Sponges, Cnidarians, and Platyhelminthes Flashcards
What does Phylum Placazoa mean?
“Flat Animals”
What is the simplest of all non-parasitic multicellular animals?
Phylum Placazoa
What species is included in Phylum Placazoa?
Trichoplax adhaerens, composed of a bilayer of a few thousand cells
How do Phylum Placazoa reproduce?
Asexually by dividing into two or budding off many multicellular individuals
What’s special about Phylum Placazoa?
There’s no fossil record, and they possess no tissues or organs, no digestive, circulatory, or nervous systems
General characteristics of Phylum Porifera (Sponges)
About 5500 species, sessile, filter feeders, lack true tissues
What environment do sponges live in?
Marine (few freshwater)
What is the morphology of a sponge like?
Asymmetrical, diploblastic (2 tissue layers), skeleton made of collagen and spicules, no tissues and organs, “body” is a system of pores and canals through which water passes
Spicules
Rodlike structures found in sponges that are made of silica, calcium carbonate, and spongin (protein)
Mesoglea
Gelatinous matrix in sponges where skeletal elements, choanocytes, and other cells are embedded
Choanocytes
Specialized cells found in sponges that are flagellated and aid in the movement of water through the sponge
How do sponges feed?
They are filter feeders, so they capture food that is brought close by water currents created by choanocytes. Food particles taken in by individual cells through phagocytosis, then digestion occurs in the individual cells
Are sponges asexual or sexual?
-They are hermaphroditic (produce both male and female gametes)
-Reproduce both sexually and asexually
-Asexual via buds
Sexual reproduction occurs in mesoglea
How does sexual reproduction work in sponges?
Sperm released in water captured by choanocytes, choanocytes lose their “collars” and transform into amoeba-like cells, which carry the sperm to the eggs. Fertilized egg develops into a blastula that is released into the water. Blastula develops into a larva which can either immediately settle and transform into an adult or may swim before settling down. Adults are sessile.
What is included in Phylum Cnidaria?
Jellies, Corals, and Hydras
What type of body symmetry do Cnidarians have?
Radial
General characteristics of Phylum Cnidaria
Diploblastic, tissue level of organization (no organs), hydrostatic skeletons, gastrovascular cavity, no respiratory system, simple nervous systems
What is the nervous system of cnidarians like?
Simple; they have ganglia to coordinate nerve messages along the body and nerve nets (diffuse network of neurons which conducts impulses in all directions from a point of stimulus)
Gastrovascular Cavity in Cnidarians
One way digestive system; food goes in oral cavity, digested with enzymes, then waste eliminated out of oral cavity
Cnidoblast
Specialized cell found in Cnidarians; it’s a venomous cell used to capture prey and defend against predators
Nematocyst
Found in cnidocytes; have unique organelles and function to help capture prey and defend the animal–works like a jack in the box
How do cnidarians reproduce asexually vs sexually?
Asexually through polyps that reproduce by budding
Sexually through medusae that reproduce via gametes
Sexual reproduction Cnidarians
Medusae produced on specialized polyps, release gametes that fuse, forming a zygote, which develops into a bilateral ciliate larva. Larvae swim for a little while then settle and develop into polyps, growing asexually as new polyps grow and branch from older ones
Describe coral’s general characteristics
-colonies of polyps
-enclosed in a skeleton of calcium carbonate
-sometimes form symbiotic relationship with photosynthetic dinoflagellates
-Dinoflagellates live inside polyps, receiving shelter and CO2 from the coral, and the coral gets sugars and O2 from the dinoflagellate
-if a coral reef loses its partner it will die (coral bleaching)
What organism is Phylum Platyleminthes?
Flatworms, over 20,000 species
Flatworm general characteristics
-bilaterally symmetrical
-protostomes
-triploblastic
-hydrostatic skeleton
-acoelomate
-dorsoventrally flattened =flat worms
-no segmentation
-tissues
-organs
-distinct brain
-have a highly branched gastrovascular cavity (GVC)
-no circular system
-cephalized nervous system
What is an acoelomate?
An animal that lacks a formal body cavity or coelom
How do flatworms reproduce?
-Sexually: they’re hermaphroditic and possess male and female organs, but individuals cannot fertilize their own eggs and have to mate with another flatworm
-Asexually: body splits in two near the middle, and each piece regrows the missing part. Regrowth also occurs if the flatworm is cut in two
Phylum Platyhelminthes Class Turbellaria
-Free living flatworms (some aquatic, some terrestrial)
-Bilateral symmetry
-Dorsoventrally flattened
-Unsegmented
-Cephalization (very primitive brain and system of sheathed nerve fibers)
-Blind ending gut
Platyhelminthes Class Trematoda (Flukes)
-bilaterally symmetrical
-dorsoventrally flattened
-2 external suckers
-no respiratory system
-excretory system (flame cells)
-nervous system consists of a brain comprised of a pair of ganglia in head region
-hermaphrodites (flukes can only reproduce inside mammal)
What happens with flukes in humans?
They can only reproduce in a mammal, humans become infected when they wash or walk in water where infected snails live, blood fluke crosses their skin and reproduces in their body, causes schistosomiases
What organism is included in Phylum Platyhelminthes, Class Cestoda?
Tapeworms
P. Platyhelminthes Class Cestoda (Tapeworms) General characteristics
bilaterally symmetrical
triploblastic
protostome
endoparasitic (lives in tissues and organs of hosts)
segmented
hermaphroditic
head bears suckers and often hooks
No digestive, circulatory, or skeletal system
Excretory system composed of flame cells
Proglottids
Body segments in tapeworms behind the head
Scolex
Head of tapeworm
How are tapeworms acquired?
Eating undercooked pork or fish
