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The deuterostome context of chordate origins - Nature The mystery of chordate origins has endured for more than 150 years Shortly after Darwin's On the Origin of Species, acorn worms were discovered to have chordate-like pharyngeal gill slits 1,2
Eye evolution and its functional basis - PMC Class I tasks would then be associated with cells lacking any kind of membrane stacking and any proximity to screening pigment or other light-shielding structures Such light sensitive cells are indeed known from many corners of the animal kingdom (e g , Provencio et al , 1998 , Gotow Nishi, 2007 , 2008 ; Peirson et al , 2009 ; Ramirez et al
The origin and evolution of segmentation - Boston University groups within a single clade However, the protostome–deuterostome distinction 2, made at the beginning of the 20th century, asserted that most bilaterian phyla are more closely related to either chordates or annelids plus arthropods than these two groups are to each other Since then, the deep phylogenetic separation of chordates and
Ecdysozoans Explained: Definition, Examples, Practice Video . . . Small species breathe through their skin, while larger ones, like the Japanese spider crab, use gills Moving on to hexapods, often referred to as insects, they are arguably the most successful group of animals on Earth With over a million known species inhabiting diverse environments, their adaptability is clear
Invertebrate - Definition, Classification, Types and . . . Invertebrates are the most diverse and abundant animal group on the planet Invertebrates account for more than 140,000 species in the United States, a number that is increasing as additional species are discovered Approximately 200 Invertebrates in the United States are on the endangered species list