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Diversity of Life 1 – Autumn Term
Taxonomy – study of classification of lifeforms – has hierarcheal structure – can be shown as
dendrogram – 1 branch splits into 2, kingdom at top, splits into lower levels
Sorting life forms into groups – Classic or DNA sequencing – Classic – study organisms under
microscope, classify by features – morphology/embryology
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Kingdom, Phylum (Phyla(basic body shape/anatomy and life cycle determinable), Class, Order,
Family, Genus, Species
1 cell or more than 1 – first dendrogram division
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Protozoa – some do
Photosynth and are classed as plants but animal/plant/fungi split is not obvious
Old system – green = plant, rest = protozoa New System – protozoa = kingdom
Organs/tissues or not – no organs/tissues – parazoa (sponges), yes – metazoa (have fully
differentiated tissues e
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muscle/nerve)
Parazoa – sponges – colonial protozoa inside skeleton of spicules – have various shapes,
compositions, colours (diverse, need microscope to identify)
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Always aquatic, most marine
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Metazoa – have fully differentiated organs and tissues
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Both stages – feed with stings – stinging cells – cnidocytes/nematocysts (use entagling, injecting
barbed points/toxins
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Normally identical collar of earthworm = exception
3 classes – polychaetes – most annelids – spiky marine worms, Oligochaeta – freshwater/terrestrial,
small – earthworm, Hirudine – leeches – ectoparasites 2 suckers
Mollusca – soft body, covered with mucus – often with shell
3 Classes – lamellibranchia – bivalves – aquatic filter feeders, Gastropoda – limpets/slugs/snails –
terrestrial herbivores, Cephalopoda – octopus/squid – muscular foot, 8-10 tentacles to capture food,
evolved eyes similar to verts independently
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Pentagonal – echinoderms
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Hydrostatic + endoskeleton = echinoderms
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Partial exo – molluscs
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True segmentation – all body units
primitively repeated in each unit – annelids, arthro, chorda
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1-3 descriptive – not good evol background
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E
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gill
slits
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DNA moslt proven embryology
right
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blastoporemouth, coelom- from within mesoderm, chitin often present
Deuterostomes – egg cleavage radial, division – indeterminate division - remove 1 cell both live
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Junk DNA has no
selection pressure- varies immensely – with no pattern/sequence
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rRNA homologies – used to establish relationships between Phyla
Nuclear – both parents, Mitochondrial – normally from female (Both used to trace relationships –
nuclear more reliable)
Can use slowly changing DNA sequences + software to derive animal classification hierarchy
- DNA mostly confirms embryology

Invertebrate – animal that is not a vertebrate
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Classification – predator, bacterivore (bacteria), herbivore (producers/autotrophs), carnivore (animal
tissue – more energy in protein than plants), omnivore (autotroph/heterotrophs), detrivore
(decaying organic matter), parasite (host), symbiont host, filter feeder, deposit feeder(deposit
material on sediment surface in various decay stages)
Feeding Strategies
Protozoa – symbiont host (symbiont host or steal chloroplasts from algae), predators, parasites,
detrivores, bacterivores, herbivores
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Rotifers – predators/herb/bacteri/detriv/scavenger(necrophage) – have mouth and anus, all female,
shoot jaw into prey
Nematoda – pred/herb/bact/detriv/para – some feed on plants – stylet into plant suck phloem
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Direct deposit – arenicola – applies mouth to substratum directly injests
Indirect deposit – Amphitrite – utilise appendages to gather in deposit material to mouth
Filter feeder – peacock fan worm
Class Oligochaeta – scaven/pred/detriv – earthworm
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Mollusca – Class Bivalvia – deposit/suspension feeder via cilia produced current
Class Gastropoda – uses radula to break down plant material
Class Cephalapoda – carni (raptorial feeding) – capture – suckered arms, beak breaks prey, may
inject poison, radula breaks small pieces up
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Class Crustacea – predators, omnivores, detrivores
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Diversity feeding
diversity
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Feeding process – location (receptors), selection, capture (appendages/nets)
Receptors – visual (light/movement), Mechanical (detects changes in shape/physical deformations in
bodys environment – due to pressure/touch/motion/sound
Chemo – transmits info about total solute conc in solution, or individual molecules
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Some begin digestion then take in pre digested food –
spider/cnid/echino
Assimilation Efficiency – % of food energy taken in
AE = An/In x 100% An-food energy available for incorporation into growth/work
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Herb/detri/micro 20-50%
Mollusc Radula – rasping grazers – break down plant material – numerous teeth on projection from
pharynx/buccal cavity floor – move back and forth over odontophore
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Biting(locust)/chewing/sucking(mozzy) mouthparts – insects – labrum, mandible, maxilla, labium
Sucking mouthparts – nematode stylets- peirce plant, suck out phloem
Weapons – ciliate extrosomes – needle like – shot out, toxins – nematocysts in cnidarians, venom –
spider –disrupt nervous system +muscle communicationparalysis also cell death- necrosis (velvet
worms and centipedes too)
Classifcation by feeding strategy – aquatic habitats – still/flowing water – suspension/filter feeders –
create current with cilia, or use to transport food that sticks to body to mouth – animal adapted to
filter water for suspended particles – used by sponges (flagella), bivalves, gastropods, polychaetes,
crustaceans – create current trap foodsort food move food to mouth
Food = zoo/phytoplankton, detritus
Annelids – tentacles with cilia, Arthropods – no cilia – use
setae as apendages to filter
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Follows newtons laws – F=ma, uniform motion/at rest unless external force/ forces
have = and opposite reactions
Organisms – must generate force to move – no friction/active stopping  continuous movement
“push ground, ground pushes back”
Force = Mass x acceleration and Work = force x distance - must overcome friction to move, friction
prevents slipping back
Reynolds number – small animal – low R no = to a human swimming in tar
Must spend energy to move – must generate force (ATP/ADP, actin+myosin, Dynein arm
Locomotion – 4 ways – Amoeboid – uses assembly + disassembly of actin monomers (actin
cytoskeleton) – extends pseudopodia (projections) to move, extends leading edge, adheres,
deadheres trailing edge, cell body moved forward
Flagella and Cilia – plasma membrane around 9 microtubule doublets surrounding 2 central
microtubules – bending of flagella/cilia caused by doublets moving past each other
Force provided by dynein arm, lots of diff cilia and flagella arrangements, flagella – longer than cilia
(occur in 1’s or 2’s) common in unicellular organisms – not common in adult metazoa (choanocytes
in sponges are feeding not movement)
Ciliated cells – occur in most metazoan phyla, not in arths, function – feeding current lining of
digestive tract – locomotion for ctenophores
Muscles – myosin + actin – cross bridges etc
Musculature – muscle cells and tissue, located in epithelium – mixed with other cells or below
epithelium in connective tissue – true muscle cells
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Burrowing – penetration anchor – prevents slipping back, terminal anchor –
holds organism in place while body pulled forward
Mollusca – bivalves –use foot (pedal musculature) to burrow – extension, terminal anchor,
contraction
Hydrostatic skeleton involved
Gastropoda – foot – glands produce lubricating mucus to facilitate locomotion – waves of
muscular contraction, direct and indirect
Direct wave – pass along foot in same direction of animal movement
Indirect wave – contractile waves that move along body in opposite diresction to movement
Cephalopoda – walk and swim – undulation of lateral fins back + forth + jet propulsion –
fill mantle cavity with water press water out at high speed, siphon acts as direct control
Echinodermata – tube feet
Arthropoda – segmented animals – paired jointed, segmented appendages (each leg pair served by
nerve ganglia – jointed limbs allow locomotion
Crustacea –walk/swim – jointed limps – biramous – 2 branches – exopod/endopod – can be
1 branch (loss of exo, endo)
Phyllopod – “leaf” – swimming, respiration
Stenopod –
nd
“slender” – walk and grasp, swim with annetenae – cladocera – 2 pair Oar, ostracoda – 2nd pair
swim/walk
Insects – flight – movement through air in which force of gravity and air resistance has been
overcome – true flight – thin light, lamellar membrane (supported by stiffened by veins) – 2 layers –
cuticle + epidermis – strengthened by veins
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Wings – 4 wings, 2 pairs – 1 pair may be modified and reduced e
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flies – 2nd pair used for flight
stability
Flight muscles - direct – outside – lowers wing, inside – raises
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Depolarisation opens K+ gates – K+ out, shuts Na+ gates, pumps continue to pump Na+
Polarity re-established
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Physalia – portugese man of war – dips gas bladder to keep it moist
Anens – walk on basal muscle slowly, fight neighbours with nematocysts released from acontia
around mouth
Coral – solitary free living corals right selves if upside down
Senses + touch + chemosensitivity (for gamete release synchronisation)
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Pattern – commonest – central nervous system, runs ventrally along body axis, terminates in large
cephalic ganglion running around oesophagus (circumoesephogeal ganglion), found in flatworms,
annelids, arthropods,
More complex lifestyle – more developed nervous system e
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faster moving – more coordination
Muscle coordination done by closest ganglion to section
Burn reflex is vestige of the closest ganglion co-ordinates
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Respiration = processes of securing and using O2
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Linked by transport mechanisms, repiratory surface  metabolising tissues
O2 availibility – depends on conc
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gradient
Respiratory surface – always (aq), in terrestrial organisms – kept moist by fluid layer
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Open system – arths – large haemocoel
Closed system – annel – system of arteries + veins
Insects – haemocoel – not used for O2 transport, insects, peripatus + myriapods developed trachial
respiration

Trachial respiration – diffusion of O2 through air filled pipes, trachae – ectodermal origin – formed
by invagination (ingrowth) from surface, lined with cuticle – thickened forming ridges/spiracle
(taenidia) - maintain open lumen through system
O2 transported to all tissues via tubules – branch to all body parts, end in tracheoles (very fine
tubules) which surround cells and end in them blindly
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than simple water, evolved independently multiple times, Haemoglobin – most widespread
Haemoglobin - in almost all verts, sporadic in inverts – present in annelida, and entomostra –
dissolved in body fluids of crustacean
Occurs in some molluscs + bivalves, found dissolved in blood or tissues in trematodes, nemertines
and ascaris
Chlorocruorin – related to Hb, green respiratory pigment, occurs in solution only, found in 4
polychaete families only, evolved from Hb by genetic mutation
Haemerythrin – rare pigment – in sipunculids, 1 polychate genus, 2 pirapulid genus and 1
brachiopod, always present in cells in coelomic fluid, in cells due to low molecular weight, not lost in
excretion
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Ambient O2 conc
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Excretion – removal of metabolism waste products – CO2, water, nitrogenous wastes
CO2 removal – done using respiratory system, Nitrogenous waste removal – excretion
Waste AA’s – oxidised to ketoacids + NH3, NH3 rapidly removed or converted to less toxic,
NH3 + water  rapid NH3 removal
Ammoniatellic organism – excrete majority of Nitrogenous waste as NH3 – very toxic, only doable in
lots of water – usually done by aquatic inverts e
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Sepia (marine), astacus (fresh), all but one
periwinkle species (1 uses uric acid as It is in the dry splash zone)
Uricotelic organisms – excrete majority of Nitrogenous waste as Uric Acid - insoluble not very toxic,
can be excreted as solid, water conserved e
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Insects + myriapods + other terrestrial inverts

Ureotelic organisms – excrete majority of Nitrogenous waste as urea, less toxic than NH3, Needs
water for removal, few inverts used e
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platyheliminthes, annelids, molluscs
Ecretory systems – in all invert phyla – except cnid + echino, 2 roles – Nitrogenous waste removal +
osmoregulation, 2 basic structures found – Nephridia + coelomoducts
Nephridia – lumen of nephridium – formed by hollowing of nephridial cells, closed internally –
protonephridium, some organisms acquire opening in nephridium into the coelom – nephridial
funnel
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No ultrafiltration in malphagian tubes – haemocoel aat same pressure as tubule – various
ions/solutes actively excreted into lumen
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Secretion – into excretory system, reabsorption – out of excretory system
Pressure generated for ultrafiltration by beating cilia in protonephridia and blood pressure in
coelomoducts
Wanted molecules – glucose, (Na, K in freshwater) removed in system tubules by active transport,
leaving toxic and unimportant molecules behind for excretion
Metanephridia + Nephromixia – no ultrafiltration, fluids directed from coelomic cavity by ciliary
action into tubules, fluid composition modified by active transport

Osmosis – when solutions are separated by a permeable membrane, permeable to solvent and
solute, solutes move from less to more conc solution by diffusion
Osmotic pressure – osmosis, not dependant on no of solute particles but type
Net flow of osmosis is high  low, opposite flow of low high occurs in very small amounts
Animals – body fluids resemble sea water – dilute saline solutions, NaCl main salt – life comes from
sea, able to colonise land by evolving ability to maintain saline solution inside using homeostasis,
maintaining extracellular fluid (internal environment) allows efficient cell function
Most marine inverts are osmoconformers + stenohaline
Osmoconfomers – osmotic conc of body fluids conform with environment – remain iso-osmotic with
it
Osmoregulators – maintain constant internal environment despite changes in external osmotic conc
– freshwater + estuary habitats
Stenolahline – limited salt tolerance, Euryhaline – more tolerant to changing salt conc
Iso-osmotic – same osmotic pressure
Most marine inverts – iso-osmotic with sea water – ionic composition of body fluids differs – ionic
regulation needed
Regulation of ions must occur as – Jellyfish Aurelia – regulates SO4 – too much = too heavy – filters
out to become more buoyant
Mytilus (mussel) – needs high K+, Crab – needs low Mg2+ and SO4, Sepia – chambered cuttlebone –
more gas =lighter, more fluid = heavier
Ca and K more conc in extracelluar body fluid than external body medium, Mg and SO4 usually less
conc
Fluctuating salinity levels – occur in brackish water e
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estuaries, occur at tidal zone – tide out +
heavy rain = low salinity, animals are euryhaline osmoconformers/osmoregulators, freshwater in
estuary  hypo osmotic medium for animal – animal gain water by osmosis, lose salt by diffusion
Hypotonic – solution has lower osmotic pressure than another (lower solute conc)
Hypertonic – solution has higher osmotic pressure than another (higher solute conc)
Euryhaline osmoconformers – adapt to fluctuations, produce more iso-osmotic urine, lower
osmotially active AA conc in cells – reducing osmotic conc of cell e
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Mytilus edulis – bivalve – blood
osmotic pressure approx = to sea water
Euryhaline osmoregulators – adapt – decrease permeability of integument (exterior surface) to salt
and water – e
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crustacean, lose excess water in urine + actively take up salts
Freshwater osmoregulators – adapt to brackish water – regulate whole lives, reduce osmotic
gradient between body fluids + environment – less energy spent, reduce integument permeability,
use excretory organs – eliminate excess water – produce dilute hypotonic urine, actively uptake salt
from surroundings – crustaceans use gills, mozzy larvae use anal papillae
Urine dilution – occurs in long secretory canal – not present in marine
Terrestrial Environment - dessication prevention needed – impermeable surfaces – insect (waxy
integument covering), land snails (shell) – still need permeable gas exchange surfaces
Reduction/protection of gas exchange surfaces – spiracles + closing mechanisms (insect)
Behavioural adaptation - seek out damp environment e
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leaf litter
Urine production = water loss – replace by drinking + food water, metabolic water produced during
cellular respiration
Desert kangaroo rat – dosnt lose much water – special nasal passages, very conc urine, recovers
water from cellular respiration, live in cool burrows – venture out at night, no water loss due to heat
Water bears – tardigrades – lose 95% water  Anhydrobiosis (just add water to!)
Reproduction – creation of new individuals – asexually or sexually, organism sets aside material for
reproduction, inverts – many diff strategies, all organisms have basis of reproduction in common –
genes

Asexual - new individual created as copy, sexual – new individuals created by combing genome of 2
individuals
Asexual – offspring are exact copies of parent, single individual is sole parent, passes copies of all
genes to offspring – genetic differences rise to mutation – not clone – there is some genetic
difference e
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Protozoa, Cnidaria, Sea squirts, certain worm types (most can sexually too)
Mitosis – 2n 2n, no genetic material exchange between 2 individuals, 3 methods
1 – subdivision of existing body into 2 or more – by binary fission 1  2, fission/fragmentation e
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starfish – regrow from one leg, budding e
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polyp of Hydra
2 – regeneration – not a reproduction mode a species would normally use e
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freshwater planarian
3 – production of diploid eggs e
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Daphnia or Parthogenesis – production of daughters from
unfertilised eggs – Rotifers
Sexual – genetic material exchanged – direct exchange of genetic material – conjugation – single
celled protzoans + bacteria
Exchange of genetic materials via gametes – production + fusion of haploid cells (gametes) from a
diploid zygote  new individual
2 x 2n  n  n + n (fertilisation)  2n  2n
Gametes – produced in specialised cell tissue/organs – gonads – testis + ovaries
Sperm – spermatozoa (sperm cells), spermatophore (sperm packet)
Egg – ova (ovum)
Why sex? – genetic variation (greater in sexual than asexual)  evolution
Variation caused by independent assortment, crossing over and random fertilisation
Asexual advantages – exploit temp abundant food/living space, create cysts (dormant forms to
survive harsh/uncomfortable environmental conditions), less energy costly than sex
Sexual advantages – maintains genetic variation, recombination  high polymorphism in pops,
species genetically prepared for environmental changes-physical/predators/parasites, evolution of
species
– maintains genetic variation, recombination  high polymorphism in pops, species genetically
prepared for environmental changes-physical/predators/parasites, evolution of species
Phyla examples – Protozoa – asexual binary fission, sexual conjugation
Porifera – asexual internal budding (gemmules) and sexual – sponges are hermaphrodites – either
F+M or F or M – release gametes simultaneously into sea (broadcasting) through osculum
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Produce eggs – fertilised or unfertilised, fertilised 
diploid – Female – Queen/workers, unfertilised  Male – drone
Hexapoda – Aphid – cyclical parthogenesis – parthogenesis (F born vivipartity + ready to reproduce)
Parthogenesis – F + M, mating – female lays eggs – no vivi, increases explotation of food in summer
Parthogenesis – ova diploid – essentially have same genome as parent
Chelicerata – arachnae – elaborate courtship, with high visual, sperm transfer by pedipalps, sperm
induction into female reproduction tract via pedipalps, courtship – bright colours, attitudes
semapohore
Crustacea – daphnia – winter – dancing – conditions less favourable, produce haploid ova needing
fertilisation, eggs have thick resistant shells improving winter survival, increased genetic variation –
improve suruvival success in harsh conditions – temp, food scarcity, overcrowding
Summer – parthogenetically reproduces – summer eggs – diploid, produced mitotically, large
number of eggs rapidly, rapid rising pop to exploit favourable conditions – optimum water temp,
abundant food
Echinodermata – sexual + asexual, Asexual – fissiparity – asterodia – sea star, ophiorodae – brittle
star Sexual – have gonads, separate sexes, discharge gametes into sea water in response to
chemostimulus of other gametes, gonopores – 2 per arm (asteroidea) large gonads – almost fill arm
Mollusca – cephalopod – nautilus, squid, octopus, cuttlefish – sexual – separate sexes, internal
fertilisation – no penis, 1 arm differentiated – Mpulls chitinous sperm packet out of self – passes to F
Tracking – mate tracking important for inverts in dispersed pops, pheromones released by F to attact
M (M can also release)
Courtship – varies in complexity, posturing to assure F, M is not a predatorelaborate signalling
using body size/feature size/colour/motion
Inverts – care for young – brooding – egg sacs (daphnia), brood chambers – myriapod
Development – zygote cleavage – early zygote divisions, mitosis EmbryomitosisBlastula
(cell ball)GastrulationGastrula  Juvenile/larvae  Adult
Progressive differentiation of parts, fertilised eggs to adult, development and growth often occur
simultaneously
Ovum – specialised sex cell – egg- once fertilised with male gamete zygote
Egg – nutrient material/yolk, protein + lipoprotein, yolk spheres (vitellin), lipid droplets,
mitochondria, RNA
Zygote – polarised cell along animal-vegetal axis, polarity recognisable as development proceeds
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5M
2 Groups – Enteropneusta – acorn worms, sediment burrowers or suspension feeders
Pterobranchia – sessile + colonial (usually), suspension
Chordata – 3 subphyla – cephalochordate, urochordata, vertebrata
Cephalochordata - lancelet or amphioxus, all marine, sand burrowing filter feeders, notochord –
extends to head, rudimentary sense organs, no differentiated brain, all 4 chordate features
throughout life
Urochordata – 3 classes – Ascidiacea – sea squirts, some solitary, some colonia, larvae are planktonic
– few days then metamorphosis – Adults are sessile – plankton filter feeders have body wall “tunic”
(tunicates)
Thaliacea – free living, pelagic (open ocean), filter feeders, liver solitary or as aggregates (clumps)
Larvacea – small, few mm, planktonic, abundant in surface layer of warm water areas, adults retain
larvae characteristics, body= trunk+tail, trunk – holds major organs, tail – thin+flat with notochord,

produces gelatinous house for feeding
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Where is the Notocord? – Agnathans – persists and grows as animal does
Most fishes, some salamanders – persists along length of trunk + tail, constricted within each
centrum (vertebrae)
Some amphibs + reptiles + birds = almost all gone
Mammals – vestige remains as numerous pulposus within intervertebral discs
Fish – Sub-Phylum – Vertebrata, Super class – Piseces – 4 Classes – Agnatha, placodermi,
chondricthyes, osteichthyes
Evolution of Jaws and Teeth – major transition in vert evolution
Preverts (suspension feeders e
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amphioxus – can only eat what is in water – small niche)
evolution of muscular pumpJawless fish e
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Hagfish evolution of JawsJawed fish – can eat
much more – large niche
Earliest Verts – Jawless marine fish – Early/mid Cambian 530mya, 2 species – both had gills and
myotomes (zigzag muscle arrangement only found in fish), 25-28mm long, cartilaginous skeleton –
no bone
Ostracoderms – armoured fish, late camb  Devonian (400-525mya), heavy exoskeleton of solid
bone – well armoured, in brackish, marine + freshwater
Major Fish Characteristics – Cranium (protects brain), Gills (respiration and waste ion disposal
throughout life), fins (locomotion)
Agnathans – Jawless fish – only verts with no jaw, cyclostomes – round mouths – adapted for
holding/rasping, primitive – have notochord, no jaws/vertebrae or paired appendages
Hagfish and Lamprey, Hagfish – scavengers + things in burrows, cyclostome mouth used for rasping +
cutting, poor vision (live in abyss) good touch (ring of sensitive mouth tentacles) and smell, partial
cranium, skeleton of cartilage, no jaw – 2 pairs of rasps on top of tounge like projection, primitive tail
fin, secrete very sticky slime if preyed upon (not easy to eat), no metamorphosis – direct
development from egg, ALL MARINE, tie in knots to clean, defend and eat
Lamprey – fresh water or anadromous (marinefreshmarine), metamorphosis – Egg Larvae 
adult, complete cartilaginous brain case and rudimentary true vertebrae (no bones/scales), round
jawless mouth – rows of horny teeth and rasp like tounge, medial unpaired fins, parasitic – latch on,
bore hole with tounge, drink body fluids, leave gaping wound death of fish due to water full of
pathogenic bacteria + viruses, marine – feed on whales!
Gnathostomes – Jawed fish – upper + lower bony element of 3rd gill arch  maxillary + mandibular
elements of gnathostomous jaw, upper + lower bony element of 4th Gill arch hypoid apparatus
Placoderms – earliest jawed fish – 420-335mya, heavy bony armour on head + neck, rest of body –
naked/small scales, jaws – no teeth (biting/grinding structures in dermal bones lining mouth), huge
radiation  dramatic extinction, small mostly but dunkleosteus 6m! (bigger bite force than great
white shark), first evidence of live birth in verts
Chondrichthyes – cartilaginous fish – sharks, rays, ratfish, skeleton of cartilage, no bone (ancestor
had bone), male pelvic fins are claspers to aid internal fertilisation, pointed/conical placoid scales
Subclass elasmobranchi – sharks + rays, characteristic slitlike external gill openings, ancestral 1st gill
slit reduced to spiracle – little role in respiration – now a sensory structure, mouth is ventral (headmouth-tail)

Subclass holocephali – ratifish, marine fish, gills covered by bony operculum (covers fragile gills – can
open and close), spiracle and scales absent, pelvic claspers + cephalic claspers (grabs pectoral fin +
swims with female) for mating
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Air 200Kppm, water – 10ppm
Fish must be efficient – Rate of diffusion = (diffusion constant X area of exchange X difference in
partial pressure) / distance involved
R = (D X A X Delta p)/D
Area of exchange, difference in partial pressure, distance travelled can be modified – have a large
surface area, keep constant water flow over gills, ensure only a short distance involved
Gill structure – 2 columns of gill filaments – primary lamellae extend of each gill arch, gas exchange
occurs at 2ndary lamellae (projections off filaments)
Current maintained by bucal pump/ram ventilation (open mouth, swim forward), unidirectional flow
of water = high difference in partial pressure
Gill filament – 2 arteries each, afferent – gill arch to filament tip, Efferent – returns blood to gill arch
Secondary lamellae – 1 layer of epithelium, 1 layer of endothelium = minimal distance
Blood flow through lamellae opposite to water flow – counter current exchange
Counter Current exchange – opposing flow of water and blood, maintains high difference in partial
pressure across lamellae length – always a high conc
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gradient decreases to O, R = O – exchange stops
Counter current – flow opposing – conc
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Circulation – Function – transport gases, nutrients, waste products, hormones, heat and other
materials
Components – heart, arteries, capillaries and veins
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Capillaries – exchange between blood + body
cells – thin walls, endothelium only
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to environment, permeable membranes
 osmotic movement of water and ions occurs physiological processes disrupted when internal
ionic conc
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gradient, Na+ follows
Saltwater – cartilaginous fishes – interal urea conc maintained at high level, high enough to keep
total internal osmotic conc above sea water, gain of water by diffusion, tolerate high urea levels
Urea – produced as end product of nitrogenous metabolism, actively reabsorbed from kidney
tubules, not lost through gills – urea too big to be permeable
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GAVE RISE TO TETRAPODS
Major Transition – Movement onto land – 1st crossopterygii – Rhipstidians
Pandericthyes – end Devonian – 386mya, 1m long – no dorsal or anal fins, 4 fins – 2 pectoral, 2 pelvic
(4 Limbs), skull bones equivalent to earliest tetrapods, middle ear architecture very similar, fin bones
fit tetrapod pattern – forelimb (humerus, ulna, radius), hindlimb (tibia, fibula), But have lungs,
nostrils + Gills, limbs still have fins
FinsLimbs – sarcopterygian paired fins – moved under body and developed digits
Earliest known tetrapods – Acanthostega – 360mya, 4 limbs, 8 digits on each, had functional internal
gills still, No true elbow, wrist, ankle, limbs not weight bearing
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1%support that water does) – need strong apendages, girdles, need to be well attached to axial
skeleton, robust spine
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Apoda – without feet – caecilians, 170 species, no limbs/girdles, burrowing lifestyle, carnivourous
eats insects, insect larvae, worms), range of reproductive patterns -oviparous – egg layer, viviparous
– live bearers, ovoviviparous – eggs hatch inside mother, live in till maturity
Maternal feeding of young – secretions + mother’s skin
Integument - smooth skin (dermal scales vestigial in some Apoda), important role in gas exchange –
capillaries in lower epidermis, Leydig cells – secrete substances as bacteria + virus protection,

mucous gland – keep skin moist BUT moist = bacteria thrives, poison gland – distasteful/toxic – anti
predation –accumulated from food, chromatophores – structures allowing skin colour change, insect
repellent in frog skin secretions
Poison – comes from ants/mites, accumulation gives frogs poision
Skeletal System – skull – simplified unlike fossil ancestors, many dermal bones lost/fused, caecilians
– compact ossified – push through sediment – need ossified
Vertebrae – 3 types – amphicoelous – concave both ends (caecil + few salamanders), Procoelous –
concave front, convex back (anurans), Opisthocoelous – convex front, concave back (most salama)
Appendicular skeleton – varies according to lifestyle/habitat – need to be strong to withstand huge
forces from jumping
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Other use - mate choice in cane toads – too small,
no mating
Non pulmonary – skin major respiratory organ, some species only respiration, moist skin, thin
keratin, rich capillary supply in skin, folded skin increases surface area, moving water – maintains
pressure, still water – organism must move, Hairy frog – temporal specialisation develop skin
filaments during breeding season – large SA, extensive blood supply, needed for more activity,
guarding eggs
No lungs – barbourula Kalimantanensis – in fast flowing streams – lots of O2, aids submersion (lungs
would cause buoyancy
Internal/External gills – aquatic amphibs – pharangyeal slits + internal gills, external gills common
Pedomorphosis – in larva (and adult) – need water flow, movement or pumping



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