Lecture 6 and 7 Notes
Lecture 6 and 7 Notes 81463 - BIOL 3030 - 001
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This 11 page Class Notes was uploaded by Abigail Towe on Wednesday September 16, 2015. The Class Notes belongs to 81463 - BIOL 3030 - 001 at Clemson University taught by Richard W. Blob in Fall 2015. Since its upload, it has received 44 views. For similar materials see Vertebrate Biology in Biological Sciences at Clemson University.
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Date Created: 09/16/15
Life in Water First vertebrates were MARINE Characteristics of aquatic environments place specific demands on vertebrates Water is 800x denser than air 9 That means that the water Will support and help hold their body together skeletons don t have to be as massive because the water Will do the job 9 Aquatic animals can have bigger maximum sizes rather than land animals 0 example whales 0 aquatic big gt gt land big Water is 18x more viscous than air 9 This means that it s harder to ow Example syrup motor oil More viscous uid resistance is greater 999 Therefore it s hard to move through water because it s dense and has more resistance Because of this aquatic life tends to have a streamline body shape that helps reduce friction drag so that they can move more easily 9 It s also harder for the animal to be moved 0 Respiration 9 water is dense and heavy so it takes a lot of energy to move it around Water has less oxygen than air 9 important consequences for respiration 9 Water has low oxygen content so animals must be able to move lots of water across respiratory surface location Where blood vessels that are extracting oxygen out of environment for use of the body are located 0 so if you aren t getting enough oxygen from source then you need to move to new source water has greater heat capacity and conductance than air 9 so water has more stable temperatures water has greater electrical conductivity than air 9 animals benefit by using water for different sensory opportunities water is surrounded by water 9 important implications for bodily functions like water and ion loss because water has low oxygen content and requires animals to move lots of water across respiratory surface to get enough oxygen and because water is dense and viscous heavy to move O GILLS highly vascularized 9 developed on walls of pharyngeal pouches 9 between each pouch a skeletal GILL ARCH of skull supports gill filaments with capillaries for acquiring O2 9 gill filaments have the vessels that actually extract the oxygen 9 The gills of fishes are supported by a series of gill arches encased within a chamber formed by bony plates the operculum A pair of gill filaments projects from each arch between the dorsal upper and ventral lower surfaces of the filaments there is a series of secondary folds the lamellae where the gas exchange takes place The blood vessels passing through the gill arches branch 9 the concentration of oxygen is the same across gills O Gills are efficient at extracting oxygen from water because 0 the water comes in a oneway ow to save energy rather than using energy to change direction 0 Mechanism 0 Buccal pumping can perform without swimming 9 water in mouth 9 close mouth 9 squeeze head to force water over gills 0 Ram Ventilation must be swimming 9 mouth held open 9 water passes through amp over gills O countercurrent exchange water ows in opposite direction from blood in gill capillaries 0 oxygen content of blood always lower than in water 0 so blood can always extract oxygen 80 95 efficiency o gases ow areas of high to low concentration Fishes with gas 9 Swim bladder in many bony fishes lungs are modified into swim bladder that can regulate buoyancy 9 However the problems of the swim bladder o if you dive the pressure compresses bladder so that fish sinks o the gas gland has to secrete more oxygen 9 To get gas out of the bladder to prevent fish from exploding when rising because the low pressure expands the oxygen in the bladder o physostomous fish burp air out via swim bladder to gut tube connection 0 physoclistous fish relax muscles closing off ovale which releases gas to blood Remember no bladder in sharks and rays 9 They have oily liver for regulating buoyancy instead Sensory systems 9 Vision perception of light 0 we are naturally very perceptive individuals 0 light bends refracts when it passes through a substance such as water 0 as it passes through parts of the body cornea front of eye the light also bends Cornea and water have same refraction index about 13 0 Once light passes through the cornea a sphere shaped lens focuses light on retina to allow a clear image 0 So because of this if you have light focuses through water and your cornea then you need a spherical lens so that it focuses light before retina so that you can see o This spherical lens will focus imagines in the middle of the eye at a lower refraction index at 1 so it won t be able to see in air 0 Therefore there are different shaped lenses fish have spherical lens mammal eyes have at lens 9 Animals that live in water and air 0 one example anableps four eyed fish 0 These fish have a divided cornea and oval lens to allow light from water and air to both focus on retina o cornea is divided half in air half in water 0 lens has a spherical and at shape oval 9 special for aquatic vertebrates o a specific system devoted to detection of movement Lateral line system made up of neuromasts that are connected to pores or canals and connect to the surface 0 ancestral system detecting water movements 9 chondrichthyes bony fish some amphibs o Neuromast organs 9 in pores or canals opening to surface 9 each has pair of hair cells long and thin 0 called hair cells because they have tiny projections that grow out of them that are called kinocilia 0 they project into a wad of gel called cupula 0 water moving to cupula de ects moves hair cell kinocilia sending out nerve signal 0 it detects what direction the water movement is coming from o Electroreception close association with Lateral Line system because it detects changes in electricla potential of environment o can detect muscle movement you can tell if there s a hidden prey fish 0 finds hidden prey from electric discharge of muscles 0 Well developed in sharks 9 ampullae of lorenzini pores filled With electrically conductive gel 9 gel filled canal gt sensory hair 0 Electric Discharge 0 some rays eels catfish use to catch prey or stun predators up to 600 V 0 some weakly electric fish communicate With electric discharges O gymnotids knife fish mormyrids elephant noses Excretory System of Aquatic Vertebrates O removes nitrogenous wastes excess salts and water via nephrons collected into kidneys 0 environment in uences kidney structure and function 9 Fish has greater solute concentration than water therefore water diffuses passively into fish 0 Does not drink 0 BIG glomerulus gt lots of dilute urine 0 Absorb ions to replace salts through gills 9 Water has gt solute concentration than fish fish loses water to environment risks drying out 0 Drinks sea water don t try this at home 0 Pump ions out through gills void through feces o SMALL glomerulus gt small amounts of concentrated urine a a Clade Chondrichthyes Gnathostomes gnath jaws stomes mouth 9 Gnathostome synapomorphies 1 jaws 2 2 pairs of paired appendages 3 a 3rd horizontal semicircular duct in vestibular system helps you determine your positionorientation in space of ear Gnathostomesred line a species include o sharks rays bonus b There is a very early basal split of gnathostomes into subclades 0 looks like Chondrichthyes vs Osteichthyes in cladogram slide 3 but really a little more complex o first clade purple line includes sharks and rays and then a clade that includes almost everything else green group two big groups Major Gnathostome subclades a b Eugnathostomes 0 true teeth Teleostomi 0 terminal mouth 0 bony gill covering operculum gt First of Gnathostomes PLACODERMS a early carboniferous b 425325 MYPB c heavily armored d distinct joint between head and trunk shield 0 so that they could raise their head high so that the bottom jaw would maintain parallel orientation with ocean floor e does have true jaw but not true teeth they have bony cutting edges along the edges of the jaw yes it s sharp but it s not a tooth in a socket f heterocercal tail 0 upper lobe is larger than the lower lobe g This is the outgroup to all other gnathostomes h some reached huge sizes 6 meters 20 feet Antiarch a One clade of Placoderms b pectoral fins enclosed in bone to produce spine o purpose punting bottom feeders C sharp projections going to the bottom always them to stab down pull forward repeat to move o The fins are entirely encased in an outer covering of bone c Spine originally short and unjointed becomes longer and jointed in later species 0 to offer more flexibilitymovement d often found in aggregations of several individuals o first example of schooling behaviors Arthrodire a b 9 another clade of placoderms most diverse placoderm clade o includes about 60 o of all species often huge larger than 20 feet long large nuchal gap allows greater head movement and a more forceful bite has sclerotic ring in eye 0 bones in eye 0 shows up for the first time ever in this species o jaw edges can show toothlike projections o to allow for grasping prey item to bite and then be able to pull onto evidence of both healed and unhealed bite wounds 0 possible cannibalism Placoderm puzzle a b What caused their extinct o they were a high food chain member large strong one explanation decline in sea levels in Late Devonian term may have eliminated shallow water which is where they were found o highoxygen habitats forced competition with other lineages osteichthyes and chondrichthyes gt CLADE CHONDRICHTHYES Cartilaginous fishes 8 1200 living species b first fossils from Devonian 4OO MYBP C d e includes Clades o Holocephali o chimeras and ratfish o elasmobranchii o sharks and batoids skates and rays batoids are a subclade of elasmobranchs sharks are a GRADE unless batoids are included Synapomorphies 1 cartilaginous skeleton secondary loss of bone 2 claspers a This is the modified pelvic fin in males conducts sperm during internal fertilization b evolved convergently in some placoderms 3 Placoid scales a distinctive type of scale that has a toothlike structure with pulp cavity that is surrounded by dentin and enamel b lightened body c because pointy ridges in scales it reduces turbulence decrease energy expenditure and drag to increase swimming speed Scales of Placoid compared to Ostracoderm i Placoid small pointy toothlike enamelcovered ii Ostracoderm large flat heavy 4 Vertebral centra body elaborated reduced notochord 5 Continuous prolific tooth replacement tooth whorl gt Clade Elasmobranchii O Evolutionary Trends in shark morphology 1 more mobile pectoral fins gt improves steering a in first sharks the pectoral fin at a very broad attachment and included stiff radials cartilages b but in younger sharks there is a narrower attachment and has flexible fibrous supports ceratotrichia c This is good because the fin is more mobile allows to steer in direction better 2 Has more heterocercal tail top lobe bigger than bottom a functionally this morphology serves to pitch the tail up and head down i plus mobile pectoral fins can pitch head up and tail down 0 So with both of these in combination it allows the shark refined control over rising and diving which is good for chasing evasive prey 3 mouth position a tip of snout terminal but then later located under snout ventral side 4 tooth shape and diversity a cladodont big middle cusp lots of inside cusps catch prey whole b diverse modern shapes and behaviors fewer side cusps some have multiple types heterodonts 5 Jaw attachment a Early Sharks i one connection is the upper jaw connected directly to the braincase ii the lowerjaw is connected hyomandibula which is connected to the braincase iii Amphistylic condition both connected to braincase one direct one indirectly b Later sharks i Hyostylic 1 one connection upper jaw now connected to braincase by ligament 2 The Hyostny allows jaw protrusion during closing which helps sharks bite into prey that is bigger than their heads a the jaw is thrust forward and out to allow it to clasp something that is bigger than its head because of this new jaw suspension Shark biology 0 Order of sense use in prey detection 1 olfaction smell chemoreception a locate prey at distance 1 part in 10 billion b uses this to get closer to prey 2 lateral line mechanoreceptive a slightly closer distance thrashing water b perceives disturbances in the water from a distance c sharks are attracted to helicopter motors flying above 3 vision a well developed even in low light b helps in great depth 4 tactile a may physically bump unfamiliar prey for close appraisal b 5 electroreception a very close after eyes closed during strike The brain of a shark is very big for their size it helps process all the complex sensory info Great White Prey Selectivity o bite and spit I feeding strategy where they will bite and continue biting until the prey bleeds to death 0 prey on seals bite and hold to bleed to death 0 others bite and spit I tests for blugger content c favors prey with higher blubber content esp seals I protects shark from injury like sea lions 0 sea lions have larger fins to fight back can really hurt the shark More Shark feeding habits 0 Cookie cutter shark I uses suction to stick on the side of aquatic animals then cut out a chunk and run away to do something else 0 Filter feeders I tend to be the largest body size species greater than 30 feet I swim with their mouth open 0 so they end up straining plankton with their mouth even though that s not what they want Shark Reproductive Biology 0 Modern spotted catshark I internal fertilization 0 male wraps his midlower body around female 0 some species bite and hold on to females females often have thicker skins than males to protect them from injury 0 older shark Damocles Carboniferous Montana I roles were reversed male has clasper but female was found on top and biting in some specimens 0 KSelected very few welldeveloped youngoffspring I different strategies to execute this Kselected approach o Oviparous o proteinaceous egg cases prongs to tangle in vegetation o offspring develops outside of mother o Viviparous 0 live birth yolk sac attaches to mother like placenta O o PreBirth Cannibalism babies eat unfertilized eggs or even siblings eg great whites Conversation Challenge grow slowly few young ranges cross international boundaries gt difficult to recover from harvesting or enforcing protection Batoid Synapomorphies 1 Flat bodies a also enlargement of pectoral fins b originally related to bottom dwelling some now open water 2 Ventral gills a spiracle still big faces up dorsal 3 Durophagy a eat hard shelled prey b they have these pavements of teeth crushing tooth plates to allow them to crush hard shells like clams snails 0 Main points 0 pectoral fins get bigger tail shorter 0 electric and stingrays different groups I stingrays have a venomous tail spine I electric rays used electricity 0 the tail is reducedbecomes narrower to whip not used for swimming I in stingrays and especially eagle rays 0 eaglemanta rays flappectoral fins to swim other pass waves along I basically flying under water Holocephalans o ratfish or chimeras 0 small group and small body size adaptations for durophagy eat hard prey I uses autostyly in jaw used to braincase o humans have this I reduced number of big crushing tooth plates fleshy covering over all gill slits operculum I not the same as later one in bony fish I independent origin of analogous structure diphycercal tail vertebral column between egualsized lobes swim by flapping pectoral fins up and down motion
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