Download File - Down the Rabbit Hole

INVERTEBRATES
Porifera, Cnidaria, Platyhelminthes, Nematoda

Animals that lack vertebrae (classed by a characteristic they don’t have.)

97% of all species on Earth are invertebrates.
PORIFERA: PORE BEARING
AKA- SPONGES
PORIFERA
•Representatives
Sponges, about 9000
species
•Habitat
Marine and freshwater,
usually in shallow water,
sensitive to pollution
PORIFERA
Sponges lack
symmetry, lack
nerves, lack
muscles, lack
tissues, lack
cephalization,
and lack a body
cavity
Sponges are so unlike
other animals that early
naturalists classified
them as plants.
Terminology
PORIFERA
• spongocoel one central body cavity
• osculum – opening to the spongocoel
•ostia – pores on the outside of the
body through which water (containing
food and oxygen) enters
• choanocytes collar cells, flagellated
cells that keep water currents moving
through the spongocoel
• amoebocytes digest and distribute
nutrients
•spicules – cells with silica or CaCO3
that gives the sponge some support
Sponge Anatomy
a body plan that enables them to “filter feed”
PORIFIRA
•Movement – sessile
•Excretory System
none
•Digestion - filter feeders,
water brought in through ostia
(pores) and circulated in the
spongocoel where choanocytes
digest the food by
phagocytosis (intracellular
digestion)
•Gas Exchange – diffusion,
choanocytes (flagellated) cells
keep a current of oxygenated
water moving through the
spongocoel
•Nervous System
none
•Circulatory System
none
• Skeleton
PORIFERA
none
structures called spongin
(protein fibers) and spicules
(made of either silicon dioxide or
calcium carbonate) provide
support
• Reproductive
System
– Asexually by
budding
– Sexually by
producing sperm
and eggs.
– Many sponges
are
hermaphrodites
PORIFERA
Class Calcarea
Calcareous Sponges
•Sponges are classified
based on the presence
of spongin and the type
of spicules
Class Hexactinellida
Glass Sponges
Class Demospongiae
Demosponges
CNIDARIA: STINGING CELLS
AKA- JELLIES & CORALS
CNIDARIA
• Representatives - Over 10,000 species
– Class Hydrozoa – hydra, Obelia, polyp is dominant
– Class Schyphozoa – jellyfish, medusa is dominant
– Class Anthozoa– sea anemones and corals, only polyp
• Habitat
Mostly marine
• Cnidarians have radial symmetry
• No cephalization
• The digestive cavity is called a gastrovascular
•
•
cavity (gastro= stomach; vascul= a little
vessel)
The one opening in the gastrovascular cavity
serves to ingest food and expel wastes.
The bodies of cnidarians are described in one
of two ways, depending on whether the opening
of the gastrovascular cavity is ventral or dorsal
CNIDARIANS that have the opening and surrounding
tentacles at the top of their bodies have a body
shape called a polyp (polyp = many footed).
CNIDARIANS
that float and
have the opening
and surrounding
tentacles at the
bottom, have a
body form called
a medusa
(medusa = a
jellyfish).
• Terminology
CNIDARIA
– gastrovascular cavity – central body cavity
– polyp - sessile with mouth up
– medusa – medusa is floating, flattened, with
mouth-down
– basal disc – sticky bottom end of the animal
that attaches to surface and allows it to glide
– planula – larvae
– tentacles – structures that capture
prey and shove them into the mouth
– cnidocytes – capsule cell containing a
fine coiled thread, which, when
discharged, functions in defense and
prey capture
– nematocysts – small barbed harpoon,
the stinging component of cnidocytes
CNIDARIA
 Symmetry  Skeleton
- radial
- none
- supported
by water
 Body Cavity/germ layers
- one opening
- diploblastic two tissue
layers
- has a mesoglea but
that isn’t a true germ
layer
CNIDARIA
• Movement – Polyp is sessile
or free-floating. Medusa is
free-floating or can move by
weak contractions
• Digestion – tentacles grab
and push prey into the
gastrocoel where it is
digested extracellulary. Note
that even though the
gastrocoel functions like
stomach, it can’t be called
that because it has only one
opening.
• Gas Exchange – Diffusion, no
specialized organs
• Excretory System
CNIDARIA
none
• Circulatory System
none
• Nervous System
none
• Reproductive System
Some asexual
reproduction by
budding, some sexual
reproduction with
sperm and eggs.
Asexual
CNIDARIA
Hydra will periodically develop lumps on
the sides of their bodies that are
either testes or ovaries. These make
and release sperm or eggs, which then
join to form a zygote, which eventually
grows into a new hydra.
Hydra also reproduce asexually by a
process known as budding in which a
new, small Hydra begins to grow from
the side of a large Hydra, eventually
pinching off when it is fully formed
Class Hydrozoa
Hydrozoa
Lifecycle
Class Scyphozoa
Class Anthozoa
PLATYHELMINTHES:
FLATWORMS
FLATWORMS
• Flatworms are the
•
•
simplest of the worm
groups.
There are about
20,000 species.
They are found many
places and can be free
living or parasitic.
FLATWORMS
• Example
organisms
include
planaria
FLATWORM ANATOMY
This is not a body cavity
Single
opening to
G. cavity
Use cilia
to move
FLATWORMS
• tapeworms,
FLATWORMS
• and flukes
Schistosoma, a Fluke
Complex life
cycle, but
still a
flatworm
FLATWORMS
• This phyla is the first to demonstrate
bilateral symmetry and cephalization
• Flatworms can reproduce asexually
(regeneration) and sexually (hermaphrodites)
• The digestive tract of flatworms has only one
opening
FLATWORMS
Endoderm
Ectoderm
Digestive Cavity
Mesoderm
•Though flatworms have a tissue layer of
ectoderm, mesoderm, and endoderm, they
do not have a body cavity (acoelomate)
NEMATODA
AKA: ROUNDWORMS
ROUNDWORMS
• Roundworms are slightly more advanced than
flatworms and are about 15,000 species
strong
• Roundworms can be found in terrestrial
habitats, marine water, and freshwater. Due
to their ability to live in a large number of
environments, they are one of the most
abundant animals on Earth
ROUNDWORMS
 Pseudocoelomate; they
have a body cavity
between the outer body
wall and gut (yet the
mesoderm does not
completely line the body
cavity)
body cavity
intestine
ROUNDWORMS
• Other characteristics of this phyla include
cephalization and bilateral symmetry
• The digestive tract of roundworms has 2
openings; this is the first group to display
such an advancement
• Many roundworms are parasitic and cause
diseases:
ROUNDWORMS
• Trichinosis is a food borne
disease caused by an intestinal
roundworm (not common in the
U.S.). It is contracted through
raw or undercooked meat of
infected animals. Symptoms
include muscle soreness and pain,
swelling of the upper eyelids,
sweating, chills, fever, diarrhea.
ROUNDWORMS
• Hookworm- usually in tropical third-world
•
•
areas, contracted by exposure to human
waste
The larvae of hookworms can enter
through broken skin (usually the feet)
Hookworm is easily treatable
ROUNDWORMS
•Pinworm- symptoms include itching
near rectum at night due to egg laying;
young school age children at risk
• Microfilaria- causes
elephantitis and is
transmitted by a
mosquito; affects
lymph system and
leads to severe
swelling
ROUNDWORMS
• African eye worm:
contracted through
a fly bite
•Canine and
feline heartworm
ROUNDWORMS
• Guinea worm:
contracted through
contaminated water;
after growing for
about a year it
creates a blister on
the skin surface and
emerges from it;
the worm can’t be
pulled out (can take
months or years)
ROUNDWORMS
• Ascaris: often, no
•
symptoms or abdominal
pain
When body is stressed,
the worm will try to
escape
Stay tuned for Part Two
INVERTEBRATES