Lesson 23 - The Transition to Land - Fish Amphibians Reptiles and Birds

23: the transition to land - fish, amphibians, reptiles, and birds Friday, March 22, 2024 12:58 PM which of the following statements about chordates is true? a. all chordates have a notochord as embryos b. all chordates are mobile as adults ○ sessile adult chordate: tunicate c. all chordates have pharyngeal slits as embryos that develop into essential traits as adults ○ true for aquatic vertebrates ○ feeding structures and/or gills d. all of the above which of the following statements about vertebrates is true? a. fossil evidence suggests that the direct ancestors of vertebrates evolved during the cambrian explosion ○ transitional species b. vertebrates all have spines ○ all vertebrae but not all spines ○ hagfish and lamprey do not have spines § maintain notochord c. not all vertebrates have mineralized bones because mineralization originated in (is a derived trait of) bony fish ○ mineralization was present in gnathostomes, such as sharks, before bony fish d. all of the above tetrapod evolution tetrapod evolution transition to land: Tiktaalik • • • • • • • did not live on land but has many traits of land vertebrates long-limbed bones (more pronounced lobes) more derived wrist bones (formation of digits) had a neck, which is only present in land animals large pelvis ○ makes it a strong swimmer ○ able to walk on sea floor developed rib cage ○ reinforces importance of lungs no strong connection between pelvis and spine; did not live on land ○ crucial for vertebrates to maintain their weight on land ○ Tiktaaliks could not live consistently on land vertebrate life on land • • tetrapods appear in the fossil record 365 MYA what adaptations did vertebrates need to succeed on land? ○ a new way to move ○ increased skeletal support § to deal with gravity without buoyancy ○ new gas exchange method § breathing on land ○ strategies to prevent water loss derived traits of tetrapods • limbs with digits • ○ homologous traits that are lost in some groups ○ ex. snakes head separated from body via neck derived traits of tetrapods • • • • limbs with digits ○ homologous traits that are lost in some groups ○ ex. snakes head separated from body via neck bones of pelvic girdle fused to backbone ○ more structural support most adults lack gills ○ some have embryos ○ all have pharyngeal slits as embryos tetrapods: amphibians • • • larvae are aquatic ○ maintain traits seen in ray-finned fish and lob-fin fish as larvae (ex. gills) ○ metamorphosis leads to legs, lungs, and more complex organs ○ some exceptions, such as Plethodon salamanders moist skin facilitates gas exchange ○ lungs are not entirely efficient ○ some species lack lungs altogether external fertilization in water or moist environments ○ eggs lack shell ○ cannot lay eggs on land due to desiccation (water loss) amphibians are particularly sensitive to climate change, which is contributing to current species declines. why? a. permeable skin and eggs make amphibians sensitive to changes in temperature ○ vulnerable to any environmental change b. increased CO2 in the atmosphere makes it harder for amphibian larvae to obtain oxygen through their lungs c. living in the water and on land makes amphibians poorly adapted to change d. all of the above salamanders (amphibians) • • • • • 550 species some entirely aquatic, some terrestrial as adults, some fully terrestrial some terrestrial species lack lungs ○ ex. Plethodons capable of limb regeneration 10% of global salamander diversity found in the appalachians frogs (amphibians) • • • > 7,000 species aquatic larvae distinct from adults capable of terrestrial living hop instead of walk • toads are warty frogs, but not monophyletic ○ not just sharing a recent common ancestor ○ toad lineages are found across the frog phylogeny • • aquatic larvae distinct from adults capable of terrestrial living hop instead of walk • toads are warty frogs, but not monophyletic ○ not just sharing a recent common ancestor ○ toad lineages are found across the frog phylogeny males vocalize to attract mates or defend territory some produce deadly toxins advertised with bright colors ○ modify and produce what they consume • • the amniotic egg • not all have a shell, but all have four extraembryonic membranes ○ amnion: creates fluid-filled cavity as protection § surrounds embryo but not connected to it ○ yolk sac: provides nutrients ○ allantois: collects metabolic waste from cellular respiration (nitrogenous waste) ○ chorion: facilitates gas exchange from the parent to offspring to ensure cellular respiration the amniotic egg is a major evolutionary innovation for animals. what is a parallel evolutionary innovation in plants? a. the evolution of pollen b. the evolution of seeds c. the evolution of fruit d. the evolution of heterospory other derived traits of amniotes • • • eggs with shells or internal gestation ○ reduces water loss of developing embryo less permeable skin ○ reduced water loss of adults rib cage used for ventilation ○ efficient gas exchange • ○ reduced water loss of adults rib cage used for ventilation ○ efficient gas exchange dinosaurs • • • • earliest reptiles 310 MYA dinosaurs originated around 245 MYA dominant animals for 135 million years all non-avian species extinct 66 MYA