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Phylogenetic Tree General Trends and Groupings Defining Characteristics of Each

Phylum Major Classes within each Phylum Examples or species from each

Phylum/Class

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Cellular – Porifera

Tissues – Cnidaria

Organs- all others

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None – Porifera

Radial – Cnidaria

Bilateral – All others

› Pentamerous Radial Symmetry – Echinoderm Adults only

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None – Porifera

Diploblastic – Cnidaria endoderm & Ectoderm with mesoglea between

Triploblastic – All others Endoderm, Mesoderm, Ectoderm

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•Endoderm - digestion and respiration structures

•Mesoderm - muscles, bones, blood, skin, and reproductive organs

•Ectoderm - skin, brain, and nervous system

Diploblastic Acoelomate – Cnidaria

Triploblastic Acoelomates – Platyhelminthes

Pseudocelomate – Nematoda

Coelomates – Annedlida and everything above

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DigestiveDigestiveCavityCavity

DigestiveDigestiveLiningLining

SolidSolidTissueTissue

Body WallBody Wall

No cavity between body No cavity between body wall & digestive tractwall & digestive tract

CnidariaCnidaria

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Digestive CavityDigestive Cavity

Digestive TractDigestive Tract

PseudocoelomPseudocoelom

Body WallBody Wall

Body cavity partially lined Body cavity partially lined with mesodermwith mesoderm

Partial LiningPartial Lining

NematodaNematoda

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Digestive CavityDigestive Cavity

Digestive TractDigestive Tract

CoelomCoelom

Body WallBody Wall

Body cavity completely Body cavity completely lined with mesodermlined with mesoderm

Complete LiningComplete Lining

AnnelidaAnnelida

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Bilateral animals can be divided into two main groups based on embryological development

Protostomes› Body cavity forms within a space

between the body wall and the digestive cavity

› e.g. nematodes, arthropods, flatworms, annelids, mollusks

Deuterostomes› Body cavity forms as an outgrowth of the

digestive cavity› e.g. echinoderms, chordatesEarland 12

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Protostome

•Coelom forms from the solid masses in the embryo•blastopore becomes the mouth

• spiral / determinate cleavage

• mosaic development

(Annelida, Arthropoda, Mollusca,)

Deuterostome

• Coelom forms from a portion of the digestive tube•blastopore becomes the anus

• radial / indeterminate cleavage

• regulative development

(Echinodermata, Chordata)

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blastopore archenteron(primitive gut)

Future anus

mouth

Blastopore becomes the mouth and the anus forms secondarily

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blastopore archenteron(primitive gut)

Future mouth

anus

Blastopore becomes the anus and the mouth forms secondarily

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2 cells 4 cells 8 cells

Blastomeres divide at an oblique angle to one another, so that each lies in the furrow created by the cells beneath them

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2 cells 4 cells 8 cells

Blastomeres divide in a symmetrical fashion, producing layers of cells directly on top of one another

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4-cell stage

One blastomere is removed

Development is arrested (or is defective)

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4-cell stage

One blastomere is removed

Development continues

each blastomere is capable of regulating its development even when separated from the others

Development continues

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Porifera

Porifera

No trueNo truetissuestissues

TrueTruetissuestissues

2 tissue2 tissuelayers; radiallayers; radialsymmetrysymmetry

Ctenophora

Ctenophora

Cnidaria

Cnidaria

3 tissue3 tissuelayers; bilaterallayers; bilateralsymmetrysymmetry

Platyhelminthes

Platyhelminthes

No bodyNo bodycavitycavity Body cavityBody cavity

PseudocoelPseudocoel

Nematoda

Nematoda

Rotifera

Rotifera

CoelomCoelom

ProtostomeProtostomedevelopmentdevelopment

Annelida

Annelida

Mollusca

Mollusca

Insecta

Insecta

DeuterostomeDeuterostomedevelopmentdevelopment

Mammalia

Mammalia

Echino-

Echino-

dermata

dermata

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Simplest Animal Adults are sessile- can’t move on their

own Lack true tissues and organs, most are

unspecialized – Cell Level of Organization

Incomplete digestive system No Symmetry

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Outer layer protects the interior and has many holes through which water can enter the sponge

Inner layer are lined with collar cells, which have flagella

Amoebocytes wander through the jelly-like material and pick up food from the collar cells for digestions, transport oxygen, dispose of waste and can change into other cells for support

Have special chemical defenses to protect from predators, disease organisms, humans use these chemicals

Related closely to protists and are the earliest animals.

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› Tissue Level of Organization - Cells organized into distinct tissues

› Rudimentary nerve network and contractile tissue

› No true organs

› Incomplete Digestive System - One digestive opening

› Reproduce sexually and asexually

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Radial symmetry, most do not have a head and are sessile

Tentacles with stinging cells called cnidocytes

Has poisonous barbs called nematocysts, that fire when touched, once prey has been captured, the tentacles move it to the gastovascular cavity

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Polyp-cylindrical body with tentacles radiating from one end, sessile

Medusa- umbrella shaped form with fringed tentacles on the lower edge, move freely

Some cnidarians exist in both forms and some one or the other

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Hydrozoa- hydras, some corals, Portuguese man-o-war

Scyphozoa-jellyfish Anthozoa- sea anemones and most

corals

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The flatworms› Development of bilateral symmetry› Ability to move forward using aggregations of

nerve cells, ganglia› True organs begin to evolve› Most are hermaphroditic (can self-fertilize)› Many are free living—planarians› Some are parasitic—tapeworm and fluke› Triploblastic-ectoderm-outside, mesoderm-

middle, endoderm-inside› Incomplete digestive system-1 way in/out› Acoelomate-no body cavity

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Chapter 22 33

(a) Digestive System(a) Digestive System

Gastrovascular CavityGastrovascular Cavity

PharynxPharynxPharynxPharynx

(b1) Excretory System(b1) Excretory System

Excretory CanalExcretory CanalExcretory CanalExcretory Canal

Excretory PoreExcretory PoreExcretory PoreExcretory Pore

(b2) Nervous System(b2) Nervous SystemNerve CordNerve CordNerve CordNerve Cord

BrainBrainBrainBrain

Class Turbellaria-planarians, free-living, non-parasitic, live in moist environments

Class Trematoda-flukes, parasites that absorb nutrients from the body of a host harming it, may have more than 1 host

Class Cestoidea-tapeworms, parasitic, live inside 1 or more hosts, contain flat segments each with reproductive organs

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Roundworms-small, cylindrical worms with pointed heads and tapered tails

3 tissue layers Complete digestive tract with mouth and anus Digestion highly specialized Free-living and non-parasitic roundworms are the

most abundant but parasitic types are hookworm, pinworm, threadworm and trichinosis

Many are introduced through poorly cooked pork or walk barefoot in infected areas

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BilateralTriploblasticPseudocoelom

Advanced gastrovascular cavity› Tubular› Two openings

Advanced sensory "ganglionic brain" Lack circulatory and respiratory

systems Depend on diffusion for gas exchange Sexual reproduction Most are harmless - Some parasitic

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Segmented worms Closed circulatory system-when blood is

contained in vessels Bilateral symmetry Coelomate

› Class Polychaeta-sandworms, bristleworms› Class Oligochaeta-Earthworms› Class Hirudinea-leeches

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Repeating rings identical nerve ganglia

Excretory structures Advanced locomotion ability Hydrostatic Endoskeleton Sexual Repro. Some hermaphrodites Evolved many rudimentary organ

systems

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Muscular mass of tissue called a foot and a multifunctional structure called the mantle

Mantle-outgrowth of the body surface that drapes over the animal, produces the shell in clams and snails

Gills are housed in the mantle cavity in aquatic species

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Bilateral Symmetry Coelomate Moist muscular body without a

skeleton Found in aquatic or moist terrestrial

habitats Have a calcium carbonate shell Complex, concentrated, ganglionic

brain Open circulatory system

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Foot – Mantle - Visceral Mass - Shell

Classes› Gastropoda—snails and sea slugs› Bivalvia— scallops, oysters,

mussels, & clams› Cephalopoda—octopuses, squid,

nautilusesEarland 44

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Pentamerous radial symmetry - Lack body segments

Rough or spiny surface Dermal endoskeleton Water vascular system-network of fluid-filled

canals that branch into tube feet that function in locomotion, feeding, circulation and respiration

Many echinoderms can regenerate lost parts and even internal organs

External Reproduction with two sexes Larva are bilateral and go through indirect

developmentEarland 46

Class Echinoidea-sea urchins Class Asteroidea-sea stars Class Crinoidea- sea lilies Class Holothuroidea- sea cucumbers Class Concentricyloidea-sea daisies

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Notochord Dorsal Hollow Nerve Chord Pharyngeal Slits Postanal Tail Segmented Muscles - Myotomes

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Phylum ChordataInvertebrates

VertebratesKeep Nerve Chord in all

Cephalochordata aquatic keep

gills Lancelets – all 5 char

UrochordataTunicates/Sea squirts – keep pharyngeal slits only

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