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Multicellular & Tissue Levels of Organization
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Porifera, Cnidaria & Ctenophora
Porifera – the most primitive animals Cnidaria & Ctenophora – possess embryological tissue layers
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Evolution of multicellularity
How did we get from single celled animal like protists to multicellular animals?.... Colonial hypothesis- dividing cells staying together or individual protists living in colonies Syncytical hypothesis- large multi nucleated cell
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Protist ancestor to the sponge?
Single celled choanoflagellate
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Phylum: Porifera “Pore Bearing”
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Characteristics Radial or Asymmetrical
3 cell types: pinacocytes, mesenchyme cells, choanocytes Lined with flagellated cells for filter feeding into central cavity or series of chambers Internal skeleton but no tissues or organs multicellular Asexual & Sexual reproduction Aquatic (marine & fresh water)
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Terminology Osculum – opening at the top where water exits
Spongocoel – large chamber Ostia – pores in sides of sponge for incoming water Epidermis – outer wall (made of Pinacocytes, thin flat tissue-like cells that contract) Porocytes – regulate water circulation Spicules – skeleton of calcium carbonate, slender rods 3-4 rayed; other substances – siliceous (glass) or spongin fibers; tough branching network
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Choanocytes – flagellated collar cells lining the inside canals, maintain current of water, they trap and phagocytize food particles Mesoglea (Mesenchyme) – gelatinous “connective tissue” layer between cells Archaeocyte – free cells, may function in digestion, or secretion of spicules or collagen.
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Shape/Size Thin flat crust, vase-shaped, branched, or irregular
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Colors Yellow, orange, green, purple
Their color fades quickly when removed from water
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The Three Main Types of Sponges Asconoid Sponge: Simple Sponges
Small, shallow-water marine sponge Vase/Tube-like (Greek for “bladder”) *The Spongocoel is flagellated EX: Leucosolenia
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Sychonoid Sponge Look like larger Asconoids
Tubular body but body wall is thicker and more complex with canals *The spongocoel and canals are flagellated EX: Scypha
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Leuconoid Sponge Form large colonial masses each member having own osculum *Flagellated chambers that lead to canals, then to osculum
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Food Getting and Digestion
Feed on detritus, plankton, and bacteria Choanocyte collar collects food with fingerlike microvili Digestion (intracellular). Food particles will be phagocytised by choanocytes to or archaeocytes.
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Respiration and Excretion
Diffusion
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Reproduction Sexually
Monoecious – both male and female sexes are in one body (hermaphroditic) Ova are fertilized by motile sperm (sperm arise from choanocytes) Zygotes develop into flagellated larva
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Asexually Regeneration – replacement of lost parts
Budding – external buds of tissue drop off of parent Gemmules – internal buds (dormant), masses of cells that are encapsulated and survive periods of harsh conditions
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Locomotion Adult is sessile Larva are flagellated
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General Characteristics
Phylum Cnidaria General Characteristics Radial symmetry Diploblastic Cnidocytes – stinging capsules Tentacles around mouth Body sac-like – gastrovascular cavity No blood, respiratory, or excretory organs Network of nerve cells & fibers in body wall Two body forms (polyp & medusa)
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Radial & Biradial Symmetry
Most are Radial Some are Biradial Have no dorsal/ventral sides or no anterior posterior Based on position of the mouth , oral end and opposite is aboral Beneficial for sedentary animals because sensory receptors are evenly distributed around the body
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Functions of Cells in Different Embryologic Layer
Ectoderm – becomes epidermis Cells function to protect and gather food Endoderm – becomes gastrodermis Cells function for movement, coordination, digestion and absorbtion Mesoglea Cells – jellylike layer between epidermis and gastrodermis
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Functions of Cnidae Produces by cnidocytes Functions:
Attachment- have stick secrections that help anchor Defense – spines that penetrate Feeding – spines w/hollow tips to discharge paralyzing toxins Fluid filled capsule with internal coiled hollow tube
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Cnidocyte Operculum (lid) Barb (prickly spine)
Filament (whip like structure) Cnidocil (trigger)
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Functions of the Gastrovascular Cavity
Digestion Exchange of respiratory gases Metabolic waste Discharge of gametes All of the above enter and leave through the mouth
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Nematocysts entangle and paralyze prey
Contractile cells in tentacles shorten & pull food in Gland cells – secrete digestive enzymes Nutritive –muscular cells aide in movement and phagocytize food particles from gastrovascular cavity Contract in peristaltic circular motions & push undigested material back out through the mouth
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Skeleton – for support and movement
Hydrostatic skeleton & pressure from surrounding watery environment enables it to maintain shape Their “water balloon like” skeleton allows them to bend and twist when attempting to catch prey
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Epitheliomuscular cells make up most of the epidermis enabling it to expand to 25 – 30 mm or contract to a tiny gelatinous mass – help with contractions Interstitial cells – becomes other cells when a need arises (like stem cells)… make nerve cells, gland cells, sperm, egg Fully extended, its tentacles sweeping the water for its prey, the hydra reaches a height up to two inches.
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Two body forms Medusa Polyp tentacles & mouth down
Dioecious and free swimming Polyp tentacles and mouth up Asexual and sessile
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Moving in their Environment
Polyps – somersault, inchworm, glide Medusa – swim & float by water & wind currents
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Nerve tissue Most primitive nervous elements in the animal kingdom
Interconnected 2 dimensional nerve net
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Nerve cells Sensory cells Spread throughout body
Act with sensory organs to detect food Act as brains Sensory cells Receive stimuli (chemical or tactile), nerve cells conduct impulse, then epitheliomuscular cells contract
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Respiration & Excretion
Diffusion – large surface area to volume ratio allows for a short distance for all cells from the body surface
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Dioecious Most house male and female organs in separate bodies.
Where is the asexual stage and where is the sexual stage?
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Phylum: Cnidaria Class: Hydrazoa
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Hydrazoans Kingdom: Animalia
Phylum: Cnidaria (connected with nettle) nettle = stinging hairs Class: Hydrazoa
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3 Unique Features of Hydrozoa
Nematocysts are only in the epidermis Gametes are epidermal and released to the outside of the body rather than into the gastrovascular cavity Mesoglea is largely acellular
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Form and Function Habitat – freshwater
Polyp, tubular body (tentacles up) Tentacles surround mouth to capture prey Nematocysts (coiled filament) on the cnidocytes allow it to sting and paralyze prey Cnidocytes – hold and produce nematocysts
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Missing medusa stage Basal disc (bottom)
Secrets adhesives to stick to an object Produces gas bubbles to float on Bud Gastrovascular Cavity Epidermis Gastrodermis Basal Disc
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With its tentacles, a hydra bud snares a Cyclops, a tiny, one-eyed crustacean, also named after an ancient Greek monster. The bell-shaped protrusion on the hydra's body (upper left) is a second hydra bud. Tentacles curled, a hydra is ingesting its prey. Its mouth is at right. The hydra is at rest, digesting its meal.
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Mesoglea Statocyst Act as an elastic skeleton Small sac containing
Helps withstand great mechanical strain Gives tentacles more flexibility Statocyst Small sac containing CaCO3 moves in response to gravity
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Physiology Usually has 6-10 tentacles around mouth (only opening)
Hypostome is the mouth between the tentacles Basal disc - hydra’s “foot” Mostly made up of skin: Epidermis – cuboidal cells outside
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Reproduction Asexually
Budding – hydras “Mini Me” growing on the side of it; when the bud is large enough it falls off and becomes independent organism Regeneration One hydra bud somersaults away from its parent as another grows. Hydras often have four buds at a time.
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Sexually In the autumn Different species may be dioecious or monoecious Dioecous; eggs in ovary are fertilized by sperm shed in water, a cyst is formed around the embryo before releasing from parent (survive winter), hatch in spring
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Feeding and Digestion Food – crustaceans, insect larvae, worms
Capturing process Tentacles (nematocysts) harpoon prey Paralyze it Engulf with mouth Gland cells discharge enzymes (extra cellular digestion) Nutritive muscular cells draw in food with pseudopodia (intracellular digestion)
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Locomotion Gliding Floating attached to gas bubble Somersaulting
Sessile –twist and turn to capture food
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PHYLUM: CNIDARIA “Stinging nettle” CLASS: SCYPHOZOA Jellyfish
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FYI… Lion's Mane Jelly (Cyanea capillata) World’s largest jellyfish! In the Arctic specimens reach 8 feet in diameter, local ones may exceed 36 inches. Lion’s Mane stinging cells (nematocysts) are very potent and will cause a severe skin reaction. Jellyfish can sting people even after it is dead. Jellyfish stinging cells are sticky, they can stick to wood, buckets or shoes and deliver a nasty sting when touches
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Class Scyphozoa from Greek skyphos "cup" and zoon "animal"
Jellyfish Medusa stage – dominant stage Umbrella shaped body with fringe of tentacles hanging down Polyp stage is minute or absent The jelly is 95-96% water
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Rhopalium Club shaped sense organ found in notch of scalloped edge between tentacles Each rhopalium contains a hollow statocyst used for balance two sensory pits (olfactory) sometimes oceli (photoreceptors)
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Reproduction Dioecious Sperm swim to egg and zygote lodges on oral arm
Grows into ciliated larval planula Planula settles on bottom to become polyp (scyphistoma) By process called strobilation, buds off a series of saucer-shaped buds (ephyrae) Buds grow into medusa
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Tentacles Have nematocysts to paralyze prey
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Mouth Center of underside
Surrounded by four oral arms (lobes) used in food capture
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Gastrovascular Cavity
Digestive canals branch throughout Gonads are contained in pouches here Nerve net and circular muscles coordinate rhythmical movements
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FYI: The Portuguese Man-of-War technically is not a “jellyfish” (it does not belong to the class Scyphozoa, it is from the class Hydrazoa)
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Class Anthozoa “flower animals”
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Corals and Sea Anemones
marine polyps with no medusa stage and no cnidocil
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Oral Disc Crown of tentacles arranged in many circles around mouth; at the ends of the mouth are siphonglyph (ciliated grooves) that create water currents into and out of the mouth and down pharynx & maintain hydrostatic skeleton Pedal disc - The “foot” of the sea anemone
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Anemone locomotion Gliding Crawling Walking on tentacles Floating
Thrashing bodies
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Gastrovascular Cavity
The mouth is the only opening to the anemone's sac-like gut (gastrovascular cavity) Undigestable food (snail shells, etc.) taken in, must be eliminated back out the mouth Gastrovascular Cavity #2
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Reproduction Sexually
depending on the species may be dioecious or monoecious depending on the species may Release sperm into seawater in broadcast spawing OR Sperm released by the male may fertilize eggs held in the female’s body Asexually regeneration can reproduce by splitting in half (a process called fission) Splitting off small pieces of tissue from the basal disc (a process called pedal laceration)… a whole anemone can gradually regenerate from even a fragment of tissue Anemone larval stage called the planula, is a solid ball of cells Hair-like cilia on its surface propel it over the bottom or up into the water When the planula finds a suitable surface, it adheres to the bottom and changes form to become a young polyp with mouth, tentacles, and gut Since the adult anemones cannot move very far in their life, the planula is the most important dispersal stage in the life cycle of sea anemones.
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Painted Anemone (Urticina crassicornis)
Unable to sting through a persons skin May live up to 60 years
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Aggregating Anemone (Anthopleura elegantissima) common on rocks and in sandy areas
Competing colonies attack each other, forming a "no-mans-land" between them.
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Coral Reefs 200 C or warmer water; large formations of calcium carbonate laid down by organisms over thousands of years
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1. Fringing Reef Less than a quarter of a mile from shore
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2. Barrier Reef Runs parallel to shore, has a wider and deeper lagoon
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3. Atoll Reef Reef that circles a lagoon of water rather than an island
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Here they are together…
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Phylum Ctenophora (pronounced /tiːn.ou.fɔː(r)/) “comb bearing”
Marine forms with 8 rows of comblike plates used for locomotion Examples: sea walnuts and comb jellies
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Radial symmetry Marine Free swimming
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Comb plates Ciliated Used to propel mouth end forward
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Physiology Reproduction Nerve net
Statocyst (fluid filled sensory organ) Two tentacles Gastrovascular cavity Reproduction monoecious
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Question time Are jellyfish monoecious or dioecious?
2. What is “scyphozoa” greek for? 3. What is the difference between a fringing reef and a barrier reef? 4. What does “ctenophora” mean?
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5. What are the collar cells in sponges called?
6. What is the term for the stinging cell in the hydra? 7. What is the function of spicules?
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Question time Are jellyfish monoecious or dioecious? Dioecious
2. What is “scyphozoa” greek for? cup animal 3. What is the difference between a fringing reef and a barrier reef? Fringing – close to land, barrier – has lagoon between the reef and the land 4. What does “ctenophora” mean? Comb bearing
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5. What are the collar cells in sponges called?
choanocytes 6. What is the term for the stinging cell in the hydra? cnidocytes 7. What is the function of spicules? structure
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