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Zoo 3700 Midterm Notes.docx

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ZOO 3700
Douglas Fudge

ZOO 3700 PRE-MIDTERM NOTES What is science for? How does it differ from other ways of knowing? -science always leaves room for a better explanation, has no bias Assignment 1 observation - question - hypothesis - prediction - How can science progress by disproving hypotheses? -creativity followed by criticism -what about induction? - rarely happens Plankton? Drifting organisms that inhabit the pelagic zones of oceans, seas or freshwater bodies of water Ecological not phylogenetic definition Holoplankton-spend their whole life as plankton (examples: diatom, copeopod, krill, polychete, pyrozomid (tunicate), sea angel, ctenophore, daphnia) Meroplanktion - only part of life as plankton (examples: auricularia, trochophore, tornaria, tadpole, veliger, planula, pluteus, megalops, pilidium, nauplius, cyphonautes) Zooplankton - heterotrophic plankton Phytoplankton - photosynthetic plankton Advantages of a planktonic larval phase? -  take advantage of abundant and seasonal food resources (zoo and phytoplankton),  colonization of new habitats,  avoidance of catastrophe due to local habitat failure,  avoidance of local and sib-competition,  exposure of diverse offspring to max degree of habitat diversity Challenges of a planktonic lifestyle?  predator avoidance-lack of hiding places, buoyancy-holding position, swimming-at low reynolds number. solutions?  transparent body,  protective spines,  diel vertical migration-possible selection forces-evidence from Gilwicz, sensitive detection of predator movement,  escape responses,  bioluminescence. buoyancy regulation  use of floats,  lipid accumulation,  shell loss,  selective ion regulation,  decreasing the sinking rate movement at low Reynolds numbers, Re=PiU/u (ratio of intertial effects/ viscous effects) Re>2300, inertia dominates Re<2300, viscosity dominates swimming at low Re-  viscosity dominates and inertia is negligible  streamlining not important, flow reversible  symmetrical flapping strokes not effective  need different power and recovery strokes  or helical waves of bending ex. corkscrew Planktonic Research History John V. Thompson - early 1800's Johannes Muller - mid 1800's Victor Hansen - late 1800's Alexander Agassiz - late 1800's Ernst Haeckel - late 1800's described lots of species Modern Research Using Plankton nets:  zooplankton-300um  phtoplankton-20um  opening/closing nets  CTD - studying water - density, salinity, temperature  Remote fluorometry - find fluorescent molecules in water ie. how much chlorophyll to find the amount of phytoplankton  sonar  optical counting  sampling submersibles  shotgun genomic sequencing Challenges of Living on Land  desiccation  mechanical support  fluctuating temperatures  UV exposure  Excretion of nitrogenous waste  Reproduction  Gas Exchange Major Terrestrial Taxa  Hexapoda  Arachnida  Myriopoda  Gastropoda  Crustacea  Oligochaeta Lifestyles on Land  Aquatic - surrounded by water  Cryptozoic - desiccation intolerant - hidden under leaf litter etc.  Hydrophilic - active in high humidity, desiccation tolerant -  Xerophilic - active in dry environments - can survive extreme dessication ex. tardigrades, mold, yeast Critical Adaptation  Desiccation - waxy epicuticle, malphigan tubules  Mechanical Support - exoskeleton, musculature  Fluctuating temp - biochemical adaptation, endothermy  UV exposure - sunscreens, exoskeleton  Excretion of N waste - urea, uric acid, guanine  Reproduction - internal fertilization, resistant eggs  Gas Exchange - invaginated lungs, spiracles (no gills) Gas Exchange Which Gases? Oxygen and Carbon Dioxide Where do they come from? Why is it important to exchange them? CO2 can acidify the body if it is not removed How do gases move?  Diffusion  Ficks Law - M = xD A(x -C extLintdiffusion rate, D-diffusion coefficient, A-Area, C concentration gradient, L-barrier thickness  1 mm rule of thumb - diffusion is very difficult across a barrier of 1mm or more Importance of Surface Area 3  Volume increases with body L 2  Surface area increases with body L  SA/V ration varies with body L 2/3 How do organisms increase their SA/V ratio?  stay small  stay flat  create invaginations/evaginations How do organisms maximize C -C ?ext int How to disrupt boundary layers?  fluid flow via cilia  Fluid flow via appendages  Whole body movements In water vs. Air?  O 2ontent of water is 1-12 ppm  O content of air is 210,000ppm 2 5  O 2iffusion in water is 3x10 slower than in air Respiratory Structures-Unity and Diversity  Polychaetes - tentacles(gills), parapodia  Molluscs - ctenidia,  Arthropods - Isopods - pseudotrachea  Arthropods - terrestrial crustaceans -  Arthropods - myriapoda - trachea, spiracles  Arthropods - Hexapoda - trachea(good at open and closing when necessary), deliver oxygen and remove carbon dioxide from every cell, tracheal pumping-limits to body size Kaiser et al. 2007 PNAS 1.02 XSA of trachae penetrating the legs to the body mass 0.77 XSA of leg orifice proportional to body mass  Arthropods - aquatic insects - gills, mosquito larva-snorkel, damsel flies-lamellae (leaf like structures) serve as a respiratory and locomotosry structure, diving beetles take down a bubble with them.  Echinoderms - invaginations (look up starfish) Hypoxia Changes in the environment cause "dead zones", hypoxic regions meaning lack of oxygen. This happens due to agricultural wastes (fertilizers) entering the water and causing algal blooms. There are too many to be consumed by predators so they die. Bacteria, in turn come to eat the decomposing plankton and use up all of the oxygen, causing fish kills etc. CO 2evels 1/3 of CO 2eleased by humans over the last 200 years absorbed by oceans. CO 2ecreases PH of water Shifts equilibria re: calcification - calcifying organisms need normal PH to develop their shells Circulation -escaping the 1mm rule -Fick's law -Circulation provides:  connective delivery  disruption of boundary layers  transport of gases  transport of nutrients  transport of waste  hormones, immune responses Open system: the gas exchange does not happen within the system, it "bathes tissues" - circulatory is separate from respiratory Closed system: the blood never leaves the circulatory system, gas exchange in capillaries - circulatory and respiratory are connected Pumps: open - ex. cilia closed - ex. hearts Convergence among Cephalopods and Higher Vertebrates molluscs - open --->ceph closed  closed system  capillaries  endothelium  systemic heart  branchial heart we have 2 sides to our hearts... almost like each side is its own heart Respiratory Pigments  hemoglobin: red, Fe, free /corpuscular, all major groups  hemocyanin: blue/green, Cu, free, molluscs, arthropods  Chlorocruorin: green, Fe, free, sessile marine polychaetes  hemerethryn: colourless/pink, Fe, corpuscular, sipuncula, brachiopods Transport of nutrients  in large organisms the transport of nutrients from gut not possible via diffusion alone  in hexapods, myripods this is the main function of circulation  in molluscs Excretion  Excretion of nitrogenous wastes carried out in specialized structures  source of nitrogenous waste  the problem with n
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