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Biologist D.E. Nilsson has independently theorized about four general stages in the evolution of a vertebrate eye from a patch of photoreceptors. [5] Nilsson and S. Pelger estimated in a classic paper that only a few hundred thousand generations are needed to evolve a complex eye in vertebrates. [6]
Several layers such as the neural tube, neural crest, surface ectoderm, and mesoderm contribute to the development of the eye. [2] [3] [4] Eye development is initiated by the master control gene PAX6, a homeobox gene with known homologues in humans (aniridia), mice (small eye), and Drosophila (eyeless). The PAX6 gene locus is a transcription ...
Responsible for this process in mammals is the visual sensory system, the foundations of which were formed at an early stage in the evolution of chordates. Its peripheral part is formed by the eyes , the intermediate (by the transmission of nerve impulses ) - the optic nerves , and the central - the visual centers in the cerebral cortex .
The evolution of color vision in primates is highly unusual compared to most eutherian mammals. A remote vertebrate ancestor of primates possessed tetrachromacy, [1] but nocturnal, warm-blooded, mammalian ancestors lost two of four cones in the retina at the time of dinosaurs.
A newfound fossil of a jawless fish is the oldest known vertebrate cranium preserved in 3D. The 455 million-year-old find could illuminate how vertebrate heads evolved.
A majority of paleontologists use the term "tetrapod" to refer to all vertebrates with four limbs and distinct digits (fingers and toes), as well as legless vertebrates with limbed ancestors. [ 15 ] [ 16 ] Limbs and digits are major apomorphies (newly evolved traits) which define tetrapods, though they are far from the only skeletal or ...
In the book vertebrate evolution is studied utilizing comparative anatomy & functional morphology of existing vertebrates, and fossil records. The book is considered a classic and has been used very frequently as a college-level or university introductory level text on the subjects of basic paleontology and vertebrate evolution. [2]
The heads of vertebrates are complex structures, with distinct sense organs for sight, olfaction, and hearing, [12] and a large, multi-lobed brain protected by a skull of bone or cartilage. [13] Cephalochordates like the lancelet ( Amphioxus ), a small fishlike animal with very little cephalization, are closely related to vertebrates but do not ...