Exam 2 Study Guide
Exam 2 Study Guide 81463 - BIOL 3030 - 001
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This 70 page Study Guide was uploaded by Abigail Towe on Thursday October 15, 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 296 views. For similar materials see Vertebrate Biology in Biological Sciences at Clemson University.
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Date Created: 10/15/15
Before Exam, we were looking at fish in shallow water transitioning into land. Invading land ● Example: Tiktaalik from: http://www.google.com/url?sa=i&source=imgres&cd=&cad=rja&uact=8&ved=0CAkQjRwwAGoVChMIsoS_7pabyAIVBM2ACh1flwuw&url=http%3A%2F%2Fwww.sci- news.com%2Fpaleontology%2Fscience-new-fossils-tiktaalik-roseae-01686.html&psig=AFQjCNGEWtwfMuAKYUeqopmsNDa8JmPMkA&ust=1443579505969423 Comparing Land and Water by looking at Oxygen: 1. air is less dense a. meaning the environment above water doesn’t support the body b. skeleton is needed to aid in body support 2. air is less viscous than water a. easier to move in air 3. air has more oxygen than water a. respiration requires less energy (especially since it’s easier to move in air) 4. air temperature less stable than water a. land vertebrates need to thermoregulate 5. sensory mechanisms: a. sensation of electrical fields not viable on land b. air movement won’t stimulate lateral line system and is lost by land vertebrates 6. because land vertebrates aren’t surrounded by water: a. there is water loss b. and locomotion changes Summary: Water Air MORE dense less dense MORE viscous less viscous less oxygen MORE OXYGEN MORE stable temperatures less stable temperatures allows use of lateral line system electrical fields not viable on land no water loss there IS water loss locomotion consistent for years locomotion changes Invading Land: Design Issues ● how will it support itself with this new environment? Support: ● density of body tissues is about 1050 kg/m^3 ● density of water: 998 to 1024 kg/m^3 ● density of air: 1,205 kg/m^3 (about 00 times less than water) ● Because the tissue density is close to water (1050 compared to 1024), it minimizes effects of gravity. ○ Therefore, the skeleton functions to provide muscle attachment sites and a means for transmitting forces through the body. DOES NOT require skeletal system to maintain body shape in water. ● But on land, since the body (1050 kg/m^3) is denser than environment/air (1,205 kg/m^3), then it requires that the skeleton function as a support system. ● Modifications to internal skeleton in land vertebrates: 1. robust ribs a. function= assist in supporting abdominal organs i. example: ichthyostega: 1. organs won’t sag to the ground 2. more protected and compact organs 2. changes in girdle attachment (pectoral girdle) a. support is off the ground b. detached from skull i. this advantage: increases head mobility c. firmly attach limb girdles to vertebral column i. for the pectoral girdle: it’s attach to muscular sling ii. for the pelvic girdle, it's attached to the sacrum 3. zygapophyses= facets between vertebrae (helps support body off ground) a. this helps to support body off the ground b. the facets were the vertebrate interlock is secure c. Invading Land: Consequences of Size ● because land does not support the animal as much as water, the animal can’t get too large... ● as the animals get bigger in length: ○ as legs go from two to four, the surface area increases and volume increases. ○ the body mass and forces that are put on the bones, increase like a volume (x^3) ○ the body cross-sectional areas that resist force increase like an area (x^2) ○ as animals get bigger, forces on their bones get bigger at faster rates than the ability to resist forces (volume increases a lot faster than surface area) This is a problem unless….there is accommodation for size increasing: ■ relatively more robust skelton ● positive allometry ■ less risky/ vigorous activity Invading Land: Locomotion and Support: ● Background: Newton’s third law- ○ for every action there is an opposite and equal reaction (applies to all locomotion) ● in water, fish can use fins, body, and their tail to use those forces in the water to move/propel them ● but in land you can’t do that-- you only have specific point of contacts (like feet) to exert force on the environment. ● Land vertebrates use same structures (limbs) for support and locomotion ○ the structures must be stiff, strong and flexible ○ the structures are connected by jointed segments ■ the bones are stiff, but joints allow mobility ○ remember: the limbs evolved from sarcopterygian fins with a robust skeleton in which rays were lost. NOT evolved from fins. ● Locomotion: ○ fish- body axis movements dominate locomotion ○ land vertebrates- body axis movements reduces and most muscle is in appendages (limbs). limbs are most important for locomotion. ■ decrease in axial muscles mass, increase in appendicular muscles Invading Land: Changes in Feeding Function ● Changes in Feeding Function: ○ fish use suction- draw viscous water into mouth, take food with it ○ remember, air is less viscous than water so suction doesn’t work ○ instead, vertebrates on land have to use a different strategy (some of these strategies many fishes can use too) ■ in common with fishes: ● ram feeding: move head over prey and engulf whole ● biting: taking chunks out of bigger prey with teeth ■ other changes required since water is not brought in with food: ● use of mobile, muscular tongue to move food around and help swallow ● salivary glands: secrete lubricating fluid to help chemically digest carbohydrates Invading Land: Changes in respiratory function ● remember: gills don’t work on land ○ too floppy, delicate, collapse in air so surface area covered and can’t extract oxygen from air ● but lungs…. do work on land! ○ air is less dense, light, & easy to move ○ little energy cost to breathe into sac and turn around to exhale ■ functions as a negative pressure system: ● when a vertebrate inhales, contraction of muscles between ribs and diagram to allow expansion of the chest cavity - decreasing lung pressure (lungs will have less oxygen than the environment/air) and allows air to be drawn inward ● when the muscles relax, the chest is compressed, which increases lung pressure and forces the air out Invading Land: Changes in Circulatory Function ● higher blood pressure required on land, since blood must be pumped (vs using gravity) ● there are 2 circulatory circuits required for use of the lungs: ○ pulmonary circuit: heart → lungs and lungs → heart ○ systemic circuit: oxygenated blood from heart pumped to body, then returned to heart ● Comparing fish to land vertebrate ○ fish have tubular heart system that pumps blood to gills, where blood picks up oxygen, then sends it to the rest of the body ○ land vertebrates have side-by- side pumps ■ the right side pumps to the lungs and returns to heart with oxygen (pulmonary) ■ left side pumps out to body and returns to heart without oxygen (systemic) ○ changes in the circulatory system: there is a loss or reorganization of blood vessels running to the gills (aortic arches) Invading Land: preventing water loss 1. skin a. terrestrial vertebrates have epidermis with 2 layers i. stratum germinativum - deeper, living tissue ii. stratum corneum- outermost- dead cells 1. this contains proteins and lipids to help protect against water loss 2. urinary bladder a. stores urine so it doesn’t drain constantly i. ancestrally, probably capable of recovering water to body, as in many modern amphibians and reptiles 1. because of the ability to recover water to help the body with hydration, the content of the bladder is much more concentrated than it was when it first entered the body. Invading land: regulating body temperature ● land temperatures are much less stable than water ● vertebrates must thermoregulate (not too hot, not too cold) ○ this helps to achieve best level of performance ● Example: garden snake ○ performance peaks at about 30-35 C ● There are several methods of thermoregulating: ○ convection: through air (gain or loss of heat) ○ conduction: through ground (gain or loss of heat) ○ evaporation : through water loss (heat loss only) ○ metabolism: internally generated (gain heat only) from: https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCPSsmIagm8gCFQnPgAodsxAM0g&url=http%3A%2F%2Fw ww.quia.com%2Fjg%2F2550021list.html&bvm=bv.103627116,d.eXY&psig=AFQjCNHRb2PMpcobef_Wj-Pji7s7V-HMmA&ust=1443581966632612 Invading land: regulating body temperature how to control heat gain or loss? ● behavioral- move in or out of hot/cold location ○ basking - in the sun ● physiological ○ dilation (expansion) or constriction of blood vessels ■ example: ● expanding blood vessels close to body surface allows more blood to flow faster through them and heat up blood at surface (if hot outside) ○ heated blood travels to body core, to warm it up Tetrapod Origins ● Review: ○ air is less dense and much less viscous than water ○ on land, the skeleton now has to support the body weight ○ feeding changes: suction feeding no longer works for the animal (doesn’t work on land) ○ for acquiring oxygen, gills are no longer viable/effective ■ but- since air is easy to move, breathing will work with lungs and it’s cheap/easy/little cost ● even though lungs weren’t evolved for that (remember lungs were already there in aquatic animals) ○ loss of electrical and lateral line sensory system on land ○ air temperatures are less stable than temperatures in water ○ risk of drying out on land because water doesn’t surround you anymore Tetrapod Relationships with Sarcopterygians: ● Remember: Sarcopterygians are osteichthyans that have robust bony skeleton in appendages (fins or limbs) ○ within sarcopterygians, tetrapods appear ● Tetrapods are sarcopterygians with 4 feet ○ feet= fingers/toes (not fins) ● Tetrapodomorpha → united by sharing choanae (internal nostril) ○ the choanae allows air to pass through external nostrils to lungs with mouth closed ○ the animal can stay in shallow water but bring nose out of water to breathe. therefore, they can stay in water to sneak. Fossil Relatives of Early Tetrapods (Devonian) ● First look at the Eustenopterm (osteolepiform) ○ This fish has a choana and has some bones in the fins, but still a fish. ● Panderichthys (elpistostege) ○ lose dorsal and anal fins, flat body ○ forefin closer to tetrapod limb than hindfin (this is mosaic evolution) ● Early tetrapod: Acanthostega ○ Dactylus limbs (limbs with digits) ○ but no robust skeleton ● The head and body profile changes: to become more flat ● The dorsal and anal fins are lost ● The fore and hind fins transition into well defined bones to form fingers/toes. ○ the fore fins develop to a tetrapod limbs faster than the hindfin ■ the fore fin develops a space in between bones (like radius and ulna), but hind fin doesn't have this gap in transitional fossils. ■ changes in fore fins occurs much sooner than hind fin - makes sense because you are moving yourself with your fore fins ● mosaic evolution- major transitions that happen in particular places/times and each transition helps to get to tetrapod. Tetrapods ● Synapomorphy: ○ 4 feet (dactylus limbs - with fingers and toes) ● Early tetrapods found in Greenland dated to Late Dovian period, 378-352 million years ago (Acanthostega) ○ But Greenland has high contrast of seasons, so it doesn’t seem like a good home. But during the Late Dovian period, Greenland was actually close to the equator so the environment would have been more suitable. ● Other distinctive qualities of tetrapods: 1. retain tail fin rays 2. hand and foot polydactylous (7+ hind digits, 8+ fore digits in the early tetrapod: Acanthostega) a. also the digits were not symmetrical, no pattern: it can range from small, large, large, then small fingers that doesn’t look normal 3. Gills a. blood vessel grooves on arches ● All of this helps tetrapods live near-shores/shallow water. This features evolved in water, helped them in water. Remember the 1st tetrapods were aquatic. ○ The are very similar to modern crocodiles (flat bodies, nostrils and eyes on dorsal side of head) Early Tetrapods & Evolution of Development ● Polydactyly in fossil taxa - 5 digits is not a primitive condition/ not ancestral for tetrapods ○ This means that being polydactyly with 7 or 8 digits is ancestral ● The transition from 8 to 5: one possible mechanism of this transition is a pattern known as developmental truncation ○ truncation = means “cutting it short” ○ If development is shortened, last features don’t appear ○ The order of development of digits is that it starts on one side of the arm, the digits develop across the palm of the hand. So if the development time changes, then less digits are formed. Early Tetrapods: Changes in Feeding & Hearing: ● Acanthostega (early tetrapod) skull: ○ the skull is flat. ○ the nose and eyes are on top of skull ○ This encourages feeding at surface/in shallows. So since they are not surrounded by water, they cannot use suction feeding anymore. They had to rely on ram feeding and biting. ■ So to better use these two mechanisms to eat, the bones of the skull will need to be solid, fused together, and help keep the head stable to help keep the head still as food/prey is attacked (important because prey usually moves/fights back) ● Hyomandibula bone- this is the major bone that changed. ○ it used to connect jaw to braincase with mobile joint. ○ but now that tetrapod are no longer flaring jaws out for suction, the hyomandibula bone changes to adjust to new feeding mechanisms. ○ The function of the hyomandibula changes- from skull flaring to hearing (stapes) ■ stapes bone is smaller than the hyomandibula ● but it’s still a chunky, thick bone. This prevents being able to vibrate very frequently- so it can’t hear high pitches. So most sounds they would hear would have been low pitched. ○ The hyomandibula bone now connects skull to tympanic membrane (eardrum) to serve to pass sound waves to brain Early Tetrapods and the Invasion of Land: ● But WHY invade land? ○ They didn’t HAVE to! So why? ○ they were well adapted and good at living in water. So why? ● Old idea: escape drying conditions in water ○ problem with this idea: if you look at rock records from Devonian period, there is NO record of droughts ● New Idea: exploration of novel food sources ○ invertebrates already invaded land (before tetrapods, there was insects on land) ○ so tetrapods could have left water for new food sources ● Newer New Idea: heat up faster ○ moving to land could allow vertebrates to heat up their body temperatures ■ remember: vertebrates rely on outside environment to heat up body ○ water temperatures are stable- not always a good thing because if water is cold it will stay cold and vertebrates can’t heat up ○ therefore, vertebrates could rely on the sun for heating their body (sun basking) ○ At first, they went on land for heat then went back into water and carry the heat back with them ○ But after a while they stopped going back ● It’s possible that both of the new ideas contributed to the reason of why Early Tetrapod Relationships: ● Main points: ○ Basal tetrapod diversity ■ first lineages (not a clade) ■ Acanthostega: early tetrapod - highly aquatic ● no robust skeleton, larger tail fin ■ Ichthyostega: one of the first of which good evidence was found ● more terrestrial- robust ribs and girdle. less tail fin ● but the hearing is still suited for underwater heating ● the feet are not true feet- close to a seal flipper than a foot ● could be secondarily aquatic- the transition was back and forth between water and land. recurring theme in early tetrapods to go back to water. ○ batrachromophs vs reptiliomorpha ■ the difference between these two groups is very close to the different between amphibians vs amniotes ■ batrachomorphs: most taxa thought of as amphibians ● distinguished by: ○ flat skull ○ no kinesis ○ 4 or fewer fingers on hand ■ one taxa of batrachomorphs: lepospondyls (diverse small taxa) ■ One example: Nectrideans ● found in Texas, dated from Permian period ● aquatic ● bizarre horns on skulls of adults (head forms into boomerang shape as adult) ○ doesn’t know what the function of this head shape is ■ Another example: Aistopoda ● first example of limbless vertebrates ● operates more like a snake ● lived on land ● fossils found in Europe, dated back to Carboniferous-Permian period ■ Temnospondyls- ● from Carboniferous period- recent ● many big terrestrial taxa early ● but later survivors mainly aquatic ● grade of taxa from which modern amphibians groups evolved ● survive Permian period but died out in cRetaceous (except for modern groups) ■ Basal reptiliomorpha diversity: ● distinctions: deeper skull, more terrestrial ● example: Anthracosaurus (carb-trais period) ○ large, long-limbed ● example: Diadectomorpha (permian) ○ Herbivorous (among first tetrapods to feed this way during this time- most were carnivorous) ○ pre-batrachomorph diversity ■ looking at the diversity before the batrachomorphs ■ the book groups all these species together in lepospondyls ○ representative temnospondyls and origin of modern amphibia (lissamphibia) Paleozoic World: A completely different place: ● The continents were converged into pangea ○ almost all terrestrial exposed land would have been together- in continuum ○ there were 10s of millions of years of this supercontinent (pangaea) ○ However, no flowering plants. There was giant seed ferns, giant horsetails, giant club mosses. There were higher levels of oxygen. These unusual high oxygen levels made it possible to have giant insects (dragonflies 3 feet long) ● But at least half of all of this was removed with the major vertebrate extinction at the end of the Permian period. ½ of all tetrapods died. ○ Extinction because massive volcanic eruptions in Siberia release lava and greenhouse gases, raise water temperatures to 6 degrees Celsius ■ This disrupted ocean circulation and climate and air flow ○ Amphibians and mammal-like reptiles took biggest hits ○ past disasters help shape present diversity ○ What we see today is the groups that made it through this disaster Amphibian Diversity Review: ● temnospondyls- from where modern amphibians are derived ○ so no, we are not temnospondyls ● earliest tetrapods lived in aquatic environments ○ then eventually moved to land ● tetrapods split into two major clades: batrachomorpha and reptiliomorpha ○ a group under batrachomorpha called lissamphibia lead to modern amphibians ● batramorpha: ○ caecilians (clade gymnophiona) ■ no limbs ○ salamanders (clade urodela) ■ yes limbs ○ frogs (clade anura) ■ yes limbs - and specialized: jumpers Lissamphibia Synapomorphies: 1. skin= smooth, glandular a. highly permeable to gas and water i. oxygen exchange but also exchanges of water b. two types of glands: i. mucus glands- secrete mucus. 1. the mucus keeps animal moist to prevent water loss (prevent evaporation) and a predator defense because if prey is slippery it helps it escape or avoid being eaten by predator ii. poison glands: 1. located all throughout the skin 2. secretes poison: chemicals 3. not all poisons are deadly, various toxicities a. potential to kill, or cause hallucinations c. no armor: i. we can tell that the skin of these amphibians are different from reptiliomorpha because these lissamphibians do not have armor. d. amphibians shed their skin regularly i. the stratum corneum layer comes off 1. this layer is less permeable ii. skin sloths off 2. has pedicellate teeth a. these teeth are bicuspid (has two cuspids) b. pedicel- the distinct region where the crown of the tooth is connected to the jaw c. this classifies them as predators because these teeth help to kill other animals for food d. exception: some frog tadpoles do it plant material but by the time they metamorphosize into their adult size they are predators Lissamphibians: Bimodal life history and the exceptions: ● fertilized egg → aquatic tadpole → undergoes metamorphosis (dramatic reorganization of body systems) → changes into much more terrestrial inhabiting adult ● therefore, they are considered to have a double life because aquatic than terrestrial life ● exceptions: ○ direct development: ■ tadpoles are kept in a sac but on land, and when they hatch they are already in their terrestrial state = live on land ■ paedomorphosis: exhibit juvenile features ● examples: mudpuppy salamander ○ sexually mature mudpuppies have gills, which are juvenile features fossil record of lissamphibians: ● caecilians= Jurassic period ○ known from Arizona ○ distinguished by mode of locomotion: limbless ○ but caecilians have tiny limbs ● salamander= mid- Jurassic ○ actually show outlines of soft tissues features (that usually aren’t preserved) and you can see gills ● Frogs= Triassic ○ “anura” = literally means no tail amphibians Caecilians: ● Clade Gymnophiona ● about 200 species ● fossil record: Jurassic ● today they live in tropics ● limbless ● under a foot long ○ but one single species are 1.5 meters ● specialized for burrowing ○ they look like a worm and because no limbs , they use their head to burrow ○ therefore, their skull is highly ossified (solid bone) skull ○ if you’re burrowing in soil, then you eat food in soil such as earthworms and bugs. so they also has jaws = high bite forces for their body size ● also because of underground lifestyle: ○ reduced eyes or no eyes ○ therefore they rely on smell= has chemosensory organ (tentacle) ■ they have two tentacles - one on each side of head ■ between the nostrils where eyes would be ■ the muscles that control these tentacles are the muscles that used to control the eyes ● eye muscles = greatest conservation of muscles (same muscles throughout many life forms ● but caecilians are the exception because they are more than the standard 6 muscles ● to burrow they use their head plus curvature in their spine ○ curvature allowed with loose skin ○ curves spine then springs itself forward ● has terminal anus ● loss or reduction of left lung ● external evidence of segments (annuli) ○ sometimes marked by presence of dermal scales ● has a large range of reproductive habits/lifestyles ○ females can guard/wrap around eggs to protect ○ or live-bearing where they remain inside mother while growing ■ they eat the uterine lining as they grow Salamanders and Frogs: ● Clade Batrachia ● salamanders and frogs are sister taxa ● they are considered together because: they share the distinct anatomical structure called the opercular apparatus ● Synapomorphy shared= opercular apparatus ○ different from the feature that is in ratfish, more complicated than in fish ○ it’s a collection of structures that together connects the ear region to their shoulder girdle ■ connected by muscle, operculum, and columella ● columella = stapes ( inner ear bone) ○ the advantage of this system: transfers sound up from feet to the structure in ear so that they can now detect ground-borne vibrations (along with sound like usual) ■ since these animals are low and on the ground, it helps them hear and feel when predator is coming ● Salamander Synapomorphy: ○ development traits ● Salamanders are recognized by long tail (primitive) but NOT a synapomorphy because everything had a tail! ● Frog Synapomorphy: ○ saltatory locomotion (jumping) Salamander Diversity: ● Northern Hemisphere ● don’t have to memorize branching pattern, just recognize the diversity and changes ● basal group= Sirens ○ can slither around on land but mostly highly aquatic ○ lose hindlimbs ○ small forearm ● next: Cryptobranchus ○ one species called hellbender lives in mountains of North CArolina ○ about 3 feet ○ but in Japan- 5 feet in length ○ still aquatic ● next branch off is: sister taxa: columbidae and plethodondriate ○ even smaller forearms and hind legs ○ but they do keep all 4 of them ○ plethodontids make up ⅓ of total ■ key features: lungless ● uses cutaneous respiration ■ terrestrial because a more ready source of oxygen for this respiration system is advantageous ● remember limb loss is independent for each species. ancestrally salamanders have 4 limbs ● proteidae: mudpuppies ● salamandridae: newts ● ambystomatidae: tiger salamander + allies Frog Diversity: ● Pipids: ○ totally aquatic swimmers ○ flat body ● Bufonidae: ○ true toads ○ toads are a group within frogs ○ toad = short legs so it's specialized for hopping (short jumps) ■ warty skin ■ toxins released from behind eyes ■ more terrestrial form of frogs ● Hylids: ○ treefrogs ○ generally smaller in body size ○ long skinny legs = great jumpers ● Dendrobatids: ○ poison dart frogs ■ because they eat certain insects (ants), gets toxins from ants, stores the toxins and then uses them to protect themselves ■ they can eat non-toxic ants and lose toxicity ○ small body size ○ tropical ● Ranids: ○ bullfrogs ○ jumpers ■ water frogs - jumps in shallow water Amphibian Musculoskeletal Function: Salamanders ● so whereas fish just have head and vertebrate (no neck) , salamanders have neck ● salamanders have regional specialization of vertebral column to allow neck ○ the atlas (cervical) is the structure that forms neck ● also because of the regional specialization: ○ they have trunk with ribs ○ scarum that is fused to hip girdle ○ casuals (tail) ● because of the regional specialization, it allowed the locomotion to change to lateral bending during walking (side to side walking) → this increases stride length /faster locomotion ○ the lateral bending of body helps them walk since their body type has limbs that are in a sprawling posture ○ lateral bending allows them to walk without having to change their posture Amphibian Musculoskeletal Function: Frogs ● the trunk becomes longer and stiffer → prevents axial movement ● shortening and development of urostyle ● tibia and fibula are fused together and elongated ● ankle bones are lengthened ● shorter forelimbs, but longer hind limbs that are highly muscled aids in high power production for jumping ● with various body shapes, frogs jumping changes ○ long hind limbs but short forelimbs= swimmers ○ long hind limbs and long forelimbs = jumpers ○ short hindlimbs but long forelimbs = hoppers ○ short hind limbs and short forelimbs = burrowers ● webbing between toes helps in gliding to have a more gentle/graceful landing = “flying frog” Amphibian Musculoskeletal Function: Locomotion ● Arboreal species: ○ has toe pads that secrete mucus to aid in adhering to surfaces by surface tension ■ there are glandular disks at toe tops to aid in grasping ○ intercalary bones: ■ helps set tip of the toe it further away from digit to allow more surface contact to help it stick to the surface ○ if they don’t have toe pads or intercalary bones, frog can have recurved spatulate terminal phalanx ■ the distal end of the toe/ phalanx can curve so that it can have a greater force to stick onto surface by increasing surface area ● example: green salamander ● tongue protrusion: ○ tongue flips from bottom side in mouth (tongue is attached at front of jaw) ○ common in frogs ■ but pepids do not use this underwater ■ but those on land do use this method ○ plethodontidae: lungless lineage ■ best developed tongue flip ■ can shoot out the length of body or more ■ achieved by: loss of lung = mouth no longer related to breathing so it can specialize for feeding behaviors ● so loss of lung could allow specialize for feeding to occur because no trade off = more energy devoted to feeding Amphibian Diversity - Part 2 (lecture 12 is part 1) Respiratory System: ● organs over the course of amphibian life include gills, lungs, and skin ○ operate to complete cutaneous respiration (gas exchange through the moist, highly vascular skin) ● organs shift from gills to lungs as the amphibian grows from larvae to adult. As they go through metamorphosis, the go through changes to prepare them for life on land (hence, gills to lungs). ● However, some adults keep the gills. These adults are paedomorphic (keeping juvenile traits in adulthood). ● Some adults have no lungs. These adults are plethodontids are the example. They have a shift from gills to strictly cutaneous respiration. ● And all of these types of adults can use cutaneous respiration at any stage (as larvae, tadpole, on land, in water, as adult). ● in amphibians that have lungs, there are patterns that can be seen as lungs are used: ○ pattern: as demand for oxygen increases, they switch to lungs as their primary mechanism. ■ lungs would be required if they are at high temperatures and activity is high. Lungs can keep up with high metabolic activity. ○ lungs work by Ventilation Cycle: ■ air is moved into the lungs through ventilation via a force-pump mechanism. ■ they drop the floor of their mouth to expand buccal cavity so that they can suck air in through external nostril into this buccal cavity through the choana (the internal nostril) ■ the air stays in the buccal cavity because the glottis (the connectiving slit to the lungs) is held closed ■ the nostrils close, floor of buccal cavity rises forcing fresh air into lungs through open glottis ■ the glottis then closes and the floor of the mouth oscillates back and forth (flutters) to clear any residual air that is left in the mouth (so that the air doesn’t get into the lungs) ■ the glottis reopens - the muscles of the body wall contract so that it the air is forced out of the lungs (because the air is stale because the oxygen has been extracted from the air) Circulatory System: ● along with the organ changes from gills to lungs, the circulation system also changes to accommodate the metamorphosis. ● in tadpoles, there are 3 main sets of veins that deliver blood → heart (right atrium) ○ 1st- anterior cardinal (jugular) - blood from head → heart ○ 2nd - vitelline - blood from gut organs like liver → heart ○ 3rd - posterior cardinal- blood from rest of body like tail → heart ○ the heart pumps blood through the external carotid arteries to head and then the aortic arches 3-6 send blood to gills and rest of the body ■ used to be 6 arches in aortic arches in gills but in tetrapods arches 1 and 2 are gone. ● In adults, there are 4 sets of veins that deliver blood to heart ○ 3 of these veins that take blood to right atrium ■ anterior cardinal (jugular)-- from head ■ hepatic - from gut organs-- from liver ■ posterior vena cava -- from rest of body ■ ○ but 1 sends blood to left atrium ■ pulmonary vein returns blood to heart from lungs (delivers rich oxygenated blood to heart) ○ the aortic arches changes in adults: ■ whereas in tadpoles, they have arches 3-6 ■ adults now have lost arch 5 ■ arch 3 = internal carotids ■ arch 6= pulmocutaneous arteries to lungs and skin to pick up oxygen Patterns of blood flow within the heart of an adult with LUNGS: ● when blood first arrives in heart - right atrium- it’s deoxygenated ● then it will go into the ventricle ● then pump blood into major blood vessel : aorta ● this blood will then go to the lungs ○ it’s channeled to go there because the spiral valve is a flap of tissue that directs blood to the right location (lungs) if it is deoxygenation ● it gets oxygenated in lungs, then returns to the left atrium ● then it will go back into the same ventricle (only has one ventricle) ● the ventricle sends it through aorta where the spiral valve directions the blood ● the ventricle has both oxygenated and deoxygenated blood within, but mostly separated within. largely separated. red blood + blue blood (NOT purple blood) ● the spiral valve also helps to keep the blood separated. ● summary: right atrium to ventricle to aorta to lungs to left atrium to ventricle to aorta to body Patterns of blood flow within the heart of an adult with CUTANEOUS: ● the blood arrives into the right atrium and it’s oxygenated ● the left atrium doesn’t receive blood from lungs because it doesn’t use the lungs ● the spiral valve of the aorta doesn’t send any blood out to the lungs - instead it allows all the blood to be distributed to the body ● summary: skin to right atrium to ventricle to aorta to body Amphibian’s water intake and water loss: ● water uptake: ○ they do NOT drink ○ rapid uptake through highly vascularized patch of pelvis skin (pelvic patch) ■ this patch allows use of very shallow water to uptake water ○ urinary bladder helps to reabsorb water back from the urine to prevent further dehydration. ■ the bladder is large in terrestrial species (to help recover water) ■ bladders are typically 20-30% of body volume ■ special example: Australian frog Heleioporus eyrei has bladder size that is up to 79% of body size ● preventing water loss: ○ secrete lipid based compound that is waxy to reduce the permeability of their body to the outside environment. They spread this lipid base over skin of body with legs. ○ posture change- ■ upright body posture to exposure themselves if it’s wet outside ● they use this time to call for mates ■ hunkered down posture- saves them about 20% water loss that they would have if they were upright. ○ being hydrated helps evade/escape predators ○ for desert amphibians (frogs), they may live underground for most of the year (9 or 10 months) while there is no rain. comes out for rainy seasons ■ aestivation = prolonged torpor or dormancy of an animal during a hot or dry period.. Amphibian skin color: ● crypsis / cryptic pattern ○ this pattern (color or bumps) that conceal animals to hide from predators or prey ● aposematic patterns: ○ many species have this pattern to show themselves off to warn predators that they are toxic. ■ examples: ● newts are black on top but when threatened they spaz out and flip their tail up to show red- showing the predator they are toxic ● poison dart frog- bright yellow, blue, and blue pattern on back of animal ● mimicry: ○ non-toxic but has some qualities of aposematic pattern to trick predators. ○ doesn’t have to use as much energy because they aren’t making toxics, they are only making skin patterns to trick predators. Amphibian Reproduction and Development: ● 3 different methods seen- ○ internal - caecilians males insert intromittent organ into female cloaca to deliver sperm ○ salamanders- few external, most internal but spermatophore ■ spermatophore- sperm packet ● the sperm packet often has a species specific shape for the cloaca of the female ● males will bite and hold onto to females and insert spermatophore with feet ● some cases: females collect with cloacal lips to receive sperm into cloacal sacs (spermatheca) to store the sperm for months or years until environmental conditions are suitable enough for babies to succeed. ○ frogs- mostly use external fertilization via amplexus ■ male graps females with forelimbs and fertilizes eggs as she lays them ■ amplexus is maintained for hours ● therefore, males will grow huge forelimbs from hormonal release during breeding season to help hold onto the female but during the rest of the seasons the muscles are smaller because hormones aren’t produced ● courtship- males convincing females to allow mating ○ male convincing female that he’s the right one as he impresses her ○ salamanders: males use pheromones, abrade with teeth, or use visual display ○ in frogs, the displays related to courtship tend to be vocal display rather than visual. ■ frogs have very developed larynx and throat so that it can be inflated to allow calls to attract females ■ examples Hyla versicolor and Hyla chrysoscelis ● these frogs look identical (but aren’t because different chromosomes) - they have different calls ■ downside to calls: ● high energy cost ● attracts predators too…. not just mates ■ upside: ● males with longest calls develop faster ● the call is advertising good genes to females, so the benefits of securing lots of mates must outweigh the risk of being eaten by predators - that’s why the call persists. ● eggs and yolk- the fertilized egg ○ eggs are often deposited in nest, sometimes guarded by female but not always ○ sometimes eggs are deposited on back of females into the skin ■ in pipa pia, the skin on back swells up to protect eggs. they hatch through the skin and come out of the back as froglets. they can then live independently. ● gastric brooding frogs: ○ 2 species of Rheobatrachus discovered in Australia 1973 and 1984 ○ mother swallows fertilized eggs, several froglets born via mouth after 6-7 week ○ mother doesn't eat or produce gastric juices during this period ○ both species now extinct ● standard normal pattern of development: ○ 3 phases of metamorphosis: 1. growth 2. emergency of hindlegs 3. emergence of frog legs and repression of tail ○ process is mediated by endocrine system ■ the pituitary gland secretes thyroid stimulating hormone (TSH) ■ thyroid gland secretes thyroxine (stimulates metamorphosis) ○ final metamorphosis stage must be rapid since legs and tail together impede jumping and swimming (which would increase vulnerability to predators) ● tadpole diversity ○ different feeding habits of tadpoles show corresponding specialization of the mouthparts ○ some species have multiple tadpole morphs ■ example is the spadefoot toad- can be herbivore and carnivore morphs ● in dry years, faster developing carnivore may eat herbivorous siblings, ensuring that some frogs metamorphose and escape ponds ● global amphibian extinctions and declines ○ amphibian extinctions and population decline have increased dramatically through the past 20 years ○ some causes have been identify: local ■ habitat destruction ■ pesticide use interfering with reproduction ○ several potential global causes: ■ global warming- eliminates cooler habitats in some places ■ acid rain- higher mortality and deformities in amphibian larvae ■ disease- especially infections by chytrid fungi ● not exactly clear why infection of chytrid fungi levels have accelerated recently ○ possibly due to stress from the other factors ○ one idea to help this is to keep amphibians in captivity until it’s safer to be reintroduced into normal habitats Lecture 14 Review: ● reptiliomorpha - ○ terrestriality - deeper skull and longer legs ● amniotes- non-amphibian tetrapods ○ examples: ■ cats - synapsids ■ turtle- sauropsids ■ humans ○ continued independence from aquatic habitat Amniote Synapomorphies (what makes amniotes so special): 1. named after the use of amniotic egg during reproduction a. amniotic egg- named after one membrane “the amnion” membrane i. there are a total of 4 extraembryonic membranes that the embryo is surrounded by 1. amnion- forms fluid-filled sac that cushions embryo 2. yolk sac- connects to gut tube to provide nutrients a. the function does change a little bit of those held within the mother 3. allantois- connects to end of gut tube to helps provide a distinct location of all waste so that it’s not floating around within the egg 4. chorion- outer membrane (against shell) and aids in gas exchange b. surrounded by shell or retained internally i. not all amniotics have a hard shell, it can just be that it’s kept inside mother ii. the shell or being kept inside mother helps to protect the egg from drying out = resistance to drying out c. unlike amphibians, reproduction is not tied to aquatic habitat i. no longer a restriction on where to reproduce ii. they can reproduce anyplace = they can live anyplace d. all of these new qualities of reproduction and construction of these eggs help to allow the egg to be born anywhere and allow for diversity. Other distinctive aspects of amniote function: ● astragalus - a new bone in ankle that provides articulation between hind leg and foot ○ in human anatomy, it’s called “talus” ● amniotes attach pelvic to body axis with 2 or more bones (these bones are sacral vertebrae) ○ unlike amphibians that have a single bone to connect the pelvic to the axis ○ more bones = increases stability for locomotion on land ● these changes helped amniotes invade land, to live on land, move through it, and be more successful Distinctive aspects of amniote function: ● costal breathing- “rib-mediated” ○ contraction of muscles between ribs (intercostals) expands the ribs and brings them forward to increase volume. With this increase in volume, air is forced inside lungs (inspiration) ○ amphibious force-pump used body muscles for exhalation but not inspiration ● trachea- tubular connection to lungs through long necks ○ functions to reinforce with cartilage rings to prevent collapse ○ allows air in Amniote Phylogeny: ● Major branches (clades) are: sauropsids vs synapsids ○ sauropsids = reptiles ■ example: turtles, croc, lizards, snakes, dinosaurs, and birds ○ synapsids= mammals and fossil ancestors ● major groups of amniotes distinguished by holes in skull (temporal fenestrae) ○ synapsids- has eye hole + 1 fenestra (temporal fenestrae) that is surrounded by 3 bones: ■ postorbital, jugal, and squamosal ○ sauropsids- display one of two conditions ■ either no fenestrae = anapsid state ● this is a primitive condition not a synapomorphy ■ or 2 fenestrae = diapsid state ● the upper fenestra- bound by 3 bones: ○ parietal, postorbital, and squamosal ● the lower fenestra - bound by 3 bones: ○ postorbital, squamosal, jugal, and quadratojugal ● these fenestra evolved independently ○ know that having fenestra are independent synapomorphy by the fact that they are surrounded by different bones (don’t need to know the bones) ■ the two groups have independently evolved from each other Why is it advantageous to have temporal fenestrae (hole in side of head)? ● the hole helps with jaw motion - allows for jaws to open and close easier and with more power because hole in skull roof allows bigger jaw closing muscles to spread onto skull roof. ○ the jaw muscles originate from the inside of the jaw roofing bones to attach to lower jaw to allow movement. the muscles expand out and over the the topside of the head to allow an increase in size and to prevent the bulge of muscle (when it contracts) to have plenty of room to contract. ● humans have temporal fenestral ○ we have one of the largest fenestrae ○ you can feel the muscles were the temporal fenestrae allows muscles to expand by placing hands above ears and clinching jaw as if chewing. Other differences between sauropsids and synapsids: 1. method of increasing locomotor stamina a. basic problem that tetrapod inherit from ancestors= bending lateral. This limits stamina/endurance because it interferes with breathing. As an animal bends laterally, only one of the lungs are able to inhale oxygen. Therefore, you can only really use one lung at a time. So if you don’t use both lungs, it holds you back from having maximum stamina. b. To increase stamina sauropsids and synapsids change: i. sauropsids: bipedality (walk on 2 feet) 1. by walking with 2 feet, the trunk motion is removed so that both lungs can be sued 2. examples: birds and dinosaurs 3. however, crocs and monitor lizards use different methods…. 4. however, many sauropsids still experience low stamina ii. synapsids: upright posture with flexing back up and down 1. examples: kangaroos 2. excepts: humans 3. allows both lungs to inflate at once 4. this upright posture creates bending dorsal-ventrally because they bend their back a. when legs are bent under body, the lungs have positive pressure so the air is gained b. when legs are in front of body, there is negative pressure so that air leaves lungs 5. new muscular feature evolved: diaphragm a. sheet of muscle that separates lung cavity from abdominal cavity with other organs b. new functional capacity related to breathing: i. when the diaphragm muscle is relaxed, the volume inside the lung cavity is small ii. when it contracts, it flattens out to increases volume and decreases pressure of lung chambers to aid in inhalation c. using the diaphragm is completely independent of locomotor function so there is no conflict 2. lung structure a. both sauropsids and synapsids increase in internal surface area (they have more than amphibians) b. sauropsids: faveolar lungs i. single branches to common spaces with several small chambers that branch off in that space c. synapsids: alveolar lungs i. repeated branching to tiny chambers (alveoli) 1. alveoli- the location of gas exchange within lung d. both types of lungs increase internal surface area, but they increase differently. independent evolution. 3. skin structure- integument a. both have alpha keratin protein but differing skin structures ultimately affect social and reproductive behaviors b. sauropsids: i. unique beta keratin proteins that form hard surfaces of scales, and helps with feathers ii. no glands = no sweating = no milk glands iii. males make up most of parent care c. synapsids: i. NO beta keratin proteins (so no scales or feathers) ii. they have smooth skin where hair emerges due to alpha keratin iii. also several types of glands to produce variety of secrets (sweat and milk glands) 1. sweat released when hot to cool off body 2. mammary glands - females take care of young mostly a. direct maternal care may explain why care by males are rarer in synapsids than in sauropsids 4. excretory system a. function of excretory system: remove nitrogenous waste products and locations of water conservation b. sauropsids: i. waste excreted as uric acid (thicker form- like bird poo) ii. conserve water: the blood travels to kidneys through glomerular to go through bowman’s capsule and tubules then finally the bladder where the waste precipitates out. the water is largely resorbed in the bladder back into the body iii. salt excreting glands: remove excess salt from body 1. mostly found in seabirds, sea turtles, sea snakes 2. glands found in face and tongue iv. also: penis is not urinary - strictly on intromittent organ = meaning only used to introduce sperm to female c. synapsids: i. waste excreted as urea (liquid urine) ii. conserve water: water is extracted in loop of henle inside of nephrons within kidney 1. instead of tubules, there is a LONG loop of henle for the waste to flow through 2. the loop of henle becomes more or less permeable to water depending on how hydrated the body is 3. the control of the loop of henle is important because the loop of henle is the last resort of extracting water before waste leaves the body iii. no water absorption in bladder 5. sensory perception and brain structure a. retina cell types: rods and cones b. sauropsids: i. color vision is highly developed 1. depends on rods and cones a. rods- broad sensitivity b. cones- sensitive to particular light wavelengths - responsible for color perception 2. strong vision but weaker smell 3. vision controlled by region called: optic tectum large in brain c. synapsids: i. strong sense of smell but lack of vision (primates are the exception) ii. poor vision: some 2 cone types, primates have 3 1. possible passed through nocturnal phase in evolution iii. small optic lobe- therefore the visual processing performed mostly in cerebrum Ectothermy VS Endothermy ● Goby fish climb the streams of water falls in Hawaii. ○ Adults live in the pools at the top. ■ advantage: no predators at the top ○ this fish are ectothermy ○ humans are endothermic (so you need a wetsuit in cold waters) ● When comparing, one is not better than the other- they are just different ○ Ectotherm- relies on external heat source to raise body temperature ○ Endotherm- relies on internal heat source to raise body temperature Amniote Phylogeny: ● Endothermy has evolved TWICE in amniotes: ○ Sauropsids (among birds) ○ Synapsids (mammals) Evolution of Endothermy ● Gains internal heat of endotherms from 2 main sources: ○ Resting (basal) metabolism ■ basic processes producing and using energy to keep body functioning ■ Endotherm basal metabolic rates are higher! ● this produces enough heat to warm body without external input ○ muscle activity ● High metabolic rate is necessary but is not sufficient alone- needs insulation ○ fears and hair ■ used to trap layer of air to block heat conduction out of animal ■ example: Sauropsids ○ hair (pelage) - fluffy fur that traps heat ■ but when wet → compresses and lowers insulation effectiveness ● Two competing hypotheses for the evolution of endothermy: ○ answers why did a higher resting metabolic rate evolve in endotherms? ■ aerobic capacity hypothesis: increased activity → higher resting metabolic rate ■ parental-care hypothesis: increased rates of mother speed embryo development → carries on during parental care of nest eggs ● Evolution of lungs: ○ Turbinates (conchae) - thin scrolls of bones in nasal passage that is covered with moist tissue ■ this functions to warm and moisten the dry/cold air that is coming in ● also extracts water from warmer air on way out ● ^^ important because lungs are damaged by cold, dry air ■ This is advantageous to increase capacity for sustained locomotion in both sauropsids and synapsids ● Teeth changed: ○ high metabolic rates require more food for energy, which must be processed quickly ■ example: synapsids- teeth changed to heterodont dentition = different tooth shapes ● provides teeth to serve different functions ● closely-occluding teeth = teeth fit together nicely to allow
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