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  1. 1. What are characteristics of pseudocoelomates? (phyla? Coelum type? Embryonic development? Symmetry? Organs? Evolved from? Epidermis? Excretory system? Unique structures? Digestive system?
    • MANY phyla (know Nematoda, Rotifera, Acanthocephala, and Nematomorpha)
    • Cavities lack peritoneal sac (no mesoderm surrounding endoderm)
    • Protostome
    • Bilateral symmetry
    • Well developed organs (lack respiratory/circulatory organs)
    • Polyphyletic (potentially evolved from many phyla)
    • Have syncitial epidermis
    • Protonephridia (extretory system releases waste into acoelomate area) (NOT nematodes)
    • Males have cloaca (place where reproductive material AND waste material exit)
    • Eutely (set # of cells throughout life)
    • Complete digestive system (Acanthocephala has no digestive system)
  2. Characteristics of clade ecdysozoa?
    • Molting/ecdysis: animals shed a tough external coat (cuticle)
    • Eight phyla (know Nematoda, arthropoda)
  3. 2. Why syncytial epidermis is an advantage to these animals (ecdysozoa)?
    • Allows alteration of surface proteins to protect from host’s immune system
    • Secretes tough non-living cuticle (protects from hostile environments/enzymes)
  4. 3. Why Caenorhabditis elegans is important in Biochemistry?
    • Easily cultured in lab
    • DNA is eutely
    • Entire genome is mapped
    • Used in gel electrophoresis as a standard
    • Easily used as a reference, because everything is known
  5. 4. What are characteristics of phylum nematoda? (Common name? Example species? Species #? Symbiosis? Unique structures? Movement? Sexual reproduction info? Development info?
    • Common name “round worms”
    • Caenorhabditis elegans
    • About 12,000 known species (500,000 more to discover)
    • Eutely
    • Free-living and parasitic
    • Nonliving cuticle secreted by hypodermis
    • Cuticle is made up of collagen
    • No cilia or flagella in tegument
    • ONLY longitudinal muscles
    • Glycogen for muscle contraction
    • Muscles extend to axons (only phylum in animal kingdom, normally axons go to muscle)
    • Thrashing movement
    • Majority are dioecious
    • Some males have copulatory bursa: serves to grip onto female
    • Most males have spicules: serves to open genital pore of female and transfer sperm
    • Fertilization is internal
    • Four juvenile stages (Egg -> L1 -> L2 -> L3 -> L4 -> adult)
    • L3 is infective stage
  6. 5. What is the life cycle of nematoda like?
    • Egg -> L1 -> L2 -> L3 -> L4 -> adult
    • Egg -> L3 in environment
    • L3 is infective stage
    • L3 -> adult in host
    • Molting (shedding cuticle) occurs between each stage
    • Can be viviparous (live birth) or oviparous (lay eggs)
  7. 6. What are the advantages of coelom?
    • Freedom of movement (animal can move more easily)
    • Space for development (more eggs can develop within pseudocoelum)
    • Better circulation (food and nutrients can move through the pseudocoelum)
    • Storage for waste (waste can be stored in pseudocoelum area)
    • Hydrostatic pressure (pressure exerted by fluid in pseudocoelum)
  8. 7. What are the characteristics of Ascaris lumbricoides? (hosts? Body information/structures? Sexual reproduction information? Various species + symptoms (not larval migrants)?)
    • Found in Human and swine
    • Eggs remain in environment for a long time (found in mummies)
    • About 15-40 cm long
    • Mouth has three lips
    • Anus on ventral side
    • Dioecious
    • Male have spicules on the curved posterior end (no copulatory bursa)
    • Males are smaller/thinner and curve at posterior end
    • Female has Y shaped reproductive tract (thin ovary- larger oviduct- even larger uterus)
    • Direct life cycle (no intermediate host)
    • Fertilization after copulation
    • Ascaris suum (pig round worm) L3 can go to brain and cause lesions, death. Located in US.
    • Ascaris lumbricoides not normally an issue unless there are many
  9. 8. What are the differences between the male and female reproductive tract of the A. Lumbercoides?
    • Male have spicules on the curved posterior end (no copulatory bursa)
    • Males are smaller/thinner and curve at posterior end
    • Female has Y shaped reproductive tract (thin ovary- larger oviduct- even larger uterus)
    • Direct life cycle (no intermediate host)
    • Fertilization after copulation
  10. 9. What is the visceral larva migrants and is caused by what organism?
    • Toxicara canis (dog round worm), Toxicara cati (cat round worm), Toxascaris leonine (wild carnivores)
    • When L3 is ingested by human (from feces of animal) it cannot become L4, so L3 continues to migrate through viscera (visceral larva migrants). Causes pain/discomfort, very difficult to diagnose.
    • Have life cycle similar to Ascaris lumbricoides
  11. 10. What are hook worms? (Species? Why given name? Unique anatomy? Symptoms? Life cycle?)
    • Necator americanus and Ancylostoma duodenale (Parasites)
    • “hook on” to the intestine
    • Mouth part have teeth and/or cutting plates
    • Voracious blood sucker (don’t drink blood, but use the O2 from blood. Host will see blood in feces)
    • Cause anemia due to lack of blood
    • Only Nematode where L3 PENETRATES SKIN to infect host (not ingested)
    • Direct lifecycle
    • The southern states claimed to have lost civil war due to lethargy caused by these parasites
  12. 11. What is the cutaneous larva migrants?
    • Ancylostoma caninum (dogs and cats)
    • L3 penetrates human skin, but cannot develop further. L3 then roams around beneath the skin, causing burning/itching. Immune system will kill in 24-48 hours, and host will see rash.
    • Dogs/cats banned from beaches due to this parasite.
  13. 12. Explain thrashing movement
    • Cuticle + Pseudocoelum filled w/ fluid (hydrostatic pressure) cause animal to be straight
    • Longitudinal muscles contract, causing animal to bend. This “pushes” its environment away (like swimming)
    • Re-straightening occurs automatically due to cuticle + hydrostatic pressure
  14. 13. Explain Trichinosis and the name of the organism that caused it? (species? Lifecycle? Infection? Unique stages? Symptoms? Other information?)
    • Trichinella spiralis
    • Viviparous (live birth of L1)
    • Get from eating uncooked meat (commonly pork)
    • Nurse cell: L3 can encyst, creating a thick CaCO3 layer, in skeletal muscle
    • Nurse cells are the infective stage (L3) waiting in meat to be eaten by a carnivore so that they can become adult
    • Larva (not adult) is devastating to human – cause muscles aches, gravitate to human diaphragm making it difficult or impossible to breath
    • Cannot be treated after a certain stage
    • Some studies claim that cooking will not penetrate nurse cell
    • Almost the same epidemiology as Toxoplasma gondii
    • France/Germany check EVERY pig diaphragm after slaughter, US runs less accurate blood-samples (they will not buy pork from US)
  15. 14. What is the scientific name for a pinworm and explain its effect and life cycle? (Symptoms? Life cycle? Significance? How to test?)
    • Enterobius vermicularis
    • Little or no disease (slight itching)
    • ***Never has to leave host!
    • Life cycle: Adults live in the large intestine. Male dies after copulation, females migrate to the anal region at night to lay their eggs, and die after oviposition. Scratching the itch contaminates hands, bed, and clothes.
    • Retroinfection (autoinfection) often occurs in case of constipation.
    • Eggs not infecive after prolonged exposure to environment
    • 1 study showed 100$ of US kids had/have pinworm. Eggs were found in sand of schools/preschools (has since been replaced by rubber or wood shavings).
    • If you suspect your child has pinworm you put stick scotch tape on the anus and bring to lab for testing.

    • Scientific name of whipworm + other info? (why named? Geographical location? Symptoms? Special anatomy?)
    • Trichuris trichuris
    • Looks like whip (anus is on “whip handle” while mouth is on “whip tip”)
    • Appalachian mountains (NC, SC, TN)
    • Cause little harm if numbers are low
    • Have operculated eggs (2 operculum, 1 on each end)
  16. **15. What are filarial worms and explain pathology of them?
    • L1 known as microfilariae, found in blood
    • Microfilariae are released directly from female (viviparous)
    • Wuchereria bancrofti
    • Live in the lymphatic system, cause elephantiasis (edema)
    • Females release microfilariae into the blood and lymphatic system of human. Mosquitos ingest microfilariae as they feed, which develop inside the mosquitos to the infective stage (L1 -> L2 -> L3). L3 escapes from the mosquito as it is feeds on a different host.
    • Onchocerea volvulus
    • Transmitted by black flies (Simiulium)
    • Causes river blindness (bacteria associated with worm, not worm itself)
    • Dirofilaria immitis
    • Common name: dog heartworm
    • Carried by mosquitos
    • Adult lives in the hearts of dogs, cats, and rarely humans
    • Typically one adult male and one adult female live in heart, copulate, and release microfilariae into the blood
    • Surgery required to remove worms, even if they are killed by drugs
  17. Explain the sign of medicine + additional info.
    • Dracunculus medinensis (not a filarial worm)
    • The sign of medicine is a Dracunculus being pulled out of someone’s leg by wrapping around a stick
    • Intermediate host is copepod (microscopic shrimp) (L1 -> L2 ->L3)
    • Final host is human (L3 -> L4 -> adult)
    • Female gets out of human through leg, and lays eggs in body of water.
    • Eggs ingested by copepod, develop into L3
    • Humans ingest copepod through contaminated drinking water, L3 escapes into human develops to adult
  18. 16. Explain Phylum Rotifera? (Genus? Habitat? Unique anatomy? Internal structure? Reproduction?)
    • Philodina
    • Freshwater animals
    • Corona: structure for locomotion and brings water/food to mouth
    • Some sessile, some colonial
    • Some epizoic (live on the surface of other animal, but doesn’t harm)
    • Encystment
    • Body has head, trunk, tail or foot
    • Rotifers move like leech or by corona or both
    • Eutely (nuclear consistency)
    • Internal structure: cuticle, syncytial epidermis, subepidermal muscles, mastax or pharynx have muscles, salivary and gastric glands, protonephridia tubules, bi-lobed brain
    • Reproduction: dioecious, male have one testis, female have cloaca, male lack cloaca, male penis can penetrate ANY PART of the female and inject sperm
  19. 17. Explain haplodiploidy?
    • 2n female undergo mitosis to form 2n egg which develops into a 2n female, and so on (parthenogenesis)
    • When rough conditions are present the 2n female forms n eggs by meiosis. One egg develops into a n male, which creates n sperm via mitosis. The sperm fertilizes another egg resulting in a 2n encysted egg. When conditions are hospitable the egg will develop into a 2n female.
    • Some species have undiscovered male adults because of this process.
  20. 18. What are the characteristics of Phylum Acanthocephala? (common name? Anatomy? Species? Species location, development, specialization?)
    • Spiny-headed worms
    • Probosis contains spines
    • Female larger
    • Little inflammation therefore little damage to host
    • Flat in host, when outside of host it is round
    • Macracanthorhynchus hirudinaceus
    • In small intestine of pigs and human
    • Larva develop in arthropod (may transfer between pig and human)
    • *No digestive tract, food through tegement (like cestodes)
    • Protonephrida (waste material in pseudocoelum)
  21. 19. What are the charactertistics of annelids? (unique structures? Organ systems? Movement?
    • Eucoelomate
    • Metamerism: repeated segments (if one segments fails the rest work)
    • Classification based on segmentation, setae, & presence or absence of clitellum
    • Annuli: circular grooves which are outside between each metamere
    • Cephalization: visible head region
    • Prostomium: anterior of animal (first segment, not a metamere)
    • Pygidium: the terminal portion bears anus (last segment, not a metamere)
    • -new segments form from front of pygidium
    • Coelom comes from mesoderm (schizocoelus)
    • Circulatory system is closed, have true heart
    • Complete digestive system (mouth and anus)
    • Regeneration
    • Peritonea of adjacent segment meet to form the septa
    • Circular muscles outside and longitudinal muscles inside
    • Move by peristalsis
  22. 20. How do earth worms move?
    Earthworms move by peristaltic movement: Contractions of circular muscles in the anterior end lengthen the body, pushing the anterior end forward where it is anchored by setae; contractions of longitudinal muscles then shorten the body, pulling the posterior end forward. As these waves of contraction pass along the entire body, it gradually moves forward.
  23. 21. What are the characteristics of class Polychaeta? (Name means? Size? Species? Habitat? Anatomy? Sexual reproduction? Active time of the day?)
    • Many setae
    • Largest class (1000s of organisms)
    • Nereis virens (clam worm/sand worm) – burrows into sand
    • Arenicola (lugworm)
    • Tubicolous polychaetes – sedentary, spend majority of time in permanent burrows
    • Mostly marine
    • Live under rocks, burrow into mud or sand
    • Have well differentiated head (prostomium) (unlike earthworm)
    • Prostomium has eyes, tentacles, and sensory palps. Can be extended/retracted.
    • Peristomium: first segment
    • Parapodia: paired appendages on all segments except first and last
    • Parapodia are biramus (branched), each has two lobes…
    • Dorsal notopodium: On top, larger, more blood vessels for respiration
    • Ventral neuropodium: smaller
    • Both lobes are used for creeping and swimming
    • No clitellum
    • Chitinous jaws and sensory tentacles
    • Have pigments such as hemoglobin
    • Dioecious
    • Fertilization is external, and larva is called trochophore
    • Gonads swell during some time of the year and gametes go to coelum -> gonoduct -> metanephridia OR rupture from body wall (go through kidney)
    • Active at night
  24. 22. What are the characteristics of class Oligochaeta? (name means? Common name? Species? Habitat? Anatomy? Darwin? Digestion? Circulatory System? Excretory system? Nervous system? Reproductive system?)
    • A few setae
    • Earthworms
    • Lumbricus terrestris (night crawlers)
    • Most are terrestrial or freshwater, some parasitic, some marine
    • No head or true parapodia (unlike sand worm)
    • Anterior end has clitellum
    • Setae with a few exception (most have)
    • Each segment has 4 pairs of chitenous setae except the first and last segment
    • Perstaltic movements
    • Mouth in first segment, prostomium, and anus in the last segment
    • No eyes but have many photoceptors in epidermis
    • Darwin found that earthworms till the soil, making it more fertile.
    • Most defenseless animals on planet earth
    • Digestion
    • Scavengers who eat by sucking action of pharynx
    • Calciferous glands: regulate the amount of Ca2+ in blood
    • Mouth in the first segment (prostomium) and anus in the last segment (pygidium)
    • Typhlosole: “fold” in intestine to increase surface area
    • Chloragogen: outside intestine, function like human liver. Also helps regeneration when fat and glycogen go around a wound to regenerate body.
    • Circulatory system
    • Close circulatory system
    • Circulation is double (circulatory system AND coelomic fluid)
    • Dorsal blood vessel runs on top of pharynx, anus, digestive system
    • Ventral blood vessel receives blood from aortic arches, takes to brain and rest of body
    • Blood has colorless ameboid cells, called corpuscles (for immunity) and hemoglobin
    • Excretory system
    • Each somite (segment) has metanephridia except the first three and last one
    • Nephrostome is ciliated
    • Cilia brings wastes from coelom to nephrostome and join with the waste material from blood and go outside through nephridiopore (reproductive material also released through nephridiophore)
    • Aquatic oligochetes release ammonia
    • Nervous system
    • Brain has neurosecretory cells, they are endocrine in function and secrete neurohormone (function in regulation of reproduction and regeneration)
    • *myelinated axons
    • No eyes, but have many photoreceptors in epidermis (for light intensity)
    • Nonspecialized sense organs
    • Reproductive system
    • Monoecious, but practice cross-fertilization
    • Females STORE SPERM from male in two seminal receptacles during copulation
    • Reproduction can happen during any season
    • Clitellum secretes mucus that holds the worms together
    • After copulation a cocoon is formed around clitellum (which is moved off of worm)
    • Fertilization of eggs takes place in cocoon
    • Young adult emerges from eggs (direct development, no metamorphosis)
    • Juvenile do not develop clitellum until they are adult
  25. 23. What are the characteristics of class Hirudinea? (common name? Species? Habitat? How do they eat? Symbiosis? Anatomy? Reproduction? Other?)
    • Leeches
    • Hirudo medicinalis
    • Mainly freshwater
    • Black, brown, red, olive, green
    • Force their pharynx or proboscis into soft tissue, then suck blood
    • Gut store large amount of food (can eat 5-10x bodyweight then go years without eating)
    • Sawlike chitinous jaws
    • Temporary OR permanent parasites
    • Have clitellum, appear only during breeding season, hermaphroditic
    • No appendages and setae
    • Anterior and posterior suckers
    • Fixed number of segments
    • Distinct coelemic compartments (coelum is compartmentalized, not from head to tail)
    • Coelum found around gonads
    • Septa disappear except in one species
    • Lacunae: coelum which is filled with connective tissue
    • Feed on almost all species; human to insects (different host, different leech)
    • Monoecious but practice cross-fertilization
    • No larval stage
    • Gas exchange only through skin, aquatic ones through gills
  26. 24. Why do doctors use leeches for some surgeries?
    • When injury occurs, blood vessels are severed and blood escapes. Surgeon repairs vessel, but cannot repair capillaries OR remove all excess blood. Doctors place leeches to suck excess blood – “clearing out” the wounded area.
    • Repeated as necessary until vessel repair has been completed.
  27. 25. What is the relationship between molluscs, annelids, and arthropods?
    • They have many similarities (all coelomate, commonality between larval stages) and may share a common ancestor
    • HOWEVER – coelom and metamerism evolved INDEPENDENTLY
  28. 26.What are the characteristics of phylum molluska? (Embryonic development? Anatomy? Compare with anneleids? General phyla information?
    • Protostome (mouth first)
    • Spiral cleavage
    • True coelum
    • Mesenteries (supportive membrane in invertebrates)
    • True organ system
    • Gas exchange through body surface & gills or lungs
    • Open circulatory system, but most Cephalopoda have closed circulatory system
    • Cephalopods are largest invertabrates (squids, octopus)
    • **Eyes – actual image-forming eyes! First so far!
    • Coelum is limited to heart, some gonads, and parts of the kidney (compartmentalized)
    • Body contains head, foot portion, and visceral mass
    • Have shells (secreted by mantle)
    • Radula (mouth area)
    • Not metameric
    • Annelids and mollusks possibly had a common ancestor
    • Adaptive radiation
    • 2nd largest phyla in animal kingdom
    • Only bivalves and gastropods moved to shallow water and freshwater
    • Most intelligent of invertebrates are Cephalopoda (octopus)
  29. 27. What is adaptive radiation?
    • A common ancestor that has adapted to MANY environments.
    • For example: mollusks can be found in lakes, rivers, the ocean, on land, etc.
  30. 28. What are the three layers of shell (mollusks)?
    • Shell is constantly secreted by the mantle
    • Periostracum (outer layer): made of organic material/protein, protects the inner layers, can be eroded away by pollution, acidic water from leaves falling in the water)
    • Prismatic (middle layer): Thickest portion, made of CaCO3
    • Nacreous layer (inner layer): thinnest layer, shiny (gives rainbow effect of abalone), made of CaCO3
  31. 29. What is radula and its function (mollusks)?
    • Found within the mouth area
    • Pattern and numbers of teeth are different
    • Grasping, tongue-like, organ (not found in bivalves)
    • Muscles move radula like a conveyer belt (keeps food moving to mouth)
    • Used for classification purposes
  32. What is foot and its function (mollusks)?
    • Locomotion, attachment, and combination
    • Bivalves have a hatchet foot
    • Incurrent siphons allow H2O in
    • Excurrent siphons excrete H2O
    • Mucus is secreted that allows adhesion and a slime tract
  33. Visceral portion of mollusk information?
    • Mantle: sheath of skin, secretes shell, acts as a gas exchanger
    • Mantle cavity: houses respiratory organs, products from digestive, excretory, and reproductive systems are emptied here
    • Countercurrent exchange mechanism (blood flows against water in gill area which allows blood to get more O2, nutrients, etc from the water)
  34. Some internal structures of mollusks information?
    • Heart, blood vessels, blood sinuses (open areas in open circ. System)
    • Cephalopods have heart, blood vessels, and capillaries
    • A pair of kidneys (metanephridia -> nephrostome -> coelomic area)
    • Ducts of kidney may also serve as discharge of egg or sperm
    • Nervous system has neurosecretory cells
    • Advance sense organs (including image-forming eye)
  35. Life cycle and reproduction in mollusks information?
    • Dioecious and some monecious
    • Trochophore larva (doesn’t look like mature organism)
    • Veliger larva (looks like mature organism) (clam)
    • Some cephalopods and bivalves have no free-swimming larvae
  36. 30. What are the characteristics of the following class? Monoplacophora
    • Thought to be extinct until found in 1950s
    • Small, round shell and creeping foot
    • Organs are serially repeated (unusual for mollusks)
    • Very old/primitive
  37. 30. What are the characteristics of the following class? Polyplacophora
    • Common name Chitons or mail shells
    • Flattened dorsoventrally
    • Have 8 plates or valves on shell (that’s where they get their name)
    • Water current goes through pallial groove, through gills
    • Sense organs in mantle groove
    • Heart has three chambers
    • A pair of metanephridia
    • Trochophore larva NOT veliger larva
  38. 30. What are the characteristics of the following class? Scaphopoda
    • Common name tusk shells or tooth shells
    • Foot into sand and shell end into water
    • Cilia extend from tentacles of head (can sense environment, bring food to mouth)
    • Radula carry food to crushing gizzard
    • Sexes separate and there is trochophore larva
  39. 30. What are the characteristics of the following class? Gastropoda
    • Largest class, includes Helix (garden snail), Limpet, and Abalone
    • Univalve (one shell)
    • Apex: the oldest part of the shell
    • Whorl: One complete ring
    • Columella: division from bottom of animal to top
    • Dextral: whorls are counter clockwise
    • Sinistral: whorls are clockwise (VERY RARE)
    • Aperture: opening of shell
    • Operculum: covering of aperture
  40. Torsion vs Coiling?
    • Torsion: only in gastropods, moving mantle, twisting the visceral organs 90-180degrees, happens in veliger stage, anus opening above mouth, Fouling (name of process when waste excretes)
    • Coiling: spiral winding of shell, may occur during the larval stage, planospiral in early gastropods
  41. 30. What are the characteristics of the following class? Bivalvia (name means? Organisms? Anatomy? Feeding? Shells? Body and Mantle? Locomotion? Water currents? Reproduction?)
    • 2 shells
    • Freshwater mussel, hatchetfoot animals, clams, scallops, oysters, and shipworms
    • Shipworm (Teredo teredo) munches wood, used to be an issue for boats (termite of the sea)
    • Only class without radula
    • No head, no radula, very little cephalization
    • Open circulatory system
    • Hemocyanin: a pigment in colorless blood
    • Nephridia near heart
    • Most are sedentary filter feeders
    • Shells
    • Hinge ligament
    • Anterior and posterior adductor muscles work antagonistically
    • Umbo: oldest part of shell (like apex)
    • Pearl production
    • Meleagrina (Japanese pearl-producing oyster)
    • Body and Mantle
    • Foot is attached to visceral mass
    • The edge of mantle folds are modified to form excurrent and incurrent opening
    • Locomotion
    • 2 methods of movement
    • Blood is pumped into foot: pushing anterior foot into sand, then forward
    • Clapping their valves: can open shell and squirt water out for quick movement (easily exhausted)
    • Water currents
    • Incurrent siphon -> gill pore -> common suprabranchial chamber -> excurrent siphon
    • Reproduction
    • Dioecious
    • Embryo -> trochophore larva -> veliger larva
    • Fertilization is internal
    • Glochidium larva in some species (attach to fish gill and suck blood until maturity)
    • Eggs and larva found in marsupium (a part of gill)
    • ((Embryos not necessarily sequential, could be on or other or both))
  42. 30. What are the characteristics of the following class? Cephalopoda? (Organisms? Habitat? Anatomy? Study of mollusks? Locomotion? Reproduction?)
    • Squids, Octopuses, Nautiluses, Devilfish, and Cuttlefish
    • Architeuthis (scientific name of giant squid)
    • All marine
    • All predators
    • Closed circulatory system
    • Modified foot is in head region
    • Some do not have shell
    • Have chitinous beaks inside mouth
    • Squids have poison glands
    • Squids have pen (chitinous, skeletal structure which protects the brain)
    • Squids have two long tentacles and four pairs of arms
    • Both squid and octopus arms have suckers
    • Octopus have ink glands
    • Octopus do not have shell
    • Have chromatophore pigments on the surface (camoflauge)
    • Nautilus shell is divided by septa (water perculates through septa), Siphuncle divides the septa
    • Malacology: study of mollusks
    • Locomotion
    • Expel water from mantle cavity though a ventral siphon
    • Lateral fins in squids, fins not found in octopus
    • Ink sac in octopus
    • No cilia on gills
    • Reproduction
    • Dioecious
    • Seminal vesicle store spermatozoa
    • Hectocotylus: one of the arms that transfers sperm from male to female
    • Eggs fertilize in the oviduct
  43. 31. How is pearl formed?
    • When something gets stuck between the shell and the mantle of an oyster it begins surround it with CaCO3, creating a pearl.
    • Nucleation: inserting a piece of mantle from another oyster gives the best artificial pearl.
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2011-11-21 21:26:45

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