Bio II Chapter 34
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Where do vertebrates deive their name from?
Vertebrae, the series of bones that make up the vertebral column, or backbone.
Vertebrates are members of the phylum ______, the chordates.
Chordates are bilaterian (bilaterally symetrical) animals, and within Bilateria, they belong to the clade of animals known as ___________. As determined by the fate of the blastopore opening forming into the anus during embryo development.
What is the other group within the clade of animals known as deuterostomes besides the vertebrates?
The echinoderms, the group that includes sea stars and sea urchines.
What are the four key characters of chordates?
- A notochord
- A dorsal, hollow nerve cord
- Pharyngeal slits or clefts
- A muscular, post-anal tail
What is a notochord?
A longitudinal, flexible rod located between the digestive tube and the nerve cord.
It is comprised of large, fluid-filled cells encased in fairly stiff, fibrous tissue.
It provides skeletal support throughout most of the length of a chordate, and in larvae or adults that retain it, it also provides a firm but flexible structure againsts which muscles can work during swimming.
In humans, the notochord is reduced to celatinous disks sandwiched between the vertebrae.
What does the nerve cord of a chordate embryo develop from?
The nerve cord of a chordate embryo develops from a plate of ectoderm that rolls into a tube located dorsal to the notochord.
Other animal phyla have solid nerve cords, and in most cases they are ventrally located.
The nerve cord of a chordate embryo develops into the central nervous system: the brain and spinal cord.
What are pharyngeal slits or clefts?
In all chordate embryos, a series of pouches separated by grooves froms along the side of pharynx.
In most chrodates, these grooves (known as pharyngeal clefts) develop into slits that open to the outside of the body. These pharyngeal slits allow water entering the mouth to exit the body without passing through the entire digestive tract.
In vertebrates (except tetrapods), these slits and the structures that support them have been modified for gas exchange and are known as gill slits.
In tetrapods, the pharyngeal clefts do not develop into slits. Instead, they play an important role in the development of parts of the ear and other structures in the head and neck.
(T/F) Chrodates have a tail that extends posterior to the anus, although in many species, it is greatly reduced during embryonic development.
(T/F) The Cephalochordata (lancelets) closely resember the idealized chrodate that is believed to be the common ancestor for all chrodata.
It burrows into the group with its mouth out exposed to obtain food.
The Urochordata (tunicates) are more closely related to other chordates than are lancelets. The tunicates have two stages, the larval stage and the adult stage - which stage does the tunicate exhibit the characteristics of chordates?
The larval stage. However, this stage may be very short.
Once it undergoes a radical metamorphosis in which many of its chordate characters disappear.
Its tail and notochord are resorbed; its servous system degenerates; and its remaining organs rotate 90 degrees.
Lancelets and tunicates exhibit genes associated with vertebrate organs such as the heart and thyroid gland. Tunicates lack many genes in vertebrates that are associated with the long-range transmission of ____________.
This result suggests that such genes arose in an early vertebrate and are unique to the vertebrate evolutionary lineage.
Chordates with a head are known as __________.
The origin of a head - consisting of a beain at the anterior end of the dorsal nerve cord, eyes and other sensory organs, and a skull enabled chordates to coordinate more complex movement and feeding behaviors.
Living craniates share a set of derived characters that distinguish them from other chordates such as two clusters of _______ genes.
Hox. Lancelets and tunicates have one cluster.
What is the neural crest?
A feature unique to craniate - a collection of cells that appears near the dorsal margins of the closing neural tube in an embryo.
Neural crest cells disperse throughout the body where they give rise to a variety of stuctures, including teeth, some of the bones and cartilage of the skull, the inner layer of skin (dermin) of the facial region, several types of neurons, and the sensory capsules in which eyes and other sense organs develop.
Craniates have muscles lining their digestive tract to aid digestion by ___________.
moving food through the tract.
Craniates have a heart with at least two chambers, redblood cells with ______, and _________ that remove waste products from the blood.
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