Vertebrate Evolution and Diversity

Vertebrate Evolution and Diversity

VERTEBRATE EVOLUTION AND DIVERSITY Vertebrates have unique endoskeletons composed of: A cranium (skull) A backbone made of a series of bones called vertebrae Cranium (protects brain)

Vertebra Figure 17.26 Characteristics of Chordates Chordates (phylum Chordata) all share four key features that appear in the embryo and sometimes the adult:

A dorsal, hollow nerve cord A notochord Pharyngeal slits

A post-anal tail Dorsal, hollow Notochord nerve cord Brain

Muscle segments Mouth Anus Post-anal Pharyngeal

tail slits Figure 17.27 Another chordate characteristic is body segmentation, apparent in the:

Backbone of vertebrates Segmental muscles of all chordates Chordates consists of three groups of invertebrates: Lancelets are bladelike animals without a cranium. Tunicates, or sea squirts, also lack a cranium. Hagfishes are eel-like forms that have a cranium.

All other chordates are vertebrates. Mouth Tail Lancelet Tunicates

Figure 17.28 Ancestral chordate Chordates

Tunicates Lancelets Hagfishes Vertebrates Lampreys Cartilaginous

fishes Bony fishes Amniotes Reptiles Mammals

Figure 17.29 Tetrapods Amphibians (a) Hagfish (inset: slime)

Figure 17.30a Lampreys: Are vertebrates Have a cranium But lack jaws (b) Lamprey (inset: mouth)

Figure 17.30b The two major groups of living fishes are the: Cartilaginous fishes (sharks and rays) with a flexible skeleton made of cartilage Lateral line

(c) Shark, a cartilaginous fish Figure 17.30c And bony fishes with a skeleton reinforced by hard calcium salts Bony fishes include:

Ray-finned fishes Lungfishes Lobe-finned fishes Operculum Lateral line

(d) Bony fish Figure 17.30d Cartilaginous and bony fishes have a lateral line system that detects minor vibrations in the water. To provide lift off the bottom: Cartilaginous fish must swim but

Bony fish have swim bladders, gas-filled sacs that make them buoyant All fish are ectothermic: external environment determines temp. Fish heart :2 chambers

Amphibians Amphibians: Exhibit a mixture of aquatic and terrestrial adaptations Usually need water to reproduce Typically undergo metamorphosis from an aquatic larva to a terrestrial adult Were the first vertebrates to colonize land Descended from fishes that had lungs and fins with

muscles Evolved around 370 million years ago Are ectothermic Have a 3 chambered heart Breath their skin (50 % of oxygen through diffusion) called cutaneous respiration. Amphibian Heart

(a) Tadpole and adult golden palm tree frog Red-eyed tree frog Texas barred tiger salamander (b) Frogs and salamanders: the two major groups of amphibians

Figure 17.31 Dissected frog Terrestrial vertebrates are collectively called tetrapods, which means four feet. Tetrapods include: Amphibians

Reptiles Mammals Reptiles Reptiles (including birds) and mammals are amniotes, which produce amniotic eggs that consist of a fluid-filled shell inside of which the embryo develops.

Reptile adaptations to living on land include: Amniotic eggs Scaled, waterproof skin Partial 3 chambered heart except for crocodilians have a complete 4 chambered heart internal fertilization for most ectothermic.

Reptiles include:

Snakes Lizards Turtles Crocodiles Alligators Birds Snake

Lizard Turtle Figure 17.33 Birds

Recent genetic evidence shows that birds evolved from a lineage of small, two-legged dinosaurs. Birds have many adaptations that make them lighter in flight:

Honeycombed bones One instead of two ovaries A beak instead of teeth feathers evolved from scales. Unlike other reptiles, birds are endotherms, maintaining a warmer and steady body temperature.

Complete 4 chambered heart. Internal fertilization with various mating rituals. Mammals The first true mammals: Arose about 200 million years ago Were probably small, nocturnal insect-eaters

Most mammals are terrestrial although dolphins, porpoises, and whales are totally aquatic. Mammalian hallmarks are: Hair Mammary glands that produce milk, which nourishes the young There are three major groups of mammals:

Monotremes, egg-laying mammals Monotremes (hatched from eggs) Echidna adult and egg Figure 17.35a

Marsupials, pouched mammals with a placenta Marsupials (embryonic at birth) Kangaroo newborn and mother Figure 17.35b

And eutherians, placental mammals Eutherians (fully developed at birth) Wildebeest newborn and mother

Figure 17.35c Primates are distinguished by characteristics that were shaped by the demands of living in trees. These characteristics include:

Limber shoulder joints Eyes in front of the face Excellent eye-hand coordination Extensive parental care Hominoids, the ape relatives of humans

Ring-tailed lemur Tarsier Black spider monkey (New World monkey)

Patas monkey (Old World monkey) Gorilla (ape) Orangutan (ape) Gibbon (ape)

Chimpanzee (ape) Human Figure 17.37 Upright posture and an enlarged brain appeared at

separate times during human evolution. Different human features evolved at different rates. Australopithecus and the Antiquity of Bipedalism Before there was the genus Homo, several hominid species of the genus Australopithecus walked the African savanna. Fossil evidence pushes bipedalism in A. afarensis back to at least 4 million years ago.

(a) Australopithecus afarensis skeleton (b) Ancient footprints (c) Model of an Australopithecus

afarensis male Figure 17.39 Homo Habilis and the Evolution of Inventive Minds Homo habilis, handy-man: Had a larger brain, intermediate in size between Australopithecus and modern humans Walked upright

Made stone tools that enhanced hunting, gathering, and scavenging on the African savanna Homo Erectus and the Global Dispersal of Humanity Homo erectus was the first species to extend humanitys range from Africa to other continents. The global dispersal began about 1.8 million years

ago. Homo erectus: Was taller than H. habilis Had a larger brain Gave rise to Neanderthals 2010 Pearson Education, Inc.

The Origin and Dispersal of Homo Sapiens The oldest known fossils of our own species, Homo sapiens: Were discovered in Ethiopia Date from 160,000 to 195,000 years ago DNA studies strongly suggest that all living humans can trace their ancestry back to a single African Homo

sapiens woman who lived 160,000 to 200,000 years ago.

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