Invertebrates
Chapter 33
Animal Origins
Euglenozoa
Parabasala
Diplomonadida
Alveolata
Stramenopila
Radiolaria
Cercozoa
Amoebozoa
Plantae
Chlorophyta
Rhodophyta
Animalia
Choanoflagellates
Fungi
Animal Origins
Ancestral eukaryote
Figure 28.4
Characteristics of the Animal Kingdom
None 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
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
Organized federation of cells vs. cells in tissues
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
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
For organisms with tissues:
two vs. three principal embryonic tissues
Characteristics of the Animal Kingdom
Two embryonic tissue layers:
Blastocoel
Zygote
Blastula
Blastocoel
Endoderm
Ectoderm
Archenteron
Blastopore
Gastrula
Gastrulatio
n
Fig. 32.2
Characteristics of the Animal Kingdom
Two 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
Blastocoel
Endoderm
Ectoderm – Outermost “germ layer”;
differentiates into tissues that cover the
body and into the nervous tissues
Ectoderm
Archenteron
Blastopore
Gastrula
Fig. 32.2
Characteristics of the Animal Kingdom
Three embryonic tissue layers:
Fig. 32.9
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
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
Radial vs. bilateral symmetry
Fig. 32.7
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
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
Among organisms with 3 germ layers:
Acoelomate, pseudocoelomate, or coelomate
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
Among organisms with 3 germ layers:
Acoelomate, pseudocoelomate, or coelomate
Fig. 32.8
Acoelomate: lack a coelom, i.e., lack a body cavity
between digestive track and body wall
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
Among organisms with 3 germ layers:
Acoelomate, pseudocoelomate, or coelomate
Fig. 32.8
Pseudocoelomate: Fluid-filled body cavity between
digestive tract and body wall partially lined by mesoderm
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
Among organisms with 3 germ layers:
Acoelomate, pseudocoelomate, or coelomate
Fig. 32.8
Coelomate: fluid-filled body cavity between digestive
tract and body wall completely lined by mesoderm
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
Protostome vs. deuterostome development
Characteristics of the Animal Kingdom
A great diversity of body plans occur;
some key features include:
Protostome vs. deuterostome development
See Fig. 32.9
Arthropoda
Nematoda
Rotifera
Annelida
Mollusca
Nemertea
Platyhelminthes
Ectoprocta
Phoronida
Brachiopoda
Chordata
Echinodermata
Cnidaria
Ctenophora
Silicarea
Calcarea
“Radiata”
“Porifera”
Deuterostomia
Lophotrochozoa
Ecdysozoa
Bilateria
Eumetazoa
Metazoa
Ancestral colonial
flagellate
Fig. 32.11
&
Table 33.7
The Animal
Kingdom
~ 35 phyla
Ancestral colonial
choanoflagellate
Chordata
Echinodermata
Other bilaterians (including
Nematoda, Arthropoda,
Mollusca, and Annelida)
Cnidaria
Porifera
Phylum Porifera –
Sponges
Deuterostomia
Bilateria
Eumetazoa
Figure
33.2
Phylum Porifera –
Sponges
Organized aggregation of
cells
Probably the most similar
extant group to the
protistan colonial
precursors to the animals
Phylum Porifera –
Sponges
Organized aggregation of
cells
Three main cell types, but
no true tissues
Asymmetric body plan
Mostly marine, but some
inhabit fresh water
Phylum Porifera –
Sponges
Internal skeleton of
protein spicules
E.g., natural bath
sponge
Eumetazoa
Chordata
Echinodermata
Other bilaterians (including
Nematoda, Arthropoda,
Mollusca, and Annelida)
Cnidaria
All eumetazoans have
true tissues
Porifera
All animals except
sponges belong to the
clade Eumetazoa
Deuterostomia
Bilateria
Eumetazoa
Ancestral colonial
choanoflagellate
Figure
33.2
Phylum Cnidaria –
Corals, Jellyfish,
Anemones
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
Phylum Cnidaria –
Corals, Jellyfish,
Anemones
Tentacles contain
cnidocytes
Fig. 33.6
Phylum Cnidaria –
Corals, Jellyfish,
Anemones
Polyp and medusa
forms
Fig. 33.5
Phylum Cnidaria –
Corals, Jellyfish,
Anemones
Polyp and medusa
forms
Phylum Ctenophora –
Comb jellies
8 rows of comblike plates
of cilia
Bilateria
Chordata
Echinodermata
Other bilaterians (including
Nematoda, Arthropoda,
Mollusca, and Annelida)
Cnidaria
Porifera
Bilaterally symmetric,
cephalized animals with 3
germ layers
Deuterostomia
Bilateria
Eumetazoa
Ancestral colonial
choanoflagellate
Figure
33.2
P. Platyhelminthes –
Flat worms
Gastrovascular cavity (if a
gut is present)
Some true organs are
present (tissues grouped
into functional structures)
Hermaphroditic and
capable of self-fertilization
Acoelomate
P. Platyhelminthes –
Flat worms
Mostly free-living
P. Platyhelminthes –
Flat worms
Mostly free-living
Some parasitic
E.g., tapeworms
P. Rotifera – Rotifers
Distinguishing feature is a
“crown of cilia” around the
mouth
Complete digestive tract
surrounded by
pseudocoelom
Parthenogenesis
(development from
unfertilized eggs) is the
most common mode of
reproduction
P. Ectoprocta
P. Phoronida
P. Brachiopoda
All bear a lophophore –
fold of the body wall
bearing ciliated tentacles
surrounding the mouth
Coelomate
P. Ectoprocta
a.k.a. bryozoans
Colonial
Many contribute to marine
reefs
P. Phoronida
A group of tube-dwelling
marine worms
P. Brachiopoda
a.k.a. lamp shells
Marine, mostly extinct
P. Nemertea
a.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. Mollusca
a.k.a. mollusks
P. Mollusca
a.k.a. mollusks
Coelomate body
with a muscular
foot, visceral mass,
and mantle (which
secretes a shell in
many species)
P. Mollusca
a.k.a. mollusks
8 classes,
including:
C. Polyplacophora
(chitons)
Shell divided into 8
plates
P. Mollusca
a.k.a. mollusks
8 classes,
including:
C. Gastropoda
(snails and slugs)
Single shell or
lacking shell
P. Mollusca
a.k.a. mollusks
8 classes,
including:
C. Gastropoda
(snails and slugs)
Single shell or
lacking shell
P. Mollusca
a.k.a. mollusks
8 classes,
including:
C. Bivalvia (clams,
oysters, mussels,
etc.)
Hinged, twopart shell
P. Mollusca
a.k.a. mollusks
8 classes,
including:
C. Cephalopoda
(squids, octopuses,
nautiluses)
Only mollusks with
closed circ. system and
complex brain
P. Mollusca
a.k.a. mollusks
8 classes,
including:
C. Cephalopoda
(squids, octopuses,
nautiluses)
Only mollusks with
closed circ. system and
complex brain
P. Annelida
a.k.a. segmented
worms
P. Annelida
a.k.a. segmented
worms
Segmented
Coelomate
Coelom
Closed circulatory
system
P. Annelida
a.k.a. segmented
worms
3 classes:
C. Oligochaeta
Earthworms and
their kin
Coelom
P. Annelida
a.k.a. segmented
worms
3 classes:
C. Polychaeta
Bristled parapodia
on each segment
P. Annelida
a.k.a. segmented
worms
3 classes:
C. Hirudinea
Leeches
P. Nematomorpha
a.k.a. horsehair or
gordian worms
Not required
to know
P. Priapulida
a.k.a. penis worms
Not required
to know
P. Tardigrada
a.k.a. water bears
Not required
to know
P. Onychophora
a.k.a. velvet worms
Not required
to know
P. Nematoda
a.k.a. roundworms
Nonsegmented
P. Nematoda
a.k.a. roundworms
Nonsegmented
No circulatory or respiratory systems
Anus
Gut
Mouth
P. Nematoda
a.k.a. roundworms
Nonsegmented
No circulatory or respiratory systems
Pseudocoelomate
P. Nematoda
a.k.a. roundworms
Nonsegmented
No circulatory or respiratory systems
Pseudocoelomate
Free living or parasitic
E.g., dog
heartworm
P. Arthropoda
Segmented
Coelomate
Exoskeleton of chitin
Jointed appendages
P. Arthropoda
Open 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. Arthropoda
As 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. Arthropoda
Cheliceriforms – horseshoe crabs
P. Arthropoda
Cheliceriforms – sea spiders
P. Arthropoda
Cheliceriforms:
Arachnids –
spiders, ticks,
scorpions, mites
P. Arthropoda
Cheliceriforms:
Arachnids –
spiders, ticks,
scorpions, mites
spider (tarantula)
mite
tick
scorpion
P. Arthropoda
Cheliceriforms:
Arachnids –
spiders, ticks,
scorpions, mites
Adults generally have 4
pairs of walking legs
Some produce silk
P. Arthropoda
Cheliceriforms:
Arachnids –
spiders, ticks,
scorpions, mites
Eyes of black widow spider
Simple eyes (each with a
single lens)
P. Arthropoda
Myriapods – millipedes; 2 pairs of legs per segment
P. Arthropoda
Myriapods – centipedes; 1 pair of legs per segment
P. Arthropoda
Hexapods: insects
P. Arthropoda
Hexapods: insects
Adult often has 2 pairs
of wings
P. Arthropoda
Hexapods: insects
Sometimes 1 pair of
wings; sometimes
none
P. Arthropoda
Hexapods: insects
Adult generally has 3
pairs of legs
P. Arthropoda
Hexapods: insects
Metamorphosis – transition between distinct (often
dramatically different) developmental stages
Larva
(maggot, caterpillar)
Pupa
(transition to adult)
Adult
(often winged)
P. Arthropoda
Hexapods: insects
Metamorphosis – transition between distinct (often
dramatically different) developmental stages
Larva
(maggot, caterpillar)
Pupa
(transition to adult)
Adult
(often winged)
P. Arthropoda
Hexapods: insects
Adult generally has
compound eyes
See also Fig. 33.37
Insects
Some of the major orders (26 in total):
Order Coleoptera – Beetles
Order Hemiptera – True Bugs
Order Homoptera – Aphids and their kin
Order Hymenoptera – Ants, Bees, Wasps
Order Isoptera – Termites
Order Lepidoptera – Butterflies and Moths
Order Odonata – Dragonflies and
Damselflies
Order Orthoptera – Crickets, Grasshoppers,
Katydids
Order Siphonaptera – Fleas
P. Arthropoda
Crustaceans
As in all arthropods,
crustaceans have
segmented body plans
P. Arthropoda
Crustaceans
waterflea
hermit crab
sowbug
barnacle
P. Arthropoda
Crustaceans
Often have 5 or more
pairs of legs
P. Arthropoda
Crustaceans
Generally have
compound eyes
Deuterostomia
Deuterostome
developmental pathway
Chordata
Echinodermata
Other bilaterians (including
Nematoda, Arthropoda,
Mollusca, and Annelida)
Cnidaria
Porifera
Coelomates
Deuterostomia
Bilateria
Eumetazoa
Ancestral colonial
choanoflagellate
Figure
33.2
P. Echinodermata
P. Echinodermata
At first glance they may
seem more radially than
bilaterally symmetrical…
P. Echinodermata
However, their larvae are
obviously bilaterally
symmetrical
Sea star
adult
Sea star larva
P. Echinodermata
Brittle star
Sand
dollar
Sea cucumber
Sea
urchin
P. Echinodermata
Calcium carbonate
endoskeleton
Brittle star
Sand
dollar
Sea cucumber
Sea
urchin
P. Echinodermata
Unique water vascular
system of hydraulic canals
branching into tube feet for
locomotion, feeding, and
gas exchange
P. Chordata
At some stage in
development, all chordates
possess:
