Protosomes

synapomorphies of bilateria

• gain of mesoderm

• bilateral symmetry

two sub-clades that make up bilateria

protosomes and deuterostomes

what is the blastopore

the pore/hole that forms when cells fold inward and form the archenteron during gastrulation

difference in blastopore fate in protosomes and deuterostomes

protostomes (mouth first): blastopore becomes the mouth

deuterostomes (mouth second): blastopore becomes the anu$

two main subclades of protosomes

• lophotrochozoa

• ecdysozoa

what are lophophores and what organisms have them

mouths with ciliated tentacles

• byrozoans, brachiopods, rotifers, flatworms

what are trachophore larvae and which animals have them

distinct larval stage with band of cilia

• mollusks, annelids, and entoprocts

what is ecdysozoa

animals that undergo ecydysis/molting

bryozoans

sessile organisms, use lophophores to capture bacteria and planktonic eukaryotes. Form large colonies that look like corals (convergent evolution)

what are flatworms

soft bodied animals with few organs and incomplete digestive tract

3 examples of flatworms and details about each

• planarian: free-living predator, asexual fragmentation, model organism used to study regeneration

• blood flukes: parasite that causes schistosomiasis (kills 200k per year)

• tape worms: parasite in large intestine, larvae infect brain and cause neurocysterosis

details about rotifers (mouths, complexity, reproduction)

• ciliated mouths

• very complex

• reproduce sexually, some reproduce asexually via parthenogenesis

brachiopods

• sessile

• use lophophores

• look like clams but aren’t even mollusks

• lophophores between brachiopods and bryzoans likely convergent evolution

most complex and diverse lophotrochozoans

annelids and mollusks

how are the annelids and mollusks larval stage categorized

trochophorae larvae

annelids

segmented worms

sedentary annelids

earthworms and leaches

subclades of mollusks and organisms in each

• bivalves: clams, oysters

• gastropods: snails, slugs, sea hares

• cephalopods: octopi, squids

synapomorphy of mollusks

mantle that produces calcium carbonate shell in most mollusks

what do all extant cephalopods lack and what is this an example of

a shell (except for nautiluses) - evolutionary reversal

synapomorphy of ecdysozoa

cuticle that sheds

what does ecdysozoa’s cuticle protect from

dehydration on land

first animals to colonize land

ecdysozoans

members of ecdysozoan phyla

nematodes, tardigrades, and arthropods

nematodes

unsegmented worms that possess a cuticle made of collagen

• free living predators, many are parasitic

what disease do nematodes cause

block lymphatic ducts and cause elephantiasis

important model organism where every cell division can be tracked. used to discover programmed cell death and siRNAs

c. elegans

microscopic animals with unsegmented appendages that can withstand extreme conditions

tardigrades

arthropod subclades

• chelicerata: arachnids

• myriapods: millipedes and centipedes

• crustaceans

• hexapods: insects

arthropods synapomorphies

• segmentation

• jointed appendages

• exoskeleton (chitin evolved via convergent evolution)

• tracheal system: allows them to breathe through exoskeleton

which two groups used to be grouped together as “segmented protosomes”

annelids and arthropods

arthropods are more closely related to ____ than annelids

nematodes

annelids are more closely related to _____ than arthropods

lophotrochozoans

the golden bug

drosophila melanogaster