all phylum invertebrate
TRANSCRIPT
Animal Origins and the Evolution of Body Plans
Animals
• 1. multicellular heterotrophs
• 2. structural proteins
• 3. unique tissues
Animals
• 4. diploid with development proceeding via a blastula
zygote blastula gastrulacleavage gastrulation
Evolutionary Relationships
• monophyletic group
• differences lie in body plans and developmental patterns
Body Plans
• based on symmetry– asymmetric– radial – bilateral
• cephalization is correlated with bilateral symmetry
Body Plans
• Hox cluster– found in all bilaterally symmetrical
animals– determines morphological development
• e.g. genes that determine head development are the same in flatworms and humans
Developmental Differences
• germ layers– endoderm
– mesoderm
– ectoderm
• diploblastic vs. triploblastic
Developmental Differences
• body cavities– acoelomate– pseudocoelomate– coelomate
• protostome• deuterostome
Protostome/Deuterostome Characteristics
Characteristic Protostome Deuterostome
Cleavage Pattern
spiral, determinate
radial, indeterminate
Coelom Formation
schizocoelous enterocoelous
Fate of blastopore
mouth anus
Phylum Porifera
• sessile
• no true tissues
• marine and freshwater
Phylum Porifera
• body plan– two layers separated by
mesohyl• amoebocytes• spicules
– spongocoel– osculum– choanocytes– hermaphrodites
Phylum Cnidaria
• blind gut (gastrovascular cavity)
• sessile polyp, floating medusa
• tentacles with cnidocytes– nematocysts
Phylum Cnidaria
• diploblastic (2 germ layers)– mesoglea
• nerve net
• sexual and asexual reproduction
Phylum Ctenophora
• all marine• 8 rows of comb-like
plates • tentacles with
colloblasts• complete gut
Protostomia vs. Deuterostomia
• bilaterally symmetrical
• protostomes– CNS with brain surrounding entrance to a
digestive tract– ventral nervous system– free floating larva
Protostomia vs. Deuterostomia
• deuterostomes– dorsal nerve system
Phylum Platyhelminthes
• bilateral symmetry• no body cavity• triploblastic• marine and freshwater• free-living and symbiotic
Platyhelminthes
• dorsoventrally flattened– surface area to volume
• gastrovascular cavity
• sexual and asexual reproduction
Class Turbellaria
• majority are free-living– e.g. planarian
• move using cilia • flame cells for water
balance• regeneration• hermaphrodites
Classes Monogenea and Trematoda
• called flukes
• filled with reproductive organs
• mostly parasitic
Class Cestodea
• tapeworms
• all parasitic
• proglottids
Phylum Annelida
• protostome coelomate• segmentation• closed circulatory system• metanephridia• hermaphrodites
– cross fertilize
Class Polychaeta
• mostly marine
• parapodia with setae
Class Oligochaeta
• terrestrial and freshwater
• few setae
• no parapodia
• cutaneous gas exchange
Class Hirudinea
• leeches• freshwater or moist
areas• parasitic or
carnivorous• no setae
Phylum Mollusca
• protostome coelomate• marine and freshwater• open circulatory system• hermaphroditic and dioecious• 3 part body plan
– foot– visceral mass– mantle
Class Polyplacophora
• termed chitons
• 8 dorsal plates
• most are marine herbivores
Class Gastropoda
• marine, freshwater, and terrestrial
• may possess shells
• gills or primitive lung
Class Bivalvia
• divided shells hinged
• gills for feeding and gas exchange
Class Cephalopoda
• carnivorous, marine• modified foot
– tentacles and part of head
• move via propulsion of water from mantle• closed circulatory system• complex brain