2. What is an invertebrate?
Name some common
invertebrates?
Are snakes invertebrates?
3. Introductory Vocabulary
Invertebrate – animal without a backbone
Coelom – fluid-filled space between body wall and
intestine
Cephalization – sensory organs concentrated at the
anterior end of the organism
Sexual reproduction – gametes are produced and fuse
to form unique diploid offspring
Asexual reproduction – single parent produces
offspring genetically identical to itself
Hermaphrodite – animals with both ovaries and testes
4. Sessile – nonmotile; animal that doesn’t move on its own
Open circulatory system – vessels empty into body spaces
called sinuses
Closed circulatory system – blood never leaves vessels as it
flows through the body
Compound eye – eye with many lenses; found in arthropods
Notochord – stiff rod found in chordates that becomes the
vertebral column in vertebrates
Dorsal nerve cord – bundle of nervous tissue found in chordates
that becomes the spinal cord in vertebrates
Pharyngeal slits – openings in the pharynx found in chordates that
give rise to many structures in vertebrates
10. Class Turbellaria
- planaria
- freeliving
- one of few
freshwater species
“typical” flatworm
Class Cestoda
•Tapeworms
•Parasites
•Attach to intestinal wall
of host with scolex
•proglottids – segments
packed with reproductive
organs
•absorb nutrition from
host –don’t need
digestive system
Class Trematoda
- endoparasites
OR ectoparasites
- complex life cycle
with more than one
host
- primitive or no
digestive system
Schistosoma –
major public health
threat; cause liver
damage
11. Phylum Nematoda - roundworms
- pseudocoelomate
- hydrostatic skeleton
- one-way digestive system
with separate mouth/anus
- Respiration and circulation by
diffusion
- Have longitudinal muscles
- Reproduction – sexual;
complex life-cycle with
multiple hosts
- Most are free-living predators
in the soil
- Some are parasitic;
hookworms, pinworms,
Trichinella
12. Mollusca
• Coelomate; bilateral symmetry;
organs; exoskeleton (shell)
• 3-part body plan:
– Visceral mass – contains
organs
– Mantle – secretes shell
– Foot – locomotion
• Radula – for feeding
• cephalization
• Open circulatory system
• One-way digestive system
• Nephridia – excretory organs
• Respiration – gills, mantle cavity,
and/or diffusion across skin
• Reproduce sexually; many
hermaphroditic; form
trochophore larvae
Classes of mollusks – based
on body plan:
*Gastropoda – stomach-
foot; snails and slugs
*Bivalvia – two-shells;
clams, oysters, mussels
*Cephalopoda – head-foot;
nautilus, squid, octopi,
cuttlefish
14. Major characteristics of all annelids:
• Segmentation – separated by septa; each
segment has organs of each major system
• Cephalization – including cerebral ganglia
• Ventral nerve cord
• Coelom – hydrostatic skeleton
• Organ systems
• Setae – bristles for movement
• Parapodia – fleshy appendages for movement
&/or respiration
15. Earthworms
•Ecologically important scavengers
•Two layers of muscle: longitudinal &
circular
•5 hearts; closed circulatory system
•Nephridia for excretion
•Respiration through epidermis
•Complex digestive system with mouth,
pharynx, esophagus, crop, gizzard, intestine,
and anus
•Sexual reproduction; hermaphroditic;
clitellum forms mucus cocoon to protect
fertilized eggs
16. How are HUMANS separated
into body segments?
•Remnants of segmentation are
visible in the embryo as repeated
blocks of tissue called somites and
in the vertebral column
17. Arthropods
•largest and most diverse phylum; includes insects,
crustaceans, spiders
•segmented bodies – head, thorax, & abdomen or
cephalo-thorax & abdomen; segmentation apparent on
abdomen
•jointed appendages (3, 4 or 5 pairs of walking legs plus
assorted other specialized appendages)
•Respiration: spiracles into trachea; gills; book lungs
•Excretion through Malpighian tubules
•Incomplete or complete metamorphosis
•exoskeleton of chitin *complex muscular system
•ventral nerve cord & brain * open circulatory system
•compound eyes * ecdysis (molting)
18. Millipedes – 2 pairs of legs per segment
- herbivores or detritovores,
but can be really smelly!
- one pair of antennae
Centipedes – 1 pair of legs per
segment
- predators with jaws
- one pair of antennae
19. Insects – 3 body regions: head, thorax,
abdomen
- 3 pairs of legs attached to thorax
- exoskeleton of chitin
- jaws (mandibles)modified for
particular feeding method
- wings are extensions of the
exoskeleton; 0, 1 or 2 pairs
- 1 pair of antennae
- compound eyes
20. Arachnids – spiders, scorpions, ticks, & mites
•Chelicerae – mouthparts modified into pincers or
fangs
•Cephalothorax & abdomen
•4 pairs of walking legs
•No antennae
•Simple eyes
•Spinnerets & silk glands in spiders
•Book lungs in spiders
•Predators that consume liquified food
•Distantly related to horseshoe crabs
mite
tick
21. Crustaceans
Ecologically important – copepods & krill are planktonic crustaceans
that form the basis of many marine food chains
Crabs, lobsters, shrimp, & crayfish are other well-known
crustaceans called decapods – “10 feet”
First pair of walking legs often modified into chelipeds (pincers)
2 pair of antennae
Compound eyes
Sexual reproduction
Cephalothorax covered by carapace
Small appendages on abdomen of of some called swimmerets
Barnacles are sessile crustaceans
Pill bugs (isopods) are terrestrial crustaceans with gills
22. ECHINODERMS
*most complex of the invertebrates
•Only live in salt water (oceans)
•Five-part radial symmetry in adults; larvae are bilaterally symmetrical
•Hard, bumpy, spiny ENDOskeleton composed of ossicles
•Water vascular system with 5 rows of tube feet that aid them in
movement, gas exchange, food capture and waste excretion.
•Skin gills increase respiratory surface area & function in excretion
•Feeding in starfish involves everting stomach out of mouth, digesting prey
outside of body, and then pulling the digested material into the body; other
echinoderms tend to be filter feeds or detritivores
Ex: starfish, sand dollar, sea cucumber, sea urchin, sea cucumber, sea
biscuit, brittle stars, sea lilies, sea daisies, sea pens, feather stars
23. Invertebrate Chordates
4 characteristics of all chordates:
*Notochord
*Dorsal hollow nerve cord
*Pharyngeal gill slits
*Postanal tail
Invertebrate chordates include
tunicates & lancelets; all other
chordates are vertebrates
tunicate
lancelet
