Chapter 34: The Origin and Evolution of Vertebrates

Flashcards covering the origin and evolution of vertebrates.

Chordates

Bilaterian animals that belong to the clade of animals known as Deuterostomia and comprise all vertebrates and two groups of invertebrates, the urochordates and cephalochordates

Notochord

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

Dorsal, Hollow Nerve Cord

The nerve cord of a chordate embryo develops from a plate of ectoderm that rolls into a tube dorsal to the notochord and develops into the central nervous system: the brain and the spinal cord

Pharyngeal Slits or Clefts

Grooves in the pharynx called pharyngeal clefts develop into slits that open to the outside of the body Functions include: suspension-feeding structures, gas exchange, develop into parts of the ear, head, and neck in tetrapods

Muscular, Post-Anal Tail

Chordates have a tail posterior to the anus that contains skeletal elements and muscles and provides propelling force in many aquatic species

Lancelets

Cephalochordata named for their bladelike shape and are marine suspension feeders that retain characteristics of the chordate body plan as adults

Tunicates

Urochordata that are more closely related to other chordates than are lancelets and most resemble chordates during their larval stage

Craniates

Chordates that have a head which enabled chordates to coordinate more complex movement and feeding behaviors and share some characteristics: a skull, brain, eyes, and other sensory organs

Neural Crest

A collection of cells near the dorsal margins of the closing neural tube in an embryo that is unique to craniates. Neural crest cells give rise to a variety of structures, including some of the bones and cartilage of the skull

Vertebrates

Chordates that have a backbone and a skeletal system and complex nervous system that allowed vertebrates greater efficiency at capturing food and evading predators with derived characters including: Vertebrae enclosing a spinal cord, an elaborate skull, and fin rays in aquatic forms

Cyclostomes

The clade of living jawless vertebrates formed by hagfishes and lampreys

Gnathostomes

Vertebrates with jaws that make up a much larger clade than cyclostomes

Lateral Line System

In aquatic gnathostomes, the lateral line system, which is sensitive to vibrations

Placoderms

The earliest gnathostomes in the fossil record that are an extinct lineage of armored vertebrates

Chondrichthyans

Chondrichthyes that have a skeleton composed primarily of cartilage with the largest and most diverse group including the sharks, rays, and skates

Osteichthyans

Include the bony fishes and tetrapods and aquatic osteichthyans are the vertebrates we informally call fishes

Actinopterygii

The ray-finned fishes, that include nearly all the familiar aquatic osteichthyans and originated during the Silurian period (444 to 416 million years ago)

Lobe-Fins

Sarcopterygii that originated in the Silurian period and have muscular pelvic and pectoral fins that they use to swim and “walk” underwater across the substrate Three lineages survive and include coelacanths, lungfishes, and tetrapods

Tetrapods

Gnathostomes that have limbs and feet with digits, a neck, fusion of the pelvic girdle to the backbone, the absence of gills (except some aquatic species) and ears for detecting airborne sounds

Amniotes

A group of tetrapods whose living members are the reptiles, including birds, and mammals named for major derived character of the clade: the amniotic egg, which contains membranes that protect the embryo

Reptiles

Include the tuataras, lizards, snakes, turtles, crocodilians, birds, and some extinct groups that have scales that create a waterproof barrier and most reptiles lay shelled eggs on land

Ectothermic

Absorbing external heat as the main source of body heat, reptiles regulate their body temperature through behavioral adaptations

Endothermic

Capable of maintaining body temperature through metabolism like birds

Lepidosaurs

Include tuataras, lizards, snakes, and extinct mososaurs

Archosaurs

Lineage produced the crocodilians, pterosaurs, and dinosaurs

Theropods

Bipedal carnivores that dinosaurs included; the group from which birds are descended

Mammals

Mammalia represented by more than 5,300 species that have mammary glands, which produce milk, hair, a high metabolic rate, due to endothermy, a larger brain than other vertebrates of equivalent size and differentiated teeth

Monotremes

A small group of egg-laying mammals consisting of echidnas and the platypus

Marsupials

Include opossums, kangaroos, and koalas where the embryo develops within a placenta in the mother’s uterus and is born very early in its development and completes its embryonic development while nursing in a maternal pouch called a marsupium

Eutherians

Placental mammals that have a more complex placenta and complete their embryonic development within a uterus, joined to the mother by the placenta

Primates

The mammalian order that includes lemurs, tarsiers, monkeys, and apes

Hominins

Formerly called hominids that are more closely related to humans than to chimpanzees