rav65819_ch35_681-716

rav65819_ch35_681-716 - ; 35 chapter introduction MEMBERS...

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

View Full Document Right Arrow Icon
;;;;;;;;
Background image of page 1

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

View Full DocumentRight Arrow Icon
35 chapter introduction MEMBERS OF THE PHYLUM CHORDATA exhibit great changes in the endoskeleton compared with what is seen in echinoderms. As you saw in chapter 34, the endoskeleton of echinoderms is functionally similar to the exoskeleton of arthropods; it is a hard shell that encases the body, with muscles attached to its inner surface. Chordates employ a very different kind of endoskeleton, one that is truly internal. Members of the phylum Chordata are characterized by a flexible rod that develops along the back of the embryo. Muscles attached to this rod allowed early chordates to swing their bodies from side to side, swimming through the water. This key evolutionary advance, attaching muscles to an internal element, started chordates along an evolutionary path that led to the vertebrates—and, for the first time, to truly large animals. Vertebrates 35.1 The Chordates 35.2 The Nonvertebrate Chordates Tunicates have clearly chordate larval forms Lancelets are small marine chordates 35.3 The Vertebrate Chordates
Background image of page 2
Vertebrates have vertebrae, a distinct head, and other features Vertebrates evolved half a billion years ago: An overview 35.4 Fishes Fishes exhibit ±ve key characteristics Sharks, with cartilaginous skeletons, became top predators Bony ±shes dominate the waters The evolutionary path to land ran through the lobe-±nned ±shes 35.5 Amphibians Living amphibians have ±ve distinguishing features Amphibians overcame terrestrial challenges Modern amphibians belong to three groups 35.6 Reptiles Reptiles exhibit three key characteristic Reptiles dominated the Earth for 250 million years Modern reptiles belong to four groups Key characteristics of birds are feathers and a lightweight skeleton Birds arose about 150 MYA Modern birds are highly diverse but share several characteristics 35.8 Mammals Mammals have hair, mammary glands, and other characteristics Mammals diverged about 220 MYA Modern mammals are placed into three groups, of which placental mammals are the largest 35.9 Evolution of the Primates The anthropoid lineage led to the earliest humans Australopithecines were early hominids The genus Homo arose roughly 2 MYA concept outline 35.7 Birds 681 rav65819_ch35_681-716.indd 681 rav65819_ch35_681-716.indd 681 12/7/06 6:07:43 PM 12/7/06 6:07:43 PM 35.1 The Chordates
Background image of page 3

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

View Full DocumentRight Arrow Icon
fgure 35.2 500 μ m Sponges Cnidarians Flatworms Nematodes Mollusks Annelids Ar thropods Echinoderms Chordates A MOUSE EMBRYO. At 11.5 days of development, the mesoderm is already divided into segments called somites (stained dark in this photo), reflecting the fundamentally segmented nature of all chordates. Chordates
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 / 65

rav65819_ch35_681-716 - ; 35 chapter introduction MEMBERS...

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