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Lecture 14 Ch. 35
Terms in this set (38)
Characteristics of chordates
All chordates have four morphological features at some stage in their life cycles:
1. Openings into the throat called pharyngeal gill slits
2. A dorsal hollow nerve cord that runs the length of the body, comprised of projections from neurons
3. A stiff and supportive but flexible rod, called the notochord, that runs the length of the body
4. A muscular post-anal tail
Pharyngeal gill slits
Pharyngeal gill slits: grooves in the pharynx called pharyngeal clefts develop into slits that open to the outside of the body
• Functions of pharyngeal slits:
Suspension-feeding structures in many invertebrate chordates
Gas exchange in aquatic vertebrates
Develop into parts of the ear, head, and neck in terrestrial vertebrates
develops from a plate of ectoderm that rolls into a tube dorsal to the notochord. The nerve cord develops into the central nervous system (brain and the spinal cord).
Notochord: a longitudinal, flexible rod between the digestive tube and nerve cord that provides structural support.
• In most vertebrates, a more complex, jointed skeleton develops; the adult retains only remnants of the embryonic notochord
Post-anal tail: In many species, the tail is lost during embryonic development (true of humans)
• The tail contains skeletal elements and muscles
• It provides propelling force in many aquatic species
Types of chordata
The phylum Chordata is made up of three major lineages:
1. Cephalochordates (lancelets)
2. Urochordates (tunicates)
Lancelets are named for their bladelike shape. They are marine suspension feeders that retain characteristics of the chordate body plan as adult.
Lancelets have no bones; they taste like fish! Consumed by marine organisms, humans and birds.
Urochordates, also known as tunicates, most resemble chordates during their larval stage,
Larvae are a dispersal stage and do not feed. They swim with the aid of the notochord. Adult sea squirts are sessile, and adult salps
drift in currents.
Urochordates (tunicates) are marine suspension feeders commonly called sea squirts or salps. As an adult, they draw in water through an incurrent siphon, filtering food particles
The vertebrates are a monophyletic group distinguished by two synapomorphies:
1. A column of cartilaginous or bony structures called vertebrae, which form along the dorsal side of most species and protects the spinal cord
2. A cranium, a bony, cartilaginous, or fibrous case that encloses and protects the brain.
Together, the vertebrae and cranium protect the central nervous system and key sensory structures
• The coordinated movements of vertebrates are possible in part because vertebrates have complex brains
• Vertebrate fossils are present in deposits that formed during the Cambrian explosion
• The earliest vertebrates
-Lived in the ocean about 540 mya
-Had streamlined, fishlike bodies with a skeleton made of cartilage
innovations that occurred as vertebrates diversified from latest to earliest
anatomic eggs->legs capable of moving on land->bony endoskeleton->jaws->bony exoskeleton
Key vertebrate features
3. tetrapod limb
5. parental care
6. wings and flight
7. amniotic egg
1. Jaws enabled predation, a new method of feeding. With jaws and teeth, vertebrates became armed and dangerous
2. The bony endoskeleton helped with rapid swimming
3. These were the first of the tetrapods—animals with four limbs
4. Viviparous mammals have an organ called the placenta that
-Is rich in blood vessels
-Facilitates the flow of oxygen and nutrients from mother to embryo
-Facilitates the removal of nitrogenous wastes and carbon dioxide from the embryo
5. Parental care encompasses any action by a parent that improves the ability of its offspring to survive
• Extensive parental care among mothers requires a fitness trade-off
-They produce fewer offspring which are more
6. Feather evolution began with simple
projections from the skin and culminated in the complex structures seen today. Birds are light for their size because they have a drastically reduced number of bones. Their large bones are thin-walled and hollow
7. The first animals with watertight eggs, called amniotic eggs
•Have membranes surrounding a food and water supply and a waste repository
•Provide support and extra surface area for gas exchange
•Allow for larger, better-developed young
-All tetrapods other than amphibians are
Animals with jaws are gnathostomes
In most ray-finned fishes, the jaw is protrusible—it can be extended
Several lineages of ray-finned fishes have a second specialized jaw called a pharyngeal jaw
Species that give birth
In ovoviviparous species, the female produces an egg with a nutrient-rich yolk and retains it within her body
-The yolk nourishes the developing embryo
After a development period called gestation, where the mother carries the baby, the offspring emerges from the mother's body
Female mammals also lactate—they produce milk and use it to feed their offspring after birth
hagfish and lampreys
Hagfish and lampreys
- Jawless vertebrates
- 120 species.
- Hagfish- marine, 3ft or
less in length; scavengers, predators. They deposit feed on dead fish and whales
- Lamprey- fresh and
marine waters; ectoparasites-They attach to hosts by suction and rasp a hole in their victim's side by
using spines in their mouth and tongue. Once the hole is formed, they suck blood and other body fluids
The cartilaginous fishes includes sharks, skates, rays, and chimaeras.
•They have a skeleton made of a tough, elastic tissue called cartilage, jaws with teeth, paired fins, and often active lifestyles.
•Sharks and rays tend to be larger than bony fishes.
•Whale sharks are the largest fish.
•Can be greater than 18 m (60 ft) in length.
•Feed on plankton.
ray-finned fishes have
-Fins supported by long, bony rods arranged in a ray pattern
-A bony skeleton
-A stiff but flexible body covering of interlocking scales
Nearly all living ray finned fishes have a bony endoskeleton.
• Fishes breathe by drawing water over gills in chambers covered by a bony flap called the operculum.
what fishes use for buoyancy
Lobe-fined fishes (coelacanths and lungfishes)
Lobe-finned fishes are common and diverse in the fossil record, but only eight species are alive today
-The bony elements of their fleshy, lobe-shaped fins extend down the fin and branch
-The fins, supported mainly by long, flexible rays, are modified for maneuvering, defense, and other functions
sharks have an oily liver for buoyancy
1. Anura (frogs, toads)
2. Urodela (salamanders)
1. Anurans, such as this poison arrow frog, lack a tail as adults. Note parental care!
2. Mudpuppies and axolotl are salamanders that demonstrate neoteny -
they have juvenile characteristics (gills) as adults. They retain there tails as adults
3. caecilians which lack limbs and resemble snakes or
worms -They burrow underground in wet tropical regions. Caecilians, are legless,
burrowing amphibians. Caecilians are mostly distributed in the tropics of South and Central America, Africa, and southern Asia
• are deuterostomes
• have bilateral symmetry at some stage in their development
-anus develops from blastospore
mouth develops from blastospore
chordates are the same as vertebrates?
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