lab 7 - protosomes

symmetry, tissues/organs, body cavity type, embryonic development, and DNA evidence

what are the 5 ways that animals are classified?

acoelomates

triploblastic animals that lack a body cavity

(ex: flatworms)

pseudocoelomates

triploblastic whose body cavity contains only a line ectoderm -> creates a "fake" cavity

(ex: nematodes)

coelomates

triploblastic whose body cavity contains a lined ectoderm AND endoderm

(most complex, specialized animals have this)

the importance of body cavities

what is being described?

- allow independent organ movements

- permit higher complexity in animals

- allow formation of circulatory system

protosomes

animals whose blastopore becomes the mouth and the coelom forms through splitting

schizocoelus

solid masses of mesoderm split to form coelom (protostomes)

ecdysozoa

supergroup of protostomes

- characterized by periodic molting of their exoskeleton

- includes: roundworms and arthropods

lophotrochozoa

supergroup of protosomes

- characterized by presence of spiral cleavage

- have lophophore or trocophore

- includes: platyhelminthes, annelida, mollusca, and brachiopoda

lophophore

a crown of ciliated tentacles that function in feeding

trocophore

a free-swimming, ciliated larval stage of many worms and some mollusks

phylum nematoda

phylum that includes roundworms (vinegar eels, trichinella, ascaris)

- pseudocoelomates

- complete digestive tract

- dioecious (separate sexes)

- nervous system: dorsal + ventral cords

phylum arthropoda

phylum that includes insects, arachnids, and crustaceans

- segmented body + jointed appendages

- exoskeleton made of chitin

- open circulatory system

- have ventral nerve cord

subphyla myriapoda

subphyla characterized by their many legs

- centipedes -> carnivores (1 leg pair per segment)

- millipedes -> herbivores (2 leg pairs per segment)

subphyla chelicerata

subphyla that's characterized by their lack of antennae

- have chelicerae = fangs

- have 6 appendages (4 pairs of legs, 1 pair of chelicerae, 1 set of pedipalps)

- includes spiders and horseshoe crabs

subphyla hexapoda

subphyla that includes insects

- have 3 pairs of legs

- usually have wings

- spiracles + trachea (breathing system)

subphyla crustacea

subphyla that includes lobsters, crabs, isopods, krills, etc.

- mainly marine

- have 2 antennae pairs

- breathe w/ gills

phylum platyhelminthes

phylum that includes flatworms

- acoelomates

- incomplete digestive system

- no circulatory system

- hermaphrodites (have both male and female reproductive organs)

class turbellaria

planarians

- free living animals

- photoreceptive eye spots

- have flame cells

class trematoda

flukes

- parasites

- complex life cycle

- have suckers

class cestoda

tapeworms

- no digestive system

- parasites that absorb nutrients from host

- have proglottids for reproduction

phylum annelida

segmented worms, earthworms, leeches

- closed circulatory system

- have trocophore larval stage

- have ventral nerve cord

- segmented by septa

phylum mollusca

soft bodied animals

- mostly open circulatory system

- body plan:

-> foot - movement

-> visceral mass - organs

-> mantle - shell production

-> radula - feeding

class polyplacophora

chitons

- have shell w/ 8 plates

class gastropoda

snails and slugs

- have tentacles w/ eyes

class bivalvia

clams, mussels, scallops, oysters

- filter feeders w/o radula

- have 2 shells

class cephaloda

squid and octupus

- most advanced animals in phylum mollusca

- 3 hearts and complex eyes

phylum brachipoda

brachiopods

- sessile lophophorates

- have 2 shells

- u-shaped digest tract (incomplete or complete)

class inarticulata

simple brachiopods w/ no hinge and soft shells

class articulata

complex brachiopods w/ complex hinges, teeth, and hard shells