Chapter 31: Deuterostome Animals

deuterostomes

- radial cleavage (ancestral feature)

- coelom develops frorchenteron

- blastopore forms anal opening first, mouth second

deuterostomes characteristics

- triploblastic

- coelomate

- internal skeletons present

deuterostomes clades

- echinoderms: sea starts, sea urchins

- hemichordates: acorn worms

- chordates: sea squirts, lancelets, vertebrates

ambulacrarians

echinoderms and hemichordates

- ciliated, bilaterally symmetrical larvae

hemichordate adults

bilaterally symmetrical

echinoderms adults

pentaradial symmetry

ambulacrarians structure

- oral side facing sea floor

- aboral side is anus

echinoderms

- pentaradial symmetry

- internal skeleton of fused calcified plates

- good water vascular system with extensions called tube feet

echinoderms water vascular system

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

- gas exchange, locomotion, feeding

- water enters through modreporite and enters ring canal around esophagus

- radial canals radiate from ring canal

echinoderms clades

crinoids, echinozoans, asterozoans

crinoids

- sea lilies and feather stars

- attach to substrate by stalk

- feather stars grasp substratum with flexible appendages that allow limited movement

Echinozoans

- sea urchins and sea cucumbers

sea urchins

- no arms

- moveable spines

- spines used for locomotion and some produce toxins

- catch plankton with tube feet or scrape algae with rasping structure

sea cucumbers

- lack arms

- body axis is front (mouth) to back (anus)

- tube feet used to anchor to substrate

- modified anterior tube feet are used for feeding

Asterozoans

- sea stars and brittle stars

sea stars (starfishes)

- have gonads and digestive organs located in arms

- tube feet have suction cups --> locomotion, gas exchange, attachment

brittle stars

- flexible arms

- gonads and viscera in central disc

- tube feet lack suction cups

hemichordates

- bilateral symmetry

- acorn worms and pterobranchs

Hemichordates body plan

- proboscis

- collar (contains mouth)

- trunk (other body parts)

acorn worms

- up to 12 mm long

- live in tubes secreted by proboscis

chordates

- dorsal, hollow nerve cord

- post anal tail

- notochord: dorsal supporting rod that is rigid and flexible

lancelets

- cephalochordates

- very small

- notochord is retained throughout life

- enlarged pharynx forms pharyngeal basket for filtering prey from water

pharyngeal basket

- strainer to catch food

tunicates

- urochordates

- adult body enclosed in a tough "tunic" of proteins and polysaccharides secreted by epidermis

- sessile adults

- pharyngeal basket filters prey from water

vertebrates

- vertebral column instead of notochord

vertebrates features

- vertebral column

anterior skull holds large brain

- rigid internal skeleton

- internal organs suspended in coelom

- well-developed circulatory system driven by a ventral heart

hagfishes

- sister group of vertebrates

- marine

- partial cranium

- no jaws

- cartilage skeleton

- no vertebrae

- blind

- produce slime for defense

lamprey

- clade of vertebrates

- complete skull

- adults usually parasitic

- round mouths attach to fish and rasp a flesh

- some adults nonfeeding

- lampreys either live in freshwater or are anadromous

gnathostomes

- second clade of vertebrates

- jaw mouths

- jaws and teeth improve feeding efficiency and prey capture

- most jawed fish have paired fins for stabilization

chondrichthyans

- clade of gnathostomes

- skeletons of cartilage

- flexible, leathery skin

- sharks swim using lateral undulations of body

- skates and rays swim vertically flapping enlarged

ray-finned fishes

- clade of bony vertebrates

- covered by scales

- swim bladder for buoyancy

- operculum covers gills and helps water flow

- exploit all types of food

anadromous

- move from ocean to fresh water

coelocanths

have a cartilaginous skeleton, jointed lobed fins, and a fat filled pseudo-lung

lungfishes

- lungs and gills

- burrow in mud when ponds dry up and can survive many months through aestivation

Aestivation in lungfish

- bury under dirt and become dormant in a mucus cocoon to prevent desiccation

tetrapods

vertebrate animals having four feet, legs or leglike appendages

tetrapods clades

- amphibians and amniotes

amphibians

- moist habitats

- eggs will dry out if exposed to air

- some entirely aquatic

- will return to water for something even if living on land

3 groups of amphibians

- caecilians

- tailless frogs and toads

- tailed salamanders

anurans

- some have tough skins and other adaptations for dry habitats

- many are arboreal

- some are aquatic

- short vertebrae column and pelvic region modified

salamanders habitat

- moist soil and rotting logs

salamanders gas exchange

- skin and mouth lining

- lost lungs over time

salamanders type of species

- aquatic

- develop through neoteny

neoteny

retention of juvenile characteristics

amphibians social behaviors

- male anurans call to attract females and defend territories

- some species lay a few eggs and guard nest or carry eggs on their bodies

amniote feature that helps them conserve water

amniote egg

amniote egg

- relatively impermeable to water

- allows the embryo to develop in a contained aqueous environment

amniote egg shells

- leathery or brittle

- retard water evaporation

- allow gas exchange

- stored in form of yolk

extraembryonic membranes

- protect embryo from drying

- assist in gas exchange and excretion of nitrogen

adult amniotes prevent drying

tough skin with scales, feathers, or hair

kidneys

- water retention

- excretion of concentrated urine

reptiles

- squamates

- turtles

- crocodilians

- birds

squamates examples

lizards and snakes

squamates features

- horny scales

- lungs for gas exchange

- can be insectivores, herbivores, and/or predators

snakes

- limbless squamates

- carnivorous

- venom glands

- can disconnect their jaws to consume huge prey

turtles

- barely have changed from Mesozoic era

- dorsal and ventral bony plates form a shell

- dorsal shell is modification of ribs

crocodilians examples

- crocodiles

- caimans

- gharials

- alligators

crocodilians carnivores

- mostly stay in water in tropical and warm temperate regions

crocodilians eggs storage

nests on land or floating piles of vegetation

birds

- group of dinosaurs (theropods)

birds shared trats with dinosaurs

- bipedal stance

- hollow bones

- a furcula (wishbone)

living bird species 2 groups

- secondary flightless birds

- flying birds

secondary flightless birds

- paleognaths

- tinamou, rhea, emu, kiwi, cassowary, ostrich

flying birds

neognaths

feathers of birds

- lightweight but strong

- provides flying surfaces

- insulation

- help attract males

bones of birds

- hollow with internal struts

- lightweight but strong

birds structure

beak and no teeth

- plant dispersal

- decrease competition

mammals

- coexisted with dinosaurs

- range in size (tiny shrews --> blue whales)

- highly differentiated teeth

key features of mammals

- sweat lands

- mammary glands

- hair

- four-chambered heart

four-chambered heart function

completely separates oxygenated from deoxygenated blood

- convergent trait with dinosaurs, birds, and crocodiles

mammals fertilization

- mammals eggs fertilized internally

- embryos develop in female uterus

- embryo contained in amniotic sac

- placenta connects embryo and uterus wall

placenta purpose

- nutrient and gas exchange

- waste elimination

- NOT ONLY MAMMALS

insulation in animals that do not have fur

- layers of fat replace hair for insulation

- humans learned to use clothing for insulation

2 groups of living mammals

prototherians and therians

prototherians

- duck-billed platypus and echidna

- lay shelled eggs

- provide milk to young

therians 2 groups

marsupials and eutherians

marsupials

- carry and feed young in ventral pouch

- altricial

- herbivores, insectivores, and carnivores

- none can fly, some can glide

marsupials locations

- Australia and South America

- Virginia opossum in North Mexico

Eutherians

- well developed placenta

- young are more developed at birth than marsupials

what did plants do when animals kept eating them

- built up defenses

herbivores development for obtaining nutrients

long digestive tracts

eutherian lineages

- returned to aquatic habitats

- cetaceans (whales and dolphins) evolved from hoofed ancestors