1. Chapter 33 ~
Chapter 33 ~ Invertebrates

2. Parazoa Invertebrates: animals without backbones
Closest lineage to protists
Loose federation of cells (unspecialized); no tissues
Phylum.: (only one) Porifera (sponges)

3. Phylum: Porifera (“pore bearer”)
no distinct tissues or organs
do have specialized cells
no symmetry
sessile (as adults)

4. Eumetazoa: Animals with true body tissue The Radiata, I
Diploblastic
Radial symmetry
Phylum: Cnidaria (hydra, jellies, sea anemones, corals)
tissues, but no organs
two cell layers
predators
tentacles surround gut opening
extracellular digestion
release enzymes into gut cavity
absorption by cells lining gut

5. Stinging cells of Cnidarians
hydra
stinging cell
with nematocyst
trigger
discharged
nematocyst
undischarged
tentacles
mouth
sensory
cell

6. The Radiata, II Phylum: Ctenophora (comb jellies)
8 rows of comblike plates of fused cilia (largest animals that use cilia for locomotion)
Tentacles with colloblasts (adhesive structures that capture prey)

7. Eumetazoa: The Acoelomates
Phy: Platyhelminthes (flatworms, flukes, tapeworms)
Bilateral; no body cavity
Predators, scavengers, parasites
Some cephalization~ development of brain concentration of sense organs in head
ectoderm
mesoderm
endoderm
acoelomate

8. Eumetazoa: Pseudocoelomates, I
Body cavity partially derived from mesodermally derived tissue
Phylum: Rotifera
1st with a complete digestive tract
Hydrostatic skeleton
Parthenogenesis: type of reproduction in which females produce offspring from unfertilized eggs

9. Eumetazoa: Pseudocoelomates, II
C. elegans
Phylum: Nematoda (roundworms)
Very widespread group of animals (900,000 sp. ?)
Cuticle (tough exoskeleton)
Decomposition and nutrient cycling
Complete digestive track; no circulatory system
many are parasitic
hookworm
Trichinella spiralis

10. The Coelomates: Protostomes, I
Phylogenetics debated….
Phy: Nemertea (proboscis and ribbon worms)
Complete digestion and closed circulatory system (blood)
Phy: the lophophorates (sea mats, tube worms, lamp shells)
Lophophore: Circular shaped body fold with ciliated tentacles around the mouth

11. The Coelomates: Protostomes, II
Phylum: Mollusca (snails, slugs, squid, octopus, clams, oysters, chiton)
Soft body most protected by a hard shell of calcium carbonate
Foot (movement), visceral mass (internal organs); mantle (secretes shell); radula (rasp-like scraping organ)
true coelem
increases complexity & specialization of internal organs

12. The Coelomates: Protostomes, III
Phylum: Annelida (earthworms, leeches, marine worms)
True body segmentation (specialization of body regions)
Closed circulatory system
Metanephridia: excretory tubes
“Brainlike” cerebral ganglia
Hermaphrodites, but cross- fertilize
leech
fan worm

13. The Coelomates: Protostomes, IV
Phy: Arthropoda trilobites (extinct); crustaceans (crabs, lobsters, shrimps); spiders, scorpions, ticks (arachnids); insects (entomology)
2 out of every 3 organisms (most successful of all phyla)
Segmentation, hard exoskeleton (cuticle)~ molting, jointed appendages; open circulatory system (hemolymph); extensive cephalization

14. Arthropod groups arachnids crustaceans insects 8 legs, 2 body parts
spiders, ticks, scorpions
crustaceans
gills, 2 pairs antennae
crab, lobster, barnacles, shrmp
insects
6 legs, 3 body parts

15. The Coelomates: Deuterostomes, I
Phylum: Echinodermata (sea stars, sea urchins, sand dollars, sea lilies, sea cucumbers, sea daisies)
Spiny skin; sessile or slow moving
Often pentaradial

16. Invertebrate quick check…
Invertebrates: Porifera, Cnidaria, Ctenophora,Platyhelminthes, Rotifera,Nemertea,Nematoda, Annelida, Mollusca, Arthropoda, Echinodermata
Which group includes snails, clams, and squid?
Which group is the sponges?
Which are the flatworms?
…segmented worms?
…roundworms?
Which group has jointed appendages & an exoskeleton?
Which groups have radial symmetry?
What is the adaptive advantage of bilateral symmetry?
Which group has no symmetry?
Which group includes snails, clams, and squid? Mollusks
Which group is the sponges? Porifera
Which are the flatworms? Platyhelminthes
…segmented worms? Annelids
…roundworms? Nematodes
Which group has jointed appendages & an exoskeleton? Arthropods
Which two groups have radial symmetry? Cnidaria, Echinoderm
What is the adaptive advantage of bilateral symmetry? cephalization
Which group has no symmetry? Profiera