Animals Colonize Land Flashcards
Vertebrate Evolution
jawless fish (Cambrian) => fish w/ jaws (Silurian, Acanthodians & Placoderms) => Devonian Period “Age of Fishes” => Rhipidistian “lobe fin” fish (Devonian) => by Devonian early tetrapods (i.e. amphibians like Ichthyostega) Jaws are modified gill arches
Acanthodians
earliest jawed fish (appeared at late Silurian)
Placoderms
heavily armored jawed fish (appeared at late Silurian)
Rhipidistian fish
lobe-finned fish. Developed nostrils and internal air passages by late devonian; the transitory form for tetrapods (Acanthostega, Panderichthys, Eusthenopteron)
transitional forms from fish to tetrapods exist in fossil record
Ichthyostega, Tiktaalik
morphological evidence
Shoulder/limb bones
Wrist/ankle bones
Tiktaalik doing push ups, which leads to evolution of actual limbs
Tiktaalik’s amphibian-like traits: flat head, flexible fins, actual neck bones (fish don’t have necks, while amphibians= do, ribcage
Tiktaalik’s fish-like traits: scales, fins, gills
Amphibians have inefficient lungs and have to absorb oxygen through their skin
Carboniferous: Temnospondyl Amphibians (labyrinthodont teeth) & Tetrapod Radiation
Amphibians ruled throughout the Carboniferous
Temnospondyls - large, flat bodied amphibians. Most common group
Anthracosaurs - thought to be reptile ancestors
How would evolution of first forest canopy facilitate tetrapod radiation in Devonian
Damp climate was the ideal environment for these early tetrapods
Lots of food (insects) that was not found in the water
No predators on land
Protected wetland environments from intense sunlight
ADD ANYTHING I MISSED HERE PLS THANKS
Parallel evolutionary between seed plants & amniotes?
Amniotes and plant seeds decoupled reproductive biology from aqueous environments, made it possible for life to habitat drier climates inland
Anthracosaur amphibians lack otic notch => earliest reptiles – when? First reptiles – when?
Late carboniferous/Early Permian
Lack of otic notch in Anthracosaurs suggest that they evolved into reptiles
Hylonomus: one of the first reptiles
Reptiles (amniotes) => evolution of the Amniotic Egg breaks reproductive bond with water Amniotes & Temporal Fenestrae: Synapsids vs. Diapsids
Pelycosaurs (Permian) => synapsids => Therapsids (mammal-like reptiles)
Synapsids
one temporal opening (mammal-like reptiles)
Diapsids
two temporal openings (dinosaurs, crocs, birds, snakes, etc)
Therapsids likely warm-blooded (endothermic)
Upright posture and complex chewing apparatuses suggest they are warm-blooded
Therapsids diversified and spread out very quickly - advantage of being warm-blooded?
Temperature control, able to live in cooler environments than cold blooded organisms
