Chapter 18:
Evolution of Invertebrate
Diversity
Domain
Eubacteria
AP Biology
Domain
Archaea
Domain
Eukarya
2007-2008
Common ancestor
Animal Characteristics
 Eukaryotic HETEROTROPHS
_________________

must ingest (not absorb) nutrients
MULTICELLULAR
 __________________

Specialized cells, complex body
NO CELL WALLS
 ________________

allows active movement
SEXUAL REPRODUCTION
 _____________________
Dominant diploid (2n) organism
 only haploid gametes

AP Biology
Characteristics (Con’t)
 Store glucose as _______________
GLYCOGEN
MOTILE at some point in life
Most __________


cycle;
_________
LARVA (free living sexually
immature form) may be only time in
some
A larva undergoes a major change in body
form, called metamorphosis, and
becomes a reproductively mature adult.
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EMBRYONIC DEVELOPMENT
Image from: http://io.uwinnipeg.ca/~simmons/16cm05/1116/16anim3.htm
AP Biology
 ZYGOTE
__________ undergoes CLEAVAGE
____________

(MITOSIS)
BLASTULA (hollow ball of
Forms ____________
cells)
AP Biology
AP Biology
AP Biology
When did we see first Animals?
 The oldest generally accepted animal fossils


that have been found are 575–550 million
years old.
Cambrian- fossils from Burgess Shale
Cambrian explosion, 2 Ideas:
increasingly complex predator-prey
relationships or
 an increase in atmospheric oxygen.

AP Biology
….about ½ billion years ago.
 Much of the diversity in body form among

the animal phyla is associated with
variations in where and when homeotic
genes are expressed within developing
embryos.
Of the 35 or so animal phyla, all but one
are invertebrates, named because they
lack vertebra.
AP Biology
Animals Characterized by basic features
Animal body plans vary in
 symmetry,
 presence of true tissues,
 number of embryonic layers,
 presence of a body cavity, and
 details of their embryonic development.
AP Biology
Types of Symmetry
Asymmetry
AP Biology
Radial
Bilateral
Images from:
http://mbgnet.mobot.org/salt/animals/sponges.htm
http://biodidac.bio.uottawa.ca/
http://sps.k12.ar.us/massengale/animal%20dissections.htm
http://www.okc.cc.ok.us/biologylabs/Documents/Animals/Symmetry.htm
AP Biology
BODY PLAN
INVERTEBRATES
 Dorsal heart
 Ventral nerve cord
http://animaldiversity.ummz.umich.edu/site/resources/biodidac/crus001and2b.gif/small.jpg
AP Biology
VERTEBRATES
• Ventral heart
• Dorsal nerve cord
GASTRULATION:
1. Cells in blastula
move inward over
lip of
BLASTOPORE
_______________
Form digestive
system (tube within
a tube)
Becomes
digestive
system
AP Biology
Gastrulation
2. Germ layers form
TWO GERM layers form
________________
DIPLOBLASTICEX: Sponges and
cnidarians
THREE GERM layers form
TRIPLOBLASTIC Most animals
__________________-
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Germ Layers
Endoderm forms lining of digestive tract,
digestive (LIVER, PANCREAS)
& respiratory organs (LUNGS)
Mesoderm forms muscle, skeletal,
circulatory, excretory,
reproductive systems
Ectoderm forms outer covering
(epidermis) , brain, central
nervous system
AP Biology
1. Where does BLASTOPORE end up?
Images
modified from: http://io.uwinnipeg.ca/~simmons/16cm05/1116/16anim3.htm
AP Biology
Patterns of Development
(Triploblastic)
PROTOSTOMES
DEUTEROSTOMES
Blastopore becomes Blastopore becomes
ANUS
MOUTH
DETERMINATE
Decide very early
INDETERMINATE
Decide later
MOST INVERTEBRATES
except ECHINODERMS
ALL VERTEBRATES
(Fish, amphibians, birds,
reptiles, mammals)
plus ECHINODERMS
AP Biology
When do cells decide what they will become?
AP Biology
Image from: http://www.rbej.com/content/figures/1477-7827-1-100-1.jpg
THAT’S WHERE TWINS COME FROM !
ONLY
Deuterostomes
can have
identical twins!
MONOZYGOTIC TWINS
(Maternal twins)
Identical DNA
AP Biology
DIZYGOTIC TWINS
(Fraternal twins)
DIFFERENT DNA
Image from: http://www.bsac21.freeserve.co.uk/images/Critters/Starfish%20Bloody%20Henry.JPG
“Exception to the rule”
ECHINODERMS ARE
THE ONLY
INVERTEBRATE
DEUTEROSTOMES
http://my3boysandi.files.wordpress.com/2007/11/spongebob_1.jpg
Porifera and Cnidarians
have only TWO germ layers
Not considered PROTOSTOMES
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http://z.about.com/d/healing/1/0/Y/O/gtotem_jellyfish.jpg
FUNCTIONS of having a COELOM (body cavity):
COELOM
Fluid filled space = ________
Separates digestive tube from body wall
Allows organs to move independently
Space/cushion for organs
In animals without a skeletonFluid in coelom space can act as
HYDROSTATIC skeleton
_______________
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Types of Coeloms (See-Lums)
COELOM
Fluid filled space = __________
No cavity (space) around
organs
Image from: http://io.uwinnipeg.ca/~simmons/16labman05/lb5pg10.htm
ACOELOM = “without space”
_________
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No space, <2 openings
FLATWORMS are ACOELOMATES!
AP Biology
Types of Coeloms (See-Lums)
Space around organs but only lined with
mesoderm on one side
(lines body wall BUT NOT around gut)
Image from: http://io.uwinnipeg.ca/~simmons/16labman05/lb5pg10.htm
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PSEUDOCOELOM
ROUND WORMS are
_____________
PSEUDOCOELOMATES!
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Types of Coeloms (See-Lums)
Body cavity (space) lined on BOTH sides
by mesoderm
Image from: http://io.uwinnipeg.ca/~simmons/16labman05/lb5pg10.htm
EUCOELOM = TRUE COELOM = COELOM
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COELOMATES
Segmented worms,
MOST INVERTEBRATES
& ALL VERTEBRATES
AP Biology
3 Types of Coeloms
ACOELOM
ectoderm
mesoderm
endoderm
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EUCOELOM
PSEUDOCOELOM
Image from: http://www.lander.edu/rsfox/310images/310bil5.jpg
Body Cavity
acoelomate
ectoderm
mesoderm
endoderm
pseudocoelomate
ectoderm
mesoderm
endoderm
pseudocoel
coelomate
ectoderm
mesoderm
coelom cavity
endoderm
AP Biology
protostome vs. deuterostome
ADVANTAGE OF an COELOM?
Digestive organ muscles and body wall
muscles come from MESODERM in different
places so organism can digest food and
move at same time.
Images from:
http://www.lander.edu/rsfox/310images/310bil5.jpg
AP Biology
http://www.okc.cc.ok.us/biologylabs/Images/Animal_Images/coelomate.gif
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AP Biology
Animals
Invertebrates
(animals without a backbone)
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Porifera
Cnidaria
Worms
Mollusks
Echinoderms
Arthropods
LIFE ON EARTH
Image from: http://ology.amnh.org/biodiversity/treeoflife/pages/graph.html
AP Biology
Animal Evolution
Cnidaria
Porifera
sponges
jellyfish
Nematoda
Platyhelminthes
Annelida
Mollusca
Echinodermata
Arthropoda
flatworms roundworms mollusks segmented
worms
redundancy,
segmentation
specialization,  mobility
insects
spiders
starfish
Chordata
vertebrates
 body & brain
backbone
size,  mobility
 body size endoskeleton
coelom  digestive sys
radial
body cavity  body complexity
 digestive & repro sys
bilateral symmetry
tissues
multicellularity
AP Biology
Ancestral Protist
distinct body plan; cephalization
specialized structure & function,
muscle & nerve tissue
specialization &  body complexity
bilateral
Disagreement about phylogeny of BILATERIA
Protostomia
Images
from Campbell and Reece AP BIOLOGY
AP
Biology
http://sps.k12.ar.us/massengale/echinoderm_notes.htm
WHY ARE ECHINODERMS PLACED IN BILATERIA?
Its larvae are BILATERALLY symmetrical
and develop like deuterostomes!
AP Biology
PORIFERA
Invertebrate Phylum: __________
 SPONGES
_________





Cells are independent
Sessile (non-moving)
ASYMMETRICAL
_______________
HERMAPHRODITES
________________ - make both egg
and sperm
Suspension feeders
AP Biology
food taken into each
cell by endocytosis
 The body of a sponge consists of two
layers of cells separated by a gelatinous
region.
The inner layer of flagellated choanocytes
filters food and engulfs it by phagocytosis.
 Amoebocytes wander through the middle
body region and produce skeletal fibers
composed of flexible protein and mineralized
particles called spicules.

AP Biology
AP Biology
CNIDARIA
Invertebrate Phylum: ________
Jellyfish, hydra, sea anemone, coral
 _____________________

Diploblastic (two germ layers)
_______________________
Tissues, but no organs
polyp
RADIAL SYMMETRY)
 _______________

Two Forms
 One Opening

 Gastrovascular cavity
 tentacles surround
gut opening
AP Biology
 Hydra
 Jelly Swim
 Hydra Eat
medusa
mouth
Stinging cells of Cnidarians
NEMATOCYSTS
tentacles
sensory
cell
stinging
cell
hydra
trigger
stinging cell
with nematocyst
AP Biology
discharged
nematocyst
undischarged
nematocyst
EUMETAZOA
SUBKINGDOM: ___________
 (true animals = 3 germ layers)
 ALL WORMS:
PROTOSTOMES
 INVERTEBRATE _____________
BILATERAL SYMMETRY
 have ____________________

(BILATERIA)
THROUGH SKIN
Breathe _______________
AP Biology
3 KINDS OF WORMS - 3 KINDS OF COELOMS
ectoderm
mesoderm
FLATWORMS
acoelomate
ROUND WORMS
ectoderm
mesoderm
endoderm
pseudocoelomate
ectoderm
mesoderm
SEGMENTED
WORMS
True coelomate
AP Biology
endoderm
endoderm
PLATYHELMINTHES
Invertebrate Phylum: __________________
ACOELOM
 _____________

GASTROVASCULAR
CAVITY
_______________________


Animals now
face the world
head on!
<2 openings
______
OPEN circulation
 __________________
CHEPHALIZATION= development
of brain
 mostly parasitic
 EX: Planaria, flukes, tapeworms
some parasitic: Schistosomiasis (blood
fluke)
ectoderm
AP Biology
mesoderm
acoelomate endoderm
PLATYHELMINTHES
 3 major groups
1.
Free-living (Planarians)




AP Biology
heads with light-sensitive eyespots,
flaps to detect chemicals,
dense clusters of nerve cells that form a
simple brain and a pair of nerve cords that
runs the length of the body, and
a branched gastrovascular cavity with a
single opening.
PLATYHELMINTHES
2. Flukes are parasitic flatworms with


complex life cycles and
suckers to attach to their hosts.
3. Tapeworms






are parasitic,
Inhabit the digestive tracts of vertebrates,
consist of a ribbonlike body with repeated units,
have an anterior scolex armed with hooks and suckers that grasp
the host,
have no mouth, and simply absorb nutrients across their body
surface.
The units at the posterior end of tapeworms are full of ripe eggs that
pass out of the host’s body.
AP Biology
NEMOTODA
Invertebrate Phylum: __________
PSEUDOCOELOM = 3 layers
 _______________




2 opening digestive system
= COMPLETE DIGESTIVE SYSTEM
tube running through length of
body (mouth to anus)
________Circulation
OPEN

Free living = important
decomposers

many are parasitic
 Hookworm, pinworms
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C. elegans
Nematodes
 ~25,000
species named,
out of estimated
~500,000.
 Humans host at
least 50 species
of parasitic
nematodes.
AP Biology
MOLLUSCA
Invertebrate Phylum : _________
 ___________
COELOMATE = true coelom
2 openings digestion
 _______
FOOT used for locomotion
 ‘SOFT
________________
BODIES” visceral mass
 Shells secreted by __________
MANTLE
 Radula mouth part used to scrape up food

AP Biology
AP Biology
Invertebrate Phylum : Mollusca
 _________
BIVALVES : 2 shells, clams, scallops and oysters
GASTROPODS : 1 shell, “stomach foot”, snails,
 _____________

slugs, and nudibranchs, aqautic and terrestrial
CEPHALOPODS
______________ : no shell, “head-foot” , octopus,
squid, nautilus
AP Biology
ANNELIDA
Invertebrate Phylum : __________
COELOM true coelom
 __________




2 opening digestive system
SEGMENTATION
______________
CLOSED circulation = vessels
Most HERMAPHRODITES
__________________
fan worm
AP Biology
leech
Annelids are segmented worms
 Annelids are found in damp soil, the sea,

and most freshwater habitats.
The three groups of annelids are
earthworms and their relatives,
 polychaetes- largest group, pair of bristles
on each segment, tube or free living, marine
 Leeches- free-living carnivores

 Earthworms ingest soil and extract
nutrients, aerating soil and improving its
texture.
AP Biology
AP Biology
ARTHROPODA
Invertebrate: _____________
COELOMATE
 _____________




most successful animal phylum
INVERTEBRATE PROTOSTOMES
Only ___________________________________
BILATERL
______________
symmetry, head, thorax, abdomen
SEGMENTATION
_____________________
 specialized segments
JOINTED APPENDAGES
 allows ______________________

EXOSKELETON made of _________,
CHITIN molt to grow
_________________
AP Biology
Phylum Arthropoda
• ______
OPEN circulatory system
METAMORPHOSIS
• Many undergo __________________
• Four Major Groupings (subphylums, class)
• Chelicerates
• Milli/Centepedes
• Crustaceans
• Insects
AP Biology
Phylum Arthropoda - Chelicerates
1. Chelicerates
Include: horseshoe crab, crabs and
ARACHNIDS
___________
 8 legs
ABDOMEN
CEPHALOTHORAX __________
 2 body parts __________________,
MALPIGHIAN TUBULES
 With_____________________
LUNGS -respiratory
 BOOK
_____________
Ex: Spiders, ticks, scorpions
AP Biology
Phylum Arthropoda Millipedes and Centipedes
Identified by number of legs
Millipedes are herbovores that have two legs per
segment
Centipedes are carnivores that have one pair of legs per
segment
AP Biology
Phylum Arthropoda CRUSTACEANS
_____________
10 legs
CEPHALOTHORAX
2 body parts __________________,
__________
ABDOMEN
______
GILLS -respiratory, nearly all aquatic
GREEN GLANDS -excretory
_______________
Ex: crayfish, lobster, crab,
shrimp and barnacles
AP Biology
Phylum Arthropoda INSECTS most successful group
 _________
HEAD _______
THORAX ,
• 6 legs, 3 body parts _____,
•
•
•
ABDOMEN some with wings
________,
URIC ACID with MALPIGHIAN TUBULES
Excrete ________
_________________
TRACHEA & SPIRACLES
__________________ - respiratory
Complex life cycle
•
•
Complete metamorphosis (larva-pupa-adult)
Incomplete metamorphosis (no pupa, multiple
molts)
•
Ex- Grasshopper, bee, ant
AP Biology
Why so Successful?
 Modular Body – each segment develops




separately
Specialized Mouth parts – chewing,
biting, lapping, piercing and sucking
Multiple legs for walking, jmping, grasping,
digging, paddling
Wings
Protective Color
AP Biology
ECHINODERMATA
Invertebrate: _______________
stars, sea urchins, sea cucumber, sand dollars
 Sea
______________________________________



SPINY skin
________
MARINE (live in salt water)
All are _________
BILATERAL SYMMETRY
Larva ______________________;
as adults RADIAL
_________
__________
SYMMETRY
loss of bilateral symmetry?
AP Biology
Invertebrate: Echinodermata
ENDOSKELETON have bone plates
 _______________
INVERTEBRATE DEUTEROSTOMES
 Only ______________________________
WATER VASCULAR SYSTEM with TUBE
 ________________________

FEET
OPEN circulation
______
AP Biology
INVERTEBRATES
(animals without a backbone)
AP Biology
Porifera
Cnidaria
Worms
Mollusks
Echinoderms
Arthropods
Invertebrate quick check…
Invertebrates: Porifera, Cnidaria, Platyhelminthes, Nematoda,
Annelida, Mollusca, Arthropoda, Echinodermata
 Which phylum includes snails, clams, and octopus?
 Which phylum is the sponges?
 Which are the flatworms?
…segmented worms?
…roundworms?
 Which phylum has jointed appendages & an




exoskeleton?
Which two groups are radially symmetrical?
Which group has no symmetry?
Type of circulation most invertebrates have?
Which groups are DIPLOBLASTIC?
AP Biology
CHORDATA
Phylum _________
ALL COELOMATE DEUTEROSTOMES
 _______________________________




NOTOCHORD
PHARYNGEAL POUCHES
POST ANAL TAIL
DORSAL NERVE CORD
hollow dorsal
nerve cord
becomes brain
& spinal cord
becomes gills or
Eustachian tube
Oh, look…
your first
baby picture!
AP Biology
pharyngeal
pouches
postanal
becomes tail tail
or tailbone
becomes
vertebrae
notochord
NOTOCHORD
Notochord:
flexible rod
Helps organize developing
cells in embryo
Replaced by spinal cord in
most vertebrates
Becomes the vertebrae
http://www.xenbase.org/xmmr/Marker_pages/notochord/Tor70stg22.jpg
AP Biology
DORSAL NERVE CORD
VENTRAL HEART
Spinal cord forms along dorsal side
Images from:
http://www.nvo.com/jin/nssfolder/scrapbookanatomy/dorsal%20nerve%20cord.jpg
http://www.ekinos.com.ar/horse.jpg
AP
Biology
PHARYNGEAL POUCHES
Become gills in
some vertebrates
Become back of
throat and inner
ears in humans
AP Biology
http://www-biol.paisley.ac.uk/courses/Tatner/biomedia/subunits/notoc.htm
POST ANAL TAIL
AP Biology
Human Embryo
32 days old
http://www.evcforum.net/RefLib/EvidencesMacroevolution2_files/human_embryo.jpg
Pharyngeal arches
appear during 4th week
Tail disappears at
approximately 8 weeks
AP Biology
Simplest Chordates
 Tunicates and Lancelets
 No backbone
 Use pharyngeal slits for
suspension feeding.
AP Biology
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AP Biology
Radial Symmetry - No Change
AP Biology
Bilateral – NEW Protostome Split
 Protostomes split
based on DNA

Lophotrochozoans
 Named for feeding
apparatus – lophophore

Ecdysozoans
 Have exoskeletons
AP Biology
Deuterostomes Same
AP Biology
2 Possible Pictures
AP Biology
Ancient Genes Build Bodies
 All animals share genes for building animal bodies.
 These ancient genes are the master control genes

called homeotic genes.
Changes in the regulation of homeotic gene
expression have been significant factors in the
evolution of animal diversity.
AP Biology