containing dart-like, toxin containing structures = nematocysts.

Coelenterate life cycles represent one or both of two life forms: the sedentary or attached HYDROID stage and/or the free-swimming MEDUSA stage. Many coelenterates exhibit an alternation of hydroid and medusa stages in the life cycle, but differ from typical plant life cycles in that both phases are diploid.

Classes of Coelenterates:

Hydrozoa - Hydra and Obelia = polyp is the dominant or only stage of the life cycle. (Physalia). Alternation of Generations common.

Scyphozoa - Aurelia = medusa is the dominant or only stage of the life cycle. Jellyfishes. Mostly marine, some freshwater forms. Alternation of Generations common.

Anthozoa - Corals and anemones. Polyp only stage in life cycle = no Alternation of Generations.

EUMETAZOA: PROTOSTOMIA: Acoelomate, Bilateral Symmetry.

Phylum: Platyhelminthes- [flat worms] planarians, flukes, tapeworms.
1. symmetry bilateral; some degree of head development.
2. three body layers: outer ectodermis, middle mesodermis (future endoskeleton), inner endodermis.
3. digestive system incomplete, mouth but no anus.
4. muscle layers well developed.
5. no body cavity, mid-body region filled with mesodermal-mesenchyme.
6. nervous system a pair of anterior ganglia with 1-3 pairs of longitudinal nerve cords = nerve ladder.
7. excretory system of protonephredia (Flame cells) which functions mostly in osmoregulation.
8. sexes usually monoecious - two genders in one body.
9. complex life cycle, several larval forms, miricidia, redia, cercaria, metacercaria in some groups.

Most outstanding advances of the group include Bilateral Symmetry with its contributions to head development and the third germ layer, mesoderm, which will lead to coelom formation and endoskeleton production.

Classes of Platyhelminthes: Tubellaria - free-living flatworms. Planaria best example, move along a slime trail; amazing powers of regeneration.

Trematoda - flukes, parasites, complex life cycles including invertebrates (snails), and vertebrates (fish and humans) = digenea. Construction of Aswan Dam in the Nile Valley of Egypt has lead to the massive distribution of snails in the irrigation canals that serve as hosts for the human blood fluke which has caused a tremendous outbreak (60% of the population) of schistosomiasis.

Cestoda - tapeworms, parasites, have no digestive organs. Most severe when burrow into tissues of intermediate host.

Monogenea - mostly external parasites, mostly on fish. Simple life cycle.

EUMETAZOA: PROTOSTOMIA: Pseudocoelomate, Bilateral Symmetry.

Phylum: Nematoda - [thread worms] roundworms.
1. false body cavity, pseudocoelom.
2. complete digestive tract within body cavity, "tube within a tube" body plan.
3. hydrostatic skeleton (fluid filled body cavity), allows for locomotion.
4. dioecious, male smaller than female.
5. many parasitic forms, both plant and animal.
6. lack cephalization.

The second most diverse group of animals with over 500,00 different species, live in all possible moist and aquatic habitats. Represents the most abundant group of animals known. Ten species dangerous to humans as parasites, 50 others parasitize humans with minimum impact.

Ascaris lumbricoides - pigs and humans. Infect stomach.
Trichinella spiralis - pigs and humans. Infect muscles.
Necator americanus - hookworm, infect skin from soil.
Pinworms - most common of all human roundworms.

Classes of Nematodes (higher taxonomic levels poorly developed)
Rhabditea - Enoplea -

EUMETAZOA: PROTOSTOMIA: Eucoelomate

Phylum: Mollusca - [soft body] snails, bivalves, squid and octopi.
1. body short and encased in mantle.
2. most secrete hard shell (exoskeleton) around body with mantle.
3. sexes usually dioecious.
4. locomotion by a single, centrally located foot.
5. open circulatory system in most, closed in cephalopoda.
6. no body segmentation (metamerism).
7. monoecious, trocophore type larvae.

Snails have undergone body twisting "torsion" to accommodate the single shell. Torsion twists the digestive system so the anus opens just over and behind the head, only one lung and one kidney is present.

Bivalves produce pearls when foreign debris gets between mantle and shell. Cephalopod eye is highly developed similar to humans, can judge distances.

Classes of Molluscs:
Gastropoda - snails and slugs Pelecypoda - oysters and clams
Cephalopoda - squids and octopi
Polyplacophora - chitons
Scaphopoda - tusk shells
Monoplacophora (=single plate) - serial gills and kidneys = metamerism??

EUMETAZOA: PROTOSTOMIA

Phylum: Annelida - [little ring] (segmented worms) earthworms, marine worms, leeches.
1. elongate, conspicuously segmented body.
2. eucoelomate, body cavity separated by septa in body segments.
3. closed circulatory system, five pairs of aortic arches and hearts.
4. paired metanephredia per segment.
5. hydrostatic skeleton.
6. seta on segments for locomotion.
7. monoecious, trocophore larvae in marine forms.

Extreme segmentation believed to be an adaptation for burrowing in soil. Nephredia greatly improved over protonephredia in that they selectively reabsorb water and salts from excretory filtrate.

Classes of Annelids: Oligochaeta - earthworms
Polychaeta - marine worms; largest class, well developed head.
Hirudinea - leeches

EUMETAZOA: PROTOSTOMIA

Phylum: Arthropoda - [jointed leg] insects, crustaceans spiders and ticks, millipedes, centipedes.
1. body of fused, conspicuous segments (tagmosis), head, thorax, abdomen.
2. hardened exoskeleton of chitin.
3. molting or shedding of exoskeleton necessary for growth.
4. circulatory system open.
5. respiration by gills, air ducts, lungs, or integument.
6. sexes usually separate (dioecious).
7. larval nymphal stages prior to metamorphosis in many.

Considered to be the most successful group of animals on earth, some 900,000 species described to date, approximately another million species yet undescribed.

Very specialized life styles and different stages within the life cycle minimize competition and allow many arthropods to live side-by-side.

Two major categories of arthropods based upon jaw apparatii:
A. Chelicerata - the more primitive group, feeds by sucking fluids and juices from victims by modified mouthparts, Chelicera. Chelicera inject toxin or poison into victim before sucking liquids. Horseshoe crab, spiders, ticks, mites, daddy longlegs.
B. Mandibulata - the more modern group, feeds by normal chewing with traditional mouthparts, Mandibles. Insects, millipedes, and centipedes (Uniramia), and crustaceans (Biramia).

Taxonomy of Arthropoda:

Subphylum Chelicerata - chelicera mouthparts

Class Merostomata - aquatic chelicerates = horseshoe crab.

Class Pycnogonida - sea spiders, usually 4 pairs of legs.

Class Arachnida - scorpions, spiders, ticks, mites.

Subphylum Crustacea - mandibulate mouthparts

Class Malacostraca - aquatic gill breathers, 2 pair antennae, biramous limbs.

Subphylum Uniramia - mandibulate mouthparts, 1 pair antennae, uniramous limbs.

Class Diplopoda - millipedes, 2 pair legs/segment.

Class Chilopoda - centipedes, 1 pair legs/segment.

Class Insecta - insects, 3 pairs legs.

EUMETAZOA: DEUTEROSTOMIA

Phylum: Echinodermata [hedge-hog skin]. starfish, brittle stars, sea urchins, sea lilies, sea cucumbers
1. radial symmetry as adults; bilateral symmetry as larvae.
2. adults typically having five radiating arms.
3. internal skeleton of small, calcareous (salt crystal) plates having external spines which form the typical echinoderm "spiny" skin.
4. sexes separate; microscopic bipinnarian larvae.
5. show no obvious segmentation; a characteristic of higher protostomes and deuterostomes.
6. locomotion results form a unique water vascular system with tube feet which operate on the basis of water suction in tiny "tube feet".
7. all representatives are marine and none are parasitic.
8. open hemal circulatory system.

Bizarre, freakish forms as adults, completely unlike any other adult deuterostome forms as adults. Represent a very specialized group of animals as adults. Position in animal kingdom due to deuterostome characteristics, most seen during embryogenesis and in the larval stage. Group generally has tremendous powers of regeneration; starfish and brittlestars can replace lost arms and sea cucumber can discharge internal organs as a defense mechanism against predators and then regenerate new internal organs.

Starfish have powerful commerical impact on shellfish industry being active predators on oysters, clams, and scallops.

Classes of Echinoderms:

Class Crinoidea - sea lilies; 5 arms with basal stalk; prominent fossil forms.

Class Asteroidea - sea stars and starfish.

Class Ophiruoidea - brittle stars.

Class Echinoidea - sea urchins and sand dollars; no arms, many sharp spines.

Class Holothuroidea - sea cucumbers; no arms or spines.

EUMETAZOA: DEUTEROSTOMIA

Phylum: Hemichordata - [half chordates] acorn worms.
1. three body regions - proboscis burrowing structure, collar with mouth, trunk or body with gill slits and digestive tract.
2. dorsal hollow nerve cord.
3. pharyngeal gill slits.
4. sexes separate.
5. all marine.

Formerly thought to be a chordate; removed from chordate phylum due to absence of a notochord - what was formerly thought to be a notochord proved to be an anterior extension of the digestive tract = a stomachord.

While a bizarre form, it is difficult to equate the adult acorn worm to the main line of chordate ancestry as was the case with the echinoderms - the tornarian larva however shows very distinct similarities with the bipinnarian larva of the echinoderms and represents the line of relationship. All other deuterostome characteristics also operate making the hemichordates position in the ancestral line of chordates as unquestionable.

Classes of Hemichordates:

Class Enteropneusta - acorns worms. C

lass Pterobranchia - pterobranchs.

EUMETAZOA: DEUTEROSTOMIA

Phylum: Chordata [string] - sea squirts, sea lancets, vertebrates.
1. dorsal hollow nerve cord.
2. pharyngeal gill slits sometime in life.
3. notochord sometime in life.

Ancestry of chordates from earlier deuterostomes and origins of earliest chordates cannot be explained on the basis of adult features but rather on the basis of larval events.

The phenomenon of progenesis, the appearance of adult features (sexual maturity) in the larval body form, appeared in the larval forms of echinoderms, hemichordates, and urochordates providing the main line relationship among non-chordate deuterostome - chordate groups.

The accepted ancestral line today is: auricularian echinoderm larva - tornarian hemichordate larva - appendicularian tunicate larva - amphioxus - ostracodern agnathans.

Classification of Chordates:

Subphylum -

Urochordates - dead-end, highly specialized, bizarre group off the main line of Chordate formation. Sessile marine forms as adults.

Cephalochordates - small 2-4 inch marine organisms. Considered responsible for moving into freshwater environments and applying preadaptations for success. Successful inhabitation of freshwater and resulting anatomical changes produced the first vertebrate animals. Modifications of cephalochordate forms in becoming vertebrates; or, modifications of cephalochordate forms that occurred in inhabitating freshwater: developing of pumping (glomerular) kidney for pumping excess water. development of exoskeleton of dermal armor to prevent excessive uptake of environmental water and to maintain internal salt reserves, developing of increased musculature to maintain position in fast moving water bodies, development of improved internal skeleton to enhance muscular attachment.

Final product to these anatomical changes was a heavily armored, bottom dwelling, filter-feeding organism having no jaws, no paired fins, and a strong cartilaginous supporting rod running the length of the body = the first vertebrate.

Vertebrates - vertebral column replaces notochord during embryogenesis

ultimately represented by 8 Classes:

Agnatha - [without jaws] first vertebrates, off-shoots of cephalochordate modification in freshwater. (lampreys and hagfish)

Placodermi - [plate skin] earliest typical fish forms, developed jaws, paired fins, segmented the body armour, increased body size, improved kidney system, skeletal system, digestive system and life cycle. (only vertebrate class considered to be extinct.)

Chondrichthyes - [cartilage fishes] specialized groups of fishes originating in freshwater and moving back into the marine environment. (sharks and rays). Only 1 or 2 species presently occurring in freshwater. Developed a unique method of maintaining osmoregulation in the marine environment.

Osteichthyes - [bony fishes] became the dominant group of fishes and animals worldwide in the Devonian = The Age of Fishes. Radiated worldwide in marine as well as freshwater. Lobe-finned forms provided preadaptations for origin of first terrestrial vertebrates = the amphibians.

Amphibia - [dual life] first terrestrial vertebrates. Tied to water as a result of external fertilization of eggs. Not an eminently successful group because of its water restriction for reproduction. Not long after its origin, certain members developed a unique egg (Cleidoic) which allowed for internal fertilization and development on land. Thence arose first truly terrestrial vertebrates.

Reptilia - [to creep] first completely terrestrial vertebrate group. Possess the ability to spend the complete life cycle on land. Became the dominant organism group worldwide from 65-135 million years ago = The Age of Reptiles. Greatest adaptive radiation success ever witnessed. Changing atmospheric conditions, ice ages, competition from early mammal types all contributed to the downfall of the group. Unique features include ectodermal scales, molting of epidermis, cleiodic egg, four chambered heart, temperature warming behavior.

Aves - [birds] one of three successful groups coming out of the reptilian radiation (modern reptiles, birds, mammals). Unique features include feathers, hollow bones, flow-through respiratory system, no teeth, homiothermy, egg laying.

Mammals - [mamma = glands]. Another of the successful groups emerging from the reptile group. Unique features include dry, dead, scaly skin, hair, homiothermy, birth to living young, suckle young.

Progressive development of systems among Classes:
a. Integument -living epidermis underlain with dermal scales in fishes, to living epidermis in amphibians, to dead ectodermal and dermal scales in reptiles to feathers and hair with dry, dead, water proof skin in birds and animals.
b. Circulatory system -two chambered heart in fish to three chambered heart in amphibians to four chambered heart in some reptiles and four chambered heart in all birds and mammals.
c. Temperature control -ectothermy in fishes and amphibians to behavior controlled body temperature in reptiles to endothermy in birds and mammals.
d. Skeletal system -internal and external bone and cartilage skeleton in fishes to internal and external bone skeleton in reptiles to mostly internal skeleton in birds and mammals. Trend through the animal groups is toward fusion of skeletal parts.
e. Reproductive system -from external fertilization and development of fishes and amphibians to internal fertilization and eternal development of reptiles and birds to internal fertilization and internal development of mammals.

Key to Zoology Lab Specimens