Biology Reading Guide for Chapter 35: The Vertebrates
Reading Guide for Chapter 35 – The Vertebrates
1. What are the five features of the chordates?
• A hollow dorsal nerve cord just beneath the dorsal surface of the animal. In vertebrates this differentiates into the brain and spinal cord.
• A flexible rod called the notochord that’s on the dorsal side of the primitive gut in the early embryo, present at some developmental stage in all chordates, located just below the nerve cord. May persist in some chordates; in others, it is replaced by the vertebral column that forms around the nerve cord. (Mainly for movement and support)
• Pharyngeal slits connect the pharynx with the external environment. Terrestrial vertebrates have pharyngeal pouches. These are present in the embryos of all vertebrates. They BECOME slits, open to the outside in animals with gills.
• A post anal tail which extends beyond the anus, at least during their embryonic development. Nearly all other animals have a terminal anus.
• An Endostyle which is a longitudinal ciliated groove on the ventral wall of the pharynx which produces mucus to gather food particles found in urochordates and cephalochordates.
2. Do all chordates have all of these five features at all life stages? Give examples where they do not.
No. For example, the post anal tail exists only during embryonic development in some vertebrates. The notochord may persist in some chordates while in others, it is replaced by the vertebral column that forms around the nerve cord. Pharyngeal slits are exclusive to vertebrates that breathe underwater. All chordates have these features at some point in their lives.
3. Which chordate features are present in adult tunicates? Which are missing in adults? Why are tunicates chordates if the adults are missing key chordate features?
Adult tunicates have pharyngeal slits and endostyles to trap microscopic food particles. The post anal tail, the nerve cord and the notochord are lost. They are still chordates because, as larvae,
1. What are the five features of the chordates?
• A hollow dorsal nerve cord just beneath the dorsal surface of the animal. In vertebrates this differentiates into the brain and spinal cord.
• A flexible rod called the notochord that’s on the dorsal side of the primitive gut in the early embryo, present at some developmental stage in all chordates, located just below the nerve cord. May persist in some chordates; in others, it is replaced by the vertebral column that forms around the nerve cord. (Mainly for movement and support)
• Pharyngeal slits connect the pharynx with the external environment. Terrestrial vertebrates have pharyngeal pouches. These are present in the embryos of all vertebrates. They BECOME slits, open to the outside in animals with gills.
• A post anal tail which extends beyond the anus, at least during their embryonic development. Nearly all other animals have a terminal anus.
• An Endostyle which is a longitudinal ciliated groove on the ventral wall of the pharynx which produces mucus to gather food particles found in urochordates and cephalochordates.
2. Do all chordates have all of these five features at all life stages? Give examples where they do not.
No. For example, the post anal tail exists only during embryonic development in some vertebrates. The notochord may persist in some chordates while in others, it is replaced by the vertebral column that forms around the nerve cord. Pharyngeal slits are exclusive to vertebrates that breathe underwater. All chordates have these features at some point in their lives.
3. Which chordate features are present in adult tunicates? Which are missing in adults? Why are tunicates chordates if the adults are missing key chordate features?
Adult tunicates have pharyngeal slits and endostyles to trap microscopic food particles. The post anal tail, the nerve cord and the notochord are lost. They are still chordates because, as larvae,