Organic Evolution

adaptation adaptive radiation adult aërial Africa amphibia ancestral ancient animals aquatic aquatic adaptation arboreal become birds body bone camel carnivorous cave cells Chapter characteristic characters climate color comparable creatures Cretaceous cursorial Darwin desert developed digits dinosaurs elephant elongated entire Eocene epigean evidence evolution evolutionary existence extinct fauna feet female fins fishes flight flying foot forms fossil fossorial genera genus geologic gills habitat hand hence hind limbs horse ichthyosaurs increase individual insects instance known land larvæ later living lizards lower male mammals marine marsupials mastodons Mesozoic migration Miocene modification muscles Museum natural selection North America notochord Oligocene organs origin Osborn pair Paleozoic parasitic patagium plants Pleistocene Pliocene primitive proboscidean protoplasm race realm reptiles sexual shell skeleton skull species structure surface tail teeth terrestrial theory tion tooth trees true tusks types ungulates upper variation vertebrates whales wings