How does Cnidaria fit in?

Porifera

unknown common ancestor

eukaryotemulticellular

heterotrophicBlastula stage

cellular level of organization

choanocytes

3 body types

Cnidaria

tissue level of organization

diploblastic

3 classes:Hydrozoa, Scyphozoa, Anthozoa

2 body types: polyp, medusa

How do the Acoelomates fit in?

Porifera

unknown common ancestor

Cnidaria

Platyhelminthes Nemertea

the acoelomates

The Acoelomates

Acoelomate Characteristics

Organ level of organization

Tissues are organized to for organs which are used to accomplish physiological functions

Acoelomate Characteristics

3 Embryonic Germ Layers

endoderm

mesoderm

ectoderm

3 Tissue Layers

gastrodermis

mesoderm

epidermis

Triploblastic

Acoelomate Characteristics

No body cavity

Gut

ectoderm

mesoderm

endoderm

ectoderm

mesoderm

endoderm

Acoelomate Characteristics

Ectoderm

Endoderm

Mesoderm (mesenchyme, parenchyma)

Gut

Triploblastic

Acoelomate Characteristics

Anterior: toward the front of the body

Posterior: toward the rear of the body

Bilateral Symmetry

Acoelomate CharacteristicsCephalization

Eye spots

Auricles

the concentration of sensory organs in the head of the animal

Phylum Platyhelminthes

the flatworms

Physiology

Feeding– Free-living, carnivorous – parasitic

Digestion– intestine is simple or branched– incomplete system (no anus)– digestive system reduced or absent

in parasitic species

Physiology

Osmoregulation and excretion – Protonephridia and flame cells– much excretion is via diffusion

protonephridia flame cell

Physiology

Nervous system-ladder-like

-cephalization

-nervous system is

reduced in parasitic

species

Lateral nerve cords

Cerebral ganglia

Skeletal and circulatory systems– absent

Physiology

Reproduction

Asexual

Sexual– usually monoecious, but most must cross

fertilize– Internal fertilization (usually reciprocal)

Phylum Platyhelminthes

Class Turbellaria

Class Trematoda

Class Cestoda

Class TurbellariaFree-living flatworms

• move on slime trails using cilia

Class Turbellaria

• predatory

• use a pharynx to capture prey

pharynx

Class Turbellaria

• have a branched (or lobed) gut

ClassTurbellaria

Reproduction

Asexual– Fission

ClassTurbellaria

Reproduction

Sexual– internal fertilization– simple life cycle

Adaptations for Parasitism

• increased reproductive potential• monoecious• presence of adhesion organs (suckers, hooks)• poorly developed sensory systems• reduced, or absent, digestive system• resistant cuticle• complex life cycles with more than 1 host

Class Trematoda

Parasitic Flukes

• endoparasitic

Trematoda Life Cycle• have at least two hosts in their life cycle• final host = vertebrate

adult fluke (in host liver)

Vertebrate host #1

infective stage in host muscle

Vertebrate host #2

Invertebrate host eats eggs

Class Cestoda

Parasitic tapeworms

Class Cestoda

scolex

proglottids

2 body regions: scolex and proglottids

Class Cestoda

Scolex suckers

rostellum

Class Cestoda

Proglottids • repeating segments containing reproductive organs

• may be immature, mature, or gravid

Class Cestoda

Immature proglottids

• found at the anterior end of the tapeworm

• contain no noticeable sex organs

Class Cestoda

Mature proglottids

• found in the middle of the tapeworm

• contain noticeable sex organs

• sperm must come from either a different proglottid or a different individual

Class Cestoda

genital pore

ovary

uterus

testes

sperm duct

vagina

Mature proglottids

Class Cestoda

Gravid proglottids

• found at the posterior end of the tapeworm

• contain fertilized eggs

• entire proglottid is shed in the host’s feces

eggsuterus

Cestoda Life CycleAdult tapeworm (in host intestine)

Gravid proglottids

eggs

Vertebrate host #1

Infective stage in host muscle

Vertebrate host #2

Ecology

•Parasitic flatworms infect many people in some parts of the world (for example, the Chinese liver fluke infects approx. 30 million people in Asia)

•Some Trematodes have display polyembyony: a single larvae can have up to 4 younger larvae developing within it

•Trematodes are a model system for studying host parasite coevolution

Phylum Nemerteathe ribbonworms

Physiology

Feeding– Free-living, carnivorous – have an eversible proboscis that is

not connected to the digestive system

– Proboscis is used to stab prey and may have a poisonous tip (or stylet)

Physiology

rhynchocoel

proboscis

mouth

rhynchocoel

Physiology

Digestion– intestine is unbranched– complete system (mouth and anus)

This is the first animal to have an anus!!!

Physiology

Reproduction

Asexual– Some species are capable of reproducing

asexually through fragmentation and regeneration

Sexual

– usually dioecious

– internal fertilization

Physiology

Osmoregulation and excretion

– same as Platyhelminthes

Nervous system– same as Platyhelminthes

Skeletal systemsame as Platyhelminthes

Physiology

Circulation– closed circulatory system

consisting of contractile blood vessels

This is the first animal to have a closed circulatory system!!!

Ecology

•Nemerteans are mostly marine, although there are a few species found in freshwater (and even a few on land!)

•They range in size from a few millimeters to 30 meters

•Their biology is little known in part because they are extremely fragile and fragment easily

How do the acoelomates fit in?

Porifera

unknown common ancestor

Cnidaria

triploblastic

organ level of organization

Platyhelminthes

protonephridia

cephalization

Ladder-like nervous system

Nemertea

proboscis

Complete digestive system

Closed circ. systemacoelomate

acoelomate