1. Invertebrate Evolution
Chapter 18

2. Defining Animals Invertebrates Vertebrates Commonality majority
Multicellular eukaryotes
Chemoheterotrophs
Obtain food through ingestion
Diploid (2n) organisms reproduce sexually
Nonliving substances produced
Facilitate movement
Provide support

3. Classifying Animals
‘Body plans’ used for morphologically based phylogenetic trees
Tissue organization
Symmetry
Embryonic development
Body cavity
Hypotheses only
DNA discoveries maintain constant restructuring
Kingdom Animalia

4. Tissue Organization 2 or 3 layers of cells
Diplo- or triploblastic
Phylum Porifera excluded
Gastrulation of blastula forms germ layers
Endoderm = digestive tube, liver, and lungs
Ectoderm = outer covering and some nervous systems
Mesoderm = muscles and bone

5. Symmetry Asymmetry Radial symmetry Bilateral symmetry Most sponges
Top and bottom, but no front, back, or sides
Sessile or drifts
Bilateral symmetry
Anterior and posterior, dorsal and ventral
Most demonstrate cephalization
Motile with complex movements

6. Embryonic Development
3 germ layer animals
Based on fate of gastrula
Deuterostomes
Chordates and echinoderms
Protostomes
All others

7. Body Cavities Only bilateral, 3 germ layer animals
Presence or absence of a fluid filled space called a coelom
Coelomates
Pseudocoelomates
Acoelomates
Allows independent organ movement and growth
Hydrostatic skeleton

8. Phylum Porifera (Sponges)
Asymmetrical, sessile, aquatic animals
Suspension feeders
Water pores osculum
Cellular organization
Choanocytes move water in
Traps food in mucus
Amoebocytes digest food and produce skeletal support
Spicules: mineralized material
Spongin: flexible protein
No muscles or nerves
Hermaphrodites
Reproduce by budding of fragmentation
Produce toxins for protection
Used for antibiotics

9. Phylum Cnidaria (Cnidarians)
Radial symmetry
Polyp, medusa, or both
Diploblastic with inner mesoglea
Creates hydrostatic skeleton
Single opening to a gastrovascular cavity = sac plan
Simplistic muscles and nerve net
Facilitates movement
Cnidocytes in tentacles to capture and immobilize prey

10. Phylum Platyhelminthes (Flatworms)
Bilateral, triploblastic, acoelomate, sac plan
Planarians (free-living)
Simple brain, eyespots, auricles, and branched gastrovascular cavity
Live on underside of rocks in freshwater
Flukes (animal parasites)
Suckers and interior almost all reproductive organs
Larval intermediate stage
Pinch in half to reproduce
Tapeworms (animal parasites)
Scolex, no mouth (absorption), hemaphrodites, eggs released from end (proglottids) in feces
Larval intermediate in prey species develop into adults in predators

11. Phylum Nematoda (Roundworms)
Pseudocoelomate, tube within a tube plan, separate sexes, and lateral muscles
Can shed cuticle, outer covering when grows
Free-living decomposers in soil (C. elegans)
Parasitic
Dog heartworm
Mosquito vector
Trichinella spiralis
Uncooked pork
Pinworms
Hook worms
hookworms
heartworms
pinworms
Trichinella

12. Phylum Mollusca (Molluscs)
Coelomates with 3 part body plan
Foot: muscular organ for locomotion,
attachment, or feeding
Visceral mass: contains internal organs
Mantle: surrounds visceral mass and
may secrete shell; cavity for gills or lungs
Feed via a radula
Most separate sexes, except snails
Open circulatory system, blood not confined to vessels (except cephalopds)
Neural ganglia connected by nerve cord
Advanced sensory systems in cephalopods

13. Mollusc Classes Class Gastropoda (snails and slugs)
Head w/ eyes
Only terrestrial species; no gills
Class Cephalopoda (squids and octopuses)
Mouth at end of foot, shell small or absent
Most advanced invertebrate brain and sense organs (eyes)
Siphon for steering movements
Class Bivalva (scallops, oysters, and clams)
Paired hinged shells
Suspension feeders
Mantle with gills

14. Phylum Annelida (Segmented Worms)
Segmentation
Longitudinal and circular muscles
Closed circulatory system
Class Oligochaeta (earthworms)
Hermaphroditic, exchange sperm
Solid ventral nerve cord, anterior brain, and a ganglia in each segment
Nephridia for excretion
Unsegmented, compartmentalized digestive system
Nutrients diffuse across body wall

15. Annelida Classes (Cont.)
Class Polychaeta
Largest class
Marine organisms
Segmented appendages for mov’t or gills
Live in tubes of mucus and sand
Class Hirudinea (leeches)
Blood-sucking
Release an anesthetic and anticoagulant
Consume 10X’s weight
Medicinal uses

16. Phylum Arthropoda (Arthropods)
Most successful phylum (1,000,000+ species)
Exoskeleton (hydrostatic earlier)
Cuticle of protein and chitin for protection and joint attachment
Molted with growth, eaten for nutrients
Segmentation
Head, thorax (fused is cephalothorax), and abdomen
Sensory, protection and walking, and swimming respectively
Jointed appendages
Open circulatory system
Gas exchange
Aquatic  gills
Terrestrial  spiracles
Advanced sensory systems

17. Arthropd Linneages Chelicerates (arachnids) Millipedes and centipedes
First terrestrial carnivores
Hollow mouth appendages; may deliver venom or toxins
E.g scorpions (night), spiders (day), and ticks/mites
Millipedes and centipedes
Herbivores with 2 leg sets per segment
Carnivores (poisonous) with 1 leg set per segment
Crustaceans
Insects
70+ % all known animal species
Unrivaled evolutionary success
Flight
Waterproof cuticle
Life cycle complexity

18. Class Insecta Life cycles Body plan Coloration
Complete and incomplete metamorphosis
Larvae and adult with different roles
Only adults can reproduce or have functional wings
Food sources differ  enhances adaptability
Body plan
3 parts: head, thorax, and abdomen
Embryonic segments develop independently
3 pairs of legs, wings not at cost to legs
Mouthparts for food sources  few limits
Coloration
Camouflage, mimicry, and coloration from independent development
Gene regulation role

19. Phylum Echinodermata
External radial symmetry as an adult, bilateral as larvae
Ca2+ plates form endoskeleton
Locomotion, feeding, and gas exchange via tube feet
Water vascular system
Mouth and stomach adaptations
Capable of regeneration
Deuterosomes
Include sea stars, urchins, and same dollars