BIOL211#12and#13

BIOL211#12and#13 - Chapter 34 Early in the Cambrian period,...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Chapter 34 The Vertebrates Early in the Cambrian period, some 530 million years ago, an immense variety of animals inhabited the oceans One of these types of animals gave rise to the vertebrates Vertebrates derive their name from vertebrae, the series of bones that make up the backbone There are approximately 53,000 species of vertebrates Include the heaviest and largest animals ever to exist on Earth – Dinosaurs: 40,000 kg – Blue whales: 100,000 kg Vertebrates are members of the Phylum Chordata (chordates) Chordates are bilaterian and belong to the clade Deuterostomia Figure 34.1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Craniates A major transition in chordate evolution was the appearance of a head Chordates with a head (skull) are called craniates The head opened up a new type of feeding behavior – active predation Characteristics of craniates – A brain that is encased in a protective bony or cartilaginous housing called a cranium – A group of embryonic cells called the neural crest that disperse and contribute to the development of the skeleton – At least two clusters of Hox genes Hagfishes (Class Myxini) – Lack eyes, jaws, fins, and vertebrae – All are marine bottom feeders – Have slime glands Figure 34.2 Figure 34.1 Vertebrates Craniates with a backbone Derived characters – Vertebral column enclosing a nerve cord – Endoskeleton of cartilage or bone – Diversity of internal organs Lampreys (Class Petromyzontida) – Oldest living lineage of vertebrates – Lack hinged jaws and true appendages – Found in marine and freshwater environments – Marine lampreys are parasitic as adults
Background image of page 2
3 Lampreys Sea Lamprey Figure 34.1 Gnathostomes Vertebrates that have true jaws Far outnumber jawless vertebrates More sophisticated head and body structures Include cartilaginous fishes, ray-finned fishes, coelacanths, and lungfishes Gnathostomes appeared in the fossil record about 400 million years ago Their success is due to two features of their anatomy – Paired fins and a tail for locomotion – Jaws for grasping prey and feeding The earliest gnathostomes were armored vertebrates called placoderms Gnathostome jaws evolved from skeletal supports of the pharyngeal slits Figure 34.4
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 Other derived characters – Enlarged forebrain – Enhanced senses of smell and vision – The lateral line system in aquatic species Class Chondrichthyes (chondrichthyans) – Cartilaginous fishes – Skeleton composed of flexible cartilage rather than bone – All chondrichthyans are aquatic and have bodies that are denser than water – Include the sharks, skates, and rays Chondrichthyans Blacktip Reef Shark Freshwater Stingray Sharks – Fast swimmers with streamlined bodies – Have acute senses – Eggs fertilized internally Oviparous development Ovoviviparous development Viviparous development Skates and rays – Flattened bottom dwellers – Enlarged pectoral fins – Whiplike tail Figure 34.1
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 16

BIOL211#12and#13 - Chapter 34 Early in the Cambrian period,...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online