Ichthyology Notes BIOE 127 - 01
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Date Created: 10/05/15
Ichthyology Notes Week One Fishes make up 41 of fresh water 58 of salt water and 1 are diadromous We use countsmeasurements to describe sh Meristics Counts Morphometrics Measurements usually by ruler in hand 0 Always draw left side of the sh because incisions take place on the right side Cadistics A method of classi cation of sh according to the proportion of measurable characteristics that they have in common It is assumed that if two organisms share a high amount of these characteristics the more recently they diverged from a common ancestor 1 Systematics 2 Fish Evolution 3 Molecular systematics Genetic approach Darwin amp Wallace Believed all species were related through common descent Wii Hennig Developed cladistics method to infer relatedness Goal was to correctly group ancestors and all of their descendants Cade Two considerable de nitions 1 All individuals descend from single ancestor 2 All descendants of that ancestor are part of the clade FishF F Tetra po F A i Ancestor O Figure Description Different species at the end of each branch of the phylogenetic tree Circled in Blue is a clade Two different sh with the same ancestor who have shared and derived characteristics 0 Having one ancestor and shared derived characteristics is termed a characteristic of a branch 0 characteristic found in ancestral state lnterchangeable Terms Clade Natural Group Monophyletic group Assemblage Second De nition Not true for sh because they aren39t a clade Tetrapods are included on the gure which are mammals birds etc Fish are an unnatural group Fish are paraphyletic Clades are not used as a taxonomic ranking species related to others but not necessarily in the group you are studying ingroup Helps determine polarization of groups within the phylogenetic tree Outg ro ABC gure Example of Species A Species B and Species C are connected but we do not Know the root of Wreeronasgfelenewtheancestor Cladistics Or thlooenetic Svstematics Fundamenta Approach 0 Divide characters into B groups 0 Apomo phies the recently derived characteristics 0 Plesiom phies an estral primitive characteristics 0 Identify synapo orphies 0 Ex swim bl dder jaw eyes gills etc Also Poyphyetic taxa descende from seve al ancestors Problems with Traditio A ladistics C homopasies traits evolved due to convergence 0 Ex Shark vs Tuna keel statisticaly inconsistent can lend more support for the WRONG answer 0 Vs statistically consistent right answer support unequal rates of evolution Lineages can evolve at different rates HI 0 Figure Above By chance A and C have the same mutations blue arrows B and C have two synapomorphies that de ne their clade Molecular Svstematics and Genetic Approaches compare similarities and differences in DNA sequences 0 Identify informative sequences synapomorphies different parts of the genome evolve at different rates 0 Choose appropriate sequences to compare address questions about biogeography and evolutionary history that traditional systematics cannot Ex African Cichlids amp Great African Rift Lakes Lake Victoria Lake Tanganyika Lake Malawi 0 Cichlids were sensitive to color females would choose mates based off of this 0 Species survived from one predator turned to hybridization mating with those they wouldn39t normally mate with Parallel Vs Converoent Evolution Parale Evolution When two species that share a common ancestor evolve a similar trait independer A A of each other ss Convergent Evolution When two species without a close common ancestor evolve a similar trait independently of each other Molecular Clocks and Calibration in Sharks fossils and geologic events caibrate sequence divergence estabish molecular clock 78x slower than in mammals because sharks use urea to osmoregulate to displace water water generates urea Moecular Clock calibrate trees how quickly they evolved Linus Poling The divergence of molecules is related to divergence of split Can calculate when split occurred Fossil and molecular clock perfect match Evolution of Endothermv Endothermy internal temperature is warmer than external monophyetic or convergence two contrasting hypotheses Probem Have large warm blooded shes but why 0 Were they derived from single ancestor and that ancestor was warm blooded NO because heating organs have showed they have evolved four times tuna bill sh mackerel etc 0 Warm because they are large and evolved YES Early Fishes Early Chordates invertebrates Conodonts Early Vertebrates Jawless Fishes Agnatha Ghathostomes Junction Placoderms Chondrichthyes NP P PP N Orders end in forms Cypriniformes Famiies end in idea Cyprinidae 1 Most primitive chordates Urochordates tunicatesattachedsalpsfree oating Cephalochordates lancelets sisters to vertebrates 0 Lack vertebrae have notochord 23 ConodontsVertebrates Craniata vertebrates o Synapomorphies cranium present cartilage and bone present heart chambered neural crests neural system near backbone Conodonts 600200 mya Early rst vertebrates controversial Fossilbone looking shapes ID age of layer similar teeth quotelementsquot were abundant in fossil beds Not until 80 s did we nd fossilized soft body parts Cartilaginous head and skeleton Don39t have jaws yet Are they lter feeders or predators Predators because as a predator you don39t need more food or a larger mouth to sustain oneself Filter feeder mouthes grow exponentially with body size whereas a predator39s mouth the conodont39s grows linearly OOOOOOOO 45 Jawless FishesAgnatha Paraphyletic No synapomorphies Two types alive and dead Extinct are termed Ostracoderms meaning shell skinned heavily armored with a tail lower lobe larger than top of n not monophyletic Hag shes Living Jawless Vert Class Myxini Order Myxiniformes o 77 species 000000000 0 0 Live deep scavengers No osmoregulation isosmotic Rudimentary hearts 70200 pairs of slime glands Eye spots Lack vertebrate Have rasping tongue slimyno jaws with denticles Feed on decaying animals by creating knots with body Secretes slime as defense mechanism Fish or predator of hag sh will choke to death on slime if hag sh is kept inside their mouth Nobody knows how they reproduce Produce eggs in contrast with ampreys no larval stage hatch and look like parents Lampreys Living jawless vertebrates O O O O O O 0 42 species Class petromyzontidae Order petromyzontiformes Larvae called ammocoete undergoes metamorphosis lter feeds Osmoregulation found in fresh and salt water ocean Ocean forms suck on salmon in lakes killed off all of the salmon and some died from starvation others managed to reform Reproduction semelparous and males build nest Non parasitic species thelodonts and parasitic quotquotabove 5 Gnathostomes jawed vertebrates Synapomorphies jaws modi ed from gill arches paired limbs vertebral 6 Placoderms plate skinned in fresh and salt water arose 430 mya synapomorphies head and shoulder girls with dermal bony plates has 5 gill arches 7 Chondrichthyes Cartilaginous Fishes arose 420 mya some live in the ocean others in fresh water two types Rat sh SharksRays extant cartilaginous shes synapomorphies cartilaginous skeleton calci ed not ossi ed skull with no sutures internal fertilization with claspers high blood concentration of urea ocean cartilaginous shes used for osmoregulation Nitrogen waste reproduction Oviparous lay eggs 40 species Viviparous live organisms 10 species Ovoviviparous egg hatches internall and then gives birth 50 species spit into two subclasses Elasmobranchiisharksrays Holocephaliratfishes Hoocephai Chimaeras or Rat sh Whole head Oviparous Synapomorphies gill cover over four gill openings upperjaw fused to cranium like humans only using lowerjaw Some have head claspers females hold onto males