Chap. 34 (1) Flashcards
Chordates (phylum Chordata) are _____ animals that belong
to the clade of animals known as _____.
bilaterian
Deuterostomia
Chordates comprise all vertebrates and two groups of invertebrates, the (2).
urochordates and cephalochordates
Four key characters of chordates
- Notochord
- Dorsal, hollow nerve cord
- Pharyngeal slits or clefts
- Muscular, post-anal tail
notochord
The notochord is a longitudinal, flexible rod between the digestive tube and nerve cord
-It provides skeletal support throughout most of the length of a chordate
Dorsal, hollow nerve cord
The nerve cord develops into the central nervous system: the brain and the spinal cord
Pharyngeal slits or clefts
In all chordate embryos, grooves form along the outer surface of the pharynx called pharyngeal clefts
* In most chordates, these grooves develop into pharyngeal slits that open to the outside of the body
Pharyngeal slits functions (3)
Suspension-feeding structures in many invertebrate chordates
* Gas exchange in vertebrates (except vertebrates with limbs, the tetrapods)
* Develop into parts of the ear, head, and neck in tetrapods
Muscular, post-anal tail
Chordates have a tail posterior to the anus
* In many species, the tail is greatly reduced during embryonic development
* The tail contains skeletal elements and muscles
* It provides propelling force in many aquatic species
Lancelets (Cephalochordata)
- are named for their bladelike shape
- They are marine suspension feeders that retain characteristics of the chordate body plan as adults
- sister group to all living chordates
Tunicates (Urochordata)
- are more closely related to other chordates than are lancelets
- Tunicates most resemble chordates during their larval stage, which may
last only a few minutes
A skeletal system and complex nervous system have allowed
vertebrates to be efficient at two essential tasks…..
- Capturing food
- Evading predators
The neural crest
cells that appear along the edges of the closing neural tube of an embryo, is another unique feature of vertebrates
lineages of jawless vertebrates remain today (2)
the hagfishes and the lampreys
-lack backbone but have rudimentary vertebrae
cyclostomes
clade of jawless vertebrates
gnathostomes
Vertebrates with jaws make up a much larger clade
Other characters common to gnathostomes (3)
- Genome duplication, including duplication of Hox genes
- An enlarged forebrain associated with enhanced senses of smell and vision
- The lateral line system
The lateral line system
rows of organs sensitive to vibrations that are located along each side of the body of aquatic gnathostomes
Chondrichthyans (4)
- have a skeleton composed primarily of cartilage
- The largest and most diverse group of chondrichthyans includes the sharks, rays, and skates
- A second group is composed of a few dozen species of ratfishes, or chimaeras
- have a short digestive tract with a spiral valve that increases surface area and slows the passage of food
Chondrichthyans embryos developments (3)
- Oviparous: Eggs hatch outside the mother’s body
- Ovoviviparous: Eggs are retained within the oviduct; young are born after hatching within the uterus
- Viviparous: The embryo develops within the uterus and is nourished from the mother’s blood through a yolk sac placenta
The vast majority of vertebrates are _____.
osteichthyans
- include the bony fishes and tetrapods
Tetrapods have some specific adaptations (5)
- Four limbs and feet with digits
- A neck, which allows separate movement of the head
- Fusion of the pelvic girdle to the backbone
- The absence of gills (except some aquatic species)
- Ears for detecting airborne sounds
Tiktaalik, nicknamed a “fishapod,”
shows both fish and tetrapod
characteristics
* Traits it shares with fish include fins, gills, lungs, and scales
Amphibians three clades
- Salamanders (Urodela, “tailed ones”)
- Frogs (Anura, “tail-less ones”)
- Caecilians (Apoda, “legless ones”)
Salamanders (Urodela) are…. (3)
- amphibians with tails
- Some are aquatic, but others live on land as adults or throughout life
- Paedomorphosis, the retention of juvenile features in sexually mature organisms, is common in aquatic salamanders
Frogs (Anura)
- lack tails and have powerful hind legs for locomotion on land
- Frogs with leathery skin are called “toads”
Caecilians (Apoda) are….. (2)
- an amphibian
- legless, are nearly blind, and resemble earthworms
- The absence of legs is a secondary adaptation
amphibian Fertilization
- Fertilization is external in most species, and the eggs require a moist environment
- In some species, males or females care for the eggs on their back, in their mouth, or in their stomach
amphibian pop. decline causes (4)
The causes include a disease-causing chytrid fungus, habitat loss, climate change, and pollution
