Vertebrates

Chapter 34

vertebrates

What are animals called when they have a series of bones that make up a backbone?

vertebrates, urochordates, and cephalochordates.

What are the three main groups that comprise chordates?

clade Deuterostomia.

To which clade do the bilateral chordates belong?

Notochord

dorsal hollow nerve cord

pharyngeal slits or clefts

muscular post-anal tail.

What are the four key characteristics of chordates?

only during embryonic development.

During which stage do some species exhibit chordate traits?

longitudinal, flexible rod located between the digestive tube and nerve cord.

What is the notochord and where is it located?

It provides skeletal support throughout most of the chordate’s body length.

What function does the notochord serve?

A more complex, jointed skeleton develops, and only remnants of the notochord remain in adults.

What happens to the notochord in most vertebrates?

from a plate of ectoderm that rolls into a tube dorsal to the notochord.

From what does the dorsal, hollow nerve cord develop?

into the central nervous system, including the brain and spinal cord.

Into what does the nerve cord develop?

Grooves called pharyngeal clefts

What structures form along the outer surface of the pharynx in chordate embryos?

They function as suspension-feeding structures in invertebrate chordates

aid in gas exchange in vertebrates

and develop into ear, head, and neck structures in tetrapods.

What do pharyngeal slits develop into in different chordates?

posterior to the anus.

Where is the muscular, post-anal tail located in chordates?

It provides propelling force in aquatic species and contains skeletal elements and muscles.

What are the functions of the post-anal tail?

The tail is greatly reduced.

What happens to the tail in many species during embryonic development?

marine suspension feeders with a bladelike shape.

What are lancelets and what is their shape?

They retain chordate characteristics as adults.

How do lancelets retain chordate characteristics?

they are more closely related to other chordates than lancelets.

How are tunicates related to other chordates?

During their larval stage, which may last only a few minutes.

At which stage do tunicates resemble chordates the most?

A skeletal system and a complex nervous system.

What two features allow vertebrates to be efficient at capturing food and evading predators?

Vertebrates have two or more sets of Hox genes, whereas lancelets and tunicates have only one.

What genetic feature distinguishes vertebrates from lancelets and tunicates?

consists of cells that appear along the edges of the neural tube in embryos and gives rise to structures unique to vertebrates.

What is the neural crest and what does it do?

lacked jaws.

What do fossil records indicate about early vertebrates?

Hagfishes and lampreys.

What are the only two living lineages of jawless vertebrates?

No, but they have rudimentary vertebrae.

Do hagfishes and lampreys have a backbone?

A cartilaginous skull, reduced vertebrae, flexible cartilage rod from the notochord, a small brain, eyes, ears, and tooth-like formations.

What features do hagfishes possess?

marine bottom-dwelling scavengers

What type of animal is a hagfish?

To repel predators and competitors.

Why do hagfishes produce slime?

Some species are parasites that clamp onto live fish and feed on their blood.

How do parasitic lampreys feed?

notochord and a cartilaginous skeleton

What do lampreys consist of?

have jaws with teeth for gripping and slicing food.

What distinguishes gnathostomes from jawless vertebrates?

Sharks

ray-finned fishes

lobe-finned fishes

amphibians

reptiles (including birds)

mammals.

What animals belong to the gnathostomes?

Genome duplication

an enlarged forebrain

the lateral line system.

What are some other derived traits of gnathostomes?

enhanced senses of vision and smell

what is the benefits of having an enlarged forebrain?

its a row of organs sensitive to vibrations that are located along each side of the body of aquatic gnathostomes

What is the lateral line system in Gnathostomes?

Cartilage

What is the skeleton of chondrichthyans primarily composed of?

Sharks, rays, and skates.

Which animals belong to the largest group of chondrichthyans?

By continuously swimming to prevent sinking and to keep water flowing over their gills.

How do sharks maintain buoyancy?

Dorsal fins for stabilization and paired pectoral and pelvic fins for maneuvering.

What do sharks use for stabilization and maneuvering?

streamlined body

what kind of body do sharks have?

Oviparous

ovoviviparous

viviparous

What are the different reproductive strategies in sharks?

eggs that hatch outside the mother’s body

What is oviparous?

eggs are retained within the oviduct: young are born after hatching within the uterus

what is ovoviviparous?

the embryo develops within the uterus and is nourished from the mother’s blood through a yolk sac placenta

what is viviparous?

A common chamber for the reproductive, excretory, and digestive systems with an external opening.

What is the cloaca in sharks?

reproductive tract, excretory system, and a digestive tract

What is emptied into the cloaca?

Rays are flattened bottom-dwellers that feed on mollusks and crustaceans.

How do rays differ from sharks in body shape and feeding habits?

Whiplike tails with venomous barbs.

What defensive adaptations do some rays have?

flattened and enlarged pectoral fins

what kind of fins function as water wings in chondrichthyans?

The vast majority of vertebrates are osteichthyans.

What percentage of vertebrates are osteichthyans?

a bony endoskeleton

what do osteichthyans have?

Fishes

What are aquatic osteichthyans commonly called?

bony fishes and tetrapods

What do animals do osteichthyans include?

By drawing water over gills protected by an operculum

How do most fishes breathe?

swim bladder (air sac)

What structure helps bony fishes control buoyancy?

mucus; Flattened, bony scales.

what does the skin secrete and what is it covered by in fishes?

Detecting vibrations in water.

What is the lateral line system in fishes used for?

Most are oviparous, but some have internal fertilization and live birth.

What are the reproductive methods in bony fishes?

nearly all familiar aquatic osteichthyans.

What type of fish do ray-finned fishes include?

long, flexible rays.

What supports the fins of ray-finned fishes?

maneuvering, defense, and other functions.

How are the fins of ray-finned fishes modified?

Silurian period.

When did lobe-fins originate?

rod-shaped bones surrounded by a thick layer of muscle in their pelvic and pectoral fins.

What distinguishes the fins of lobe-finned fishes?

They may have used them to maneuver across the substrate of aquatic habitats.

How might ancient lobe-finned species have used their fins?

coelacanths (Actinistia), lungfishes (Dipnoi), and tetrapods.

What are the three surviving lineages of lobe-fins?

A living coelacanth was caught off the coast of South Africa in 1938, even though they were thought to be extinct for 75 million years.

What was a surprising discovery about coelacanths?

Southern Hemisphere.

Where are lungfishes found?

While their primary organs for gas exchange are gills, they can also surface to gulp air into their lungs.

How do lungfishes breathe?

tetrapods, which adapted to life on land.

What is the third surviving lineage of lobe-fins?

They have four limbs with digits

a neck allowing head movement

fusion of the pelvic girdle to the backbone

absence of gills (except in some species)

ears for detecting airborne sounds.

What are some adaptations of tetrapods?

about 6,150 species, classified into three clades: Salamanders, Frogs, and Caecilians.

How many species of amphibians exist, and how are they classified?

tails, and some live in aquatic or terrestrial environments.

What distinguishes salamanders?

the retention of juvenile features in sexually mature organisms, common in aquatic salamanders.

What is paedomorphosis, and in which amphibian is it common?

Frogs lack tails and have powerful hind legs for jumping.

What distinguishes frogs?

toads

What are frogs with leathery skin called?

legless, nearly blind amphibians that resemble earthworms. Their lack of legs is a secondary adaptation.

What are caecilians, and what is unique about them?

“both ways of life,” referring to their aquatic larval stage and terrestrial adult stage.

What does the term “amphibian” mean?

aquatic herbivores with gills, a lateral line system, and a long, finned tail.

What are some characteristics of a tadpole?

Tadpoles develop legs, lungs, external eardrums, and a carnivorous digestive system.

What changes occur during metamorphosis in frogs?

damp habitats.

Where are amphibians typically found?

moist skin that complements their lungs in gas exchange.

How do amphibians breathe?

external, and eggs require a moist environment.

How does fertilization occur in most amphibians?

They may carry eggs on their back, in their mouth, or in their stomach.

How do some amphibians care for their eggs?

Amphibian populations have been declining, with at least 9 species extinct in the past 40 years and over 100 possibly extinct.

What is happening to amphibian populations?

tetrapods with terrestrially adapted eggs, including reptiles, birds, and mammals.

What are amniotes?

amniotic egg, which has protective membranes.

What is a key feature of amniotes?

amnion, chorion, yolk sac, and allantois.

What are the four extraembryonic membranes in the amniotic egg?

It allowed reproduction away from water.

Why was the amniotic egg an important adaptation?

Impermeable skin and rib cage ventilation.

What other adaptations do amniotes have?

Tuataras, lizards, snakes, turtles, crocodilians, and birds.

Which animals are included in the reptile clade?

Scales that form a waterproof barrier.

What is a key feature of reptiles?

They lay shelled eggs on land, and fertilization is internal

Where do reptiles lay eggs, and how does fertilization occur?

Most reptiles are ectothermic, using external heat, while birds are endothermic, generating their own heat.

What is the difference between ectotherms and endotherms?

They are legless reptiles that evolved from lizards.

What is unique about snakes?

Chemical sensors, heat-detecting organs, venom, flexible jawbones, and elastic skin.

What adaptations help snakes capture prey?

They lack holes in the skull behind the eye socket.

What distinguishes turtles from other reptiles?

It is made of upper and lower shields fused to the vertebrae, clavicles, and ribs.

What is a turtle’s boxlike shell composed of?

Some live in deserts, while others are aquatic.

Where do turtles live?

Accidental capture in fishing nets and beach development.

What is threatening sea turtles?

They are archosaurs, related to dinosaurs and birds.

What group do crocodilians belong to?