How does Cnidaria fit in? Porifera unknown common ancestor eukaryote multicellular heterotrophic Blastula 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 PlatyhelminthesNemertea 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 Characteristics Cephalization 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 protonephridiaflame 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 Turbellaria Free-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 Cycle Adult 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 Nemertea the 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 system same 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. system acoelomate