Chapter 31: Deuterostome Animals

deuterostome characteristics

-have radial cleavage

-blastophore develops into anus and mouth forms on the opposite side

-coelomate

deuterostome coelom

develops from mesodermal pockets that bud off from the gastrula cavity

radial cleavage

an ancestral state for all bilaterians

are all deuterostomes monophyletic

yes

derived traits of deuterostomes

triploblastic, coelom, and internal skeleton

two major clades of deuterostomes

ambulacrarians and chordates

types of ambulacrarians

echinoderms and hemichordates

echinoderm animals

sea stars, sea urchins, and their relatives

hemichordates animals

acorn worms and pterobranches

chordate animals

sea squirts, lancelets, and vertebrates

yannanozoans

extinct organisms in China that were ancestral deuterostomes

yannanozoan traits

bilateral symmetry, pharyngeal slits, and external gills

yannanozoan skeleton

similar to echinoderms

ambulacrarians

have ciliated, bilaterally symmetrical larvae

echinoderm symmetry

pentaradial

echinoderm body plan

-have no head and move in both directions

-mouth is on oral side and anus is aboral

echinoderm skeleton

internal with calcified plates

water vascular system

-network of water filled canals leading to extensions called tube feet

water vascular system function

gas exchange, locomotion, feeding

water vascular system mechanism

-water enters through the madreporite and enters the ring canal around the esophogus

-radial canals radiate out from the ring canal

types of echinoderms

crinoids, echinozoans, asterozoans

crinoids

sea lilies and feather stars

sea lilies

attach to substrate via a stalk

feather stars

grasps the substratum with flexible appendages that allow limited movement

echinozoans

sea urchins and sea cucumbers

sea urchins

-lack arms

-moveable spines attach to the underlying skeleton by ball and socket join, some produce toxins

sand dollars

are flattened relatives of sea urchins

sea cucumbers

-lack arms

-bondy is oriented with mouth anterior and anus posterior

-tube feet anchor to substrate rather than walkig

asterozoans

sea stars and brittle stars

sea stars (starfishes)

-have gonads and digestive organs located in the arms

-tube feet are used in locomotion, gas exchange, and attachment

brittle stars

have flexible arms composed by jointed parts

tube feet in echinoderms

used to capture prey

tube feet in sea lilies

tube feet on the arms for filter feeding

tube feet in sea urchins

catch plankton with their tube feet or scrape algae from rocks with thei rasping structure

tube feet in sea cucumbers

anterior tube feet are modified into feathery, sticky tentacles that are portuded from the mouth

tube feet in brittle stars

ingest sediment and gigest organic material in it

tube feet in sea stars

-used to capture large prey

-clamp onto bivalave and exhaust the muscle the bivalve uses to hold the shell closed

-stomach is pushed out through the mouth and through the space between the shells

-enzymes are secreted to digest the bivalve

hemichordates

have bilateral symmetry amd a 3 part body plan

hemichordate body parts

proboscis, collar, and trunk

acorn worms

-up to 2m long

-burrow in soft marine sediments

-prey is captured with the large proboscis which is covered in sticky mucus

chordates

evolutionary relationships are evident in the early developmental stages

derived traits of chordates

-dorsal, hollow nerve cord

-tail that extends beyond the anus

-a notochord

notochord

-dorsal supporting rod

-it has a core of large cells with fluid filled vacuoles making it rigid but flexible

notochord in vertebrates

replaced by skeletal structures (vertebral column)

pharyngeal slits

ancestral but often lost or modified in adults

pharyngeal slits in tunicates and lancelets

pharynx is used to filter food particles from the water

pharyngeal slits in vertebrates

slits are supported by pharyngeal arches

pharyngeal slits in fish and larval amphibians

pharyngeal arches become gill arches that support the gills

pharyngeal arches

also develop into elements of the vertbrate jaw, parts of the tongue, larynx, trachea, eustachian tube, and middle ear

lancelet name

cephalochordates

lancelets

-very small

-notochord is retained throughout life

-burrow in sand with head portruding

lancelet pharynx

forms a pharyngeal basket for filtering prey from the water

lancelet fertliization

takes place in water

tunicate name

urochordates

tunicates

sea squirts, thaliacean, larvaceans

sea squirts (ascidians)

-form colonies by budding from a single founder

-adult body is enclosed in a tunic of proteins and polysaccharides secreted by the epidermis

thaliaceans

marine with chainlike colonies

larvaceans

marine, solitary, planktonic

tunicate pharyngeal basket

filters prey from the water

tunicate larvae

-have pharyngeal slits , hollow nerve cord, and notochord in the total region

-swimming, tadpolelike larvae suggest a relationship with vertbrates

tunicate adults

are sessile

vetebrates

-have vertebral column

-anterior skull enclsing large brain

-rigid internal skeleton

-internal organ systems suspended in a coelom

-well develped circulatory system with ventral heart

vertbral column

replaces notochord in early development

jawless fishes

sister group to all other vertebrates

hagfish

-blind

-produce large amounts of slime for defense

-have specilized structure to capture prey and tear up dead organisms

hagfish development

direct, with adults changing sex from year to year

lampreys

-have a complete skull and vertebrate

-development is complete metamorphosis from filter feeding larvae

many adult lamprey are…

-parasitic, and use a round mouth to attach to fish and rasp at the flesh

-some are nonfeeding

where do lamprey live

-live in freshwater and are anadromous

-may live in saltwater and migrate to fresh water to breed

are lampreys endangered

yes

chondrichthyans

-sharks, rays, skates, and chimeras

-have skeletons of cartilage

-flexible, leathery skin

sharks

swim using lateral undulations of the body

shark feeding

predators

skates/rays

swim by flapping enlarged pectoral fins

skates/rays feeding

feed on animals in sediment

chimeras

live in deep sea cold waters

early bony vertebrates

had gas filled sacs that supplemented the gills in gas exchnage

swim bladders

develop from gas filled sacs in ray finned fishes

ray finned fishes

-most are covered by scales

-gills open to a chmaber covered by the operculum

operculum movement

enhances water flow over gills

ray finned fish feeding

-filtering plankton

-rasping algae from rocks

-eating chorals

-digging animals from sediments

-predation

-terrestrial fruits and organims that fall into water

ray finned fishes form aggregates called

schools

where to fish lay eggs

shallow water, often in coastal waters and estuaries

what allowed for the evolutioon of land animals

evolution of lung like sacs that supplemented the gills

in lobe limbed vertebrates

pelvic and pectoral fins developed inot more muscular fins, joined to the bod by an enlarged bone

-gave support in shallow water allowing for the move to land

coelocanths

-were thought to be extinct

-found off the coast of south africa in 1938

-cartilageneous skeleton is a derived feature

lungfishes

-were important in the devonian

-6 species left

-have lungs and gills

-can burrow in the mid when ponds dry up and srvive many months in the inactive state while breathing air

teatrapods

-evolved from aquatic lobe limbed vertebrates that began using terrestrial food sources

tetrapod appendages

between fish fins and terrestrial tetrapod limbs

types of tetrapods

amphibians and amniotes

most amphibians are tied to…

moist habitats and lose water easilt thru the skin

amphibian eggs

dry out if exposed to air

entirely aquatic amphibians

-live on land and return to water to lay eggs

-larvae develop in the water

salamanders

-may live in moist soil or on rotting logs

-one group lost the lungs and relies on gas exchange thru skin and mouth lining

completely aquatic salamanders

have evolved several times though neotony

neotony

retention of juvenile characteristics

amniotes

-have features that enable them to conserve water and exploit terrestrial habitats

amniote egg

-relatively impermable to water

-leathery or brittle shells retard water evaporation but allow gas exchange

amniote embryo

develops in a contained aqueous enviroment

amniote egg food

-stored to yolk

-embryos develop using energy from the yolk and hatch at an advanced stage