29: Vertebrates Flashcards
Chordates, Fishes, Amphibians, Reptiles, Birds, Mammals, the Evolution of Primates
How many species of vertebrates are there?
More than 62,000 vertebrate species have been identified.
How many vertebrate species are under threat of extinction?
According to the International Union for the Conservation of Nature, more than 6,000 vertebrate species are classified as threatened. Amphibians and mammals are the classes with the greatest percentage of threatened species, with 29 percent of all amphibians and 21 percent of all mammals classified as threatened.
What is an example of an attempt to prevent the extinction of threatened species?
The Biodiversity Action Plan is an international program, ratified by 188 countries, which is designed to protect species and habitats.
What is Cephalochordata?
A chordate clade whose members possess a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail in the adult stage.
What is Chordata?
A phylum of animals distinguished by their possession of a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail at some point during their development.
What is Craniata?
A clade composed of chordates that possess a cranium; includes Vertebrata together with hagfishes.
What is a cranium?
A bony, cartilaginous, or fibrous structure surrounding the brain, jaw, and facial bones.
What is a dorsal hollow nerve cord?
A hollow, tubular structure derived from ectoderm, which is located dorsal to the notochord in chordates.
What is a lancelet?
A member of Cephalochordata; named for its blade-like shape.
What is a notochord?
A flexible, rod-shaped support structure that is found in the embryonic stage of all chordates and in the adult stage of some chordates.
What is a pharyngeal slit?
An opening in the pharynx.
What is a post-anal tail?
A muscular, posterior elongation of the body extending beyond the anus in chordates.
What is a tetrapod?
A phylogenetic reference to an organism with a four-footed evolutionary history; includes amphibians, reptiles, birds, and mammals.
What is a tunicate?
A sessile chordate that is a member of the subphylum Urochordata.
What is Urochordata?
A clade composed of tunicates.
What is a vertebral column?
A series of separate bones joined together as a backbone.
What is Vertebrata?
Members of the phylum Chordata that possess a backbone.
Where is the notochord located and what is its purpose?
The notochord is located between the digestive tube and the nerve cord, and provides skeletal support through the length of the body. In some chordates, the notochord acts as the primary axial support of the body throughout the animal’s lifetime. In vertebrates, the notochord is present during embryonic development, at which time it induces the development of the neural tube and serves as a support for the developing embryonic body. The notochord, however, is not found in the postnatal stage of vertebrates; at this point, it has been replaced by the vertebral column (that is, the spine).
What characterizes the nerve cords of non-chordates?
Other animal phyla than chordates are characterized by solid nerve cords that are located either ventrally or laterally.
How does the nerve cord develop in chordates?
The nerve cord found in most chordate embryos develops into the brain and spinal cord, which compose the central nervous system.
What is the purpose of pharyngeal slits?
In organisms that live in aquatic environments, pharyngeal slits allow for the exit of water that enters the mouth during feeding. Some invertebrate chordates use the pharyngeal slits to filter food out of the water that enters the mouth. In vertebrate fishes, the pharyngeal slits are modified into gill supports, and in jawed fishes, into jaw supports. In tetrapods, the slits are modified into components of the ear and tonsils.
What is the purpose of the post-anal tail?
The tail contains skeletal elements and muscles, which provide a source of locomotion in aquatic species, such as fishes. In some terrestrial vertebrates, the tail also helps with balance, courting, and signaling when danger is near. In humans, the post-anal tail is vestigial, that is, reduced in size and nonfunctional.
What are the invertebrate clades of Chordata?
Tunicata and Cephalochordata.
What is the origin of the name “tunicate”?
The name tunicate derives from the cellulose-like carbohydrate material, called the tunic, which covers the outer body of tunicates.
Why are tunicates classified as chordates?
Although adult tunicates are classified as chordates, they do not have a notochord, a dorsal hollow nerve cord, or a post-anal tail, although they do have pharyngeal slits. The larval form, however, possesses all four structures.
What is the tunicate lifecycle?
Most tunicates are hermaphrodites. Tunicate larvae hatch from eggs inside the adult tunicate’s body. After hatching, a tunicate larva swims for a few days until it finds a suitable surface on which it can attach, usually in a dark or shaded location. It then attaches via the head to the surface and undergoes metamorphosis into the adult form, at which point the notochord, nerve cord, and tail disappear.
How do tunicates feed?
Most tunicates are suspension feeders. The primary foods of tunicates are plankton and detritus. Seawater enters the tunicate’s body through its incurrent siphon. Suspended material is filtered out of this water by a mucous net (pharyngeal slits) and is passed into the intestine via the action of cilia. The anus empties into the excurrent siphon, which expels wastes and water.
Where are tunicates found?
Most tunicates live a sessile existence on the ocean floor, and are found in shallow ocean waters around the world.
What is the origin of the name “cephalochordate”?
The notochord extends into the head, which is what gives the subphylum its name.
What is the oldest known cephalochordate?
Extinct members of Cephalochordata include Pikaia, which is the oldest known cephalochordate. Pikaia fossils were recovered from the Burgess shales of Canada and dated to the middle of the Cambrian age, making them more than 500 million years old.
What are some characteristics of lancelets?
Lancelets are only a few centimeters long and are usually found buried in sand at the bottom of warm temperate and tropical seas. Like tunicates, they are suspension feeders.
How is water processed by lancelets?
Water from the mouth enters the pharyngeal slits, which filter out food particles. The filtered water then collects in the atrium and exits through the atriopore.
How are hagfish distinguished from other craniates?
Hagfish have a cranium but lack a backbone.
To which invertebrate chordates are vertebrates more closely related?
Based on molecular analysis, vertebrates appear to be more closely related to lancelets (cephalochordates) than to tunicates among the invertebrate chordates. This evidence suggests that the cephalochordates diverged from Urochordata and the vertebrates subsequently diverged from the cephalochordates.
What fossil evidence supports the phylogenetic taxonomy of chordates?
The evidence that vertebrates are more closely related to lancelets than tunicates is supported by the discovery of a fossil in China from the genus Haikouella. This organism seems to be an intermediate form between cephalochordates and vertebrates. The Haikouella fossils are about 530 million years old and appear similar to modern lancelets. These organisms had a brain and eyes, as do vertebrates, but lack the skull found in craniates. This evidence suggests that vertebrates arose during the Cambrian explosion.
What are the traditional classes in Vertebrata?
Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia.
How are birds classified?
Many modern biologists classify birds within Reptilia, which correctly reflects their evolutionary heritage, but are often considered separately than reptiles for convenience.
How are jawless fishes classified?
Hagfishes and lampreys were traditionally classified together as agnathans, although emerging classification schemes separate them into chordate jawless fishes (the hagfishes) and vertebrate jawless fishes (the lampreys).
What are gnathostomes?
Animals that possess jaws are known as gnathostomes, which means “jawed mouth”. Gnathostomes include fishes and tetrapods.
What are the groups of tetrapods?
Tetrapods can be divided into two groups: amphibians and amniotes.
What are amniotes?
Amniotes are animals whose eggs are adapted for terrestrial living, and this group includes mammals, reptiles, and birds. Amniotic embryos, developing in either an externally shed egg or an egg carried by the female, are provided with a water-retaining environment and are protected by amniotic membranes.
What are Actinopterygii?
Ray-finned fishes.
What is an ampulla of Lorenzini?
A sensory organ that allows sharks to detect electromagnetic fields produced by living things.
What are Chondrichthyes?
Jawed fishes with paired fins and a skeleton made of cartilage.
What are hagfish?
Eel-like jawless fish that lives on the ocean floor and are scavengers.
What is a lamprey?
A jawless fish characterized by a toothed, funnel-like, sucking mouth.
What is a lateral line?
A sense organ that runs the length of a fish’s body; used to detect vibration in the water.
What are Myxini?
Hagfishes.
What are Osteichthyes?
Bony fish.
What is an ostracoderm?
One of the earliest jawless fish covered in bone.
What is Petromyzontidae?
A clade of lampreys.
What are Sarcopterygii?
Lobe-finned fish.
What is a swim bladder?
In fishes, a gas-filled organ that helps to control the buoyancy of the fish.
How many species of fish are there?
Modern fishes include an estimated 31,000 species.
What were the earliest vertebrates?
Fishes were the earliest vertebrates, with jawless species being the earliest and jawed species evolving later.
What features distinguish jawless fishes from invertebrate chordates?
They have a distinct cranium and complex sense organs including eyes.
Outside of jaws, lack of what feature distinguishes jawless fishes from jawed fishes?
A defining feature is the lack of paired lateral appendages (fins).
How many species of hagfish are there?
The clade Myxini includes at least 20 species of hagfishes.
How do hagfishes feed?
Hagfishes are eel-like scavengers that feed on dead invertebrates, other fishes, and marine mammals. They can twist their bodies in a knot to feed and sometimes eat carcasses from the inside out.
Where are hagfishes found?
Hagfishes live on the ocean floor and are entirely marine, and are found in oceans around the world, except for the polar regions.
What is a unique feature of hagfishes?
A unique feature of these animals is the slime glands beneath the skin that release mucus through surface pores. This mucus allows the hagfish to escape from the grip of predators.
What are some characteristics of the hagfish skeleton and notochord?
The skeleton of a hagfish is composed of cartilage, which includes a cartilaginous notochord that runs the length of the body. This notochord provides support to the hagfish’s body. Hagfishes do not replace the notochord with a vertebral column during development, as do true vertebrates.
How many species of lamprey are there?
The clade Petromyzontidae includes approximately 35-40 or more species of lampreys.
In what ways are lampreys similar and dissimilar to hagfishes?
Lampreys are similar to hagfishes in size and shape; however, lampreys possess some vertebral elements. Lampreys lack paired appendages and bone, as do the hagfishes.
Which feature characterizes adult lampreys?
As adults, lampreys are characterized by a toothed, funnel-like sucking mouth. Many species have a parasitic stage of their life cycle during which they are ectoparasites of fishes.
Where are lampreys found?
Lampreys live primarily in coastal and fresh waters, and have a worldwide distribution, except for in the tropics and polar regions. Some species are marine, but all species spawn in fresh water.
What is the lamprey life cycle?
All species of lamprey spawn in fresh water. Eggs are fertilized externally, and the larvae distinctly differ from the adult form, spending 3 to 15 years as suspension feeders. Once they attain sexual maturity, the adults reproduce and die within days.
Do lampreys possess a notochord?
Lampreys possess a notochord as adults; however, this notochord is surrounded by a cartilaginous structure called an arcualia, which may resemble an evolutionarily early form of the vertebral column.
What is a jaw?
A hinged structure attached to the cranium that allows an animal to grasp and tear its food.
What was one of the most significant developments in early vertebrate evolution?
The evolution of the jaw, which allowed early gnathostomes to exploit food resources that were unavailable to jawless fishes.
How did fins distinguish early gnathostomes?
Early gnathostomes possessed two sets of paired fins, allowing the fishes to maneuver accurately. Pectoral fins are typically located on the anterior body, and pelvic fins on the posterior.
How were the evolution of jaws and paired fins a selective advantage?
Evolution of the jaw and paired fins permitted gnathostomes to expand from the sedentary suspension feeding of jawless fishes to become mobile predators. The ability of gnathostomes to exploit new nutrient sources likely is one reason that they replaced most jawless fishes during the Devonian period.
What were some early groups of gnathostomes?
Two early groups of gnathostomes were the acanthodians and placoderms, which arose in the late Silurian period and are now extinct.
Which clades do most modern fishes belong to?
Most modern fishes are gnathostomes that belong to the clades Chondrichthyes and Osteichthyes.
What was Dunkleosteus?
Dunkleosteus was an enormous placoderm from the Devonian period, 380-360 million years ago. It measured up to 10 meters in length and weighed up to 3.6 tons.
What are some examples of Chondrichthyes?
The clade Chondrichthyes is diverse, consisting of sharks, rays, and skates, together with sawfishes and a few dozen species of fishes called chimaeras, or “ghost sharks”.
When did Chondrichthyes evolve?
This clade arose approximately 370 million years ago in the early or middle Devonian.
What are some characteristics of the skeletons of Chondrichthyes?
Chondrichthyes are thought to be descended from the placoderms, which had skeletons made of bone; thus, the cartilaginous skeleton of Chondrichthyes is a later development. Parts of shark skeleton are strengthened by granules of calcium carbonate, but this is not the same as bone.
Where are cartilaginous fishes found?
Most cartilaginous fishes live in marine habitats, with a few species living in fresh water for a part or all of their lives.
How do cartilaginous fishes feed?
Most sharks are carnivores that feed on live prey, either swallowing it whole or using their jaws and teeth to tear it into smaller pieces. Shark teeth likely evolved from the jagged scales that cover their skin, called placoid scales. Some species of sharks and rays are suspension feeders that feed on plankton.
What sense organs do sharks have?
Sharks have well-developed sense organs that aid them in locating prey, including a keen sense of smell and electroreception, with the latter perhaps the most sensitive of any animal. Organs called ampullae of Lorenzini allow sharks to detect the electromagnetic fields that are produced by all living things, including their prey. Electroreception has only been observed in aquatic or amphibious animals. Sharks, together with most fishes and aquatic and larval amphibians, also have a sense organ called the lateral line, which is used to detect movement and vibration in the surrounding water, and is often considered homologous to “hearing” in terrestrial vertebrates. The lateral line is visible as a darker stripe that runs along the length of a fish’s body.
How do sharks reproduce?
Sharks reproduce sexually, and eggs are fertilized internally. Most species are ovoviviparous: the fertilized egg is retained in the oviduct of the mother’s body and the embryo is nourished by the egg yolk. The eggs hatch in the uterus, and young are born alive and fully functional. Some species of sharks are oviparous: they lay eggs that hatch outside of the mother’s body. Embryos are protected by a shark egg case or “mermaid’s purse” that has the consistency of leather. The shark egg case has tentacles that snag in seaweed and give the newborn shark cover. A few species of sharks are viviparous: the young develop within the mother’s body and she gives live birth.
How many species of rays and skates are there?
Rays and skates comprise more than 500 species and are closely related to sharks.
How are rays and skates similar and dissimilar to sharks?
They can be distinguished from sharks by their flattened bodies, pectoral fins that are enlarged and fused to the head, and gill slits on their ventral surface. Like sharks, rays and skates have a cartilaginous skeleton.
Where are rays and skates found?
Most species are marine and live on the sea floor, with nearly a worldwide distribution.
How many species of Osteichthyes are there?
The vast majority of present-day fishes belong to this group, which consists of approximately 30,000 species, making it the largest class of vertebrates in existence today.
What are some characteristics of the skeletons of bony fishes?
Nearly all bony fishes have an ossified skeleton with specialized bone cells (osteocytes) that produce and maintain a calcium phosphate matrix. This characteristic has only reversed in a few groups of Osteichthyes, such as sturgeons and paddlefish, which have primarily cartilaginous skeletons.
What are some characteristics of the skin of bony fishes?
The skin of bony fishes is often covered by overlapping scales, and glands in the skin secrete mucus that reduces drag when swimming and aids the fish in osmoregulation. Like sharks, bony fishes have a lateral line system that detects vibrations in water.
How do bony fishes breathe?
All bony fishes use gills to breathe. Water is drawn over gills that are located in chambers covered and ventilated by a protective, muscular flap called the operculum.
How do bony fishes control their buoyancy?
Many bony fishes have a swim bladder, a gas-filled organ that helps to control the buoyancy of the fish.
What are the clades of bony fishes?
Bony fishes are divided into two extant clades: Actinopterygii (ray-finned fishes) and Sarcopterygii (lobe-finned fishes).
What are some examples of Actinopterygii?
Actinopterygii, the ray-finned fishes, include many familiar fishes - tuna, bass, trout, and salmon, among others.
How do the fins of Actinopterygii differ from those of Sarcopterygii?
Ray-finned fishes are named for their fins that are webs of skin supported by bony spines called rays. In contrast, the fins of Sarcopterygii are fleshy and lobed, supported by bone.
What are some examples of lobe-finned fishes?
Living members of Sarcopterygii include the less-familiar lungfishes and coelacanths.
How old are coelacanths?
The coelacanth was thought to have gone extinct in the Late Cretaceous period, 100 million years ago, until one was discovered in 1938 near the Comoros Islands between Africa and Madagascar.
What is Acanthostega?
One of the earliest known tetrapods.
What are Amphibia?
Frogs, salamanders, and caecilians.
What are Anura?
Frogs.
What are Apoda?
Caecilians.
What is a caecilian?
A legless amphibian that belongs to the clade Apoda.
What is cutaneous respiration?
Gas exchange through the skin.
What is a frog?
A tail-less amphibian that belongs to the clade Anura.
What is a salamander?
A tailed amphibian that belongs to the clade Urodela.
What is a tadpole?
The larval stage of a frog.
What are Urodela?
Salamanders.
What is the origin of the term “amphibian”?
The term amphibian loosely translates from the Greek as “dual life”, which is a reference to the metamorphosis that many frogs and salamanders undergo and their mixture of aquatic and terrestrial environments in their life cycle.
How many limbs do amphibians have?
As tetrapods, most amphibians are characterized by four well-developed limbs. Some species of salamanders and all caecilians are functionally limbless; their limbs are vestigial.
Why is the skin of amphibians important?
An important characteristic of extant amphibians is a moist, permeable skin that is achieved via mucus glands that keep the skin moist; thus, exchange of oxygen and carbon dioxide with the environment can take place through it (cutaneous respiration).
What are some characteristics of the teeth of amphibians?
Amphibians have pedicellate teeth, which are teeth in which the root and crown are calcified, separated by a zone of noncalcified tissue.
What are some characteristics of the ears of amphibians?
Amphibians have a papilla amphibiorum and a papilla basilaris, structures of the inner ear that are sensitive to frequencies below and above 10,000 hertz, respectively. They also have an auricular operculum, which is an extra bone in the ear that transmits sounds to the inner ear.
What are some characteristics of amphibian feeding?
All extant adult amphibians are carnivorous, and some terrestrial amphibians have a sticky tongue that is used to capture prey.
When did amphibians evolve?
The fossil record provides evidence of the first tetrapods: now-extinct amphibian species dating to nearly 400 million years ago. Evolution of tetrapods from fishes represented a significant change in body plan from one suited to organisms that respired and swam in water, to organisms that breathed air and moved onto land; these changes occurred over a span of 50 million years during the Devonian period.
What are some characteristics of the earliest known tetrapod?
One of the earliest known tetrapods is from the genus Acanthostega. Acanthostega was aquatic; fossils show that it had gills similar to fishes. However, it also had four limbs, with the skeletal structure of limbs found in present-day tetrapods, including amphibians. Therefore, it is thought that Acanthostega lived in shallow waters and was an intermediate form between lobe-finned fishes and early, fully terrestrial tetrapods.
What species preceded Acanthostega?
In 2006, researchers published news of their discovery of a fossil of a “tetrapod-like fish”, Tiktaalik roseae, which seems to be an intermediate form between fishes having fins and tetrapods having limbs. Tiktaalik likely lived in a shallow water environment about 375 million years ago.
What was the “age of the amphibians”?
The early tetrapods that moved onto land had access to new nutrient sources and relatively few predators. This led to the widespread distribution of tetrapods during the early Carboniferous period, a period sometimes called the “age of the amphibians”.
How many species of amphibians are there?
Amphibia comprises an estimated 6,770 extant species that inhabit tropical and temperate regions around the world.
What are the clades of Amphibia?
Amphibians can be divided into three clades: Urodela (“tailed-ones”), the salamanders; Anura (“tail-less ones”), the frogs; and Apoda (“legless ones”), the caecilians.
How many species of salamander are there?
Living salamanders include approximately 620 species.
In what types of environments are salamanders found?
Some species of salamander are aquatic, others terrestrial, and some live on land only as adults.
How do salamanders walk?
Adult salamanders usually have a generalized tetrapod body plan with four limbs and a tail. They move by bending their bodies from side to side, called lateral undulation, in a fish-like manner while “walking” their arms and legs fore and aft. It is thought that their gait is similar to that used by early tetrapods.
How does respiration occur in salamanders?
Respiration differs among different species. The majority of salamanders are lungless, and respiration occurs through the skin or through external gills. Some terrestrial salamanders have primitive lungs; a few species have both gills and lungs.
