KINGDOM ANIMALIA
INVERTEBRATES
Chapters 24,
25, 26, and 27
INVERTEBRATE PHYLA
Phylum
Phylum
Phylum
Phylum
Phylum
Phylum
Phylum
Porifera (ex. Sponge & sea cucumber)
Cnidaria (ex. jellyfish & hydra)
Platyhelminthes (ex. Planaria & fluke)
Nematoda (ex. hookworms & pinworms)
Mollusca (ex. Octopus, snail, & oyster)
Annelida (ex. Earthworm & leech)
Arthropoda (ex. Insects, arachnids, &
crustaceans)
Phylum Echinodermata (ex. Sea urchin & sand dollar)
Phylum Chordata (ex. Lancelet & tunicates)
INVERTEBRATE EVOLUTION
1. Phylum Porifera
2. Phylum Cnidaria
3. Phylum Platyhelminthes
4. Phylum Nematoda
5. Phylum Mollusca
6. Phylum Annelida
7. Phylum Arthopoda
8. Phylum Echinodermata
9. Phylum Chordata
PHYLUM PORIFERA
*CELLULAR LEVEL OF ORGANIZATION
 Organisms in the
phylum Porifera are
among the simplest
animals
 Many sponges
are radially
symmetrical
 Their parts
are arranged
around a
central axis
 Choanocytes are
specialized cells that
make up poriferans.
Central axis
PHYLUM PORIFERA
Filter feeders:
Flagellated
choanocytes
filter food from
the water
passing
through the
porous body
Sessile: stay
in one place
Choanocyte in
contact with
an amoebocyte
Pores
WATER
FLOW
Skeletal
fiber
Central
cavity
Choanocyte
Amoebocyte
Flagella
PHYLUM PORIFERA
The sponge lineage
arose very early.
They probably evolved
from multicellular
choanoflagellates, the
group that most likely
gave rise to the
animal kingdom.
Single cell
Stalk
PHYLUM CNIDARIA
*TISSUE LEVEL ORGANIZATION
Cnidarians are the simplest
animals with tissues.
These animals exist in two
radially symmetrical forms:
Polyp
Medusa
PHYLUM CNIDARIA
Cnidocytes on their
tentacles sting prey
– The tentacles,
controlled by nerves,
then push the food
through the mouth
into a gastrovascular
cavity.
– In the cavity, the food
is digested and then
distributed.
– Only one opening in
digestive system.
PHYLUM PLAT YHELMINTHES
*ORGAN LEVEL OF ORGANIZATION
 Flatworms are the simplest bilateral animals.
 Flatworms have organs.
 Planarians have a simple nervous system
tract organs, andNerve cords
consisting of a brain, Digestive
sense
(gastrovascular
cavity)
branching nerves.
 As in cnidarians,
the mouth of a
Mouth
flatworm is the
only opening for
Eyespots
its gastrovascular
Nervous
cavity.
tissue clusters
Bilateral symmetry
Flukes and
tapeworms are
parasitic
flatworms with
complex life
cycles
Mature flukes in blood
vessels of intestine
Male
Human
host
Female
1 Sexual reproduction
of flukes in human;
fertilized eggs pass
out in feces
6 Larva penetrates
skin and
blood vessels
2 Eggs hatch
in water
5 Larva that
infects
human
3 Larva
that
infects
snail
4
Asexual reproduction
of flukes in snail
Snail host
PHYLUM PLAT YHELMINTHES
 Tapeworms can be
eaten by cattle and
burrow into the
intestines and muscles.
 If meat is not properly
inspected, humans can
be infected by eating
rare or undercooked
beef.
Units with
reproductive
structures
Hooks
Sucker
Head
QUICK EVOLUTION CHECKPOINT
Porifera, Cnidaria, and Platyhelminthes
lack a body cavity.
Nearly all other animals have a body
cavity called a coelom.
This cavity is a fluid-filled space between
the digestive tract and the body wall.
– The cavity aids in movement, cushions
organs, and it may help in circulation.
Body covering
(from ectoderm)
Pseudocoelom
Muscle layer
(from
mesoderm)
Digestive tract
(from endoderm)
Body covering
(from ectoderm)
Coelom
Digestive tract
(from endoderm)
Tissue layer
lining coelom
and suspending
internal organs
(from
mesoderm)
PHYLUM NEMATODA
*PSEUDOCOELOM
 AKA: Roundworms
 Nematodes have a body cavity
not completely lined by
mesoderm called a
psuedocoelom.
 Like most animals, they possess
a complete digestive tract.
 This is a tube with a mouth and
an anus. (One-way tract)
 Many nematodes are free-living.
 Others are parasites.
Trichinella juvenile
Muscle tissue
PHYLUM MOLLUSCA
*COELOM
 Phylum Mollusca is a large and
diverse phylum that includes
 gastropods, such as snails and
slugs
 bivalves, such as clams and
scallops
 cephalopods, such as squids
and octopuses
PHYLUM MOLLUSCA
All mollusks have a
muscular foot and a
mantle
The mantle may
secrete a shell which
encloses the visceral
mass
Mollusks have a true
coelom and a
circulatory system
Many mollusks feed
with a rasping radula
QUICK EVOLUTION CHECKPOINT:
AFTER A BODY CAVIT Y EVOLVED…
 Segmentation is the subdivision of some or most of
the body into a series of repeated parts, or segments.
Anus
Brain
Main
heart
Coelom
Digestive
tract
Segment
walls
Mouth
Accessory
heart
Nerve cord
Blood vessels
Excretory organ
Segmentation probably evolved as an
adaptation for movement
QUICK EVOLUTION CHECKPOINT:
PROTOSTOMAL LARVAL DEVELOPMENT
Protostomal larval development:
Earliest type of larval development
according to evolution
Mouth is the first opening to develop.
Cells of the embryo cannot be altered.
PHYLUM ANNELIDA
*BODY SEGMENTATION & PROTOSTOMES
 Earthworms and other annelids
are segmented worms whose
mouths develop first in the
larval stage.
 The segmented bodies of
annelids give them added
mobility for swimming and
burrowing.
 An earthworm eats its way
through soil.
 Most leeches are free-living
carnivores, but some suck blood.
PHYLUM ARTHROPODA
*JOINTED APPENDAGES
Cephalothorax
 Arthropods are
the most
numerous and
widespread of
all animals. Antennae
(sensory
 They are
reception)
segmented
animals with
exoskeletons
and jointed
appendages.
Abdomen
Thorax
Head
Swimming
appendages
Walking legs
Pincer (defense)
Mouthparts (feeding)
PHYLUM ARTHROPODA
 In terms of numbers, distribution, and diversity, they are the
most successful phylum of animals.
 Diversity:




Insects
Crustaceans (marine arthropods)
Arachnids
Millipedes & centipedes
Horseshoe crabs are ancient
marine arthropods
PHYLUM ARTHROPODA
 Insects are the most diverse group of organisms.
 They have a three-part body consisting of head, thorax,
and abdomen.
 The development of many insects includes
metamorphosis.
Thorax
Abdomen
Head
Antenna
Forewing
Eye
Hindwing
Mouthparts
PHYLUM ARTHROPODA
 Metamorphosis:
 Larvae:
specialized for
eating and
growing
 Adults:
specialized for
dispersal and
reproduction
PHYLUM ECHINODERMATA
*DEUTEROSTOME, ENDOSKELETON, RADIAL
SYMMETRY
 Echinoderms have spiny skin, an endoskeleton, and a water
vascular system for movement.
 Phylum Echinodermata includes organisms such as sea stars
and sea urchins
 These organisms are radially symmetrical as adults
PHYLUM ECHINODERMATA
 The water vascular system has suction-cup-like tube
feet used for respiration and locomotion.
Anus
Spines
Stomach
TUBE FEET
CANALS
PHYLUM CHORDATA
*NOTOCHORD
 Notochord: flexible, tough rod that provides support
for the animal and gives muscles a place to attach
PHYLUM CHORDATA
*NOTOCHORD
 Organisms in this phylum (LIKE US) are segmented
animals with four distinctive features:
 Dorsal hollow nerve cord
 Stiff notochord
 Pharyngeal slits behind the mouth
 Muscular post-anal tail