EEB267 Exam Notes (1).docx

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University of Toronto St. George
Ecology & Evolutionary Biology
Deborah Mc Lennan

EEB267 Notes Lectures 1 & 2: The Amniota Synapomorphies of amniota: amniotic egg (amnion, chorion and allantois)  Extraembryonic membranes are laid down by the developing embryo  Yolk sac is laid down by the mother (older than the amniota) becomes connected to the embryo  Amnion: for protection  Chorion: for gas exchange  Allantois: for wastes and gas exchange  Keratin filled cells are used to make: hair, wool, scales, feathers, nails, claws, hoofs, antlers, horns, beaks, quills and some skin o Basal layer of epidermal cells divides at least 3 times and differentiates to make the top layer of keratinized cells o Either shed, or make up other things Testuidines  Position is unclear, because there are many extant living lineages separating the living groups of amniotes and because they have such unique characteristics  Synapomorphies: o no teeth (keratinous beak) o shell (carapace and plastron)  usually covered with skin or scutes o Vertebrae and ribs are fused to the carapace (except for the neck and tail) o Scapula is within the ribcage (shoulder blade)  Problems with breathing arise because the ribs are attached to the outside of the thoracic cavity and the lungs are attached to the inside of the thoracic cavity  Normal Breathing  all based on the fact that ribs can move o Inhaling; Muscles attached to the ribs contract and pull the ribs outward o This in turn pulls on the thoracic cavity, enlarging it, which pulls on the lungs, enlarging them and sucking in air o Exhaling; Other muscles attached to the ribs contract and pull the ribs inwards o This in turn pulls on the thoracic cavity and the lungs, decreasing their volume, pushing air out  Testuidine breathing:  immovable ribs! o Dorsal side of the thoracic cavity is fused to the ribs o Ventral side of the thoracic cavity is attached to the visceral cavity o Inhaling; Muscles attached to the visceral cavity move the gut, which moves air in and out of the lung o Muscles contract, and pull the visceral cavity downwards, enlarging it 1 EEB267 Notes o When the visceral cavity is pulled downwards, so is the thoracic cavity o Exhaling; A different set of muscles contracts and pulls the visceral cavity upwards, making it smaller o The 2 pairs of muscles are attached to the arms and legs so they need to move their arms and legs to move properly  Majority are omnivores, but some are specialists  Most spend their time in and around freshwater and there are some completely terrestrial and marine species  Reproductive biology o Courtship  Olfactory, visual and tactile cues (glands to mark territory, female leaking estrogen, nibbling, head bobbing, titillation)  Tortoises also vocalize and ram-flip  Most aggressive they get is pushing, stretching necks, and threatening with an open mouth  Not a social animal o Fertilization is internal and oviparous in all species female makes a nest in the ground o No parental care of eggs or babies o All nests made on land  Dangers to testuidines o We eat them o Habitat destruction o Medicinal purposes o Use them for beauty and clothing Lepidosauria  makes up Rynchocephalia and Squamata  Synapomorophy: caudal autotomy (shedding the tail) and simple male hemipenes o Occurs along fracture planes in the vertebrae of the tail (not between) and corresponds to the meeting of 2 muscle bundles... skin is weaker, muscle bundles fold over, which reduces blood loss no damage to muscle! o Costs: regenerated tail = with cartilage, not with vertebrae. New scales and colour patterns are different than before, loss of fat stores, energetically expensive, loss of specialized tail functions o But you survive, so thats good! Rynchocephalia  These are the tuataras!  Primarily nocturnal insectivores  Males are 2x as large as females and have a well developed crest for mate attraction  Internal fertilization, but they do not have well developed hemipenes 2 EEB267 Notes  Females lay 8-10 eggs every 4 years and guard the nest for about 8 days against other females  Eggs incubate for 12-15 months! Squamata  These are the lizards and snakes!  Synapomorphy: well developed male hemipenes  Most are terrestrial, insectivorous, oviparous, no parental care  Do not form pair bonds (polygamous or polyandrous)  Lay leathery eggs in a nest in the ground  Giving birth to live young has evolved over 100 times, mostly in the skinks and snakes o Babies are protected for a much longer time, but this is energetically costly to the mother o May have allowed these squamates to move to colder temperature spots  Endangered due to habitat degradation and introduced species (not due to their biology) IGUANIA: large group of mainly terrestrial, insectivorous species with scales that are often modified to form horns or spikes and have elaborate visual displays  Chameleons, anoles, frilled lizards, iguanass  Horned lizards: central NA, desert species  Basilisks: bipedal runners across land or water, fringed scales on the posteriors edges of the toes, cannot shed tail (too important for balance prehensile)  Iguania: primarily herbivorous, only marine lizard, nasal salt glands in marine.  often BIG! o Courtship: visual cues (frills, dewlaps, colours). Males are territorial (behaviour includes head bobs, push ups, mouth opening, mouth wrestling, kicking. Male-female interactions include some territorial displays and tactile cues  Chameleons: long projectile tongues, big eyes that move independently (which calculates distance very well and enlarges the prey image), prehensile tail and capable of changing colour  Anoles and frilled lizards: visual displays with flaps of skin (dewlap), often with bright colours that identify species, cannot shed tail SCLEROGLOSSA  Courtship in general: chemical and tactile cues become important in courtship o Most species are not territorial (except Gekkota), so males must search for females o Some species mob a group of females after hibernation  Gekkota: primarily nocturnal, big eyes, second most species rich group of lizards, most species do not have eyelids (only basal species... the others have a transparent scale called the spectacle which covers the eye), subdigital lamellae that help them walk up walls and stuff o Subdigital lamellae have setae (made of B keratin) which are the bonding agents o Lay hard shelled eggs and reinforced with a strong outer calcerous layer  Scincomorpha: species rich family, smooth, shiny scales, tail loss is common, long body 3 EEB267 Notes o One group of skinks forms monogamous family groups o Some species will have female only parental care (also some snakes)  Varanoidea (monitors): some are small insectivores, but the others are large and powerful, long necks, well developed limbs, powerful tails and jaws 4 EEB267 Notes Lecture 3 & 4: Osmoregulation, Female- only Species and Limb Reduction  Big challenge to balance water and salt within the body so that the proteins and nerves function  Too much salt = toxic, because it increases the blood pressure and interferes with the transmission of nerve impulses  Osmosis: the flow of water from an area of low to high solute concentration across a semi- permeable membrane  The marine problem: organism has fewer solutes than the surrounding salt water, so water flows out of the organism to try and balance the osmotic balance, but then dehydration kills it o Solution of cartilaginous fishes: store urea in the blood and tissues so that the concentration of solutes inside the body is higher  Excess water is excreted through small to moderate amount of urine  Excess salt is excreted by rectal gland and in urine o Solution of marine ray-finned fishes: drink constantly to replace lost water  Excess water is excreted in a very small amount of urine  Excess salt is excreted by specialized cells in the gills o Solution by marine reptiles: scaly skin and shells prevents a lot of waterloss  Excess salt excreted by salt glands which extract salt from the blood and excrete it to the outside  The freshwater problem: organism has more solutes than the surrounding fresh water, so water flows into the organism and they would die from bloating o Solution by freshwater ray-finned fishes: urinate constantly to eliminate excess water, but they lose salts by constantly urinating too  Recover lost salt by specialized cells in the gills o Solution by freshwater amphibians: almost the same as the ray-finned fishes  Big problem: very permeable skin!  urinate constantly  Recover lost salt ions by specialized cells in their skin which reabsorb from the surrounding area o Solution by freshwater reptiles: scaly skin prevents them from having too much water flow into them  Excess water is excreted by a slight increase in urination  Recover salt ions from food  The terrestrial problem: water is constantly flowing out of the organism o Evaporation occurs across thing, scaleless skin o Solution by terrestrial amphibians: they cannot drink so they can sit in water and expose their thin skin to water sources.  Aestivate when it gets too hot (some ran reabsorb from their urine)  Water can also be extracted from food 5 EEB267 Notes  Hide in a cool, moist place, stay out of wind o Solution by terrestrial reptiles: scaly skin prevents much, but not all of evaporation  Drink water or get from food  Excrete excess nitrogen as uric acid (less water to excrete)  Get rid of excess salt through salt glands  Channel water droplets from dew into mouth, stay out of sun and wind, burrow in the sand FEMALE-ONLY SPECIES  50 species, mainly in skink and gecko groups  All female only species reproduce by parthenogenesis: females do not mate with males, although some species do display pseudocopulation (females play both roles)  Diploid eggs are made and do NOT need males at all!  If a parthenogenic female and a normal male mate, you’ll get an XXX triploid female, which would be a new species! LIMB REDUCTION/ LOSS  Forelimb = humerus, radius, ulna, metacarpels, carpels, phalanges o Humerus articulates with the bones in the pectoral girdle, which includes the clavicle and the scapula  Hindlimb = femur, tibia, fibula, metatarsals, tarsals, phalanges o Femur articulates with the pelvic girdle  Gekkota  flap foots o No forelimb, reduced pectoral girdle o Himdlimbs are reduced to small scaly flaps, reduced pelvic girdle  Scincomorpha o Varying degrees of limb reduction o Up to complete loss of forelimbs and pectoral girdle o Up to complete loss of hindlimbs, reduced pelvic girdle (ALWAYS A REMNANT OF THE PELVIC GIRDLE)  Varanoidia slow worms, glass lizards o No forelimbs, reduced pectoral girdle o Reduced to no hindlimbs, reduced pectoral girdle  Worm lizards o No forelimbs, pectoral girdle reduced or absent o No hindlimbs, reduced pelvic girdle o 3 species (Bipes) have functional forelimbs, reduced pectoral girdle and reduced hindlimb, internal femur only, pelvic girdle present  Snakes o Living snakes do not have forelimbs or a pectoral girdle o All have some vestiges of the pelvic girdle 6 EEB267 Notes o Basal snakes have a vestigial pelvic girdle and very reduced hindlimbs o Derived snakes have no hindlimbs and no pelvic girdle (ABSOLUTELY UNIQUE!)  All limb reduced species are/have... o Burrowers or sand/ grass swimmers o Forelimb reduction happens before hindlimb reduction (except for Bipes) o Continued limb reduction and total limb loss is always preceded by body elongation 7 EEB267 Notes Lecture 5 & 6: Feeding and Gender Determination in Reptilia  Head is small compared to body when the body is; o Eat small prey and eat often (basal snakes, limbless lizards) o Tear chunks off bigger prey and eat less often (worm lizards) o Eat big prey and eat rarely (most snakes)  Cranial kinesis: the lower and upper jaws are each divided into 2 units o Hinge between quadrate and a movable bone in the skull o Hinge between quadrate and mandible  each mandible articulates with an enlarged, free swinging quadrate which itself articulates with a movable bone in the skull o Hinge in the mandible  each mandible has a joint in the middle (lower jaw can bend outwards) o Ligament between the mandible  In most amniotes, the mandibles are fused, but in snakes, fusion never occurs and the ligament is the only thing there (mandibular liberation)  The upper jaw: made of 2 separate palatomaxillary arches, each made of 4 articulating bones; o The maxilla (which has the fangs), and 3 others o The arches are attached by various muscles to the skull  each arch can move forwards, backwards, up and down independently o Therefore, most snakes walk their heads over their food  Other things that help you “eat big”: o Ribs are free at the ventral end (expandable) o Elastic skin around the mouth and throat o Trachea opens anteriorly in the mouth (not at the back of the throat, like other terrestrial vertebrates)  can breathe while eating  Lizards have thick, robust and strong skulls  Snakes have rather thing and fragile skulls due to mandibular liberation, so they can be easily injured by struggling prey! o Solution 1: Constriction! Big pointed backwards teeth that help you swallow big prey once it has been subdued o Solution 2: Venom!  colubroidea are venomous snakes  Venom gland type 1: no lumen (interior space) for storage, no muscles associated with ejection of venom  Venom gland type 2: increased size and complexity, associated with special muscles that contract and force venom out of the gland; storage space in the gland  venom is ready to be used at any moment  Venom is stored in venom glands with the help of the accessory gland, which has some cells that produce substances to acidify the stored 8 EEB267 Notes venom  also secretes mucous into the venom gland, which protects it against the secreted acids  Acidified venom is non-functional  Once the venom is injected into the prey, it encountered a much more basic environment which activates the venom  Venom is made up of a bunch of stuff o Hyaluronidase: increases absorption of venom through connective tissue (all venomous squamates) o Neurotoxins: paralysis, suffocation o Haemotoxins: anti-coagulants, which leads to tissue destruction o Venomous snakes are the Viperidae, Elapidae and Colubridae (but many colubrids are contrictors and are non venomous)  Delivering venom o Colubridae: rear fanged snakes  garters, twig snakes, boomslangs, vinesnakes  Type 1 venom glands, both with a duct that leads to the base of the fang  Fangs at the caudal end of the maxilla  Shallow groove along the lateral or anterior surface of the fang to deliver venom  Venom moves by capillary action (delivery is slow)  snake must bite and hold  Primarily a haemotoxin  All body sizes, possibly active predators o Elapidae: front fanged snakes  cobras, coral snakes, mambas, sea snakes, sea kraits  Type 2 venom glands, both with a duct that leads to the base of the fang  Short fangs on medium length maxilla, often with small teeth behind the fang  Fangs do NOT fold down when the mouth is closed  Very deep groove along the front of the fang  Bite and hold  but can eat larger prey, because more venom is delivered  Prey is rapidly immobilized by neurotoxins  Slender bodies, active predators o Viperidae: front fanged snakes  rattlesnake, horned vipers, bushmaster, eyelash viper  Type 2 venom glands, both with a duct that leads to the base of the fang  Long fangs are the only teeth on the very small maxilla  Fangs fold down when mouth is closed o  Highly mobile maxilla and can rotate up to 120  Goove on fangs is closed  hollow passage inside the fang  venom injected deeply  Bite and release (efficient!), except for arboreal species  Able to adjust amount of venom based on prey size (more efficient)  Prey is immobilized by haemotoxins  Large bodied, ambush predators which wait in a strike position and then launch forward 2/3 of its body at the prey item 9 EEB267 Notes o Other venomous Squamates are in the Varanoidea  Helodermatidae: 2 species of Gila monster and the beaded lizard  Varanidae: komodos... Varanid venom acts more quickly than helodermatids  Venom glands are in the lower jaw, and so are the teeth associated with the venom gland; each gland is lobed and there is lumen in each lobe and each lobe has a duct to the base of the teeth (numerous ducts, not just one)  Each venom gland has 3-4 distinct lobes  Each venom gland of the varanid lizard has 6 distinct lobes  Ducts from each lobe open between the teeth  Helodermatid venom conducting teeth are deeply grooved; they bite and chew and hold on and chew, waiting for the venom to take effect  Komodo teeth are not grooved, but are serrated like a knife (spreads the venom)  Varanids use the grip and rip strategy and do not inject venom... venom just mixes into the wound  The venom is a cocktail of hyaluronidase and numerous peptides that lower blood pressure/ cause irregular heartbeat, intense pain and internal bleeding (anticoagulant)  Detecting olfactory cues o 1. Nasal olfactory system  Chemical cues in the air (volatile) detected by sensory cells in the nose  olfactory nerve to main olfactory bulb in the brain o 2. Vomeronasal olfactory system  Chemical cues on objects  captured/detected by tongue  transferred to sensory cells in the vomeronasal organ (JACOBSON’S ORGAN)  accessory olfactory nerve to accessory olfactory bulb  Vomeronasal organ opens to the top of the mouth o Forked tongue  Hypothesis 1: delivers odor molecules directly to the vomeronasal organ... but this doesn’t actually happen, and the shape has nothing to do with it anyways  Hypothesis 2: allows an animal to assess the concentration of a chemical cue at two different points simultaneously  Klinotaxis: successive sampling (spot 1  spot 2). Exploratory. All
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