1. Invertebrates

2. Invertebrates Nearly all animals are invertebrates (95%)
Invertebrates are animals that lack backbones
Let’s take a survey of the major phyla of animals! 

3. Single-celled, protistanlike ancestors
Chordates
Major Animal Phyla
Echinoderms
Arthropods
Annelids
Coelomate
Ancestry
Mollusks
Rotifers
Roundworms
Bilateral
Ancestry
Flatworms
Radial
Ancestry
Cnidarians
Sponges
Multicelled
Ancestry
Figure 25.2 Page 415
Single-celled, protistanlike ancestors

4. Symmetry Bilateral Radial posterior dorsal ventral anterior
Figure 25.3 Page 416

5. The Gut Region where food is digested and then absorbed Saclike gut
One opening for taking in food and expelling waste
Complete digestive system
Opening at both ends; mouth and anus

6. Body Cavities - Acoelomate
epidermis
gut cavity
no body cavity; region between gut and body wall packed with organs
Figure 25.4a Page 417

7. Body Cavities - Pseudocoel
epidermis
gut cavity
unlined body cavity (pseudocoel) around gut
Figure 25.4b Page 417

8. lined body cavity (coelom)
Body Cavities - Coelom
gut cavity
lined body cavity (coelom)
peritoneum
Figure 25.4c Page 417

9. Segmentation Repeating series of body units
Units may or may not be similar to one another
Earthworms - segments appear similar
Insects - segments may be fused and/or have specialized functions

10. Animal Origins
Originated during the Precambrian (1.2 billion million years ago)
From what? Two hypotheses:
Multinucleated ciliate became compartmentalized
Cells in a colonial flagellate became specialized

11. Phylum Porifera Representative organism: sponge
Have no true tissues (Parazoa)
Their cells are relatively unspecialized
Sponges are sessile (nonmotile)
Ancient Greeks believed them to be plants
Filter-feeders:
Trap food from the
water that flows
through them
Most sponges are
hermaphrodites
Each individual
produces both
sperm and eggs

12. Sponge Structure Figure 25.7a Page 419 water out
glasslike structural elements
amoeboid cell
pore
central cavity
semifluid matrix
flattened surface cells
water in
Figure 25.7a Page 419
flagellum
microvilli
nucleus

13. Phylum Cnidaria Have stinging cells inside of nematocysts On tentacles
capsule’s lid at free surface of epidermal cell
trigger
barbed thread inside capsule
Figure 25.8 Page 420
nematocyst

14. Phylum Cnidaria Representative Organisms: Jellyfish & Sea Anemones
Have true tissues and radial symmetry
Body plan: sac with a central digestive compartment known as the gastrovascular cavity (mouth & anus)
2 variations on the body plan:
Polyp: sessile, mouth up, waits for prey (sea anemone)
Medusa: floats, mouth down (jellyfish)
Attack prey with tentacles

15. outer epithelium (epidermis) inner epithelium (gastrodermis)
Two Main Body Plans
Polyp
outer epithelium (epidermis)
mesoglea
(matrix)
Medusa
inner epithelium (gastrodermis)
Figure 25.9 Page 420

16. Obelia Life Cycle (Hydrozoan)
female medusa
male medusa
reproductive
polyp
sperm
ovum
feeding polyp
zygote
polyp forming
planula
Figure Page 421

17. Phylum Platyhelminthes
Representative Organisms:
Tapeworms, flukes, & planarians
Bilateral symmetry
Acoelomates –
no body cavity enclosed by mesoderm
Many are parasitic

18. Planarian Organ Systems
flame cell
nucleus
pharynx
cilia
protonephridia
fluid
filters through membrane folds
opening of tubule at body surface
flame cell
Fig a,b Page 422

19. Planarian Organ Systems
brain
nerve cord
oviduct
ovary
genital pore
testis
penis
Fig cd Page 422

20. Flukes: Class Trematoda
Parasitic worms
Complicated life cycle
Larval stage infects a mollusk
Adult infects a vertebrate
Worms mate in human host
Larvae bore into human skin
Larvae form, leave snail
Fertilized egg
Asexual reproduction in intermediate host
Ciliated larva
Figure Page 424
Southeast Asian blood fluke

21. Tapeworms: Class Cestoda
Definitive host
Larvae encysted in muscle tissue
Scolex attaches to host intestinal wall
Intermediate host
Figure Page 424
Mature proglottid with fertilized eggs

22. Phylum Nematoda Representative organism: roundworms Pseudocoelomate
have a body cavity, but not encased by mesoderm
Round worms with tapered ends
Can be parasitic (trichinosis)

23. Roundworms (Nematoda)
False coelom (pseudocoelomate)
Complete digestive system
pharynx
intestine
eggs in uterus
gonad
anus
false coelom
muscularized body wall
Figure Page 423

24. Two Coelomate Lineages
Protostomes
Mollusks
Annelids
Arthropods
Deuterostomes
Echinoderms
Chordates

25. Cleavage Patterns Protostome embryo (spiral cleavage)
Blastopore becomes
mouth
Deuterostome embryo
(radial cleavage)
Blastopore becomes
anus
In-text figure Page 426

26. Phylum Mollusca Representative organisms: Coelomates Protostomes:
snails, slugs, oysters, clams, octopuses, squids
Coelomates
Have a true coelom
Protostomes:
Blastopore becomes mouth

27. Phylum Mollusca Body plan has 3 main parts:
Muscular foot used for movement
Visceral mass covering the internal organs
Mantle covers the visceral mass (may produce a protective shell)

28. Closed circulatory system with heart and accessory heart
Cuttlefish Body Plan
Closed circulatory system with heart and accessory heart
esophagus
Figure Page 429
digestive gland
kidney
stomach
brain
arm
jaw
mantle
reproductive organ
internal shell
siphon
ink sac
heart
accessory heart
tentacle
radula
anus
gill

29. Phylum Annelida Representative Organism: earthworm
Annelids have segmented bodies
Metanephridia (similar to kidneys)
Remove wastes from the blood
Worms are hermaphrodites
Produce both sperm and eggs
Setae provide traction for burrowing in the soil
Earthworms eat their way through the soil