WILD 3580 1st Edition Lecture 14Outline of Last Lecture I. Functions of SmellII. ElectroreceptionIII. Magnetic ReceptionIV. Exam review Outline of Current Lecture I. Amphibian Evolution II. ClassificationIII. Ecological Roles IV. Skin Current LectureI. Amphibian Evolution - Rhipidistians fishes: subclass Osteolepimorphio Gave rise to amphibians terrestrial tetrapods- Choanae: internal nares connection between nasal cavity and respiratory system - Maximum diversity during Carboniferous period (“Age of Amphibians”) in the Paleozoic eraII. Classification - 3 Orders: Anura (frogs and toads) most diverse= 4700 species, Caudata (salamanders)-475 species, and Gymnophiona (Caecilians)- 170 species 1. Ectothermic- variable temperature, body temperature depended on environment a. Energetically inexpensive 2. Small body size a. 90% of frogs and salamander species weigh less than 20 gramsi. Minimizing overlap with other larger species between nichesii. Tendency to lose energy ectothermic iii. Smaller endothermic species have higher metabolic ratesb. Largest amphibian is the giant salamander (~5 feet) 3. Double lifea. Many amphibians have a larval stage and an adult stage i. Larvae Metamorphosis Adult 4. Skin lacks scales and is permeable to water These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Some breath through their skins and absorb water through the skinb. However, water can also be lost in drier environments 5. Toes lack claws or nailsIII. Ecological Roles - Mostly active at night no sun, higher humidity, maintain water (near water)o Hard to observe during the day timeo Easily to underestimate their importance 1. Invertebrate Predatora. Primary vertebrate predator in some areasb. Adult amphibians are carnivorous- feed on invertebrates c. Efficient at converting food to body mass don’t have to maintain metabolism, can convert food energy into growth and development 2. Plant “Predators”a. Larval amphibians feed on plants 3. Energy transfera. Between invertebrates and plants in higher tropic levelsb. Amphibians are the link between lower trophic levels to higher levelsIV. Skin- Water permeable- Functions: o Barrier between external and internal environments protection from pathogens and abrasionso Respirationo Absorption and release of water o Secretions to keep the skin moist o Protection through toxic secretions o Coloration- concealment or warning - Structureo Epidermis (outer layer) is divided into 3 sublayers Stratum corneum- outer most layer- Dead cells that shed that are filled with keratino Keratin- a dense fibrous structural protein Alpha keratin: makes up softer structures (hair, skin, nails, ect.) amphibians only have this Beta keratin: make up harder structures (shells, beaks, scales, ect.)- Relatively thin layer compared to other vertebrates- Ecdysis- periodic shedding of skin o Amphibians eat the skin (recycle nutrients)o How often they shed depends on many factors Stratum granulosum- middle layer “where cells go to die”- Living cells die and are filled with keratin - Keratin replaces the cytoplasm of the cells Stratum germinativum/basal- bottom, innermost layer - Cells that undergo
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