Question 1

How many species of vertebrates are there?

Accepted Answer

More than 62,000 vertebrate species have been identified.

Question 2

How many vertebrate species are under threat of extinction?

Accepted Answer

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.

Question 3

What is an example of an attempt to prevent the extinction of threatened species?

Accepted Answer

The Biodiversity Action Plan is an international program, ratified by 188 countries, which is designed to protect species and habitats.

Question 4

What is Cephalochordata?

Accepted Answer

A chordate clade whose members possess a notochord, dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail in the adult stage.

Question 5

What is Chordata?

Accepted Answer

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.

Question 6

What is Craniata?

Accepted Answer

A clade composed of chordates that possess a cranium; includes Vertebrata together with hagfishes.

Question 7

What is a cranium?

Accepted Answer

A bony, cartilaginous, or fibrous structure surrounding the brain, jaw, and facial bones.

Question 8

What is a dorsal hollow nerve cord?

Accepted Answer

A hollow, tubular structure derived from ectoderm, which is located dorsal to the notochord in chordates.

Question 9

What is a lancelet?

Accepted Answer

A member of Cephalochordata; named for its blade-like shape.

Question 10

What is a notochord?

Accepted Answer

A flexible, rod-shaped support structure that is found in the embryonic stage of all chordates and in the adult stage of some chordates.

Question 11

What is a pharyngeal slit?

Accepted Answer

An opening in the pharynx.

Question 12

What is a post-anal tail?

Accepted Answer

A muscular, posterior elongation of the body extending beyond the anus in chordates.

Question 13

What is a tetrapod?

Accepted Answer

A phylogenetic reference to an organism with a four-footed evolutionary history; includes amphibians, reptiles, birds, and mammals.

Question 14

What is a tunicate?

Accepted Answer

A sessile chordate that is a member of the subphylum Urochordata.

Question 15

What is Urochordata?

Accepted Answer

A clade composed of tunicates.

Question 16

What is a vertebral column?

Accepted Answer

A series of separate bones joined together as a backbone.

Question 17

What is Vertebrata?

Accepted Answer

Members of the phylum Chordata that possess a backbone.

Question 18

Where is the notochord located and what is its purpose?

Accepted Answer

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).

Question 19

What characterizes the nerve cords of non-chordates?

Accepted Answer

Other animal phyla than chordates are characterized by solid nerve cords that are located either ventrally or laterally.

Question 20

How does the nerve cord develop in chordates?

Accepted Answer

The nerve cord found in most chordate embryos develops into the brain and spinal cord, which compose the central nervous system.

Question 21

What is the purpose of pharyngeal slits?

Accepted Answer

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.

Question 22

What is the purpose of the post-anal tail?

Accepted Answer

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.

Question 23

What are the invertebrate clades of Chordata?

Accepted Answer

Tunicata and Cephalochordata.

Question 24

What is the origin of the name “tunicate”?

Accepted Answer

The name tunicate derives from the cellulose-like carbohydrate material, called the tunic, which covers the outer body of tunicates.

Question 25

Why are tunicates classified as chordates?

Accepted Answer

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.

Question 26

What is the tunicate lifecycle?

Accepted Answer

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.

Question 27

How do tunicates feed?

Accepted Answer

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.

Question 28

Where are tunicates found?

Accepted Answer

Most tunicates live a sessile existence on the ocean floor, and are found in shallow ocean waters around the world.

Question 29

What is the origin of the name “cephalochordate”?

Accepted Answer

The notochord extends into the head, which is what gives the subphylum its name.

Question 30

What is the oldest known cephalochordate?

Accepted Answer

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.

Question 31

What are some characteristics of lancelets?

Accepted Answer

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.

Question 32

How is water processed by lancelets?

Accepted Answer

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.

Question 33

How are hagfish distinguished from other craniates?

Accepted Answer

Hagfish have a cranium but lack a backbone.

Question 34

To which invertebrate chordates are vertebrates more closely related?

Accepted Answer

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.

Question 35

What fossil evidence supports the phylogenetic taxonomy of chordates?

Accepted Answer

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.

Question 36

What are the traditional classes in Vertebrata?

Accepted Answer

Agnatha, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves, and Mammalia.

Question 37

How are birds classified?

Accepted Answer

Many modern biologists classify birds within Reptilia, which correctly reflects their evolutionary heritage, but are often considered separately than reptiles for convenience.

Question 38

How are jawless fishes classified?

Accepted Answer

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).

Question 39

What are gnathostomes?

Accepted Answer

Animals that possess jaws are known as gnathostomes, which means “jawed mouth”. Gnathostomes include fishes and tetrapods.

Question 40

What are the groups of tetrapods?

Accepted Answer

Tetrapods can be divided into two groups: amphibians and amniotes.

Question 41

What are amniotes?

Accepted Answer

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.

Question 42

What are Actinopterygii?

Accepted Answer

Ray-finned fishes.

Question 43

What is an ampulla of Lorenzini?

Accepted Answer

A sensory organ that allows sharks to detect electromagnetic fields produced by living things.

Question 44

What are Chondrichthyes?

Accepted Answer

Jawed fishes with paired fins and a skeleton made of cartilage.

Question 45

What are hagfish?

Accepted Answer

Eel-like jawless fish that lives on the ocean floor and are scavengers.

Question 46

What is a lamprey?

Accepted Answer

A jawless fish characterized by a toothed, funnel-like, sucking mouth.

Question 47

What is a lateral line?

Accepted Answer

A sense organ that runs the length of a fish's body; used to detect vibration in the water.

Question 48

What are Myxini?

Accepted Answer

Hagfishes.

Question 49

What are Osteichthyes?

Accepted Answer

Bony fish.

Question 50

What is an ostracoderm?

Accepted Answer

One of the earliest jawless fish covered in bone.

Question 51

What is Petromyzontidae?

Accepted Answer

A clade of lampreys.

Question 52

What are Sarcopterygii?

Accepted Answer

Lobe-finned fish.

Question 53

What is a swim bladder?

Accepted Answer

In fishes, a gas-filled organ that helps to control the buoyancy of the fish.

Question 54

How many species of fish are there?

Accepted Answer

Modern fishes include an estimated 31,000 species.

Question 55

What were the earliest vertebrates?

Accepted Answer

Fishes were the earliest vertebrates, with jawless species being the earliest and jawed species evolving later.

Question 56

What features distinguish jawless fishes from invertebrate chordates?

Accepted Answer

They have a distinct cranium and complex sense organs including eyes.

Question 57

Outside of jaws, lack of what feature distinguishes jawless fishes from jawed fishes?

Accepted Answer

A defining feature is the lack of paired lateral appendages (fins).

Question 58

How many species of hagfish are there?

Accepted Answer

The clade Myxini includes at least 20 species of hagfishes.

Question 59

How do hagfishes feed?

Accepted Answer

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.

Question 60

Where are hagfishes found?

Accepted Answer

Hagfishes live on the ocean floor and are entirely marine, and are found in oceans around the world, except for the polar regions.

Question 61

What is a unique feature of hagfishes?

Accepted Answer

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.

Question 62

What are some characteristics of the hagfish skeleton and notochord?

Accepted Answer

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.

Question 63

How many species of lamprey are there?

Accepted Answer

The clade Petromyzontidae includes approximately 35-40 or more species of lampreys.

Question 64

In what ways are lampreys similar and dissimilar to hagfishes?

Accepted Answer

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.

29: Vertebrates Flashcards

Chordates, Fishes, Amphibians, Reptiles, Birds, Mammals, the Evolution of Primates

Brainscape's Knowledge GenomeTM

29: Vertebrates Flashcards

Chordates, Fishes, Amphibians, Reptiles, Birds, Mammals, the Evolution of Primates

Brainscape's Knowledge Genome^TM