Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Porifera - sponges







Lack true tissue
Choanocytes for filter feeding
Spicules for gas exchange
Water vascular systems – Asconoid, Syconoid or Leuconoid
Sequential hermaphrodites
Zygotes => motile flagellated larva (Parenchymula – mobile blastula)

Cnidaria – corals, anemones & jellies








Hydrozoa

True tissues
Diploblastic, radial symmetry & sessile/motile
Poly or medusa body plan
Tentacles armed with Cnidocyte cells (for stinging)
Contractile microfilaments for movement
Cubozoa
No brain
4 clades – Anthozoa, Cubozoa, Scyphozoa
& Hydrozoa

Scyphozoa
Anthozoa

Ctenophores – comb jellies & sea walnuts





Radial symmetry & diploblastic
8 ciliated longitudinal rows (combs) for propulsion
Tentacles have cells called colloblasts (sticky &
function in entrapment)
All are hermaphrodites

Platyhelminthes – flatworms, flukes & tapeworms









Identified by molecular data
Crown of ciliated tentacles (lophophore)
Trochophore larva (spinning top)
Triploblastic & acoelomates (no body cavity)
No organs for gas exchange or circulatory system
Mouth, pharynx & intestine
Nerve cords with a simple brain
Rhabditophora - Turbellaria, Trematoda &
Cestoda

Turbellaria

Cestoda

Trematoda

Rotifera – wheel bearers






Crown of cilia
Pseudocoelomates
Modified muscular Pharynx => mastax (has intricate
jaws called trophi)
Segmented foot
Gonochoristic, parthenogenesis or obligate parthenogenesis

Ectoprocta – moss animals





Colonial & sessile
Hard exoskeleton
Extending lophophore for capturing prey
Statoblast – encapsulated bud of a freshwater
bryozoan, develops into a new organism in the spring

Brachiopoda – mussels & cockles








Sessile bottom dwellers
Shell on dorsal & ventral side
2 classes – Articulata and Inarticulata
Pedicle valve (dorsal) is larger than the brachial valve (ventral)
Pedicle attaches animal to seabed
Lophophore takes up front space, body at the back
Nephridia – expulsion of gametes into the mantle cavity

Mollusc - clams, oysters, squids, octopods and snails
















All soft bodied (no skeleton), most secrete a
hard shell (via mantle)
Coelomates
The shell and underlying mantle overhang the
body, creating a cavity = Mantle cavity
Pairs of retractor muscles
Pair of gills project from the mantle cavity
Water enter lower mantle cavity and is pushed through by the beating of cilia
Mucous lubricates the substratum for locomotion
The mouth contains a unique feeding organ called a
radula
Open circulatory system
Excretory organs are a pair of tubular metanephridia
A nerve ring loops around the oesophagus
‘Ripe’ eggs and sperm break into the coelomic cavity and are
then transported to the external environment through the nephridia
Most molluscs have planktonic trochophore and veliger larval stages
Muscular foot: movement sensory organs
Visceral mass: digestive, circulatory, respiratory, reproductive
and sensory organs

Polyplacophora –








The foot functions in adhesion and locomotion
The plates of the shell (8) enable them to stick to
to curved surfaces
Chiton roll up into a ball if dislodged
If disturbed the girdle is used also, clamping tightly and the margins
are raised to create a vacuum
The radula bear 17 teeth in transverse rows within the buccal cavity
Most chitons are gonochoristic and have a single gonad but no copulation
Gametes are transported by 2 gonoducts instead of nephridia

Gastropoda – snails, slugs, limpets, whelks,
sea hares, periwinkles, sea slugs, sea butterflies











Trochophore and Veliger larval stages
Planospiral to Asymmetrical Shell Coiling
Shell – 4 layers, outer layer (conchin), inner layer (calcium carbonate)
Retractor muscles close the shell and a operculum acts a door or lid
Torsion - Process of moving mantle cavity to the front of the body
and the visceral mass twists 180 degrees (veliger larval stage)
Mantle cavity & anus open above head & mouth (sanitation issues)
Loss of right gill so one way water flow (in left, out Right)
Respiration via gills/skin -terrestrial snails & slugs have a pallial lung
3 subclasses – Prosobranchia, Opisthobranchia & Pulmonata
When the snails are intertwined, one pushes the oval dart into the body wall of the
other

Bivalvia - mussels, clams, scallops and oysters














Sedentary suspension feeders
No head or radula
No brain- nerve network with a few ganglia
Shell is dorsally held together by hinge ligaments
Valves are locked together by teeth/ridges located on the hinge
The valves of the shell are pulled together by adductors muscles
There are scars on the inner surface of the valve where the muscles attach
The edges of the mantle folds form incurrent and excurrent siphons
Cilia direct water flow over gills for gas exchange and filter feeding
3 chambered heart
The cilia on the gills capture food particles –
transported in the mucus to the mouth
Extension and anchoring of foot or byssal threads
Gonochoristic - fertilsation normally external
(Trochophore, Veliger and Spat larval stages)

Cephalopoda – octopus, squid, cuttlefish & nautilus












Only the nautilus has an external shell (divided up into chambers by transverse
septa & middle perforation of septum which secretes gas making it buoyant –
siphuncle)
Cuttlefish & squid have an internal shell
Prey captured by tentacles and arms, some have suckers
Radula is present – tissue pulled into buccal cavity by radula
Closed circulatory system – blood remains separate from fluid in the body cavity
In cephalopods, the ganglia are concentrated and fused to form the brain
Most are colour blind – nerve fibres behind retina
Colour change – chromatophores
Ink sac opens behind the rectum (not Nautilus)
Fertilization takes place in the mantle cavity - one of the arms of the male is a
modified intermittent organ

Annelids – worms & leeches






Are metameric - having a linear series of body
segments
Prostomiun, peristomium & pygidium are not
segments
Coelomic fluid functions as hydraulic skeleton
2 sets of muscles – longitudinal & circular
Waves of peristaltic contraction cause elongation/shortening in each segment

Polychaetes – marine worm









Well differentiated head with specialised
sense organs
Chitinous jaw (light & strong)
Polychaetes have parapodia – fleshy appendages extending
from the body segments and setae are found on the terminal
end (used for locomotion & respiration)
Brain lies in the prostomium and supplies nerves to the
palps, antennae & eyes
Sense organs – retinal cup eye detects light intensity &
source, nuchal organs on the head region detect food and
statocytes in burrowers detect orientation
Most reproduce sexually & are gonochoristic but don’t have
permanent sex organs and fertilisation is external

Oligochaetes – earthworms











Less differentiation of head region
Reduced sense organs
No parapodia
Clitellum (always visible) – thickened non-segmented part of the body that
secretes aviscid sac in which the eggs are deposited
Each segment has 4 pairs of chaetae (chitinous bristle)
Best developed septa & have sphincters around septa to control the flow of fluid
Move by Peristalsis & use coelom as a hydrostatic skeleton
Contract & shorten longitudinal and circular muscles for locomotion
Hermaphrodites & during copulation there is mutual sperm transfer
Clitellum secretes mucous egg sac (slime tube) & the clitellum secretes a chitinlike material to form a cocoon – fertilisation with the cocoon

Hirudinea – leeches







Fixed number of segments
Anterior & Posterior suckers
No parapodia or chaetae
Loss of structure is related to their mode of locomotion
Challenges – finding hosts, accessing blood, evading host defences
and keeping the hosts blood flowing
Used to treat blood clots

Echidnodermata – sea stars to Sea cucumbers etc





Deuterostome Development – cleavage is radial &
indeterminate, coelom formation has folds/outpocketings
of the archenteron and the blastopore becomes the anus
The larvae have bilateral symmetry, the radial symmetry
of adults is secondary
6 Echidnodermata classes

Asteroidea – sea stars














Often Pentarmerous with 5 tapering arms
A Ambulacral Groove radiates on oral side
2 or 4 rows of tube feet run along the length of the arm
for locomotion & respiration
Outer surface covered by an epidermis & underneath is a
wall of connective tissue that forms the endoskeletal
system (spine are part of this)
Spines may rest on or be an extension from ossicles
Pedicellariae – claw shaped structure
Papulae – gills that serve in respiration and waste removal
Lack a centralized brain so there is a nervous system with a
nerve ring that connects to radial nerves - receives input
from the eyespots and organs that respond to touch
Any part of the arm can regenerate if at least 1/5th of the central disc is present
Asexual reproduction also occurs and involves division of the central disc
Most gonochoristic with external fertilisation (Bipinnaria larval stage (bilateral
symmetry)→ Brachiolaria larval stage)

Ophiuroidea – brittle starts & basket stars





Pentaradial symmetry with a distinct central disc
Ambulacral grooves are closed
Tube feet are present minus the suckers
No pedicellariae or papulae

Crinoidea – sea lilies & feather stars





Mainly sessile so suspension feeders
with pentaradial symmetry ( 5 or more flexible arms)
U-shaped gut; anus next to mouth
No madreporite, pedicellariae or spines

Echinoidea – sea urchins, sand dollars & heart urchins




Pentaradial symmetry but no arms
Have spines, tube feet & pedicllariae (some are poisonous)
Complex chewing mechanism

Holothuroidea – sea cucumbers








Elongated oral-aboral axis (lies on its side)
Endoskeleton is reduced to microscopic ossicles
Podia are modified to a circle of 10-30 oral tentacles
(modified tube feet)
Deposit/suspension feeders
Unique Respiratory tree: branching tubes inside anus for gas exchange
Water circulates through the tubules by the pumping action of the cloaca and
respiratory tree
Unique defence mechanisms – cuvierian tubules discharge (long, sticky & toxic
threads)
...
g
...
g
...
g
...
g

---