7: ANIMALS II PROTOSTOMES

triploblastic animals

protostomes: blastopore develops into mouth

bilateral symmetry: midline divides into two mirror images

morula

zygote undergoes mitosis to form solid mass (morula) that develops into blastula with ecto and endoderm

gastrulation

reorganizes and transforms blastula into gastrula with ecto, meso, endoderm

create pocket blastopore

cephalization

nervous system becomes concentrated at the anterior end of the organism

produces head region concentrated with sensory organs

planaria

freshwater free-living flatworm

dorsoventrally flattened bilateral symmetry

triploblastic

acoelomate (no coelom: body cavity surrounded by mesodermal layers)

no respiratory or circulatory system: diffusion meets needs

planaria digestive system

mouth, pharynx, branched gut

no anus

pharynx protrude to eat, waste comes back out mouth

planaria nervous system

simple brain in head region connected to two longitudinal parallel ventral nerve cords along its body and transverse nerves in-between longitudinal nerves

eyespots: clustered photoreceptors shaded by pigmented cells

auricles: concentrated chemoreceptors, nose

planaria movement

coordinated muscle contractions and cilia beating on ventral surface

planaria reproduction

hermaphroditic: male and female sex organs, doesnt self fertilize

sexual rep: simultaneous fertilization

asexual rep: tear into two halves and regenerate

taenia

tapeworm: long flat body

acoelomate

parasite

ascaris

roundworm

pseudocoelomate: body cavity not completely lined with mesodermal cells

intestinal parasite

earthworms

triploblastic, bilateral symmetry, cephalization

earthworm digestive system

prostomium(mouth) start → pygidium (end)

crop: temporary food storage

gizzard: grind up food

intestine: digestion and absorption

typhlosole: intestine in-fold increase surface area to maximize absorption

earthworm circulatory system

closed: blood elements stay within blood vessels

blood driven by tubular heart into ventral blood vessel to body. return by dorsal blood vessel

earthworm reproduction

hermaphrodites

clitellum: thickened non-segmented section secretes mucous sheath help to keep two copulating worms head to head together while sperm exchange

earthworm coelom

coelomate

surrounded by longitudinal and circular muscles

filled with fluid that makes up hydrostatic skeleton

separates digestive tract to contract independentlyea

earthworm movement

burrow alternating longitudinal and circular contractions

nervous system coordinate movement

circular muscle contract, push fluid to anterior to push forward

circular muscle relax: longitudinal muscles contract to pull posterior end in

setae

bristle-like on ventro-lateral sides of segments to help anchor earthworm

mollusks

bilateral symmetry, coelomates

foot: highly muscular, locomotion

mantle: body wall covering visceral mass, secrete external shell

visceral mass: internal organ systems

mantle cavity

mantle extended beyond main molluscan body

houses gills: gas exchange

chitons

mollusks

oval body covered by shell consisting of eight segmented calcareous plates

sessile: attach to rocks with broad foot

radula: toothed tongue scrapes algae from rocks

bivalves

mollusks

mussels, clams, scallops, oysters

two part hinged shell and wedge shaped foot

dorsal excurrent siphon→gills→ventral incurrent siphon by mantle cavity

gastropods

mollusks

aquatic and terrestrial

large flat food for locomotion

one part spiral shaped shell (snails) or none (slugs)

cephalopods

distinct head with conspicuous eyes and cone like mantle surrounding their visceral mass

carnivores

foot modified into arms

beak: strong, crush prey

well developed nervous system and image forming eyes

cephalopod movement

cone shaped siphon does jet propulsion

longitudinal muscles contract→draw in water→water forced out of mantle cavity

chromatophores

cephalopods

small sacs filled with pigments to change their body color for camo and courtship

ink sac

cephalopods

melanin pigments that are released to temporarily disable predators sight and smell

arthropods

segmented bodies, jointed appendages, exoskeletons: hard outer coverings composed of chitin and calcium carbonate

crustacean

arthropod

head:two pairs of sensory antenna, number paired of mouthparts for feeding, pair of compound eyes

thorax: chelipeds (pincers) for prey capture, defense, female mating; four walking legs attached to gills to circulate water

abdomen

crustacean abdomen

five pairs of swimmerets: bring oxygen rich water over gills (determine sex)

telson: terminal extension of body

uropods: broad fan shaped on each side of telson for backward swimming

insects

arthropods

head: mouthparts, compound eyes, antenna

thorax: 3 pairs of legs

carapace

piece of exoskeleton covers cephalothorax

spiracles

insects

air goes into body through small openings (spiracles)

open to tracheae→tracheoles (deliver oxygen to various metabolically active tissues)

chelicerates

arthropods

cephalothorax and abdomen

first pair of appendages are chelicerae

myriapods

chelicerates

centipedes and millipedes

two regions: head and trunk bear appendages with exoskeleons and jointed appendages