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Vertebrate Biology Exam 1 Study Guide

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by: Abigail Towe

Vertebrate Biology Exam 1 Study Guide 81463 - BIOL 3030 - 001

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This is literally everything since day one in class combined into one file! Enjoy!
Vertebrate Biology
Richard W. Blob
Study Guide
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This 78 page Study Guide was uploaded by Abigail Towe on Sunday September 20, 2015. The Study Guide belongs to 81463 - BIOL 3030 - 001 at Clemson University taught by Richard W. Blob in Fall 2015. Since its upload, it has received 521 views. For similar materials see Vertebrate Biology in Biological Sciences at Clemson University.


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Date Created: 09/20/15
What are vertebrates?  Formal criteria of being a vertebrae: o A▯i▯als that have vertebrae…  Definition of vertebrae:  Vertebrae are skeletal series of segments along the body axis. o Vertebrae have patterns of ancestry such as hair, mammary glands, etc. o These help to determine how flight evolved, and other major transformations.  To understand vertebrae diversity, we need to understand: o Vertebrate structure o How structures work (separately and together) o How vertebrates are related Understanding Vertebrate Diversity ● There is diversity in form, function, and number of species for vertebrate life forms. ○ The diversity in form consists of shape and size of special structures ○ The diversity of function refers to locomotion, feeding, and environment. ○ There is also diversity because of the various species that exist/existed. ■ There are more than 60,000 living species ● plus more than 10 more fossil species ● The biological definition/concept of “species” is: reproductively isolated group of organisms. ○ The exceptions/complications to this definition is: ■ hybrids ■ fossil taxa (morphospecies - morphologically distinct) ● The classification of “species” is the basic unit of diversity (smallest description) in the naming system. ○ The hierarchical system (Linnean system)of groups with groups starts with Kingdom → Phylum → Class → Order → Family → Genus → Species ○ Note: Species have binomial names (genus + species) ■ example: Homo sapiens & Tyrannosaurus rex ● Evolutionary Organization of Diversity: ○ The Linnean methods (naming system) predates evolutionary theory ■ Linnean groups don’t always indicate evolutionary relationships ○ Today, if organisms have a shared feature then they are grouped together based on their evolutionary relationship to each other ○ Phylogenetic Systematics/ Cladistics used to show evolutionary trend: ■ Systematics= organizing diversity with a system (non random) ■ Phylogenetic = “tribe birth” (in Greek) ■ Cladistic = “clade” (in Greek- “branch”) ● When looking at a cladogram: ○ a cladogram is a diagram that demonstrates the taxon relationships by using branches ○ clade= ALL descendants of a single common ancestor ○ The Taxon is the biologically recognized/accepted group of organisms with common ancestry ○ Character= feature of an organism (vertebrae, scales, teeth, jaw) ○ Character state= variety of a character (present or absent) ■ shared character states indicate taxa evolved from common ancestor ● Using cladistics: ○ synapomorphy= a shared, derived feature ○ plesiomorphy= a primitive (ancestral) feature ○ ** traits can be synapomorphies at one level of cladogram but plesiomorphies at others** ○ Monophyletic group= another name for clade (Greek = “one tribe”) ○ Paraphyletic group= does NOT include all descendants of a common ancestor (NOT CLADES) ○ Grade= paraphyletic taxa grouped together for convenience, often because they share similar features (NOT CLADES) ○ Outgroup= clade outside clade being considered, helps determine primitive features ○ sister taxa= adjacent branches on cladogram that form clade together ○ nodes = branching points on cladogram ■ the branching can rotate around the node, doesn’t have to be from left to right ○ The most PARSIMONIOUS cladogram = accepted (one with most support, fewest evolutionary changes) ○ If a character is in 2 groups that don’t form a clade, it means that : ■ the character was lost intervening taxa ■ convergent evolution (feature evolved independently in both taxa) ■ You can check if you check the detailed structure (bird vs bat wings are very different) ● feathers vs. skin ● bats long digits, birds short ● therefore, bird and bat wings are analogous structures (same function, evolution converged on same design) ○ Contrasts with HOMOLOGOUS structures (truly the same across taxa) ● Homology: 1. context = topographical relationships a. if structure surrounded by same elements in 2 taxa, probably homologous i. examples: finger bones of birds and bats both connect to metacarpals 2. development: essential similarity sometimes only clear in embryos ● Diversity occurred over a long time: ○ The first vertebrates lived 520 million years ago ○ absolute dates can be measured by using radiometric dating of fossils ■ But majority of fossils are only used for relative dating ● This only tells if the fossil is younger or older than others ● This can be done with geologic time scale ● The Geological Time Scale: ○ breaks time into sequential named segments ■ Cenozoic ● First period is tertiary - 55-66 million years ago ● “age of mammals” ○ mammals and birds greatly diversified ○ climate: earth began cooling and drying, staring glaciers, continents almost moved to how they are currently ● ■ Mesozoic ● First period is Triassic - 225 million years ago ● 3 dates: ○ dinosaurs and mammals appeared ○ pangea ○ climate: warm , no polar ice, sea levels higher ○ flowering plants ■ Paleozoic (oldest) ● First period is Cambrian- 540 million years ago ● 3 events: ○ first multicellular organism ○ cambrian explosion= most phyla appeared (fish, arthropods, reptiles) ○ life on land began (plans, trees) ○ huge extinction ● Plate tectonics: ○ the continents change position through time ○ supercontinent Pangaea → separated ● Therefore, the present vertebrate diversity was shaped by the past catastrophes. ○ There were two major vertebrate extinctions at the end of Permian and Cretaceous Assembling a Vertebrate ● Review: ○ Cladistics is a method of using a diagram to organize our knowledge of vertebrate diversity evolutionarily using phylogenetic systematics ■ the branching pattern of relationships based on synapomorphies ■ Cladograms are useful to determine closest relatives and what they were like. ● First Vertebrate relatives/origins (before vertebrates…. leading up to vertebrates) we are observing is chordates: ○ The Chordate synapomorphies: (they may be present at any stage of development) 1. Notochord a. the fibrous rod along the body axis 2. Dorsal hollow nerve cord (DHNC) a. dorsal = toward the back (think back of a dog = dorsal) 3. Postanal tail 4. Iodine binding structure a. endostyle, thyroid 5. Pharyngeal pouches/slits a. pouches from gut that can open to outside as slits in throat ○ Clades of chordates ■ Urochordates = tunicates or sea squirts ● there are about 2,000 species ■ Cephalochordate= lancelets or amphioxus ● there are about 22 species ● They like to burrow and have pharyngeal slits for filter feeding (not gills) ● has myomeres = segmental muscle in blocks ○ myomeres are derived from somites (embryonic tissue blocks) ○ found in vertebrates only, but just not in urochordates ■ The oldest fossil confirmed that is a chordate is one named Pikaia ● Dated from: Middle Cambrian period ( about 500 million years ago) ● Paedomorphosis= retention/ they keep their juvenile traits throughout adulthood (while they are sexually mature adult) ● Another early specie BEFORE vertebrates is the Craniate ○ The craniates have synapomorphies (have many that related to the head) that include: ■ cranium = braincases, cartilage or bony skull surrounding brain ■ complex sense organs ■ large, three-part brain (forebrain, midbrain, hindbrain) ■ Neural crest cells ■ heart, gills, hemoglobin ○ Divided into two clades: Hagfish and vertebrates ■ Hagfish: ● has the basic craniate features (with neural crest) ● lack of definite vertebrae (meaning NOT vertebrates). has notochord throughout lifetime ● about 45 species, marine predator and scavenger ● unique features: ○ exude/discharge massive quantities of slime, mouth tentacles, reduce eyes ○ switch from male to female with age ● lacking: jaw and paired fins ● These so far have not been vertebrates, but it’s progress. What exactly was our big step(s) to get us to assembling a vertebrate? ○ Well, the 2 basic mechanisms/developments are: ■ separation of embryo cells divided into 3 layers (germ layers) that each produce different structures ● endoderm cells = 1st - inner cells ● mesoderm = 2nd - middle cells ○ The mesoderm differentiates into 3 parts ■ somites in segments next to nerve tube (myomeres in vertebrates) ■ intermediate mesoderm (nephrotomes → kidneys) ■ lateral plate (not segmented , has blood vessels, heart) ● this eventually splits to form a space called “coelom” ● The gut and associated organs are suspended in body by membranes (mesenteries) formed from the lateral plate from mesoderm germ layer. ■ Coelom allows organ movement/expansion, but the mesenteries prevents reckless sloshing ● ectoderm cells= present at surface ■ folding and migration of those layers ○ Then, eventually we got the “tube within a tube” design of the digestive tract. ■ example: chicken ● Process: ○ germ layer formation in chick (representative chordate) ○ there is a primitive streak ○ then a primitive knot forms ○ within the mesoderm, the notochord is formed (produced by primitive knot as it migrates toward the tail) ○ The Dorsal Hollow Nerve Cord (DHNC) forms from a processes that involves rolling up of the ectoderm germ layer that overlies the notochord ■ basically, the notochord is located underneath the ectoderm (within the mesoderm). So when the DHNC forms, the ectoderm just rolls right up into a tube above the notochord. As it rolls up, the neural crest is dismantled and the cells migrate elsewhere in the body. ● the neural crest migrates through the body to make pigment cells, tooth dentine, parts of skull, nerves, and brain (IN CRANIATES) Assembling a Vertebrate Part 2 ● Review: ○ Concerning the evolutionary assembly of vertebrates, there was a lot of important structures that evolved before the first vertebrate (cranium) existed. ○ The development progress: ■ separation and migration of germ layers: ● ectoderm - outer body surface, nervous system, and neural crest ● endoderm- gut lining & organs from it (liver, pancreas, lungs) ● mesoderm- rest of the body’s needs ■ somites- myomeres, vertebrae, and dermis ■ intermediate mesoderm- kidneys, gonads ■ lateral plate mesoderm- blood vessels, heart, mesenteries, and more… ■ notochord ● Organ systems = organs ← tissues ← cells ○ The organ systems can be grouped into: ■ Body Support and MOtion ● Integumentary (skin, hair, nails) ● Skeltal ● Muscular ■ Energy Acquisition and Support of metabolism ● digestive ● respiratory ● cardiovascular ● excretory ● reproductive ■ coordination and integration ● nervous (plus sensory organs) ● endocrine ● Integumentary system: ○ external covering of vertebrates ■ this includes skin, glands, accessory structures (such as scales, feathers, hair, nails, keratin hoof and claw coverings) ○ Functions: boundary between internal and external environment ○ Specific functions: protection, temperature regulation, water regulation, gas exchange, vitamin D synthesis, sensory stimuli reception, defense against microorganisms, pheromone production ○ Vertebrate skin has TWO layers: 1. epidermis- superficial layer (ectoderm germ layer) that includes primary protection, sensation and glands a. Aquatic life has epidermis with living cells. This includes mucus- secreting glands. The function: it’s anti=parasitic and reduces drag. b. Terrestrial life has 2 distinct epidermal layers that include Stratum germinativum (living) and Stratum corneum (dead). The Stratum corneum dead cells protects the body from abrasion and water loss. 2. dermis: deep layer (from somite- mesoderm) that includes blood vessels, melanocytes (the pigment cells) a. Note: when a person blushes, it is the blood vessels in the dermis that get a rush of blood suddenly. ● Skeletal system: ○ internal supportive framework for the body ○ The skeletal system is divided into two groups that includes non-mineralized and mineralized structures ■ non-mineralized: notochord, cartilage ■ mineralized: bones, enamel and dentine in teeth/scales ○ There are two types of bone for skeletal system: ■ Endochondral: cartilage precursor (cartilage later replaced with bone). These structures are deep, such as limbs and deep skull. ■ Dermal: grows in dermis, no cartilage precursor= starts as bone. These structures are flat and superficial, such as the roof of skull, armor plates in crocodiles and early vertebrates. ○ Remember that skeletal tissues are ALIVE ■ bones are composed of protein fibers (collagen) and mineral crystals (hydroxyapatite= largely calcium phosphate) ■ there is a blood supply to living (non-mineralized - cartilage) parts of bone that allows it to repair from any damage ● osteoclasts= blood delivers cells to DESTROY old/damaged bone ● osteoblasts= blood delivers cells to DEPOSIT new bone ○ The region of the skeleton: ■ axial, appendicular, skull ● axial = vertebrae, ribs, sternum ● appendicular= limbs ○ There are 3 regions of the skull: 1. Chondrocranium (braincase) a. There include the deep bones of the skull that have cartilage precursors (cartilage → bone) b. surrounds sides, back, and underneath of brain i. occipital condyle, foramen magnum 2. Splanchnocranium a. arches that support gills and jaws b. derived from neural crest c. cartilage precursor 3. Dermatocranium a. dermal (with no cartilage precursor) b. superficial: skull roof, palate, lower jaw ○ Teeth ■ Teeth are developed WITHIN the skin (from integument) ■ mineralized enamel and dentine over pulp cavity (blood and nerves) ■ This process of developing teeth is similar to how scales are formed. ■ Initial use of teeth was to grasp and hold prey- homodont dentition- ● usually frequent tooth replacement ● often in various places in mouth, not just jaws ■ Later, they began using teeth for prey processing - Heterodont dentition- this process was evolved over time ● tooth replacement occurred less frequently ● the teeth are more permanent and less random so it helps the teeth to fit together better ○ The appendicular skeleton: ■ includes: paired girdles, fins, and limbs ■ Early vertebrates have NO paired appendages ■ Cladoselache (fossil shark) has 2 pairs of fins ■ Tetrapods and ancestors: had jointed segments with a variety of shapes to relate how they are used ● Muscular system: ○ Contractile tissue ■ The cellular level of muscles (fibers) shorten in response to electrical signals from nerves ■ There is a theory used to describe the shortening process of how muscles work together: Sliding Filament Theory- thought that filaments slide past each other to shorten. ● muscle shortening causes motion ● muscles work in antagonistic pairs to allow back- and-forth motion at joints ○ When looking at the muscular system in fish, you will find axial muscles, myosepta, and horizontal septum ■ axial muscles - “myomeres” - are the main muscles for locomotion (how the organism travels) ■ myosepta- separate segments of myomeres, head to tail, refine control ■ horizontal septum (left to right) divides epaxial from hypaxial muscles ○ When looking at the muscular system in terrestrial (land) vertebrates, you see that there is a decrease in axial muscle mass, increase in appendicular muscles. There are many, many more appendicular muscles than axial. ■ Reminder: axial includes trunk while appendicular includes limbs ● Digestion system: ○ When observing the digestive system in vertebrates, you will find that they are heterotrophs (meaning that they are consumers). ■ Vertebrates must acquire and break down food ● they complete this by using physical and chemical mechanisms ■ absorbs nutrients and expels waste also ○ There is a “divided” gut (digestive) tube ■ there are valves or other anatomical structures that partition the tube into different regions to divide the digestion process. ● the partitioning system depends on the organism ○ for example, it can be unspecialized (like the lamprey) or highly modified (herbivores -plant eaters) ○ the basic structures and functions of some organs in digestive system: ■ mouth (pharynx, esophagus)- food intake (mechanical and chemical breakdown) ■ stomach- food break down (physical and mostly chemical) ■ intestine- breaks down (with chemicals) food and absorbs nutrients ■ anus -waste elimination ● cloaca = common exist for digestive, excretory, reproductive system in some organisms ● Respiration: ○ The respiratory system serves to deliver oxygen to cells so that cellular oxidation of nutrients can occur and to remove wastes, like carbon dioxide. ○ the method of this system depends on body size and environment ■ One type: Cutaneous respiration ● This is present in small animals, across wet skin. This includes cephalochordates and amphibians ■ Another: gills ● receive oxygen out of water as water goes into mouth and passes over gills and out of pharyngeal slits ● this is a one-way flow, so it saves energy ● oxygen diffuses from water to blood lower in oxygen then distributed to body ■ Another type: uses lungs ● receive oxygen out of air ● internal sacs (gut outpocket) with moist membranes for gas exchange with blood vessels (air moved via pressure gradients) ● This type is used in most terrestrial vertebrates and their descendants. Modified into swim bladder in most fish. ● Circulation: ○ This system derives from the lateral plate mesoderm ○ it’s a closed system (all blood is in vessels) ○ there are 3 main parts: 1. muscular pump (heart) a. moves blood to gas exchange regions first to pick up oxygen, then carries it throughout the body 2. conduit system (vessels) a. arteries = away from the heart b. veins= toward heart c. capillaries = site of gas exchange with tissues d. portal veins= veins between two capillary beds (to help filtering organ like kidney or liver) 3. transport medium = blood a. liquid portion -plasma b. cellular portion: i. white blood cells- immune response ii. red blood cells- hemoglobin for binding with oxygen Vertebrate Organ Systems Continued…. Excretory system: ○ This system is developed from the intermediate mesoderm ■ similar to reproductive system ○ the function of the excretory system is to remove metabolic wastes, excess salts, and water via anatomical structures called nephrons. ■ nephrons are collected in the kidneys. there are several million nephrons that function together to form kidneys. ■ blood enters through capillary beds and then filtered in the glomerulus. ○ The development and evolution of the kidney: ■ Pronephros: ● located far toward head, and only in embryos ■ Then, opisthonephros ● located further toward tail, and now it is present in fishes and amphibians. ■ Then, metanephros ● located rearmost part of opisthonephros ● present in reptiles, birds, mammals ● the formation of this version is the “bean shaped” structure we are familiar with ● Reproduction ● Sex organs develop from INTERMEDIATE MESODERM, close association with Excretory system ■ sex organs= gonads: ● female = ovaries ● male = testes ● Distribution of sex organs ■ DIOECIOUS – has either male or female gonads, separate individuals (MOST COMMON) ■ HERMAPHRODITE – male & female reproductive organs in same individual ■ PARTHENOGENETIC – females produce young, no males ● parthene/o= “virgin” ● Method of fertilization ○ EXTERNAL – fertilization occurs outside of body ○ INTERNAL – fertilization occurs inside of body ■ Protect embryo ■ Delayed fertilization – some verts store sperm until more favorable time ● Breeding periodicity can correlate with environmental conditions ● (photoperiod, temperature, water availability) ● Modes of reproduction ○ OVIPAROUS – egg laying (ancestral) ○ VIVIPAROUS – give birth to non-shelled young ● Reproductive rates ○ r-strategists vs K-strategists ■ r-lots of time with each, little parental care. does not invest ■ K-strategists: fewer large young, some to lots of parental care to ensure higher survival rates among the few they have. ● example: humans ● Precocial vs Altricial ○ precocial – “born ready” ■ wildebeest, zebra - run away from lion right after birth. minimal care from parents. performs at very high level. ○ altricial – need time to develop ■ young that still need a lot of care from parents. best examples: • Humans (including professors): • K- strategists • altricial young Endocrine system: ● system of ductless glands, masses of tissues inside the body that releases out/ ● signals are transmitted via hormones (secrete chemicals) ● controls: continuous, graduate, or long term processes ○ examples: growth, metabolism, metamorphosis, sexual development Nervous system: ● divid○ brain and spinal cord (central nervous system) ○ nerves (peripheral nervous system) ● signals are transmitted via nervous (electrical impulses) ● This communication is fast, targeted distribution because nerves are electrical- that allows direct connect for specific target to be reacted. ● controls processes required rapid, specific response ○ example: muscle twitches ● composed of neurons: ○ neurons have 3 parts that make up the neuron: 1. cell body (holds nucleus) 3. axons (transmits signals- usually single axon) ● a nerve is a bundle of neurons (mostly axons) ○ there are some sensory neurons (the signal received from body and sent toward CNS) ○ there’s also some motor neurons (CNS to target) ● myelin sheath= fatty cells coating axons (except at gaps), speeds signal transmission ● brain= main center for processing and integrating all neural signals of the body ○ 3 main regions: hindbrain, midbrain, and forebrain ■ the hindbrain: processes hearing and balance (vestibular system) ■ midbrain= visionr apparatus- hearing and balance ■ forebrain= smell ○ lateral line: skin receptors in aquatic vertebrates that perceives/detects disturbances (of either prey or predator) in water ○ spinal reflex arc: spine receives sensory input, integrates, and sends out response Early Vertebrates ● In early vertebrates, the vertebrates had bony scales that were made from calcium phosphate ○ The oldest vertebrate with bony scales was Anatolepis - marine life ● Clade Petromyzontiformes ○ aka: lampreys ○ 40 species, including marine and freshwater ○ jawless, horny, rasping pseudo “teeth” ■ majority are parasitic ○ big parasite problem for Great Lakes fisheries ○ secondarily lost bone (skeleton cartilaginous) ○ lacing paired fins ● Next Clade on Cladogram: Conodonts ○ tiny, first known from fossil teeth, now body fossils ○ filter feeders = water passes in, particles get caught in teeth=like str■ opposite of lampreys, that are parasitic. ● GRADE○ around 100 million years old ○ successful in their time ○ lots of kinds: ■ arandaspis, astraspida, heterostraci, anaspida, thelodonti, galeaspida, pituriaspida, osteostraci,and placodermi ○ not a clade, just a grade ○ marine life larger than conodonts ○ bone forms body armor- some is reduced to scales ■ this is important because the bone helps store calcium and phosphorus ○ many have hypocercal tail = bottom lobe is largereller) ■ this quality in vertebrates is no longer found in living vertebrates ○ most groups lack paired fins (and most lack any sort of appendage) ■ these appendages are important for stabilization in water ● Next Clade: Osteostracan ○ large pectoral pins (this feature demonstrates the close relationship to gnathostomes) ○ the broad head aids in stability to prevent the vertebrate from rolling ○ broad, flat head and a ventral mouth creates a vertebrate that is a bottom/detritus feeder ○ new tail design: heterocercal tail ■ this will now produce downward lift ● Gnathostomes “jawed mouth” ○ include: chondrichthyans (cartilaginous fishes) and osteichthyans (bony vertebrates) ○ clades include: placoderms, holocephalans, elasmobranchs, acanthodians, actinopterygians and sarcopterygians ○ orig■ segmental structure of ancestral Craniate head ● includes skeletal elements (GILL ARCHES) ■ 1st (MANDIBULAR) arch forms jaw joint: ● Upper element: = PALATOQUADRATE CARTILAGE ○ QUADRATE BONE ■ Lower element: = MANDIBULAR CARTILAGE ● ARTICULAR BONE ● (*Mandibular arch from SPLANCHNOCRANIUM: ■ DERMATOCRANIUM bones overlie mandibular arch ■ in most taxa) ● 2nd (HYOID) arch suspends jaw joint from braincase ● Gill slit between mandibular and hyoid arch becomes ■ the small SPIRACLE in some taxa (e.g. sharks), but lost in others ■ ANY ADVANTAGE TO JAWS??? ● Faster gill ventilation (> Oxygen) ● Faster feeding ○ Synapomorphies of Gnathostomes: ■ jaws ■ 2 pairs of paired appendages ■ a 3rd (horizontal) semicircular duct in vestibular system of ear (aids in 3D orientation) Life in Water ➔ First vertebrates were MARINE ➔ Characteristics of aquatic environments place specific demands on vertebrates ➔ Water is 800x denser than air ◆ 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. ◆ Aquatic animals can have bigger maximum sizes (rather than land animals) ● example: whales. ● aquatic big >> land big ➔ Water is 18x more viscous than air ◆ This means that it’s harder to flow ◆ Example: syrup, motor oil ◆ More viscous fluid, resistance is greater. ◆ 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. ◆ It’s also harder for the animal to be moved ● Respiration ◆ water is dense and heavy- so it takes a lot of energy to move it around. ➔ Water has less oxygen than air. ◆ important consequences for respiration. ◆ 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) ● 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 ◆ so water has more stable temperatures ➔ water has greater electrical conductivity than air ◆ animals benefit by using water for different sensory opportunities ➔ water is surrounded by water! ◆ 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)…… ◆ GILLS- highly vascularized ◆ developed on walls of pharyngeal pouches ◆ between each pouch, a skeletal GILL ARCH of skull supports gill filaments with capillaries for acquiring O2. ◆ gill filaments have the vessels that actually extract the oxygen. ◆ 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… ◆ the concentration of oxygen is the same across gills. ◆ Gills are efficient at extracting oxygen from water because: ● the water comes in a one-way flow to save energy, rather than using energy to change direction. ● Mechanism: ○ Buccal pumping- can perform without swimming ◆ water in mouth ◆ close mouth ◆ squeeze head to force water over gills ○ Ram Ventilation- must be swimming ◆ mouth held open ◆ water passes through & over gills ◆ countercurrent exchange- ● water flows in opposite direction from blood in gill capillaries ● oxygen content of blood always lower than in water ○ so blood can always extract oxygen (80-95% efficiency) ● gases flow areas of high to low concentration ➔ Fishes with gas: ◆ Swim bladder- in many bony fishes, lungs are modified into swim bladder that can regulate buoyancy ◆ However, the problems of the swim bladder: ● if you dive, the pressure compresses bladder so that fish sinks. ○ the gas gland has to secrete more oxygen. ◆ To get gas out of the bladder (to prevent fish from exploding when rising because the low pressure expands the oxygen in the bladder) ● physostomous fish burp air out via swim bladder to gut tube connection ● physoclistous fish relax muscles closing off ovale, which releases gas to blood ➔ Remember: no bladder in sharks and rays ◆ They have oily liver for regulating buoyancy instead ➔ Sensory systems: ◆ Vision- perception of light ○ we are naturally very perceptive individuals ● light bends (refracts) when it passes through a substance (such as water) ● as it passes through parts of the body (cornea/front of eye), the light also bends. Cornea and water have same refraction index (about 1.3). ● Once light passes through the cornea, a sphere shaped lens focuses light on retina (to allow a clear image) ● 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. ○ 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. ● Therefore, there are different shaped lenses (fish have spherical lens, mammal eyes have flat lens) ◆ Animals that live in water and air ● one example: anableps - “four-eyed fish” ○ These fish have a divided cornea and oval lens to allow light from water and air to both focus on retina. ○ cornea is divided (half in air, half in water) ○ lens has a spherical and flat shape (oval) ◆ special for aquatic vertebrates: ● 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. ○ ancestral system detecting water movements ◆ chondrichthyes, bony fish, some amphibs ○ Neuromast organs: ◆ in pores or canals opening to surface ◆ each has pair of hair cells (long and thin) ● called hair cells because they have tiny projections that grow out of them that are called “kinocilia” ○ they project into a wad of gel called “cupula” ● water moving to cupula deflects/moves hair cell (kinocilia), sending out nerve signal. ○ it detects what direction the water movement is coming from. ● Electroreception- close association with Lateral Line system, because it detects changes in electricla potential of environment ○ can detect muscle movement. you can tell if there’s a hidden prey fish. ○ finds hidden prey from electric discharge of muscles ○ Well developed in sharks: ◆ ampullae of lorenzini (pores filled with electrically conductive gel) ◆ gel filled canal → sensory hair ● Electric Discharge: ○ some rays, eels, catfish use to catch prey or stun predators (up to 600 V) ○ some weakly electric fish communicate with electric discharges ◆ gymnotids = knife fish, mormyrids = elephant noses ➔ Excretory System of Aquatic Vertebrates ◆ removes nitrogenous wastes, excess salts and water via nephrons (collected into kidneys) ● environment influences kidney structure and function ◆ Fish has greater solute concentration than water; therefore, water diffuses passively into fish ● Does not drink ● BIG glomerulus -> lots of dilute urine ● Absorb ions to replace salts through gills ◆ Water has > solute concentration than fish; fish loses water to environment, risks “drying out” ● Drinks sea water (don’t try this at home) ● Pump ions out through gills, void through feces ● SMALL glomerulus -> small amounts of concentrated urine ➔ Clade Chondrichthyes ➔ Gnathostomes (gnath = jaws ; stomes = mouth) ◆ Gnathostome synapomorphies 1. jaws 2. 2 pairs of paired appendages 3. a 3rd (“horizontal”) semicircular duct in vestibular system (helps you determine your position/orientation in space) of ear. ➔ Gnathostomes(red line) a. species include: ● sharks, rays + bonus b. There is a very early basal split of gnathostomes into subclades ● looks like Chondrichthyes vs Osteichthyes in cladogram (slide 3) but really a little more complex ● 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. Eugnathostomes ● “true” teeth b. Teleostomi ● terminal mouth ● bony gill covering (operculum) ➔ First species Gnathostomes: PLACODERMS a. early carboniferous b. ~425-325 MYPB c. heavily armored d. distinct joint between head and trunk shield ● 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 ● 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 ( ● purpose: punting bottom feeders. ○ sharp projections going to the bottom always them to stab down, pull forward, repeat to move ● The fins are entirely encased in an outer covering of bone c. Spine originally short and unjointed; becomes longer and jointed in later species ● to offer more flexibility/movement d. often found in aggregations of several individuals ● first example of schooling behaviors ➔ Arthrodire a. another clade of placoderms b. most diverse placoderm clade ● includes about ~60% of all species c. often huge (larger than 20 feet long) d. large nuchal gap allows greater head movement and a more forceful bite e. has sclerotic ring in eye ● bones in eye ○ shows up for the first time ever in this species ● jaw edges can show tooth-like projections ○ to allow for grasping prey item to bite and then be able to pull onto f. evidence of both healed and unhealed bite wounds ● possible cannibalism ➔ Placoderm puzzle: a. What caused their extinct? ● they were a high food chain member, large, strong b. one explanation: decline in sea levels in Late Devonian term may have eliminated shallow water, which is where they were found ● high-oxygen habitats forced competition with other lineages (osteichthyes and chondrichthyes) ➔ CLADE CHONDRICHTHYES (Cartilaginous “fishes”) a. 1200 living species b. first fossils from Devonian (~400 MYBP) c. includes: Clades- ● Holocephali ○ chimeras and ratfish ● elasmobranchii ○ sharks and batoids (skates and rays) d. batoids are a subclade of elasmobranchs e. 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 tooth-like 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, tooth-like , enamel-covered ii. Ostracoderm: large, flat, heavy 4. Vertebral centra (body) elaborated (reduced notochord) 5. Continuous prolific tooth replacement (tooth whorl) ➔ Clade: Elasmobranchii ◆ Evolutionary Trends in shark morphology- 1. more mobile pectoral fins → 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 ● 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 lower jaw 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 Hyostyly 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: ○ 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 ○ “bite and spit” ■ feeding strategy where they will bite and continue biting until the prey bleeds to death ○ prey on seals: bite and hold to bleed to death ○ others: bite and spit ■ tests for blugger content ● favors prey with higher blubber content (esp. seals) ■ protects shark from injury (like sea lions) ● sea lions have larger fins to fight back: can really hurt the shark ★ More Shark feeding habits ○ Cookie cutter shark ■ uses suction to stick on the side of aquatic animals then cut out a chunk and run away to do something else. ○ Filter feeders: ■ tend to be the largest body size species (greater than 30 feet) ■ swim with their mouth open ● so they end up straining plankton with their mouth, even though that’s not what they want ★ Shark Reproductive Biology ○ Modern: spotted catshark ■ internal fertilization ● male wraps his mid-lower body around female ● some species bite and hold on to females, females often have thicker skins than males to protect them from injury ○ older shark: Damocles (Carboniferous, Montana) ■ roles were reversed. male has clasper but female was found on top and biting in some specimens ○ K-Selected - very few, well-developed young/offspring ■ different strategies to execute this K-selected approach ● Oviparous- ○ proteinaceous egg cases, prongs to tangle in vegetation ○ offspring develops outside of mother ● Viviparous- ○ live birth, yolk sac attaches to mother like placenta ○ ○ Pre-Birth Cannibalism: babies eat unfertilized eggs, or even siblings (e.g. great whites) ★ Conversation Challenge: grow slowly, few young, ranges cross international boundaries → 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 ● Main points: ○ pectoral fins get bigger, tail shorter ○ electric and stingrays different groups ■ stingrays have a venomous tail spine ■ electric rays used electricity ○ the tail is reduced/becomes narrower to whip (not used for swimming) ■ in stingrays, and especially eagle rays ○ eagle/manta rays flap pectoral fins to swim, other pass waves along ■ basically flying under water ★ Holocephalans ○ “ratfish” or chimeras ○ small group and small body size ○ adaptations for durophagy (eat hard prey)- ■ uses autostyly in jaw used to braincase ● (humans have this) ■ reduced number of big crushing tooth plates ○ fleshy covering over all gill slits (operculum) ■ not the same as later one in bony fish ■ independent origin of analogous structure ○ diphycercal tail (vertebral column between equal-sized lobes) ○ swim by flapping pectoral fins (up and down motion) Major Gnathostome Subclades: ● Eugnathostomes ○ true teeth ● Teleostomi ○ bone gill covering (operculum) ○ Acanthodians: ■ “spiny sharks” ● not sharks but definitely spiny! ○ aids in predator defense (predators don’t want to eat something so bony) ● Most poorly known (spines, teeth, outline smudges) ● • Small (most 200 mm [~1 ft] or less, biggest ~2 m) ● • Spines support all fins, intermediate spines between paired fins in some ● Clade: Osteichthyes ○ (bony “fishes”) ○ includes tetrapods (4 footed vertebrates - like humans) ○ Synapomorphies: ■ Lepidotrichia (bony ray supports in fins) ■ Lungs (or swim bladder that evolved from them) ● ancestors were aquatic. Lungs evolved in this group to support breathing air. ○ overall, Osteichthyes can be divided into 2 clades: ■ Actinopterygii ● ray finned “fishes” ○ fins supported only by rays ● what united the group of the ray finned fishes together is: the synapomorphy of the presence of the single dorsal fin ■ Sarcopterygii ● lobe-finned “fishes” ● includes tetrapods ● “meat wing” ● besides just having rays, they now have a robust internal skeleton ➢ Actinopterygian Diversity: ○ Polypteriformes (bichirs) ■ most basal living actinoptergian ■ obligate air breather (uses lungs) ■ freshwater, native to Africa ■ single continuous dorsal fin below the “skin” but gets frayed and torn above the surface ■ Most poorly known (spines, teeth, outline smudges) ■ • Small (most 200 mm [~1 ft] or less, biggest ~2 m) ■ • Spines support all fins, intermediate spines between paired fins in some ○ Chondrostei ■ Sturgeon ● retain heterocercal tail & spiracle ● lose heavy scales (big rostrum {beak}) ■ Paddlefish ● spiracle =nostril opening above the eye ○ Neoptergians (basal clades) ■ has two subclades: ○ Gar (Lepisosteidae) ○ Bowfin ● Both: ○ reduction of heterocercal tail ○ median fins can move side to side now ○ retain ganoid scales ○ lacks spiracle ○ bones of cheek region in both taxa are now able to be flared out to the side - helps this fish to use suction to pull prey into their mouth ➢ Teleost specializations: ○ new functional advantages for this group and probably contribute as to why there are tons of species within the teleostei clade but not with others. This is because: ■ feeding and swimming differences ● feeding: increase jaw mobility ○ allows jaws to be protruded (moved out from face) ○ mobile premaxilla allows the jaw protrusion ○ advantages of jaw protrusion: ■ catch food far away ■ increase volume inside head ● improved suction performance ○ Different types: ■ Ram Feeding: swim to prey and engulf it whole in mouth (ancestral) ■ Suction: draw viscous water into mouth and take food with it ○ TEETH: ■ numerous on jaws, palate, and pharyngeal bones ■ oral jaws used to capture the prey (not chewing) ● the pharyngeal teeth can provide 2nd set of jaws for processing hard prey ■ usually homodont (all teeth similar) ● acrodont - teeth attached to jaw edge, no sock ○ bone to bone connection ■ polyphyodont - teeth can be replaced (frequent, as in multiple sets) ● as they break off, they get more ○ Some teleosts use biting= take chunks off big items ● swimming: homocercal tail (the two lobes are equal size) ○ so now that the tail does all the work, the other fins can now do novel functions to increase diversity and functional uses. ○ lighter scales are allowed to increase body flexibility ■ Teleosts- locomotor specializations ● homocercal tail ○ vertebral column does not extent into tail fin ○ the end vertebral column allows the fish to keep swimming level without having to use paired fins for control ■ this allows pelvic and pectoral fins to diversify in function ● Light scales: ○ increase body flexibility ■ no enamel ■ bones grows in concentric rings indicating age ■ two types: cycloid and ctenoid ● cycloids: smooth edge around the back ● ctenoids: serrated edge ● Both may be found in same fish, some fish reduce scales drastically ● minimize drag: ○ drag= force resisting motion in a fluid ○ minimize by streamlined body shape ■ which reduces water turbulence and friction around body ● have to generate thrust: ○ a force that propels animal through fluid ○ they do this through Newton’s 3rd law of motion: ■ for every active force there is an equal and opposite reaction force ● to move through water, animals must exert force on water, which will exerts a propulsive reaction force back on animal ● Fish exert forces on water by producing vortices ○ vortices: whirlpools create a big central jet ● Fish have a huge body and caudal fin ○ this use this for swimming (Body and Caudal Fin BCF swimming) ● Another type of swimming: median and paired fin swimming (MPF swimming) ○ part of body used to swim ○ faster fish tend to move less of their body to swim, reducing drag ■ ➔ Teleosts- locomotor specialization ◆ tail shape and swimming style- sustained cruising versus sudden bursts of energy swimming ● part of body used to swim: ○ MPF- median paired fin- swimming ○ BCF- body caudal fin - swimming ● Cruisers have a narrow tail base (caudal peduncle) to reduce drag and crescent tail fin with widely spaced tips to generate larger vortex rings and greater force. ● Lookdown- cruising- (narrow tail base, crescent tail fin) ● burst swimming: broad caudal peduncle allows greater muscle mass for starting from dead stop ● sailfin molly- burst (C-start) ○ broad caudal peduncle= tail base ◆ Distinction of red and white muscle fibre proportions ● all vertebrates have distinct red and white muscle fibers ● White= fast glycolytic ○ use glycolysis (anaerobic respiration) ○ fast contraction, rapid fatigue ○ thick fibers, no fat, no myoglobin ○ Good for sudden bursts of action ● Red= slow oxidative ○ use oxidation (aerobic respiration) ○ slow contraction, slow to fatigue ○ thin fibers, high fat, myoglobin present ○ Good for slow, sustained activity ● red and white fibers are distributed through muscles. but in fish, the red and white fibers are distributed in separate regions ➔ Actinopterygian digestive system ◆ fairly simple tube in most actinopterygians, terminating at cloaca/anus ◆ evolutionary chances: ● lamprey: ○ no stomach ◆ but they are sucking in prey that don’t require a lot of mechanical processes- it’s basically all liquid/soft diet. ○ spiral valve of intestine provides large surface area for absorbing nutrients ◆ located in intestine. it’s a spiral in the tubed intestine so that the


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