Protostomes

Animal Characteristics

• multicellular

• heterotroph

• no cell walls

• nerves, muscles, motility at some point

• sexual reproduction

• specialized sensory structures and nervous system

• cells exist in extensive extracellular matrix

• unique cell junctions

Classifying Animals

1. Presence/absence of different tissue types

2. type of body symmetry

3. presence/absence of true body cavity

4. patterns of embryonic development

Metazoa types

parazoa - no specialized tissues or organs

enmetazoa - more than 1 type of tissue and organs

radial symmetry

• oral and aboral sides

  • 2 embryonic cell layers DIPLOBASTIC - develops during gastrulation

bilateral symmetry

• cephalization and dorsal/ventral ends

  • 3 germ layers TRIPLOBLASTIC - develops during gastrulation

types of coelom

• true coelom - body cavity completely lined with mesoderm

• pseudocoelom - coelom i snot completely lined by tissue of mesoderm

  • acoelomate - lack body cavity entirely

protostome

• determinate and spiral cleavage

• blastopore becomes mouth first

  • schizocoelous coelom developmentd

deutorstome

• indeterminate and radial cleavage

• blastopore becomes anus first

• enterocoeles

Basic animal tree

• Porifera

• Cnidaria & Ctenophora (sister taxa)

• Acoelomorpha

• Rotifera

• Platyhelminthes

• Annelida & Mollusca (sister taxa)

• Nematoda & Arthropoda (sister taxa)

• Echinodermata & Chordate (sister taxa)

Phylum Porifera

• parazoa

• sponges

• loosely organized and lack tissues, multicellular with several types of cells

• no apparent symmetry

• adults sessile but larvae motile

Phylum Cnidaria and Ctenophora

• radial symmetry

• marine

• diploblastic

• gastrovascular cavity for extracellular digestion

• No central control organ

Phylum Cnidaria

• 2 different body forms

  • sessile polyp (tubular body type with tentacles surrounding mouth and anus)

  • motile medusa (umbrella shaped, mouth on underside surrounded by tentacles)

• Cnidocytes contain nematocysts

  • hairlike trigger, some sticky some sting

Phylum Ctenophora

• marine

• 8 rows of cilia on surface (motility) and 2 long tentacles that don’t sting

• colloblasts secrete sticky substance

• first complete gut (mouth AND anus)

• hermaphroditic, bioluminescent

Phylum Platyhelminthes (lophotrochozoa)

• flatworm

• lack specialized respiratory/circulatory system to transport gases (respire via diffusion)

• 1st few animals to be predatory

• bilateral symmetry (triploblastic)

  • mesoderm led to more sophisticated organ

• acoelomate

Classes of Platyhelminthes

• Turbellaria - free-living (Planaria)

  • light-sensitive ocelli (eyespots)

  • distinct excretory system with protonephridia and flame cells

  • beginning of more centralized nervous system (cerebral ganglia)

  • can regenerate entire new organism

• Monogenea - fish flukes

• Cestoda - tapeworms, parasitic

• Tematoda - flukes, parasitic

  • complex life cycle with multiple hosts

    • make tadpoles grow 3 legs

Phylum Rotifera (lophotrochozoa)

• ciliated corona

• freshwater

• complete digestive tract (mastax - grinds food)

• pseudocoelom

• protonephridia, flame bulbs (more sophisticated)

• Parthenogenisis - amictic - female asexual reproduction → only makes females

  • mictic - unfertilized haploid egg becomes degenerate male

Phylum Molluska

• soft body with protective external shell

• coelom, small area around head

• 3 part body:

  • foot, visceral mass, mantle

    • radula - tongue like organ, mouth on bottom of body

• open circulatory system

• metanephridia → more complex

• separate sexes but some hermaphroditic

• external fertilization, some internal (snails)

Classes of Molluska

• Gastropods - snails, slugs, nudibranchs

  • largest class, shells can be reduced/lost, marine/freshwater and some land

• Polyplacophorans - chitons

• Bivalves - clams, mussels, oysters

• Cephalopods - octopus, squids, nautilus

  • most morphologically complex, fast swimming, marine, closed circulatory system

  • beak like jaw, nautilus = external shell, foot modified into muscular siphon for motility

Phylum Annelida (lophotrochozoa)

• rings distinct segment separated by septum

• double transport system

  • circulatory system and coelomic fluid carries nutrients, wastes, and respiratory gases

• Complete digestive tract

• some separate sexes, some hermaphroditic

  • internal fertilization

  • asexual reproduction by fission

• all annelids have setae on each segment

Advantages of segmentation

1. repetition of components provide backup

2. coelom acts as hydrostatic skeleton

3. permits specialization

Classes of Annelida

• Polychaeta - marine worms

  • most species rich, many long setae

• Oligochaeta - terrestrial and freshwater worms (earthworms)

• Hirudinea - leeches

  • freshwater, hirudin (anticoagulant), external parasites

Ecdysozoa

• ecdysis (molting)

  • all possess cuticle for support/protection

• metamorphosis

Phylum Nematoda (ecdysozoa)

• roundworms

• all habitats

• tough cuticle

• pseudocoelum = hydrostatic skeleton and circulatory system

• longitudinal muscles

• complete digestive tract = stylet

• usually sexual, separate males and females

  • internal fertilization

• lots parasitic in humans and other vertebra

Phylum Arthropoda

• Most successful!!! (body plan)

• ¾ of all described living species

• exoskeleton - chitin and protein

  • tough and impermeable to water

• segmented with appendages for locomotion etc.

• tagmata - fused body segments

• extensive cephalization

  • well developed senses organs

  • compound eyes - ommatidia

• sophisticated brain, 2-3 ganglia connected to smaller central nerve ganglia

• open circulatory system

• complex digestive system

• excretion - metanephridia or Malpighian tubules

Classes of Arthropoda

• Trilobita

  • extinct, bottom feeders, little specialization of body segments

• Arachnida - spiders, scorpions, ticks, mites

  • 2 tagmata - cephalothorax and abdomen

• Diplopoda

  • 2 pairs of legs per segment, herbivores

• Chilopoda

  • 1 pair of legs per segment, carnivores

• Insecta

  • wings

  • differ in wings and mouthpart

  • separate sexes with internal fertilization

  • metamorphosis

    • incomplete - 3 stages, young resemble adults

    • complete - 4 stages with adult and larval stage very different

• Crustacea - crabs, lobsters, barnacles, & shrimp

  • marine, fresh water, terrestrial

  • 2 pairs of antennae, mandible, maxillipeds, swimmerets, cuticle

  • nauplius larvae different from adult