Kingdom Animalia
Remember…we’re talking about
Kingdom Animalia
What characteristics do all members of
the animal kingdom share?
Characteristics of Kingdom Animalia
1) Multicellular – what might be the benefit of
being multicellular?
2) Eukaryotic – their cells each have membranebound organelles and a nucleus
3) Heterotrophic – animals are unable to obtain
energy from the sun, so they need to
consume other organisms
4) Animal cells lack cell walls (this, among other
things, makes us different from plants!)
Animal Cell vs. Plant Cell
• Look at the diagram below. Notice animal
cells are surrounded just by a cell membrane
while plants have a cell membrane and a rigid
cell wall
Animal Kingdom has 2 Main Groups
Invertebrates
• Lack a backbone
• 97% of all species on Earth
are in this category
Vertebrates
• Have a backbone for at least
part of their history
• Only one phylum (Chordata)
Evolutionary Trends of K. Animalia
• If we examine the basic body plan of the
members of K. Animalia, we find that they
exhibit four major evolutionary trends:
1) Multicellular  Development of Tissues
2) No symmetry  Bilateral Symmetry
3) 2 Germ Layers  3 Germ Layers
4) Acoelomate (no gut)  Coelomate (gut
surrounded by cells)
Trend #1 Multicellular  Tissues
• Remember: multicellular means you are made
up of more that 1 cell. Humans, for example, are
made of trillions of cells
• The benefit of being a multicellular organism is
that your cells can group together to form
“tissues” that can them be specialized for
different functions (i.e. become organs).
• Simple animals are multicellular; however they
lack true tissues (e.g. sponges). In more complex
animals, cells start to form tissues and simple
organs
Types of Tissues Found in Complex
Animals
Trend #2: Body Symmetry
• There are three main types of body symmetry: no
symmetry(asymmetrical), radial symmetry, and
bilateral symmetry
• Radial means you can divide the organism into
more than 2 equal parts while bilateral means you
can divide the organism into 2 like parts.
Trend #2: Body Symmetry
Why would it be beneficial to be bilateral?
As you can see below, bilateral species have developed
different body regions (anterior = head; dorsal = back)
allowing these regions to specialize into different
functions (head = sensory organs).
Trend #3: Development of Germ
Layers
All animal life begins with a single
fertilized egg
The single egg divides multiple
times to form a small ball of cells
called a blastula (yes you were
once a blastula!)
The blastula later develops into
“germ layers” (ectoderm,
endoderm and mesoderm)
Trend #3: Development of Germ
Layers
Each of these layers becomes specific
tissues in an adult
Ectoderm – skin, nervous system (in
more complex animals it also
becomes feathers, scales, hair and
nails)
Mesoderm – present in more complex
animals. Forms organs of circulatory,
reproductive, urinary and muscular
system.
Endoderm – form lining of the gut
Why are germ layers important?
• Germ layers give us a hint as to how the
complexity of organisms has progressed
• Lower invertebrates (sponges, jellyfish, etc.) lack
a mesoderm (only have 2 germ layers) and
therefore have no circulatory systems
• In more complex animals, a mesoderm layer (3rd
germ layer) is present and it develops into
important internal transport systems (digestive
systems, circulatory systems, etc.)
Trend #4: Body Cavities
• Another evolutionary trend is the development of an
internal body cavity called a coelom. A true coelom is
lined by cells from the mesoderm germ layer.
• Some less complex animals groups have
“pseudocoelom” (pseudo = false). This is a fluid-filled
body cavity that is not surrounded by a layer of cells
• The simplest organisms lack coeloms and are therefore
called “acoelomate.” In this case, the gut is not lined
by cells or surrounded by a fluid-filled cavity.
Trend #4: Body Cavities
The red circle above is the gut. Notice in the pseudocoelomate, the gut is
surrounded by a fluid-filled cavity. In the coelomate organism, the gut is
surrounded by a layer of mesoderm cells (in blue).
Why is a coelom important?
• Having a coelom is beneficial because it helps
to:
– Protects internal organs
– Streamlines the organism
– Allows for the evolution of more complex organs
and organ systems
Common Animal Phylum
• Remember our organization of species???
Kingdom
Phylum
Class
We are here!!
Order
Family
Genus
Species
Animal Phylums
• There are around 30 to 40 different animal phylums
(depending on the source you use), but we are only
going to talk about 9 major groups:
1) Phylum Porifera “The Sponges”
2) Phylum Cnidaria “Jellyfish/Coral”
3) Phylum Platyhelminthes “The Flatworms”
4) Phylum Nematoda “The Roundworms”
5) Phylum Annelida “The Segmented Worms”
6) Phylum Mollusca “Think Seafood - Clams, Oysters”
7) Phylum Arthropoda “Insects”
8) Phylum Echinodermata “Starfish”
9) Phylum Chordata - What we consider “animals”
Phylum Porifera – “The Sponges”
Facts About Phylum Porifera
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Examples: Sponges
Irregular body shape (no symmetry)
Lack body tissues
Sessile (don’t move) and found at the bottom of
oceans/lakes
Most primitive animals
These species are hermaphroditic (have both male and
female sex cells). Reproduce sexually by releasing these
cells (only release one type at a time so they don’t fertilize
eachother…think avoiding inbreeding!!)
Also reproduce asexually by budding (broken off pieces can
grow into new species)
Lack nervous system, circulatory system, muscle tissue, etc .
Phylum Cnidaria – “Jellyfish, Coral”
Facts about Phylum Cnidaria
• Examples: Hydra, jellyfish, sea anemone, coral
• Live in marine environment and some freshwater
(hydra)
• 2 forms: free swimming and sessile
• Have true tissues
• Posses radial symmetry
• 2 germ layers: endoderm and ectoderm
• Reproduce sexually (male and female) and some
asexually (by budding)
• Have nerve, muscle, and digestive tissues
Interesting Info on Cnidarians
• Did you know…
Cnidarians capture food by
shooting out specialized cells
on their tentacles. These
stinging cells can penetrate
the skin of their prey or
predators and inject toxic
material. This material can
then paralyze the target.
The sting of a jellyfish has
claimed 2x the number of
lives in Australia as compared
to shark attacks!
Phylum Platyhelminthes –
“Flatworms”
Facts about Phylum Platyhelminthes
• Examples: Tapeworm, planarian, fluke
• Live in aquatic and terrestrial habitats; many are
parasites
• Show bilateral symmetry, have 3 germ layers
(endoderm, ectoderm and mesoderm) and lack a
coelom (acoelomate)
• Reproduction: Hermaphrodites, reproduce sexually
with one another, can regeneration from small pieces
(asexual)
• Have true organs (simple ones for digestion and
excretion)
• Primitive brain with two nerve cords
Interesting Info on Platyhelminthes
• Many of these
species are parasites
of humans.
• One specific example
is the tapeworm
• Inside your body, a
tapeworm can grow
up to 7 meters long!!
Phylum Nematoda – “Roundworms”
Facts about Phylum Nematoda
• Examples: Ascaris, Hookworm
• Live in aquatic and terrestrial habitats; some are
parasites
• Free-living, small, and relatively harmless
• Bilateral symmetry, 3 germ layers,
pseudocoelomates (“false” coelom)
• Reproduce sexually (separate sexes)
• Digestive organs are present
• Have a primitive brain and 2 nerve cords
Interesting Info on Phylum Nematoda
• A small number of this group are
human parasites
• One example is Trichinosis. This is
a disease causes by a roundworm
parasite. The parasite can be
found living in undercooked pork
and transmitted to humans when
we ingest it.
• Symptoms include abdominal
pain, diarrhea, nausea and later
muscle aches, itching, fever, chills,
and joint pain.
• Roundworms are also common
parasites of our pets (cats/dogs)
Phylum Annelida – “Segmented
Worms”
Facts about Phylum Annelida
• Examples: Earthworm, leeches
• Live in aquatic and terrestrial habitats; a few are parasites
• Show bilateral symmetry, 3 germ layers, and have a true
coelom
• This group of worms is “segmented” meaning it has
repeating units. This is an advantage because it permits
greater specialization (head, thorax, abdomen)
• Reproduce sexually even though they are
hermaphrodites
• Have a simple circulation system and digestive organs
• Nervous system includes an advanced brain, large nerve
cord, and smaller nerve-like cells called ganglia
Phylum Mollusca – “Seafood”
Facts about Phylum Mollusca
• Examples: Clam, oyster, octopus
• Live in aquatic and terrestrial habitats
• Have bilateral symmetry, 3 germ layers, and a
true coelom
• Reproduce sexually. Some are hermaphroditic
and some have separate sexes (just male or
female parts)
• Have an open circulatory system
• Filter-feeders
• Primitive brain and light receptors
Phylum Arthropoda – “Insects”
Facts about Phylum Arthropoda
• Examples: Crayfish, spider, mosquito
• Found everywhere
• Bilateral symmetry, 3 germ layers, have a coelom
and undergo metamorphosis (change body form
at different life stages i.e. caterpillar to butterfly)
• Reproduce sexually…are either male/female
• Open circulatory system
• One-way digestive tube (with mouth and anus)
• Have definite brain with 2 nerve cords
Importance of Arthropoda
• One of the most successful
groups of species
• Insects are found everywhere…
• There are over 750, 000 different
species
• Insects are needed to pollinate
plants and grain crops
• Also carry diseases (malaria and
sleeping sickness)
• Compete with humans for
food…Billions of dollars every
year are spent on insecticides to
kill insects.
Phylum Echinodermata – “Starfish”
Facts about Phylum Echinodermata
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Examples: Starfish, sea urchin, sand dollar
Found in aquatic habitats
Radial symmetry/3 germ layers/have a coelom
Reproduce sexually….separate male and female.
Also able to regenerate (asexual reproduction).
For example, a broken off piece of starfish can
grow into a new starfish
• Open circulatory systems
• 1 way digestive tube (separate mouth and anus)
• Have nerve cords
Phylum Chordata – “Animals”
Facts about Phylum Chordata
• Members of this phylum are known as the “vertebrates.” A
vertebrate is an organism that has a backbone.
• Only 5% of all known species belong in this group
• Members of this group, at some point in their lives, all have
a backbone, nerve cord, and gills
• Examples: Whale, Humans, Dogs, Fish, Frog
• What type of symmetry do they possess?
• 3 germ layers and a true coelom
• Reproduce sexually….separate males and females
• Complex heart and closed circulatory system
• Large brain, protected by a skull, and advanced nervous
system
Class Mammalia
• There are many classes that belong to the
phylum Chordata, but the most common to us
is the Class Mamalia.
• All members of this group are warm-blooded,
air breathing, 4-legged vertebrates that are
covered with hair and sweat glands.