3 Domains
Introduction to Kingdom Animalia
•eukaryotic
•ingestive heterotrophs
•multi-cellular
•have tissues that develop from embryonic layers
•nervous and muscle tissue are unique
•bodies held together by structural proteins (e.g.
collagen)
Introduction to Kingdom Animalia
•most reproduce sexually
•involves meiosis
•allows genetic variation
•diploid stage usually dominates life cycle
•locomotion
•most can move body from one place to another
•some sessile (non-motile)
•even these motile some time in life-cycle (ex.
larval stage)
Body Symmetry- 3 Types
Asymmetric
-different in every direction
-sessile
Radial
-body parts arranged around a central axis
-sessile or limited movement
-have top/bottom, but no front/back or left/right
-able to meet “challenges” from every direction
Bilateral
-left/right sides are mirror images
-has anterior (head) and posterior (tail)
-cephalization (head formation) accompanied by
concentration of sensory organs in that region
-free moving
-meet “challenges” head on
Body Symmetry
-any cut
through central
axis divides
into mirror
image
-only one cut
can divide into
mirror image
halves
Body Symmetry
Introduction to Kingdom Animalia
•Animal body plans
•vary in symmetry
•vary according to tissue organization
•tissues are specialized cells functioning
together to perform same function
•isolated from other tissues by
membranous layers
Introduction to Kingdom Animalia
•Animal body plans
•All animals and only animals have Hox
genes
•regulate development of body form
•highly conserved family of genes
•yet produces wide variety of animal
morphology
Introduction to Kingdom Animalia
Proposed common ancestor of all animals
•may have lived 1.2
billion to 800 million
years ago
•resembled modern
day choanoflagellates
Introduction to Kingdom Animalia
•Phylogenetic tree
•About 35 Phyla currently recognized
•Systematists agree on major features of
tree
•2 main hypotheses based on criteria used
•Molecular data
•Morphology and developmental
features
Asymmetry
Parazoa
Radiata
Bilateria
Eumetazoa
Kingdom: Animalia
Subkingdom: Parazoa
Phylum: Porifera (the sponges)
The sponges are so different from the other
animals that they were given their own
Subkingdom. “Parazoa” means alongside the
animals.
Phylum: Porifera (the sponges)
• oldest known animal fossils are of sponges
• evolutionary link between single-celled
protists and multi-cellular animals
(metazoans)
• closest relative is the protist
choanoflagellate
choanocyte (collar cell)
of a sponge
Phylum: Porifera (the sponges)
Why are they in the Kingdom Animalia?
• named for Greek porus- animals with pores
• eukaryotic, multi-cellular, ingestive
heterotrophs
• suspension or filter feeders
• asymmetry
• sexual life-cycle involves a larval phase
• adult is sessile but larva (ciliated) is motile
• specialized cell types but no tissues
Phylum: Porifera (the sponges)
Why are they in the Kingdom Animalia?
•exhibits “cell-cell recognition”
• if physically separate cells and mix them
up, cells can reassemble into the animal
• has CAMs (Cell Adhesion Molecules)
• cell surface proteins
• important for cell-cell recognition
Sponge Skeletons
Phylum: Porifera
Skeleton of a sponge:
•2 main components:
(1) spongin: fibrous protein that runs
throughout animal and works with spicules
(2) spicules: aggregates of inorganic material
made of silica or calcium carbonate
*Sponges placed in
Classes based on spicule
type:
•# of points
•building material
Phylum: Porifera- Classes
Calcarea••
•
Leucosolenia is simplest sponge
small
spicules are calcium carbonate with 1, 3, or 4 rays (points)
•
Hexactinellida•
•
“Glass sponges”
no surface epithelium
spicules of silica with 6 rays
Demospongiae••
most common
bath sponges
spicules of silica with 1, 2, or 4 rays
•
Sclerospongiae•
•
coralline sponges
internal skeleton of calcium carbonate
outer skeleton of silica spicules and organic
fibers
•
*classified by spicule shape and building material
Phylum: Porifera
Anatomy of a Sponge
• Multi-cellular
• Organized by cell type
• No tissues
• Most sponges are simple tubes
• 2 cell layers form “wall” of body
• epidermis- outer layer
• choanocytes- inner layer
• mesenchyme (mesohyl)
• between outer/inner cell
layers
• gelatinous compartment
• contains mobile
amoebocytes
• spongocoel is space inside
tube
Phylum: Porifera - Specialized cell types
•choanocytes- (collar cells)
•flagella drive water currents
•ingest food by phagocytosis
•amoebocytes•mobile within mescenchyme
•digest food in food vacuoles
•asexual reproduction
•form gemmules
•sexual reproduction
•produce male/female gametes
•secrete skeletal elements
•spicules and spongin
Phylum: Porifera - Circulation
•no circulatory system
•water & food enter
spongcoel via pores
(porocytes)
•choanocyte flagella
move materials around
spongocoel and up and
out osculum
Phylum: Porifera Digestion
•no digestive system
•choanocyte takes in food by phagocytosis
•limited digestion
•food transferred to amoebocyte
•main site of digestion
•intracellular in food vacuoles
Phylum: Porifera - Sexual Reproduction
•hermaphrodite- amoebocytes produce egg & sperm
•fertilization to form zygote in mesenchyme
•cleavage (rapid cell divisions) to form hollow ball of cells called
blastula
•blastula is free-swimming cilated larva that erupts from body wall
•metamorphosis of larva
•flagellated cells migrate in to become choanocytes (collar cells)
•inner cells migrate out to become epidermal cells
•grows to form new adult sessile sponge
Phylum: Porifera - Asexual Reproduction
3 methods
•regeneration after fragmentation
•budding
•gemmules
Gemmule
•“survival pod”
•several cells w/ nutrients surrounded by spongin/spicule
“shell”
•dormant form resistant to environmental stresses
•can germinate to re-grow animal
•found in freshwater sponges
Phylum: Porifera (the sponges)
Symmetry- assymetrical, no tissues, adult is sessile
Segmentation- N/A
Mesoderm present- none, diploblastic- embryo has
2 cell layers (ectoderm, endoderm)
Body cavity- none b/c only 2 cell layers, need 3 cell
layers to make a body cavity
Embryonic Development: Formation of Germ Layers
Diploblastic (2 layers) vs. Triploblastic (3 layers)
2
1
Only one cleavage
The zygote of an animal undergoes a succession ofstage–the eight-cell
mitotic cell divisions called cleavage.
embryo–is shown here.
3
In most animals, cleavage results in the
formation of a multicellular stage called a blastula.
The blastula of many animals is a hollow ball of cells.
Blastocoel
Cleavage
Cleavage
6
The endoderm of
the archenteron develops into the tissue
lining the animal’s
digestive tract.
Eight-cell stage
Zygote
Blastula
Cross section
of blastula
Blastocoel
Endoderm
5
The blind pouch
formed by gastrulation, called
the archenteron,
opens to the outside
via the blastopore.
Ectoderm
Gastrula
Blastopore
Gastrulation
4
Most animals also undergo gastrulation, a rearrangement of the embryo in which one end of the
embryo folds inward, expands, and eventually fills the blastocoel, producing layers of embryonic
tissues: the ectoderm (outer layer) and the endoderm (inner layer).
Embryonic Germ Layers
Diploblastic- 2 layers
-ectoderm and endoderm
-no mesoderm
-ex. Cnidarians, Porifera (sponges)
Triploblastic- 3 layers
-ectoderm, mesoderm and endoderm
-all animals with bilateral symmetry
Embryonic Germ Layers
ectoderm
-outer layer
-forms animal’s outer covering, in
some phyla central nervous system
endoderm
-inner layer
-forms lining of digestive tract, in
vertebrates forms liver, lungs
Coelom
Archenteron
Coelom
Mesoderm
Blastopore
Blastopore
Mesoderm
mesoderm
-between ectoderm/endoderm in
triploblast
-forms muscles between digestive
tract and animal’s outer covering
Phylum: Porifera (the sponges)
Larva- ciliated free swimming larva
Protostome- N/A
Cleavage/cells- determinate
Nervous system- none
Respiratory system- no complex system, gas
exchange via simple diffusion through outer and
inner cell layers
Embryonic Cleavage: Determinate vs.
Indeterminate
In humans, the first few divisions are indeterminate. If cells in
the embryo separate within the first divisions, the result is
identical twins.
Phylum: Porifera (the sponges)
Digestive system- filter feeders, no complex system,
mostly intracellular digestion w/in amoebocyte;
choanocyte ingests food by phagocytosis, food
vacuole then transferred to amoebocyte for
intracellular digestion, limited digestion inside
choanocyte
Excretory system- no complex system, excrete
metabolic wastes by simple diffusion
Reproductive System- asexual- regeneration,
budding or gemmules; sexual- hermaphrodite as
with most sessile organisms
Phylum: Porifera (the sponges)
Circulatory system- no complex system, water
enters through pores and leaves through osculum
(like a chimney) choanocyte flagella beat to
circulate water in spongocoel
Members- classified according to spicule type;
fibrous skeleton of Desmospongia used for bath
sponges
Habitat- aquatic and mostly marine
Relationship to other Phyla- thought to be
descendants of choanoflagellates (Kingdom
Protista, Phylum Choanozoa)
Phylum: Porifera
A couple of more sponge facts:
•Defenses include toxic chemicals, prickly
skeletons, bad-tasting substances
•Source of some antibiotics and anti-cancer
drugs