how does cnidaria fit in? porifera unknown common ancestor eukaryote multicellular heterotrophic...
TRANSCRIPT
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
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)
Class TurbellariaFree-living flatworms
• move on slime trails using cilia
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
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
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