1. Survey of the Invertebrates

2. Kingdom Animalia Animalia: The Cambrian Explosion
Number of organisms in the fossil record is increasing
New groups were evolving fast
Bodies were larger
Skeletons and hard parts like shells

3. Animalia Specialized cells also appeared
Different groups of cells became specialized
As animals evolved they became more complex
Specialized cells organized into tissues
Tissues organized to form organs
Organs evolved into organ systems

4. Animalia: Invertebrates
Animals without a backbone
Many, many invertebrate phyla
Three trends in Invertebrate evolution
Germ layers,
Coelom,
Segmentation

5. Invertebrates: Three germ layers
Common ancestors of multicellular animals evolved two distinct cell layers: an ectoderm layer (outside) and an endoderm layer (inside)
Sponges and some jellyfish have these two only
Other jellyfish and all other animals have a middle layer, mesoderm, that develops into muscles and skeletons

6. Invertebrates: Coelom
The existence of a mesoderm lined cavity inside the body. This is space for organs to grow without being affected by the movement of the body

7. Invertebrates: segmentation
Invertebrates: Body plan built from segmentation
Body is compartmentalized in segments
Allow increases in size with minimal new genetic information (just repeat what you have)
Segments can be specialized for specific functions
Look at the diagrams on page 447

8. Invertebrates: Body plan symmetry
Look at the diagrams on page 448
Some invertebrates have no symmetry
Some have radial symmetry (body parts repeat around an imaginary line drawn through the center of the body)
Some have bilateral symmetry (animals have identical right and left sides, fronts and backs, upper and lower sides)

9. Invertebrates: Habitats
Life in fresh water, salt water and on land;
Some live part of their life in water another part on land and vice versa

10. Survey: 9 phyla of invertebrates
Porifera (sponges)
Simplest of all invertebrates; no symmetry
Cnidaria (jellyfish, sea anemones, hydra)
Mostly salt water, some fresh water, radial symmetry
Platyhelminthes (flatworms)
Simplest animal with bilateral symmetry
Many are parasites
Nematoda (roundworms)
Fist to show a tube like digestive system
Range in size from microscopic to more than a meter long

11. Survey: 9 phyla of invertebrates
Mollusca (mollusks, clams, snails, squids)
Most are salt water, some fresh water
Most have shells; octopus (8 tentacles) and squids (10 tentacles) have no shells
Annelida (segmented worms, earthworms)
Live on land and in water
Echinodermata (star fish, sea cucumbers, sea urchins)
Show five-part radial symmetry
Arthropoda (spiders, crustaceans, insects)
THE most successful of all the animals
Jointed appendages and exoskeleton
Lobsters, shrimps and crabs, spiders, insects
Invertebrate chordates (sea squirts)
Link between invertebrates and vertebrates
Endoskeleton with a notochord