INVERTEBRATE DIVERSITY SECTION (Biol.201), Spr 2000

Dr. Kathy S. Williams (email kwilliams@sunstroke.sdsu.edu)

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MAJOR POINTS BY MAJOR TAXA

You should understand the relevance of these characteristics and functions to each animal group listed. For example, you can ask yourself, "What does aquaferous system mean and what does it have to do with Porifera? How does it compare to systems in other animals?" Try writing an answer without looking at the book or you r notes, then check yourself by checking with the text, the lab manual, or you notes. This is not intended to be a complete list, nor are the terms listed under ALL of the headings to which they apply. Rather, this is a GUIDE to help you organize your studies and test yourself. If you have any questions about the accuracy of your understanding and writing, PLEASE see me or even just give it to me and I’ll look it over!

Porifera

simple body organization; aquaferous system; simple feeding; asymmetric bodies

no true tissues; some specialized cells

reproduction ? fragmentation (asexual), sexual, totipotency

 Cnidaria radial symmetry, nerve net hydrostatic skeleton two embryonic tissue layers (diplolastic)

gastrovascular cavity predation w/nematocysts variation in body forms

 Platyhelmenthes bilateral symmetry

three embryonic tissue layers (triplolastic)

acoelomate ? no true coelom

reproduction - hermaphrodism, regeneration

body plan of free-living flatworms…………………….

    branching gastrovascular cavity

    excretion - protonephridia

    nervous system (= n.s.) ? photoreceptors, cerebral ganglia, nerve cords (ladder-like nerves)

    longitudinal & circular muscles

body plan of parasitic flatworms…………………….
 

reduced digestive system (= d.s.), n.s., protonephridial functions complex life cycle with intermediate hosts tremendous reproduction (tapeworms Cestoda - proglottids) structures for attachment to host Nematoda pseudocoelom complete gut many are free-living and are ecologically very important as decomposers

longitudinal muscles only cuticle parasites of plants and animals are economically & medically important
 
 

 Coelomate animals benefits of a true coelom

features of protostomes (vs. deuterostomes)

formation of a schizocoelom (vs. enterocoelom)
 
 

 PROTOSTOMES

Mollusca

variations on a theme — provides diversity of body forms and lifestyles

general plan similar: shell, gills, mantle, foot, radula, visceral mass, mantle cavity

Chiton - sedentary: gills all around, 7-8 shell plates

Bivalve - huge foot, 2-part shell, gills for feeding & respiration

Gastropod - terrestrial forms, spiral shell, torsion, some have very reduced shell (slugs)

Cephalopod - predatory lifestyle, built for speed: shell reduced or lost, radula =>beak, foot => tentacles & siphon, great eyes & brain, closed circulatory system

benefits and costs of having a shell & open circulatory system

functions of any circulatory system

 Annelida repeated segmentation and its advantages closed circulatory system

flexible but tough skin - respiration across skin, benefits & costs metanephridia

digest. syst. & nervous syst. with some specialized regions

Polychaetea - marine worms with parapodia

Oligochaeta - free-living scavengers, adaptations for life in moist habitats on land, clitellum, extremely important ecological roles, good powers of movement, hydrostatic skeleton + strong muscles + segmentation (compartmentalization)

Hirudinidea - parasites and free-living, loss of uniform segmentation, movement differs from oligochaetes

Arthropoda

incredible diversity; benefits of their body plan (segmentation + exoskeleton + jointed appendages); advantages of compound eyes

jointed appendages can be modified (in form) to perform many functions

groups of segments of exoskeleton with jointed appendages can be specialized to perform many functions and make bodies with many shapes

 Chelicerata body form 2-part w/appendages on head modified into chelicerae and pedipalps; other modifications of spiders & scorpions

respiration with book lungs, book gills

Crustacea (biramous)

appendages on head modified into 2 pairs of antennae; legs modified for many functions

excretion by green glands in some

Uniramia (respiration with trachea, excretion with Malpighian tubules)

Myriapoda: Diplopoda (millipedes) + Chilopoda (centipedes), relatively uniform segmentation, lifestyles differ

Insecta: body form 3-part: thorax from 3 fused segments, abdomen w/o appendages, appendages on head modified into extremely specialized feeding structures, flight, metamorphosis

Trilobita (extinct form)
 
 

 Deuterostomes characteristics of all deuterostomes; formation of an enterocoelom Echinodermata secondary pentaradial symmetry

water vascular system structure and functions

diversity - can be organized by number of arms & body shape

Crinoidea - sea lilies - ancient lineage; up to several hundred arms

Asteroidea -sea stars - few arms (often 5); madreporite is aboral

Ophiuroidea - brittle stars - few arms (often 5); madreporite is oral

Echinoidea -urchins, dollars - no arms; skeletal plates fused into round test

Holothuroidea - sea cucumbers - no arms; fleshy body; exoskeleton reduced
 
 

 Chordata (may or may not cover in this section ?will be covered in the vertebrate section of course) all possess: dorsal hollow nerve cord, pharyngeal slits, notochord, post-anal tail

invertebrate chordates provide information about origins of the vertebrates

tunicates - differences in adult and juvenile forms; juveniles show dorsal hollow nerve cord,
pharyngeal slits, notochord, post-anal tail

lancelets - show all 4 features in adult stages

Biology 201 - Spr 2000 - Invertebrate Study Sheet

Vocabulary only

READ THIS: You should know the meanings the following terms and their relevance to the material covered in lab and lecture. This is not intended to be a complete list, nor are the terms listed under ALL of the headings to which they apply. Rather, this is a GUIDE to help you organize your studies and test yourself. You should know the Latin names of taxa listed below.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Anatomy of animals: cellular level of organization, tissues, organs, organ systems, muscles & nerves

• Animal phylogeny: Taxonomists use comparative anatomy & embryology to reconstruct phylogenies.

• All animals except sponges can be grouped by body symmetry:

Radiata - radial symmetry

Bilateria - bilateral symmetry & cephalization

germ layers: endoderm, ectoderm, & mesoderm

acoelomates, pseudocoelomates, coelomates


Asymmetrical animals

Porifera (sponges)

Choanocyte flagella spongocoel amoebocyte

totipotent osculum aquiferous system spicules


Radiata - diploblastic animals

Cnidaria [hydras, jellyfishes, sea anemones, & corals]

tentacles gastrovascular cavity polyp vs. medusa

planula larva cnidae, nematocycts nerve net

hydrostatic skeleton predators gastrovascular cavity

• Hydrazoa (hydra) polyp & medusa, stationary or sessile

• Scyphozoa (jellyfish) medusa is dominant form, floating - pelagic

• Anthozoa (anemones & corals) polyps w/ no medusa, sessile, CaCO3 secretions, atoll/island formation


Bilateria (or Bilaterata) - triploblastic animals
 

acoelomates/pseudocoelomates/coelomates bilateral symmetry; cephalization


Acoelomates (triploblastic but with no coelomic body cavity)

Platyhelmenthes [flatworms]
 

dorsoventrally flattened body cerebral ganglia & ladder-like nerve arrangement

hydrostatic skeleton longitudinal & circular muscles

gastrovascular cavity characteristics of parasites

• Turbellaria - [planarians]
free-living; adaptations for "terrestrial" life flame cells, protonephridia

GV cavity with high surface area eyespots (photoreceptors)

• Trematoda - [flukes]
internal parasites of animals complex life cycles w/ intermediate hosts

suckers reduced digestive system, sensory cells

tremendous reproductive output, hermaphroditic

• Cestoda - [tapeworms]
intestinal parasites of animals complex life cycles w/ intermediate hosts

scolex reduced digestive system, sensory cells

tremendous reproductive output, hermaphroditic proglottids


Pseudocoelomates (triploblastic with pseudocoelom)

pseudocoelom; complete digestive system (= complete gut w/ seperate mouth & anus)

Nematoda [roundworms]

thick continuous cuticle ; longitudinal muscles only; free-living & parasitic forms

characteristics of parasites; reproduction includes parthenogenesis; hydrostatic skeletons


Coelomates (triploblastic with true coelom)

Protostomes (schizocoelomates)

spiral, determinate embryonic cleavage; fate of blastopore; schizocoelom; trochophore larva
 

Mollusca [mollusks]

muscular foot mantle mantle cavity heart & open circulation

visceral mass radula gills = ctinidia calcareous shell

• Polyplacophora [chitons] multiple shell plates multiple gills sessile lifestyle

• Bivalvia [clams, oysters, mussels, & relatives]

filter-feeding hinged shell moves w/ muscular foot loss of radula


• Gastropoda [snails & slugs]

embryonic torsion operculum modifications for life on land
mucous moves w/ muscular foot


• Cephalopoda [nautiluses, cuttlefish, squids, octopuses]

adaptations for predation beak-like jaws closed circulatory system built for speed
reduced shell eyes; convergent evolution modifications of foot: tentacles siphon


Annelida [earthworms, leeches, & marine free-living & tube-dwelling worms]

body segmentation, septa longitudinal & circular muscles closed circulatory system
benefits of serial homology epidermal setae (singular = seta)

• Polychaeta [polychaetes] - parapodia; suspension feeding

• Oligochaeta [earthworms and various aquatic species]
 

metanephridia clitellum no trochophore larva hermaphroditic but w/cross-fertilization


• Hirudinea [leeches]
 

no trochophore larva suckers reduced segmentation; superficial annuli no setae
free-living & parasitic lifestyles hirudin anticoagulant reduced clitellum


Arthropoda [insects, spiders, mites, scorpions, crabs, shrimps, lobsters]

segmented exoskeleton chitin open circulatory system hemolymph
jointed appendages compound eyes; ommatidia

• Trilobitomorpha [trilobites] - extinct exoskeleton segments

• Chelicerata
 

cephalothorax chelicerae pedipalps

¨ Merostomata [horseshoe crabs (5 living spp)] "living fossils" telson book gills

¨ Arachnida [spiders, ticks, scorpions, & mites] book lungs (arachnid tracheae, spiracles) pincers spinnerets
 

 • Crustacea [crabs, lobsters, shrimp, crayfish; few terrestrial, like sow bugs or pill bugs]  
nauplius larva stalked eyes green glands cephalothorax, carapace


• Uniramia contains 2 distinct groups: the myriapods & the insects (hexapods)
 

compound eye Malpighian tubules uniramia trachea, spiracles 1 pr antennae

> Myriapoda composed of 2 groups
 

• Diplopoda [millipedes] - scavengers, herbivores; diplosegments

• Chilopoda [centipedes] - predators; fangs


> Insecta [insects]
 

head, thorax, & abdomen loss of abdominal appendages

incomplete vs. complete metamorphosis pupa

evolution of wings Diptera, Coleoptera, Lepidoptera


Deuterostomes (enterocoelomates)
 

enterocoely radial cleavage indeterminate cleavage fate of blastopore = anus
• Echinodermata [sea stars, urchins, and their relatives]
water vascular system; madreporite; tube feet test

secondary pentaradial symmetry

> Crinoidea
> Asteroidea
> Ophiuroidea
> Echinoidea
> Holothuroidea


• Chordata dorsal hollow nerve cord pharyngeal slits notochord postanal tail