WFSC 302 Exam # 2 Study Guide Lectures: 7 - 11Lecture 7 (September 18)Surviving on Land Know that properties of air and water are very different, the problemsfaced by early amphibious tetrapods as they ventured onto land and how theseproblems may have been overcome. What are changes to the circulatory system of earlytetrapods? How does the lateral line system work? Know the senses in tetrapods. KnowKenichthys, choanae, and the olfactory capabilities of tetrapods. Know the nasal turbinate’s andvomernasal organ.Air vs. Water:- Water has less O2; it contains as much as 3% O2 as the same volume of air.- Vertebrates who evolved from aquatic invertebrates are able to extract O2 from the water using sophisticated gill filaments that have massive surface areas for gas exchange. This occurs at the level of secondary lamellae.- The Epithelium of a secondary lamella is only one cell thick- this allows diffusion of O2 and CO2 to take place between water and blood, and allows a short diffusion distance!- Water flow is unidirectional- it enters through the mouth, passing over the secondary lamellae then exiting through the gill pores, gill slits, or opercular opening. - The arrangement of the blood vessels in the gill filaments maximizes oxygen exchange.- Counter current exchanger: blood flows through the secondary lamellae in the opposite direction from water passing over these structures. This maximizes the amount of O2 that diffuses from the water into the blood. - Gills are very efficient at extracting O2 from water, but they are of no use in air!- The gas filled bladder provided a solution to the problem of air-breathing in early Sarcopterygian’s living in stagnant water (seen today in lungfishes).- Major problems with the circulatory system:o In water gravity isn’t a problemo In terrestrial environments gravity affects simple tasks, like pumping blood around the body.o Tetrapod’s had to overcome the problem of blood pooling at low points (limbs).Changes to the circulatory system of early tetrapods.- In non-craniate chordates oxygen is obtained via diffusion across the skin- this is why all blood is DEOXIGINATED!!!- In craniates oxygen is obtained via diffusion across the surfaces of the gill filaments (secondary lamellae)- Oxygenated blood has to be pumped around the body.- In teleost lineage the gas bladder became the swim bladder (instead of aiding in respiration, it was involved in buoyancy.)- In Sarcopterygians the gas bladder retained its respiratory function.o Pulmonary circuit o Complete division of the atriumo Complete or partial division of the ventricleSo how did they deal with gravity?- Tetrapod’s have higher blood pressure which forces blood through the viens against the force of gravity.- The problem with high blood pressure is it forces fluid from the plasma out of the vessels (which are leaky)- The Lymphatic system recovers fluid that is lost due to leaky blood vessels, critical for terrestrial organisms!• The lateral line system (mechanical stimulation of hair cells on neuromasts)- Fish use sight, mechanical stimuli and electrical stimuli to sense their aqueous environment, and due to the density of water organs that sense the stimuli workswell in water.- Hard to see in water, easier in air.- Chemical stimuli is not as important for aquatic vertebrates.- Fishes rely on the lateral line system to sense movement in water.o The lateral line system: Main cell: hair cell Hair cells are excited by mechanical stimuli that pass over the surface and stimulate tiny hairs (kinocilia are the largest of these tiny hairs) This works well in water due to the density of water molecules. Olfaction, visual and auditory senses hightened in the tetrapods (mechano- andelectrosenses most important to aquatic vertebrates)Olfaction is a form of chemosensation mediated by receptor cells, responsible for smell, that respond to the presence of chemicals with certain characteristics. All vertebrates (except lampreys) have a pair of olfactory organs. In fishes water enters through the incurrent nostril, passes over the olfactory epithelium (location of the receptor cells) then exits through the excurrent nostril. In fishes olfactory organsare independent of the mouth.All tetrapods have nasal passages that have an external opening through a single pair of external nostrils, with an opening internally in the throat through choanae (a pair of internal nostrils).Kenichthys: fossil evidence from supports the nostril migration hypothesis that the posterior nostril migrated from its external to internal position over evolutionary time.Turbinates: thin scrolls of bone that are sensitive to olfactory sensitivity. Highly developed in mammals and significantly increases the surface area available for olfactory epithelium.Vomernasal organ: (Jacobson’s organ) organ of olfaction in the anterior roof of the mouth.Well developed in snakes, and some mammals: flehman behavior in ungulates (example:horses), a way of inhaling molecules of pheromones into the vomeronasal organ.Problems overcome before a tetrapod can transition from aquatic to terrestrial environment:- Locomotion- Breathing- Sensing surroundings.Lecture 2 (September 23) AmphibiansWhat are the three major lineages of terrestrial tetrapods? List the three major groups of modern amphibians. What are the properties of amphibian skin? Explain the reproductive diversity of amphibians• The three major lineages of terrestrial tetrapods:Two extant:– Batrachomorpha: Includes fully terrestrial, semi-aquatic, and aquatic forms. First appeared in the mid Carboniferous period. Divided into two groups: - Temnospondyli- extinct paraphyletic group- some gave rise to modern amphibians.- Lissamphibia- includes extant amphibians (anurans, caecilians, and salamanders)– Reptilomorpha: originates from the early Carboniferous period. Majority of extant tetrapods belong to this group.One extinct:– Lepsospondyls : a diverse early group of tetrapods including both semi-aquatic and fully terrestrial forms. There were divided into 5 groups.• Be aware of the three major groups of modern amphibians and theircharacteristics– Anura: Frogs and toads– Urodela: Salamanders (exhibit paedomorphosis- a condition in which an adult retains larval characteristics)– Gymnophiona: caeciliansProperties of Amphibian skin: moist and permeable (cutaneous respiration- skin breathing), has different type of