Animals I

• sponges; only extant parazoa group
• Classes:
• Calcarea (calcium carbonate spicules)
• Silicea (glass spicules)
• Demospongia (glass spicules and/or spongin fibers)

• Classes:
• Hydrozoa (Hydra)
• Scyphozoa (true jellies; Aurelia)
• Anthozoa (anemenies/corals; Metridium)

• flatworms
• Classes:
• Turbellaria (planaria)
• Trematoda (flukes)
• Cestoda (tapeworms)

roundworms

• multicellular
• descended from a hypothetical flagellated protist ancestor
• artificial taxons include parazoa and eumetazoa

• all other animal phyla besides porifera
• differentiated cells
• true tissues derived from germ layers

• 2 germ layers - endoderm and ectoderm
• cnidarians

• outermost primary germ layer in animal embryos
• gives rise to outer covering, skin, and its accessory organs; nervous system

• innermost primary germ layer
• gives rise to digestive tract lining and its accessory organs; lungs

• germ layer between ectoderm and endoderm
• mesodermally-derived cells include the coelom lining and organs

consists of 3 germ layers - ectoderm, mesoderm, endoderm

• cnidarians, echinoderms
• divided by many planes through the central axis of its body
• top (oral side with mouth) and bottom (aboral side)
• no distinct head

• no symmetry
• sponges

• divided into mirror halves through one longitudinal plane (medial)
• right and left sides (lateral)
• distinct head (anterior) and tail (posterior)

an evolutionary trend towards concentrating sensory and nervous system at the anterior end of the organism

• lack mesoderm
• includes porifera and diploblastic animals (cnidarians)

• body cavity
• usually deveoped from mesoderm layers

• do not possess a coelom
• possess mesoderm
• platyhelminthes

• possess an internal fluid-filled cavity, but the cavity is incompletely lines with mesoderm-derived tissue
• nematoda

• include most animal phyla
• coelom forms during embryonic development
• fluid-filled cavity completely lined with mesodermally-derived cells
• organs are suspended by double layers (mesenteries)

• room for organs to grow and develop
• an increased surface area for gas exchange and nutrient transport into/out of organs
• a hydrostatic skeleton for support and movement
• a place to store materials
• a route to pass wastes and gametes to the outside

• composed of spicules
• Calcarea (calcareous spicules)
• Silicea (glass spicules)
• Demospongiae (protinaceous spicules, spongin)

• no cephalization
• no segmentation
• every cell exchanges gases and eliminates wastes through diffusion

no distinct nervous, muscular, or endocrine systems

• no tissues, organs, organ systems
• no obvious body symmetry
• somatic regeneration - isolated cells can aggregate and form a new sponge
• totipotent - each cell can potentially give rise to any other cell type

• none; no germ layers, digestive tract, or coelom
• pores and canals lead to the central spongocoel, through which water moves
• digestion occurs in the choanocytes and amebocytes
• intracellular digestion

• flagellated cells that are involved in many activities
• important in intracellular digestion

• amoeboid cells involved in intracellular digestion (receive food vacuoles from choanoctyes) and food transport
• involved in spicule production, reproduction, contraction

• small; lead to small incurrent canals
• -- in the spongocoel
• -- water exits through a large, single osculum (outcurrent pore)
• water currents formed by teh beating of choanocyte flagella lining the radial canals

think, plate-like cells lining the outside of the sponge, the spongocoel, and canals

• thin, gel-like matrix
• amebocytes scattered here throughout

• cell clusters are sponge larvae, called amphiblastulas (formed by the zygote undergoing mitosis)
• eggs retained in the mesohyl, sperm captured by choanocytes; fertilization considered internal
• amphiblastulas break through the spongocoel and exit out the osculum
• reproduce asexually by fragmenting and budding

• diploblastic
• acoelomate
• mesoglea - an acellular gelatinous layer between the two dermal layers
• radial symmetry
• unsegmented

• sessile polyp - hydrozoans and anthozoans
• free-swimming medusa - scyphozoa

• no specialized integument
• some colonial species have a protective outer covering composed of proteins, polysaccharides, and chitin (collectively called the perisarc) that surrounded all of the polyps
• epidermis contains cnidocytes

• stinging cells
• possess a spiked, harpoon-like organelle (nematocyst) that can be discharged
• pierce, entangle, paralyze prey; self-defense

• occurs extracellularly in the gastrovascular cavity
• fluids move through due to body wall contractions and ciliated actions in the gastrodermis
• mostly carnivorous diet
• some have symbiotic algae living inside of them (eg, coral)

• no specialized circulatory, respiratory systems
• simple diffusion of gases across body wall
• ciliary action can move contents in the gastrovascular cavity

no specialized systems

• simple nerve net
• no brain/cephalization
• bidirectional synapses - nerve potentials can go both ways across a synapse (unique)
• neurosensory cells that can respond to light, touch, balance

• reproduce asexually by budding
• sexually; either medusa or polyps produce both the eggs and sperm
• external fertilization
• generally dioecious

• no major support structures
• coral species form an exoskeleton made of calcium carbonate

cells found in both the epidermis (epitheliomuscular cells) and in the gastrodermis (nutritive-muscular cells) are capable of contraction

• ciliated larval stage (the planula) settles on the bottom, forming a polyp (the scyphistoma)
• the scyphistoma eventually becomes the strobila
• the strobila forms many medusae asexually, by budding
• the ephyra is a young medusa that matures into a dioecious adult

• is a thecate - the polyp is mostly coverd in a sheath
• entire colony encased in a transparent protective tube (perisarc)
• colonies grow by asexually budding polyps
• form multiple medusae by budding; medusae grow into dioecious, sexually mature adults, which externally fertilize a zygote; grows into planula larva, which settles and develops into a polyp; young polyp grows by reproducing asexually through budding

feeding polyp with tentacles

• reproductive polyps
• -- see "Obelia life cycle"

• a stolon attached to the substrate
• gives rise to stalks, called hydrocauli
• the living part of the hydrocauli is called the coenosarc, which surrounds a common gastrovascular cavity
• individual polyps (zooids) are attached to the hydrocaulus

• all are marine
• only have polyp stage
• includes corals
• secrete a protective outer skeleton of calcium carbonate
• make up the larges class of cnidarians

• dorsoventrally flattened body
• triploblastic
• acoelomate
• unsegmented (tapeworms produce structures called protoglottids, which make them appear segmented)
• bilateral symmetry
• organ system level of organization - distinct tissues and organs including epithelial, muscular, and nervous tissues

• protonephridium - closed tubular systems that open to the outside along the length of the body at various points called nephridiopores
• nitrogenous wastes (ammonia) diffuse out of each cell into the environment

• no specialized systems
• parasitic flatworms typically use anaerobic respiration

• incomplete digestive tract consisting of a gastrovascular cavity
• initially extracellular digestion, followed by intracellular digestion inside cells lining the gastrovascular cavity
• in some parasitic species, the digestive tract is much reduced or absent; obtains its food in predigested form (by the host)

• cephalization
• cerebral ganglia in the anterior end and several pairs of lateral nerve cords running along the length of the body
• nerve cells are unidirectional
• parasitic flatworms often exhibit reduced cephalization and lack sensory organs
• distinct sensory neurons and motor neurons
• receptor organs that respond to light, tough, chemicals, gravity, and currents

• free-living carnivores
• parasites within the digestive, respiratory, circulatory systems

• typically monoecious
• cross-fertilize (exchange sperm with another organism)
• parasitic tapeworms may self-fertilize
• internal fertilization

• distinct integument that protects their body from the host's digestive enzymes
• move by muscular action and by ciliary action - mucus serves as a lubricating slime as the animal moves
• can regenerate lost body parts; cells are not totipotent

• ciliary motion
• circular and longitudinal muscles are present in the body wall
• thrash about

• larval stages (miracidia) that hatch from eggs
• infect intermediate hosts (aquatic snails); a single miracidium forms a single mother sporocyst within the snail hemocoel; asexually forms daughter parasites; germ cells within the sporocyst may develop into redia, larvae with mouths and gastrovascular cavities; within redia, germ balls develop into cercariae, another distinct larval stage
• cercaridae burrow through the snail's body wall; with a muscular tail, they infect a second intermediate host (fish) where the larva encyst as metacercariae
• a human eats the fish (plus encysted metacercariae); inside the human's digestive tract, the adult flukes leave the metacercariae cysts; mature and produce eggs; eggs are passed through the feces and into water again, where miracidia hatch from them

• adults live in veins; eggs leave through feces and into water
• miracidium excysts from an egg; burrows into an intermediate host (snail) and becomes a mother sporocyst, which asexually produces daughter sporocysts which mature in the snail's digestive tract
• each daughter sporocyst produces many cercariae, which burrow out of the snail and into the exposed skin of a human host; then loses its tail and becomes a young schistosomule, traveling through the circulatory system and maturing into adults
• no metacercaria stages
• males have split bodies with females inside (called the gynocophoral canal)

• generally lack a digestive system, developed the ability to absorb nutrients across their body wall (from the contents of their host); sensory systems are much reduced or absent
• the scolex (head) often contains suckers/hooks that allow the tapeworm to attach to the intestinal wall
• remainder of the body consists of segments called protoglottids, each of which contains both testes and ovaries (produced asexually by budding); eggs (within protoglottids or relased from) exis with the host's feces; picked up by an intermediate host, where they eggs hatch into larvae and encyst in muscles
• the human (final/definitive host) eats the intermediate host

• roundish, cylindrical
• unsegmented
• tapered ends
• pseudocoelom
• triploblastic
• bilaterally symmetrical
• cephalization
• exhibit eutely - each individual consists of exactly the same number of cells (unique)

• only longitudinal muscles in the body wall (no circular or diagonal muscles)
• no muscles surround the roundworm's digestive tract
• pressure is exerted on the contents of the gut by hydrostatic pressure
• muscles send processes to the nerves for innervation, not vice versa (unique)

• complete digestive tract
• unidirectional
• pharynx present
• extracellular digestion within the gut, followed by intracellular digestion

• cuticle (containing chitin) produced by the epidermis
• typically have four molts and four larval stages
• the cuticle maintains turgor pressure, prevents the worm from drying out quickly, provides mechanical protection, and is resistant to digestion by the host's digestive tract (for parasites)
• cuticle is similar to cuticle of arthropods

• free-living carnivores
• free-living detrivores (feed on dead plant and animal tissue)
• parasites
• sound in marine, freshwater systems, moise soils, and in the tissues and fluids of nearly all plants and animals

• no specialized systems
• gases diffuse across body wall
• parasitic forms may use anaerobic respiration

• series of excretory canals
• no flame bulbs
• renette cells - special excretory cells that absorb nitrogenous wastes, which can be passed through a pore outside
• eliminate ammonia via the gut (similar to arthropods)

• dioecious
• internal fertilization

use a hydrostatic skeleton (from the pseudocoelom) and the cuticle to provide structure

• simple
• cephalization
• nerve cords run posteriorly
• several sense organs for touch; a few can detect light

• intestinal
• eggs deposited in the host's feces; development occurs inside the egg, two larval molts occur inside the egg; after ingestion, they hatch or cyst in the host's intestines, then find their way to the lungs; work its way to being swallowed again, back down to the small intestine