1. Chapter 7
Marine Invertebrates

2. Animal Symmetry
Animals are often grouped and classified according to the geometric symmetry of their bodies.
Bilateral symmetry: body can be divided in half by a single plane. The halves on each side of the plane are a near mirror image.
Radial symmetry: body parts are arranged around a central axis. Body can be split like a pizza into identical parts.

3. Marine Animals Terms to Know Plankton – cannot swim against a current
Nekton - can swim against a current
Benthic - lives on the sea floor
Sessile – lives attached to a surface
Plankton
Nekton
Benthic
Sessile

4. The Classification Taxa
Kingdom – Animalia, Plantae, Fungi, Protista, Bacteria
Phylum
Class
Order
Family
Genus
▪Species
Human Classification:
Kingdom: Animalia
Phylum: Chordates
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: sapiens

5. Invertebrates Soft-bodied organisms without a backbone
Major phyla in order of increasing complexity
Porifera
Cnidaria
Worms
Mollusca
Arthropoda
Echinodermata

6. Phylum: Porifera “Hole Bearing”
Examples: sponges
The most primitive animals
No symmetry
Sessile (doesn’t move) and benthic (lives on the bottom)
Almost all are marine
Depend on currents for feeding and sexual reproduction.
No digestive, circulatory, respiratory, or nervous system

8. Phylum: Cnidaria “Nettle”
Examples: corals, anemones, jellyfish, hydra
Contain stinging cells: nematocysts
Used to stun prey
Radially symmetrical (can be divided like a pizza and are equal)
Size range: microscopic to 20m (60 feet!)
Carnivorous: stun prey and use tentacles to move it to mouth

9. Two forms: polyp and medusa
Polyp: sessile, mouth and tentacles face up
Medusa: plankton, mouth and tentacles face down
Simple digestive and nervous systems

11. Worms Bilaterally symmetrical: two equal halves
Possess digestive and nervous systems (small brain)
Well formed tissues and organs
Three phyla:
Platyhelminthes
Nematoda
Annelida

12. Phylum: Platyhelminthes – flat worms
Ex – flukes, tapeworms, marine flatworms
Predators and scavengers; some are parasites
Smaller than 3cm
reproduce asexually and sexually; individuals have both testes and ovaries.

13. Phylum: Nematoda – round worms
Ex. hookworms
Complete digestive system (mouth and anus)
Reproduce sexually – distinct male and female forms
Present in almost all types of environments
Most are microscopic parasites
Phylum: Annelida – ring worms
Ex. Earthworms, leeches, marine tubeworms and polychaetes
Bodies divided into segments
Each segment can have its own circulatory, respiratory, excretory, nervous, muscular and reproductive system

14. Platyhelminthes
Annelida

15. Phylum: Mollusca = soft bodied
Ex. Clams, chitons, squid, octopus, snails
Have an external or internal shell
Bilaterally symmetrical
Well-developed nervous and digestive systems

16. Gastropoda: “stomach foot”
Phylum: Mollusca: Three main classes:
Gastropoda: “stomach foot”
Snails, conch, abalone
1 External shell
Bivalvia: “two door”
Clams, oysters, scallops
2 External shells
Cephalopoda: “head foot”
Squid, octopus
Internal shell

17. Draw and label Pg. 116 figure 7.1a - Porifera
Pg. 119 Figure 7.6 sectional view - Cnidaria
Pg. 132 figure cephalopoda

18. Phylum: Arthropoda “joint foot”
Examples:
Lobster, crabs, krill, shrimp, crayfish, amphipods, barnacles, copepods
Largest phyla
Strong exoskeleton
Striated muscle (quick movement)
Articulated appendages: can bend
Classes: crustacea (sea), insecta (land)

19. Crustaceans

20. Phylum: Echinodermata hedgehog skin
Ex. Sea Stars, sand dollars, urchins, sea cucumber
All are marine
Radially symmetrical: based on five
Larvae are bilaterally symmetric
Lack eyes, heart, and brains
Calcified endoskeleton covered by skin
Water vascular system
Reproduce sexually
Slow moving
Benthic
Regeneration of limbs, organs, or spines

23. Copy this for the study guide!
Oral surface Aboral Surface
Eyespot
Ambulacral groove
Tube feet
Madroporite
Mouth
Arm
Central disk