Invertebrates

Invertebrates

Chapter 33

Animal Origins

Animal Origins

Ch

loro

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Pla

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e

Ancestral eukaryote

Rh

od

op

hyt

a

Fu

ng

i

Dip

lom

on

ad

ida

Par

aba

sal

a

Eu

gle

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Alveolata Stramenopila Ce

rco

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Ra

dio

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Amoebozoa An

ima

lia

Ch

oan

ofl

ag

ella

tes

Figure 28.4

Characteristics of the Animal KingdomCharacteristics of the Animal KingdomNone of the following are unique to animals, but

together distinguish animals from other organisms:

Multicellular

Heterotrophic

No cell walls

Motile during some stage(s) in life

A great diversity of body plans occur; some key features include:

Organized federation of cells vs. cells in tissues

Characteristics of the Animal KingdomCharacteristics of the Animal Kingdom

Tissue – integrated group of cells with a common structure and function

Tissues are generally further integrated into organs

Organs are generally further integrated into organ systems

A great diversity of body plans occur; some key features include:

For organisms with tissues: two vs. three principal embryonic tissues


Two embryonic tissue layers:


Fig. 32.2

ZygoteBlastula

Gastrulation

Gastrula

Blastocoel

Blastocoel

Endoderm

Ectoderm

Blastopore

Archenteron

Two embryonic tissue layers:


Gastrula

Blastocoel

Endoderm

Ectoderm

Blastopore

Archenteron

Endoderm – Innermost “germ layer”; differentiates into some of the internal tissues and the lining of most hollow organs, if these are present

Ectoderm – Outermost “germ layer”; differentiates into tissues that cover the body and into the nervous tissues

Fig. 32.2

Three embryonic tissue layers:


Endoderm – Innermost “germ layer”; differentiates into some of the internal tissues and the lining of most hollow organs, if these are present

Mesoderm – Middle “germ layer”; differentiates into muscles, circulatory and skeletal systems, and sex organs, if these are present

Ectoderm – Outermost “germ layer”; differentiates into tissues that cover the body and into the nerve tissues

Fig. 32.9

Characteristics of the Animal KingdomCharacteristics of the Animal KingdomA great diversity of body plans occur;

some key features include:

Radial vs. bilateral symmetry

Any plane that passes through the central axis produces roughly

mirror-image halves

A single midline plane produces roughly mirror-image halves;

generally accompanied by distinct cephalization

Fig. 32.7

Among organisms with 3 germ layers:Acoelomate, pseudocoelomate, or coelomate






Acoelomate: lack a coelom, i.e., lack a body cavity between digestive track and body wall

Fig. 32.8




Pseudocoelomate: Fluid-filled body cavity between digestive tract and body wall partially lined by mesoderm

Fig. 32.8




Coelomate: fluid-filled body cavity between digestive tract and body wall completely lined by mesoderm

Fig. 32.8



Protostome vs. deuterostome development



Protostome vs. deuterostome development

See Fig. 32.9

The Animal Kingdom

~ 35 phyla

Cal

care

a

Sil

icar

ea

Cte

no

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ora

Cn

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ia

Ech

ino

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a

Ch

ord

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Bra

chio

po

da

Ph

oro

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Ect

op

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Pla

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elm

inth

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Nem

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Mo

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An

nel

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Ro

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Nem

ato

da

Art

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da

“Radiata”

“Porifera” Deuterostomia Lophotrochozoa Ecdysozoa

Bilateria

Eumetazoa

Metazoa

Ancestral colonialflagellate

Fig. 32.11&

Table 33.7

Phylum Porifera – Phylum Porifera – SpongesSponges

Ancestral colonialchoanoflagellate

Eumetazoa

Bilateria

Deuterostomia

Po

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Cn

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ria

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er

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Figure 33.2

Organized aggregation of cells

Probably the most similar extant group to the protistan colonial precursors to the animals


Organized aggregation of cells

Three main cell types, but no true tissues

Asymmetric body plan

Mostly marine, but some inhabit fresh water


Internal skeleton of protein spicules

E.g., natural bath sponge


Eumetazoa

All animals except sponges belong to the clade Eumetazoa

All eumetazoans have true tissues


Eumetazoa

Bilateria

Deuterostomia

Po

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Cn

ida

ria

Oth

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bila

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ns

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Figure 33.2

Phylum Cnidaria – Phylum Cnidaria – Corals, Jellyfish, Corals, Jellyfish, AnemonesAnemones

Radially symmetric animals with 2 germ layers (true tissues), but generally lacking true organs

Gastrovascular cavity; mouth and anus are the same opening

Rudimentary nerve net and contractile tissue

Tentacles contain cnidocytes

Fig. 33.6


Polyp and medusa forms

Fig. 33.5


Polyp and medusa forms


Phylum Ctenophora – Phylum Ctenophora – Comb jelliesComb jellies

8 rows of comblike plates of cilia

Bilateria

Bilaterally symmetric, cephalized animals with 3 germ layers


Eumetazoa

Bilateria

Deuterostomia

Po

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Cn

ida

ria

Oth

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(incl

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Figure 33.2

Gastrovascular cavity (if a gut is present)

P. Platyhelminthes – P. Platyhelminthes – Flat wormsFlat worms

Some true organs are present (tissues grouped into functional structures)

Hermaphroditic and capable of self-fertilization

Acoelomate

Mostly free-living


Mostly free-living


Some parasitic

E.g., tapeworms

Distinguishing feature is a “crown of cilia” around the mouth

P. Rotifera – RotifersP. Rotifera – Rotifers

Complete digestive tract surrounded by pseudocoelom

Parthenogenesis (development from unfertilized eggs) is the most common mode of reproduction

P. EctoproctaP. EctoproctaP. PhoronidaP. PhoronidaP. BrachiopodaP. Brachiopoda

All bear a lophophore – fold of the body wall bearing ciliated tentacles surrounding the mouth

Coelomate

P. EctoproctaP. Ectoprocta

Colonial

Many contribute to marine reefs

a.k.a. bryozoans

P. PhoronidaP. Phoronida

A group of tube-dwelling marine worms

P. BrachiopodaP. Brachiopodaa.k.a. lamp shells

Marine, mostly extinct

P. NemerteaP. Nemerteaa.k.a. proboscis or ribbon worms

Structurally acoelomate, with a small fluid-filled sac that may be a vestigial coelom

Closed circulatory system, but no heart

P. MolluscaP. Molluscaa.k.a. mollusks


Coelomate body with a muscular foot, visceral mass, and mantle (which secretes a shell in many species)


8 classes, including:

C. Polyplacophora (chitons)

Shell divided into 8 plates



C. Gastropoda (snails and slugs)

Single shell or lacking shell



C. Gastropoda (snails and slugs)

Single shell or lacking shell



C. Bivalvia (clams, oysters, mussels, etc.)

Hinged, two-part shell



C. Cephalopoda (squids, octopuses, nautiluses)

Only mollusks with closed circ. system and complex brain



C. Cephalopoda (squids, octopuses, nautiluses)

Only mollusks with closed circ. system and complex brain

P. AnnelidaP. Annelidaa.k.a. segmented worms


Segmented

Coelomate

Closed circulatory system

Coelom


3 classes:

C. Oligochaeta

Earthworms and their kin

Coelom


3 classes:

C. Polychaeta

Bristled parapodia on each segment


3 classes:

C. Hirudinea

Leeches

P. NematomorphaP. Nematomorphaa.k.a. horsehair or gordian worms

Not requiredto know

P. PriapulidaP. Priapulidaa.k.a. penis worms Not required

to know

P. TardigradaP. Tardigradaa.k.a. water bears Not required

to know

P. OnychophoraP. Onychophoraa.k.a. velvet worms Not required

to know

P. NematodaP. Nematodaa.k.a. roundworms

Nonsegmented


Nonsegmented

No circulatory or respiratory systems

Mouth

Gut

Anus


Nonsegmented


Pseudocoelomate


Nonsegmented


Free living or parasitic

Pseudocoelomate

E.g., dog heartworm

P. ArthropodaP. ArthropodaSegmented

Coelomate

Exoskeleton of chitin

Jointed appendages

P. ArthropodaP. ArthropodaOpen circulatory system

Hemolymph (the open-circulation system equivalent of blood) carries dissolved gases through short vessels and the hemocoel (main body cavity in adults, since coelom is reduced)

P. ArthropodaP. ArthropodaAs in much of modern systematics, classes are in flux; nevertheless, here are 5 main groups:

Trilobites – all extinct during Permain mass extinction ~250 mya

P. ArthropodaP. Arthropoda

Cheliceriforms – horseshoe crabs


Cheliceriforms – sea spiders


Cheliceriforms: Arachnids – spiders, ticks, scorpions, mites


spider (tarantula)

scorpion

tick

mite



Adults generally have 4 pairs of walking legs

Some produce silk



Simple eyes (each with a single lens)

Eyes of black widow spiderCheliceriforms: Arachnids – spiders, ticks, scorpions, mites


Myriapods – millipedes; 2 pairs of legs per segment


Myriapods – centipedes; 1 pair of legs per segment


Hexapods: insects


Adult often has 2 pairs of wings

Hexapods: insects


Sometimes 1 pair of wings; sometimes none

Hexapods: insects


Adult generally has 3 pairs of legs

Hexapods: insects


Metamorphosis – transition between distinct (often dramatically different) developmental stages

Larva (maggot, caterpillar)

Pupa (transition to adult)

Adult (often winged)

Hexapods: insects


Metamorphosis – transition between distinct (often dramatically different) developmental stages

Larva (maggot, caterpillar)

Pupa (transition to adult)

Adult (often winged)

Hexapods: insects


Adult generally has compound eyes

Hexapods: insects

InsectsInsects Some of the major orders (26 in total):

Order Coleoptera Order Coleoptera – BeetlesOrder Hemiptera Order Hemiptera – True Bugs Order Homoptera Order Homoptera – Aphids and their kinOrder Hymenoptera Order Hymenoptera – Ants, Bees, WaspsOrder Isoptera Order Isoptera – TermitesOrder Lepidoptera Order Lepidoptera – Butterflies and MothsOrder Odonata Order Odonata – Dragonflies and

DamselfliesOrder Orthoptera Order Orthoptera – Crickets, Grasshoppers,

KatydidsOrder Siphonaptera Order Siphonaptera – Fleas

See also Fig. 33.37


CrustaceansAs in all arthropods, crustaceans have

segmented body plans


waterflea sowbug

hermit crab barnacle

Crustaceans

P. ArthropodaP. ArthropodaOften have 5 or more

pairs of legsCrustaceans

P. ArthropodaP. ArthropodaGenerally have compound eyes

Crustaceans

Deuterostomia

Deuterostome developmental pathway


Eumetazoa

Bilateria

Deuterostomia

Po

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Cn

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Coelomates

Figure 33.2

P. EchinodermataP. Echinodermata

P. EchinodermataP. Echinodermata At first glance they may seem more radially than bilaterally symmetrical…

P. EchinodermataP. Echinodermata However, their larvae are obviously bilaterally

symmetrical

Sea star larva

Sea star adult


Sea cucumber

Brittle star

Sea urchin

Sand dollar


Sea cucumber

Brittle star

Sand dollar

Sea urchin

Calcium carbonate endoskeleton

P. EchinodermataP. Echinodermata Unique water vascular system of hydraulic canals branching into tube feet for locomotion, feeding, and

gas exchange

P. ChordataP. Chordata At some stage in development, all chordates

possess:

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