· Multicellular
· Eukaryotic
· Heterotrophic
· Coordinate activities
· Invertebrates vs. Vertebrates
· Divided based on zygote development, body cavities and symmetry
1. Zygote è
2. Blastula (hollow sphere) è
3. Gastrulation (blastula begins to fold inwards) è
4. Germ Layers
a. Ectoderm – skin, nervous system
b. Endoderm – lining of the gut
c. Mesoderm – circulatory organs, reproductive, urinary, muscular systems
1. Simple animals – one opening
2. Complex animals – 2 openings
3. Coelem – body cavity, lined with epithelial cells (peritoneum)
4. Psedudocoelem
1. Asymmetry – simplest animals
2. Bilateral symmetry
a. R and L halves are mirror images
b. Higher animals
c. True head region (cephalization)
3. Radial symmetry
a. Symmetric about a central axis
b. Not highly adapted for movement
1. Characteristics
a. Simplest animal
b. Lacks muscle
c. No tissue or organs (some specialized cells)
d. Sessile
2. Nutrition
a. Collar cells create currents that move water into/out
b. Food particles trapped and ingested
3. Reproduction
a. Budding
b. Hermaphrodites
i.Produce both sperm and egg, however only 1 gamete at a time
ii. Fertilized egg è free swimming larva è metamorphosis
Phylum Cnidara – hydra, jellyfish, sea anemones
1. Characteristics
a. Radial symmetry
b. Endoderm and ectoderm therefore true tissues in aduts
c. 2 body shapes
i.medusa: free swimming, bell shape (jellyfish)
ii. polyp: tube like, mouth surrounded by tentacles, attached
2. Nutrition
a. Capture food with tentacles surrounding the mouth
b. Inject toxic material into prey using specialized cells called cnidocytes
3. Reproduction
a. Sexual
i.Male and female medusa
ii. Fertilized egg è free swimming larva è attaches to bottomè
iii. Polyp reproduces by budding (bud develops into medusa)
Phylum Platyhelminthes – flatworms, planaria
1. Characteristics
a. Bilateral symmetry, cephalization
i.2 nerve cords
ii. Sensory capabilities
b. Organs
i.Rudimentary excretory system
c. No coelom (acoelomate)
d. Free living & parasitic forms
i.Parasitic forms may not have digestive system but has evolved reproductive strategies
ii. Parasitic forms have tegument
2. Nutrition
a. Single opening
1. Characteristics
a. Pseudocoloemate which is important because:
i.Ciculation
ii. Movement
iii. Organ function
iv. Food movement
v. Digestion and waste removal
b. Complete digestive tract
c. Anterior ganglion
d. No respiratory/circulation systems
e. Parasitic worms are in the minority
i.Tricinella spiralis
Phylum Annelida – Segmented Worms
1. Characteristics
a. Segmentation – repetition of body units that contain similar structures
b. True coelom
2. Three Major Classes
a. Oligochaeta - Common earthworm
1. Important to agriculture
2. Peristalsis- rhythmic, wavelike contraction of muscle
3. Mouth/Pharynx to ingest food è esophagus èintestine è anus
4. Closed circulatory system
b. Polychaeta – Marine Worms
1. Projections on each segment
c. Hirudinea – Leeches
Phylum Mollusca – Clam, Squid, Slug etc.
1. Characteristics
a. Extremely diverse
b. Larval stage
c. Coelom allows for more space for more complex internal organs
i.Longer digestive tract (= better digestion)
ii. Larger reproductive organs
d. Circulation
i.Larger body requires more sophisticated circulation system
ii. Vessels
iii. Contraction of muscular heart(s)
2. Class Gastropoda – snails
3. Class Bivalvia – Clams, mussels, oysters, scallops
a. Filter feeding mechanism
4. Class Cephalopoda – Squids, Octopus
a. Water jets for swimming (catch prey)
b. Developed nervous system
Phylum Arthropoda
1. Characteristics
a. Evolved from segmented ancestors (may be fused together)
b. Jointed appendages
c. Well-defined head
d. Exosekeleton
i.Protection, heavy
ii. Chitin
iii. Inner layer is thinner to protect joints
iv. Limits size of arthropod
v. Molting
2. SubPhyla Crustacea – lobsters, crayfish, crabs
a. 2 pairs of antennae
b. 3 pairs of feeding appendages
c.
3. Class Arachida – spiders, scorpions, ticks, mites
4. Class Insecta – Insects
Phylum Echinodermata – star fish
1. Pentamerous radial symmetry
2. Larval stage has bilateral symmetry