protostomes

most animals are...

protostomes

important model organisms in protostomes

fruit fly: Drosophila melanogaster

what are the two major groups of bilaterally symmetric, triploblastic, coelomate animals?

protostomes and deuterostomes

what are the two monophyletic groups of protostomes?

Lophotrochozoa and Ecdysozoa

Lophotrochozoan

- inspired by the presence of a feedig structure called a lophophore and type of larva called a trochophore

lophophore

specialized structure that rings the mouth of these animals and functions in suspension feeding

Trochophore

type of larva common in several phyla of lophotrochozoa

what is the primary contrast between lophotrochozoans and ecdysozoans?

The methods of growth

How do ecdysozoans grow?

by molting

molting

shedding of the soft cuticle or hard exoskeleton.

what do the cuticle and exoskeleton serve as from predators in ecdysozoans?

protection

what are the most prominent phyla in ecdysozoans?

roundworms (nematoda) and arthropods (arthropoda)

T/F all protostomes are triploblastic bilaterians and undergo similar embryonic development

True

ectoderm

outertube

endoderm

inner tube

mesoderm

between the two tubes

coelom

- functions as a hydrostatic skeleton that is the basis of movement.

tagmata

Prominent body regions in arthropods, such as the head, thorax, and abdomen

How are arthropods distinguished?

by their jointed limbs and chitinous exoskeleton

hemocoel

spacious body cavity that provides space for internal organs and circulation of fluids in arthropds

Three major components of the molluscan body plan

foot, visceral mass, mantle

foot

a large muscle located at the base of the animal and usually used in movement

visceral mass

contains most of the internal organs

mantle

tissue layer that covers the visceral mass and forms the mantle cavity

Echiurans

a type of annelid that deposits feed using proboscis

proboscis

an extended structure in echiurans that forms a gutter leading to the mouth

priapulids

have a toothed throat that can be turned inside out to grab prey and then retracted

nemerteans

have a barb-tipped proboscis that extends and spears/ entangles the prey and then retracts

what are the new adaptations required for protostomes to make the transition to land?

they need to be able to

what increases the efficiency of gas exchange accross the body surface of roundworms and earthworms?

high surface-area-to-volume ratio

how do arthropods and many mollusks minimize water loss when moving onto land?

they have gills and other respiratory structures located inside the body

adaptations for feeding

suspension, deposit, liquid and mass feeders.

Adaptations for moving

depends on variation and presence or absence of limbs and the

jointed limbs

in arthropods enable rapid, precise running, walking and jumping

insect wing

one of the most important adaptations in the history of life

mollusk foot

allows individuals to crawl along a surface

jet propulsion

in cephalopods propels the animals forward when the mantle mascles force water from the siphon

parthenogenesis

how many crustacean and insect species reproduce asexually, in which unfertilized eggs develop into offspring

two unique reproductive innovations that occurred during protosome diversification

the evolution of metamorphosis, an egg that would not dry on land

Main phylums of lophotrochozoans

rotifera, platyhelminthes, annelida, mollusca,

rotifera

- live on damp soilds and marine/ freshwater environments

Platyhelminthes

-flatworms

turbellarians

free-living flatworms (platyhelminthes)

- hunters/ scavangers

-reproduce asexually by splitting themselves in half and sexually by fertilization

cestodes

(platyhelminthes) endoparasitic tapeworms

- parasitic

- flukes and tapeworms

trematodes

(platyhelminthes) endo- or ectoparasitic flukes.

- gulp host tissues through mouth

- flukes mainly

Annelida

segmented worms

- segmented body plan

-chaetae

-parapodia

- separated into polychaetae and clitellata

The common ancestor of the annelids had a key synapomorphy in addition to segmentation: numerous, bristlelike extensions called _______ that extend from appendages called _______

chaetae, parapodia

Polychaetes

include those lineages that retained many chaetae and are mostly marine

Clitellata

have lost or reduced chaetae, have two monophyletic groups: oligochaeta (oligochaetes) and hirudinea (leeches)

What are the characteristics of clitellata

live in freshwater and marine environments and compared to other annelids have a smaller coelom which consists of connected chambers

oligochaetae

(clitellata) they lack parapodia nad have fewer chaetae than do polychaetes.

They are deposit feeders in the soil.

Hirundea

(clitellata)

- are blood-sucking parasites

- most live in freshwater

-secretes an anaesthetic and hirudin

Mollusca

- most species rich and morphologically diverse

- marine

- have 4 lineages: bivalves, gastropods, chitons, cephalopods

what are the four most important lineages of mollusca?

Bivalves, gastropods, chitons, cephalopods

Bivalvia

(mollusca)

- suspension eaters

-include clams, oysters, scallops, and mussels

- two separate shells for protection

- most live in ocean

- reproduce sexually and have two larval stages: the trochophore adn the veliger

How do bivalves feed?

suspension feeding: mantle cavity contains mucus-coated gills that filter food & exchange gases

Gastropoda

(mollusca)

- marine snails, slugs and nubibranchs

-large muscular foot on ventral side

- have radula = unique structure in their mouths to scrape away food

what is the most distinctive characteristic of gastropods?

torsion , a process that occurs during embryonic development.

Polyplacophora (chitons)

(mollusca)

- eight plates that form protective shell

- marine

- have radula to scrape algae off rocks and move by gliding

- reproduction is sexual and external.

- trochophore larvae

Cephalapoda

(mollusca)

- nautilus, cuttlefish, squid, and octopuses

-well developed had and tentacles

-closed circulatory system

- reduced shells to none at all

- large brains and eyes with lenses

- have a beak

-sexual reproduction

how do cephalopodes move?

move by "flying" with their fins or through jet propulsion

ecdysozoans molt their skeleton in a process called...

ecdysis

what are the two ecdysozoan phyla?

Onychophora, Tardigrada, nematoda, arthropoda

Onychophorans

Velvet worms; small, caterpillar-like organisms that live in moist leaf litter and prey on small invertebrates