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Chapter 24 Animal Diversity II: Vertebrates Lecture Outlines by Gregory Ahearn, University of North Florida Copyright © 2011 Pearson Education Inc. Chapter 24 At a Glance 24.1 What Are the Key Features of Chordates? 24.2 Which Clades Make Up the Chordates? 24.3 What Are the Major Groups of Vertebrates? Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.1 What Are the Key Features of Chordates? All chordates have four distinctive structures – A notochord: a stiff flexible rod extending the length of the body – A dorsal, hollow nerve cord: lies above the digestive tract and expands anteriorly to form the brain – Pharyngeal gill slits: located in the pharynx that may form respiratory organs or may appear as grooves – A post-anal tail: the chordate tail extends past the anus Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Biology: Life on Earth, 9e Dorsal nerve cord, notochord, pharyngeal gill slits, post-anal tail Mammalia (mammals) Amphibia (frogs, salamanders) Reptilia (turtles, snakes crocodiles, birds) Dipnoi (lungfishes) Actinistia (coelacanths) Actinopterygii (ray-finned fish) Chondrichthyes (sharks, rays) Petromyzontiformes (lampreys) Myxini (hagfishes) Cephalochordata (lancelets) Urochordata (tunicates) An Evolutionary Tree of the Chordates Craniates Vertebrates Tetrapods Hair, milk Amniotic egg Limbs Lobed fins Lungs Jaws Vertebral column Skull Fig. 24-1 Copyright © 2011 Pearson Education Inc. 24.1 What Are the Key Features of Chordates? Humans are members of the phylum Chordata – In humans, the chordate features are best seen during embryonic development, but later, we lose our notochord, gill slits, and tails – Only the dorsal nerve cord is retained in post embryonic human development Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Chordate Features in the Human eye heart liver tail limb bud (future leg) gill slit Biology: Life on Earth, 9e limb bud (future arm) Fig. 24-2 Copyright © 2011 Pearson Education Inc. 24.2 Which Clades Make Up the Chordates? The chordates include three clades – The lancelets – The tunicates – The craniates Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 Which Clades Make Up the Chordates? Lancelets are marine filter-feeders – Lancelets are small, fishlike, invertebrate chordates that retain all the four chordate features as adults – Lancelets live half-buried in the sand, with only the anterior end of their bodies exposed – Food particles are drawn into the mouth by pharyngeal cilia and are then transported to the digestive tract Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Author Animation: The Phylum Chordata Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Invertebrate Chordates nerve cord notochord gut muscle segments tail mouth gill slits (a) Lancelet Biology: Life on Earth, 9e anus Fig. 24-3a Copyright © 2011 Pearson Education Inc. 24.2 Which Clades Make Up the Chordates? Tunicates include sea squirts and salps – Tunicates (sea squirts) live in a marine environment –The larvae are motile and exhibit all key chordate features –Adults are sessile filter-feeders that have lost their tail and notochord –Barrel-shaped tunicates, known as salps, live in the open ocean and move by contracting an encircling band of muscle that propels the organism forward Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Author Animation: Lancelets and Tunicates Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Invertebrate Chordates incurrent siphon excurrent siphon (water enters) (water exits) mouth atrial opening tail anus nerve attachment gill gut cord points slits notochord larva (b) Tunicate gill slits heart gut gonad adult Fig. 24-3b Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 Which Clades Make Up the Chordates? Craniates have a skull – The craniates include all chordates that have a skull that encloses a brain – This group includes the hagfish and the vertebrates—animals in which the embryonic notochord is replaced during development by a backbone, or vertebral column, composed of bone or cartilage (which resembles bone, but is more flexible) Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 Which Clades Make Up the Chordates? Hagfishes are slimy residents of the ocean floor – They lack jaws – They are exclusively marine, and live near the ocean floor – They feed primarily on worms – They secrete massive quantities of slime as a defense against predators Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 Which Clades Make Up the Chordates? Hagfishes are slimy residents of the ocean floor (continued) – They respire using gills, have a two-chambered heart, and are ectothermic (they rely on heat from the outside environment to regulate body temperature) – They lack a true backbone, and thus are not a true vertebrate but have a rudimentary braincase – They represent the chordate group that is most closely related to the vertebrates Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Hagfishes Fig. 24-4 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 Which Clades Make Up the Chordates? Several adaptations have allowed vertebrates to successfully invade most habitats – The presence of an internal skeleton that can grow and repair itself allowed for greater size and mobility, enabling these animals to invade most habitats – Jaws evolved to allow these animals to exploit a much wider range of food sources than jawless animals that preceded them – The development of paired appendages (fins, legs, wings) helped to stabilize movement – The increased size and complexity of the brain and sensory structures allowed these animals to perceive their environment in detail and to respond in a variety of ways Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Today, vertebrates include the following groups: – Lampreys – Cartilaginous fishes – Ray-finned fishes – Coelacanths – Lungfishes – Amphibians – Reptiles – Mammals Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Some lampreys parasitize fish – Like hagfishes, lampreys are jawless – They have a large rounded sucker that surrounds the mouth – Their spinal cord is protected by cartilaginous segments – They live in both fresh and salt waters –Marine forms must return to fresh water to spawn Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Some lampreys parasitize fish (continued) – Some lamprey species are parasitic –A lamprey will attach to a host with its suckerlike mouth –It has rasping teeth on its tongue, which are used to excavate a hole in the hosts body wall through which the lamprey sucks blood and body fluids Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Lampreys Fig. 24-5 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Cartilaginous fishes are marine predators – They are of the class Chondrichthyes, and include sharks, skates, and rays – Most are marine – They possess jaws and a cartilaginous skeleton – Their body is protected by a leathery skin embedded with tiny scales Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Cartilaginous fishes are marine predators (continued) – They respire using gills – They possess a two-chambered heart – They have internal fertilization, in which the male deposits sperm directly into a female’s reproductive tract – They tend to sink when they stop swimming because they lack a swim bladder Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Cartilaginous fishes are marine predators (continued) – While some sharks feed by filtering plankton from the water, most are predators of larger prey such as fishes, marine mammals, sea turtles, crabs, or squid – Many have several rows of razor-sharp teeth – The back rows move forward as the front teeth are lost – Most sharks avoid humans, but some can be dangerous; in 2008, there were 59 documented attacks in the world, four of them fatal Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Cartilaginous fishes are marine predators (continued) – Skates and rays are mostly bottom dwellers with flattened bodies, wing-shaped fins, and thin tails – Some have a spine near the base of the tail that is capable of inflicting dangerous wounds – Others produce an electrical shock that can stun prey Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Cartilaginous Fishes Fig. 24-6 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Ray-finned fishes are the most diverse vertebrates – Bony fish are found in nearly every watery habitat, both freshwater and marine – This group includes: –Ray-finned fishes, such as the angler fish, the moray eel, and the sea horse –Lobe-finned fishes, which include the lungfish and the coelacanth Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? The ray-finned fishes are the most diverse and abundant group of vertebrates – They are distinguished by the structure of their fins, which are formed by webs of skin supported by bony spines – They have a bony skeleton – Their skin is covered with interlocking scales – They have a two-chambered heart – Their gills are for respiration – Most have a swim bladder that allows them to float effortlessly at any level in the water Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? The ray-finned fishes are the most diverse and abundant group of vertebrates (continued) – They are an important human food source –Populations of almost all economically important ray-finned fish species have declined drastically due to increased efficiency in their capture by humans –Large predatory fish such as the tuna have been reduced to 10% of their original population sizes due to overfishing Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Diversity of Ray-Finned Fishes Fig. 24-7 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Coelacanths and lungfishes have lobed fins – Both coelacanths and lungfishes have fleshy fins that contain rod-shaped bones surrounded by a thick layer of muscle – This shared trait is indicative of the groups shared ancestry, although the lineages have been evolving separately for hundreds of millions of years – Some of these modified fleshy fins could be used to drag the fish from a drying puddle to a deeper pool – This gave rise to the first vertebrates to invade land— the amphibians – Some of the lineages of lobefins left descendents that survive today and are the tetrapods (amphibians, reptiles, and mammals) Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Lungfish are found in freshwater habitats – They tend to live in stagnant waters low in oxygen – They have both gills and lungs – Lungs allow them to supplement their supply of oxygen by breathing air directly Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Lungfish are found in freshwater habitats (continued) – Some species of lungfish can survive even if the water dries up –They burrow into the mud –They seal themselves in a mucus-lined chamber and breathe through lungs as their metabolic rate slows –They resume their underwater way of life when the rains return and the pool refills Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Lungfishes are Lobe-Finned Fish Fig. 24-8 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Amphibians live a double life – This group includes frogs, toads, salamanders, and caecilians – The double life of amphibians –Amphibians begin life adapted to an aquatic environment (e.g., tadpoles have gills) –They later mature into semi-terrestrial adults with lungs Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Amphibians – Amphibians have a three-chambered heart – Most adults respire through lungs and moist skin – Most have four limbs – They reproduce sexually using external fertilization Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Most amphibians are confined to moist habitats – Their skin must be kept moist to avoid desiccation when out of water – Their breeding behavior and use of external fertilization requires water –The male sperm swim to the female eggs –The eggs, protected only by a jelly-like coating, are vulnerable to water loss –The larvae, such as the tadpoles of some frogs and toads, develop in water Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Amphibians are represented by the frogs, toads, salamanders, and caecilians – Frogs and toads undergo a metamorphosis during their life cycle, starting out as aquatic tadpoles and developing into terrestrial hopping adults – Salamanders have lizard-like bodies with four legs and a long tail – They begin life as aquatic larvae with gills that are retained in adulthood by some species, while others metamorphose into terrestrial adults – Caecilians are limbless burrowing amphibians that resemble an earthworm and can be up to 5 feet long; they have small eyes and limited vision Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Amphibian Means Double Life Fig. 24-9 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Reptiles belong to the class Reptilia and are adapted for life on land – These animals evolved from an amphibian ancestor about 250 million years ago –Reptiles include lizards, snakes, alligators, crocodiles, turtles, and birds –They respire exclusively through lungs Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Diversity of Reptiles Fig. 24-10 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Reptiles are adapted for life on land (continued) – There are three notable adaptations that allowed the reptiles freedom from their aquatic origins –They have tough scaly skin that protects the body and resists water loss –They have internal fertilization, where the male deposits sperm in the female’s body –They have evolved a shelled amniotic egg, which encapsulates the embryo in a liquidfilled membrane, the amnion, which prevents the embryo from drying out on land Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Reptiles are adapted for life on land (continued) – All reptiles have modified three- or fourchambered hearts, which separate oxygenated and deoxygenated blood more effectively than do amphibian hearts – All reptiles have more efficient lungs than do amphibians and do not use their skin as a respiratory organ – The reptile skeleton provides better support and more efficient movement on land than do those of amphibians Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Amniotic Egg Fig. 24-11 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Reptiles are represented by lizards, snakes, alligators, crocodiles, turtles, and birds – Lizards and snakes form a common lineage whose ancestors had limbs and whose representatives are mostly predators Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Snakes have a number of adaptations that help them acquire food – Many snakes have special sense organs that help track prey by sensing body temperature – Some snakes immobilize prey with venom that is delivered through hollow teeth – Snakes have a distinctive jaw joint that allows the jaws to distend so that the snake can swallow prey much larger than its head Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Crocodilians include the alligators and crocodiles and are found in the warmer waters of Earth – Crocodilians have nostrils located high on their heads so that they are able to remain submerged for long periods with only the uppermost portion of the head above the water surface – They have strong jaws and conical teeth to crush and kill the fish, birds, mammals, turtles, and amphibians that they eat – Parental care is extensive in crocodilians; they bury their eggs in mud nests and, later, the parents guard the hatched young, moving them safely to water in their mouths Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Turtles occupy a variety of habitats, including deserts, streams, ponds, and the ocean – All turtles are protected by a boxlike shell that is fused to the vertebrae, ribs, and collarbone – Turtles have no teeth, but have a horny beak instead, which is used to eat a variety of foods, including both plant and animal matter – The largest turtle is the leatherback, which lives in the ocean and can grow to 6 feet in length and feeds largely on jellyfish – Turtles can migrate long distances to reach beaches where they bury their eggs Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Birds are a distinctive group of reptiles – They appear in the fossil record 150 million years ago – They are distinguished from other reptiles by feathers, which are highly specialized reptilian body scales Modern birds retain scales on their legs, which is evidence of the ancestry they share with the rest of the reptiles – The earliest known bird is called Archaeopteryx Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Diversity of Birds Fig. 24-12 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Archeopteryx, the Earliest-Known Bird Fig. 24-13 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Birds are a distinctive group of reptiles adapted for flight – Feathers provide lift and control as well as insulation – Hollow bones reduce the weight of the skeleton – Bird reproductive organs shrink considerably during nonbreeding periods – Females have a single ovary, further minimizing their weight to aid flight – The nervous system provides extraordinary coordination and balance for flight, combined with acute eyesight Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Birds maintain a constant body temperature – They are warm-blooded (endothermic) – Birds have a high metabolic rate, which increases the demand for energy and requires efficient oxygenation of tissues – Therefore, birds must eat frequently, and have adaptations in their circulatory and respiratory systems to meet the need for efficiency – Their heart has four chambers, which prevents the mixing of oxygenated and deoxygenated blood – Their respiratory system has air sacs that provide a continuous supply of oxygenated air to the lungs, even as the bird exhales Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Mammals are in the class Mammalia, and provide milk to their offspring – Mammals appeared in the fossil record about 250 million years ago – They did not diversify and dominate terrestrial habitats until the dinosaurs became extinct (65 million years ago) – Mammals are named for milk-producing mammary glands that females use to nourish their young Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Mammals provide milk to their offspring – Mammals are warm-blooded with high metabolic rates – They have a four-chambered heart – Most have hair that protects and insulates – Most have legs designed for running rather than crawling – They have sweat, scent, and sebaceous (oilproducing) glands, which are not found in other vertebrates Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Mammals provide milk to their offspring (continued) – The mammalian brain is highly developed – Mammals have unparalleled curiosity and learning ability, allowing them to alter their behavior based on experience – This increases their chances of survival in a changing environment – Mammals have extended parental care after birth – This allows some mammals to learn extensively through parental guidance Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Mammals are subdivided into three groups – Monotremes – Marsupials – Placental mammals Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Monotremes are egg-laying mammals – This group includes only three species, the platypus and two species of spiny anteater (echidnas), and are found only in Australia and New Guinea – Platypuses forage for food in the water and eat small vertebrate and invertebrate animals – Echidnas are terrestrial and eat insects and worms they dig out of the ground – Monotremes lay leathery eggs rather than giving birth to live young – The newly hatched young are nourished from milk secreted by the mother Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Monotremes Fig. 24-14 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Marsupial diversity reaches its peak in Australia – Species include the opossums, koalas, kangaroos, wallabies, wombats, and the Tasmania devil – In marsupials, embryos begin development in the uterus of the female –Young are born at a very immature stage and must crawl to and grasp a nipple to complete development –Post-birth development, in most, is completed in a protective pouch Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Marsupials Fig. 24-15 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Placental mammals inhabit land, air, and sea – This highly diverse class includes bats, moles, impalas, whales, seals, monkeys, and cheetahs – Rodents account form almost 40% of all mammal species Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? Placental mammals inhabit land, air, and sea (continued) – Most mammal species are placental mammals –The uterus contains a placenta that functions in gas, nutrient, and waste exchange between circulatory systems of mother and embryo –In placental mammals, young are retained in the uterus for their entire embryonic development Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. 24.2 What Are the Major Groups of Vertebrates? About 20% of mammalian species are bats, the only mammals to have evolved wings and powered flight – Most bats have adaptations for feeding on a particular kind of food, such as species that eat fruit or the nectar from night-blooming flowers – Most bats are predators and hunt frogs, fish, flying insects, or blood that they obtain from the skin of sleeping mammals or birds – Bats use echolocation to catch flying prey by emitting short pulses of high-pitched sound – These sounds bounce off objects in the environment to produce echoes that can be detected by the bats Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. Author Animation: Vertebrates Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc. The Diversity of Placental Mammals Fig. 24-16 Biology: Life on Earth, 9e Copyright © 2011 Pearson Education Inc.