chapt34_Deuterostomes(1).pdf

2 Phylum Echinodermata Exclusively marine Deuterostomes with an endoskeleton Pentaradial symmetry Sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers DEUTEROSTOMES Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 35 Protostomes Chaet...

2 Phylum Echinodermata Exclusively marine Deuterostomes with an endoskeleton Pentaradial symmetry Sea stars, brittle stars, sea urchins, sand dollars, sea cucumbers DEUTEROSTOMES Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 35 Protostomes Chaetognatha Deuterostomes Chordata Arthropoda Onychophora Loricifera Tardigrada Nematoda Kinorhyncha Nemertea Brachiopoda Mollusca Bryozoa Annelida Cycliophora Rotifera Ecdysozoa Lophotrochozoa Platyhelminthes Micrognathozoa Platyzoa Echinodermata Spiralia 3 1 2 3 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Symmetry Pentaradial as adult, bilateral as larva Oral surface defines mouth All systems organized with branches radiating from center Nervous system is nerve ring with branches Gut Developing coelom and water-vascular system Anus No centralization of function 100 µm Endoskeleton © Wim van Egmond/Visuals Unlimited Composed of calcium carbonate ossicles May be tightly or loosely joined All members have mutable collagenous tissue Thought to have evolved from bilaterally symmetrical ancestors because larvae are bilaterally symmetrical 3 Many able to regenerate lost parts Some reproduce asexually by splitting Most reproduction is sexual Epidermis covers endoskeleton Origin remains unclear Mouth Regeneration Gonochoric Gametes released into water Free-swimming larvae Each class has a characteristic type of larva 4 5 6 5 extant classes Water-vascular system Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Radially organized Radial canal extends from ring canal into each body branch Water enters through madreporite Flows through stone canal to ring canal Tube feet – may or may not have suckers Ampulla – muscular sac at base Used in movement, feeding, gas exchange Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stomach Anus Water-vascular system Skeletal plates b. Tube feet Digestive glands Gonad Important predators in many marine systems Most have 5 arms, some have multiples of 5 Echinoidea (sea urchins and sand dollars) 2. Madreporite Class: Asteroidea Asteroidea (sea stars and sea daisies) 1. a. © Alex Kerstitch/Visuals Unlimited Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Class: Echinoidea Lack arms Double rows of tube feet Protective moveable spines Radial canal Ampulla a. Tube feet © Daniel W. Gotshall/Visuals Unlimited b: © Frederic Pacorel/Getty Images 5 7 6 c. 1 7 8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Class: Ophiuroidea Phylum Chordata Ophiuroidea (brittle stars) Largest class e. Arms are equal diameter Class: Crinoidea Class: Holothuroidea 3. Ophiuroidea (brittle stars) their entire length – Largest class Arms are easily – Arms are equal diameter their entire length autotomized – Arms are easily autotomized © Jeff Rotman/Photo Researchers, Inc. 11 d. © Reinhard Dirscherl/Visuals Unlimited 7 Chaetognatha Echinodermata Chordata Arthropoda Tardigrada Onychophora Loricifera Mollusca Kinorhyncha Nematoda Nemertea 10 Class: Holothuroidea © Randy Morse/GoldenStateImages.com Bryozoa 5. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. b. © Reinhard Dirscherl/Visuals Unlimited Deuterostom es Ecdysozoa Lophotrochozoa Brachiopoda Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. d. Protostomes Spiralia Platyzoa Annelida Crinoidea (sea lilies Class: Crinoidea and feather stars) Holothuroidea4.(sea Crinoidea (sea lilies and feather stars) cucumbers) 5. Holothuroidea (sea cucumbers) 4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Cycliophora Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Rotifera Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Platyhelminthes Chordates are deuterostome coelomates Nearest relatives are echinoderms (the only other deuterostomes) Fishes, amphibians, reptiles, birds, and mammals Micrognathozoa 3. b. © Randy Morse/GoldenStateImages.com 8 4. Crinoidea (sea lilies and feather stars) 5. Holothuroidea (sea cucumbers) 11 9 10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 Features Nerve cord Notochord 1. 2. distinguish chordates Chordate muscles are arranged in segmented blocks called somites Most chordates have an internal skeleton against which the muscles work Hollow dorsal nerve cord Pharyngeal pouches Pharyngeal slits 3. 4. May be replaced by vertebral column Other characteristics also Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Pharyngeal pouches present in all vertebrate embryos Notochord Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 500 µm Oral hood with tentacles Notochord Dorsal nerve cord Postanal tail Postanal tail Pharynx Muscle blocks Pharyngeal slits All chordates have all four of these characteristics at some time in their lives Intestine Anus Postanal tail ©Eric N. Olson, Ph.D./The University of Texas MD Anderson Cancer Center 9 15 10 11 12 Subphylum Urochordata Phylum Chordata can be divided into three subphyla Tunicates and salps are marine animals Larvae are tadpolelike and have notochord and nerve cord Adults typically lose the tail and notochord 1. Urochordata Nonvertebrates 2. Cephalochordata Are free-swimming but do not feed Are immobile filter-feeders Many secrete a tunic (cellulose sac) that surrounds the animal Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Excurrent siphon Nerve ganglion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hypophyseal duct Mouth (incurrent siphon) Incurrent siphon Atriopore (excurrent siphon) Dorsal nerve cord Pharynx 3. Vertebrata Intestine Genital duct Endostyle Gill slit Stomach Tunic Stomach Gonad Pharynx with gill slits Heart a. 11 12 Notochord Heart c. b. Tunicate larva a. © Rick Harbo 19 Tunicates (phylum Chordata, subphylum Urochordata). 18 2 13 Subphylum Vertebrata Subphylum Cephalochordata Vertebrates are chordates with a spinal column Distinguished from nonvertebrates by Vertebral column – Encloses and protects the dorsal nerve cord Head – Distinct and well-differentiated possessing sensory organs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lancelets are scaleless chordates Notochord persists throughout animal’s life Spend most of their time partly buried Have no distinguishable head Feed on plankton using cilia-generated currents Closest relatives to vertebrates Head with brain (including endocrine glands) encased in skull Vertebral column (part of skeletal system) Dorsal nerve cord Kidney Heart-powered closed circulatory system Liver Limbs (or fins) Postanal tail 14 13 14 23 15 16 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ectoderm Neural tube Forming neural arch Neural arch The first vertebrates appeared in the oceans about 545 MYA Jawed fishes soon became dominant Amphibians invaded the land Reptiles replaced them as the dominant land vertebrates Birds and mammals became dominant after Cretaceous mass extinction Rib Notochord Vertebral body developing around notochord Centrum Blood vessels Vertebrates also have Neural crest – unique group of embryonic cells that forms many vertebrate structures Internal organs – liver, kidneys, endocrine glands, heart, and closed circulatory system Endoskeleton – made of cartilage or bone Mouth at one end, fin at the other Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Myxini (hagfish) Cephalaspidomorphi (lampreys) Chondrichthyes (cartilaginous fishes) Actinopterygii (ray-finned fishes) Sarcopterygii (lobe-finned fishes) Amphibia (amphibians) Mammalia (mammals) Mammary glands, 4-chambered heart, hair , synapsid skull Makes possible great size and extraordinary movement Testudines (turtles) Lepidosauria (lizards, snakes, tuataras) Crocodilia (crocodiles, alligators) Anapsid skull, bony shell Diapsid skull Aves (birds) Feathers Skull with two additional openings Amniotic egg Rayed fins Vertebral column Jaws, two pairs of appendages Lobed fins Legs with multiple digits Internal bony skeleton Head with 3 pairs of sense organs Chordate ancestor 15 16 Fish and reptiles are paraphyletic 25 17 Fishes Most diverse vertebrate group Over half of all vertebrates Provided the evolutionary base for invasion of land by amphibians Characteristics Vertebral column 1. Hagfish and lamprey exceptions Jaws and paired appendages 2. Hagfish and lamprey exceptions Internal gills Single-loop blood circulation Nutritional deficiencies 3. 4. 5. 17 18 Inability has been inherited by all their vertebrate descendants 18 3 19 20 History of the Fishes Armored fishes (placoderms) and spiny fishes both had jaws The first fishes had mouths with no jaws Agnatha extant as hagfish (class Myxini) and lampreys (class Cephalaspidomorphi) Ostracoderms are now extinct Cartilage skeleton but skin had small plates of bone Extinct at close of Permian The development of jaws occurred in the late Silurian period History of the Fishes Jaws evolved from the anterior gill arches that were made of cartilage Spiny fish were common during early Devonian – replacing ostracoderms Placoderms became common in late Devonian Jaw more improved than in spiny fishes Upper jaw fused to the skull and the skull hinged on the shoulder Extinct by end of period Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skull Gill slit Anterior gill arch At the end of the Devonian period, essentially all of these pioneer vertebrates disappeared, replaced by sharks and bony fishes in one of several mass extinctions Sharks and bony fishes first evolved in the early Devonian, 400 MYA Jaw was improved even further allowing the mouth to open much wider than was previously possible 30 19 20 21 22 Sharks were among the first vertebrates to develop teeth Aves Crocodilia Lepidosauria Testudines Amphibia Mammalia Sarcopterygii Actinopterygii Chondrichtyes Mixini Class Chondrichthyes Cephalaspidomorphi Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Evolved from rough scales on mouth’s skin Easily lost but continuously replaced Sharks (and bony fishes) have a fully developed lateral line system Series of sensory organs under the skin that detects changes Sharks, skates, rays Became the dominant sea predators in the Carboniferous period (360–280 MYA) Cartilage skeleton “calcified” with granules of calcium carbonate in pressure waves Reproduction in sharks differs from that of other fishes Eggs are fertilized internally Most pups are born alive A few species do lay fertilized eggs Light, strong skeleton Sharks have long gestation periods and relatively few offspring 21 Therefore, are not able to recover quickly from population declines 22 23 Bony fishes Evolved at the same time as sharks about 400 MYA 24 However, they adopted a heavy internal skeleton made completely of bone Bony fishes are the most species-rich group of all vertebrates (> 30,000 living species) Significant adaptations include swim bladder and gill cover Swim bladder Gas-filled sac that allows bony fishes to regulate their buoyant density In most modern fish, filled and drained with gases internally 23 Gill cover Hard plate, the operculum, covers gills Flexing plate permits water pumping over gills Efficient bellows system when stationary Gases are taken from the blood, and the gas gland secretes the gases into the swim bladder; gas is released from the bladder by a muscular valve, the oval body Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Dorsal aorta To heart Gas gland Swim bladder Oval body Gill cover (operculum) Gills 24 4 25 26 Parallel bony rays support and stiffen each fin There are no muscles within the fins Lobe-finned fishes (class Sarcopterygii) Have paired fins that consist of a long fleshy muscular lobe 1. Supported by central core of bones with fully articulated joints Almost certainly the amphibian ancestors 2. 4. Rays Ray-finned (class Actinopterygii) Lobe-finned (class Sarcopterygii) Central core of bones in fleshy lobe Rays 5. Amphibia Mammalia Chelonia Lepidosauria Crocodilia Aves 42 a. Sarcopterygii Cutaneous respiration – supplement lungs Pulmonary veins – separate pulmonary circuit allows higher pressure blood to tissues Partially divided heart – improves separation of pulmonary and systemic circuits 3. Shoulder girdle Actinopterygii Legs – adaptation to life on land Lungs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Shoulder girdle Chondrichthyes First vertebrates to walk on land Direct descendants of fishes 5 distinguishing amphibian features Class Amphibia Ray-finned fishes (class Actinopterygii) Cephalaspidomorphi Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mixini Class Amphibia First vertebrates to walk on land Direct descendants of fishes Two Major Groups of Bony Fishes b. a:© Federico Cabello/SuperStock; b: © Raymond Tercafs/Bruce Coleman Inc./Photoshot 25 26 41 27 28 Successful invasion of land by vertebrates required several adaptations Ichthyostega Legs to support body’s weight Lungs to extract oxygen from air Redesigned heart and circulatory system to drive larger muscles Reproduction still in water to prevent egg drying System to prevent whole body desiccation Amphibians evolved from lobe-finned fish Ichthyostega was one of the first amphibians Sturdy forelegs, flipper-shaped hindlimbs Long, broad, overlapping ribs form solid cage for lungs and heart 27 Moved like a seal 28 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29 Lobe-finned Fish 30 Early Amphibian Tiktaalik Shoulder In 2006, a transitional fossil was found between fish and Ichthyostega Had gills and scales like a fish, but a neck like an amphibian Shoulder, forearm, and wrist bones were like those of amphibians, but at the end of the limb was a lobed fin, rather than the toes of an amphibian Shoulder Pelvis Pelvis Femur Humerus Tibia Fibula Ulna Tibia Femur Fibula Radius a. Humerus Ulna Radius c. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Shoulder Humerus Ulna Radius Tiktaalik b. 29 30 5 31 32 3 Modern Amphibian groups Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Order Anura Order Caudata b. a. Order Apoda c. a: © Digital Vision/Getty Images RF; b: © Suzanne L. Collins & Joseph T. Collins/Photo Researchers, Inc.; c: © Jany Sauvanet/Photo Researchers, Inc. 31 5,670 species in 37 different families Order Anura (“without tail”) Order Caudata (“visible tail”) Order Apoda (“without legs”) 32 33 34 Order Anura (frogs and toads) Most live in or near water, aquatic tadpole stage before metamorphosis into adult Order Apoda (caecilians) Tropical, burrowing amphibians Legless with small eyes and jaws with teeth Fertilization is internal 35 36 Mixini Cephalaspidomorphi Chondrichthyes Actinopterygii Sarcopterygii Amphibia Mammalia Testudines Lepidosauria Crocodilia Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Thoracic breathing, which increases lung capacity 52 3. Amniotic eggs, which are watertight Dry skin, which covers body and prevents water loss 34 Class Reptilia 2. Over 7,000 living species All living reptiles exhibit three key features 1. Amniotic eggs, which are watertight 2. Dry skin, which covers body and prevents water loss 3. Thoracic breathing, which increases lung capacity Over 7,000 living species All living reptiles exhibit three key features 1. Have long bodies, tails, and smooth, moist skin Live in moist places Eggs are fertilized internally – sperm packet Larvae similar to adults Eggs fertilized externally Tadpole – swimming larval form Gradual metamorphosis into adult form Class Reptilia Most live in dry environments Not a monophyletic group 33 Eggs laid in water – lack watertight membranes Toads have bumpy, dry skin and short legs Order Caudata (salamanders) Frogs have smooth, moist skin and long legs Aves Reptiles, birds, and mammals are amniotes The amniotic egg has four membranes Chorion - Outermost layer, allows gas exchange Amnion - Encases embryo in fluid-filled cavity Yolk sac - Provides food 35 Allantois - Contains excreted wastes from embryo 36 6 38 37 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Leathery shell Embryo Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Amnion Anapsid Skull O rb it Synapsid Skull L ateral tem p o ral o p en in g O rb it D iap sid S ku ll Dorsal temporal opening Orbit Lateral temporal opening Reptiles dominated earth for 250 million years Reptiles are distinguished by the number of holes on side of the skull behind eye orbit Chorion Yolk sac 0 (anapsids), 1 (synapsids), 2 (diapsids) Allantois 37 38 39 40 The synapsids rose to dominance first Pelycosaurs History of Reptiles A number of different diapsids occurred in the Triassic period (248–213 MYA) First land vertebrates to kill beasts their own size Therapsids were replaced by Therapsids diapsids about 230 MYA Replaced them about 250 MYA May have been endotherms “Mammal-like” reptile Most became extinct 170 MYA One group survived and has living descendants today – the mammals Archosaurs were the first land vertebrates to be bipedal Gave rise to crocodiles, pterosaurs, dinosaurs, and birds Dinosaurs dominated for over 150 million years Became extinct 65 MYA Except bird descendents Asteroid’s impact 39 40 41 Modern reptiles developed two important characteristics 42 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Most Reptiles Fish Lung capillaries Gill capillaries Internal fertilization Sperm fertilizes egg before protective membranes are formed 41 Obtain heat from external sources Regulate body temperature by moving in and out of sunlight Compare to endothermic animals that generate their own heat internally Improved circulation Oxygen is provided to the body more efficiently Septum in heart extended to create partial wall Crocodiles, birds, and mammals have completely divided 4chambered heart All living reptiles are ectothermic Ventricle There are four surviving orders of reptiles Chelonia (turtles and tortoises) Rhynchocephalia (tuataras) Squamata (lizards and snakes) Crocodylia (crocodiles and alligators) Atrium Right atrium Other capillaries a. Other capillaries b. 61 About 7,000 species Reptiles occur worldwide except in the coldest regions, where it is impossible for ectotherms to survive 42 7 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 44 43 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Order Rhynchocephalia Order Chelonia Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Order Rhynchocephalia Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Contains only two species of tuataras Large, lizardlike animals about half a meter long Only found on islands near New Zealand a. ©William Weber/Visuals Unlimited ©Frans Lemmens/Getty Images Parietal eye Eye with lens and retina concealed under layer of scales on top of head Differ from all other reptiles because their bodies are encased within a protective shell Carapace (dorsal) and plastron (ventral) b. ©Jonathan Losos Order Squamata Tortoises are terrestrial while turtles are mostly aquatic Both lack teeth but have sharp beaks Marine turtles must return to land to lay eggs A characteristic of this order is the presence of paired copulatory organs in the male Snakes – 3,000 species Lizards – 3,800 species 43 Lack limbs, movable eyelids, and external ears Many have ability to regenerate lost tails 44 ©Rod Planck 45 46 Order Crocodylia Birds are the most diverse of all terrestrial vertebrates Success lies in unique structure – feather Birds still retain many reptilian traits Alligators – only 2 species Bodies well adapted to stealth hunting Cephalaspidomorphi Chondrichthyes Two major distinguishing traits Actinopterygii Feathers Modified scales of keratin Provide lift for flight and conserve heat Flight skeleton Bones are thin and hollow Many are fused for rigidity – anchor strong flight muscles Build nests and care for their young Have a 4-chambered heart Sarcopterygii Amphibia Mammalia Testudines Lepidosauria Crocodilia Aves d. (left): © Corbis/Volume 6 RF; (right): © Zigmund Leszczynski/Animals Animals 45 46 69 Crocodiles resemble birds far more than they do other living reptiles Class Aves Eyes on top of head, nostrils on top of snout, enormous mouth, strong necks Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mixini Amniotic eggs and scales on legs Lack teeth and tails of reptiles Crocodiles resemble birds far more than they do other living reptiles Order Crocodylia 28 orders, 166 families, about 8,600 species Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. – 28 orders, 166 families, about 8,600 species Birds are the most diverse of all terrestrial vertebrates Typically nocturnal Tropical and subtropical regions Success lies in unique structure – feather Class Aves 25 species of large, primarily aquatic carnivorous reptiles Crocodiles – Build nests and care for their young – Have a 4-chambered heart 68 47 48 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Feathers developed from reptile scales Linked structures provide continuous surface and a sturdy but flexible shape Barbule Shaft Quill Archaeopteryx is the first known bird Feathers developed from reptile scales Had skull with teeth, long reptilian tail Linked structures provide continuous Feathers on wings and tail surface and a sturdy but flexible shape Hooks Barb Forelimbs nearly identical to those of theropods 72 Feather probably evolved for insulation Archaeopteryx is the first known bird 47 48 – Had skull with teeth, long reptilian tail – Feathers on wings and tail – Forelimbs nearly identical to those of theropods Feather probably evolved for insulation 8 73 49 50 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. S in o sau ro p teryx V elo cirap to r C au d ip teryx A rch aeo p teryx Confuciornis M o d ern B ird s A few million years later, diversity of birds Toothed birds with the hollow bones and breastbones necessary for sustained flight This theropod dinosaur had short arms and ran along the ground. Its body was covered with filaments that may have been used for insulation and that are the first evidence of feathers. This larger, carnivorous theropod possessed a swiveling wrist bone, a type of joint that is also found in birds and is necessary for flight. Recently discovered fossils of this theropod indicate that it is intermediate between dinosaurs and birds. This small, very fast runner was covered with primitive (symmetrical and therefore flightless) feathers. This oldest known bird had asymmetrical feathers, with a narrower leading edge and streamlined trailing edge. It could probably fly short distances. B ird s Birds exhibit three evolutionary novelties Feathers Hollow bones Physiological mechanisms for flight 1. 2. D in o sau rs 3. Most paleontologists agree that birds are the direct descendants of theropod dinosaurs 49 50 51 52 Modern Birds Adaptations for flight 1. Efficient respiration 28 orders of birds Most ancient birds are flightless – like ostrich Ducks, geese, and waterfowl next Passeriformes comprise 60% of species today Air passes all the way through lungs in a single direction 2. Efficient circulation 4-chambered heart so muscles receive fully oxygenated blood Rapid heartbeat 3. Endothermy Body temperature (40–42oC) permits higher metabolic rate Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Order: Passeriformes a. b. c. d. a: © Corbis RF; b: © Tom Vezo/Minden Pictures; c: © David Boyle/Animals Animals; d: © John Cancalosi/Alamy 51 52 Cephalaspidomorphi There are about 4,500 species of mammals Actinopterygii Sarcopterygii Lowest number among 5 vertebrate classes 3200 species are rodents, bats, shrews, or moles Amphibia Mammalia Testudines 2 fundamentally mammalian traits Lepidosauria Hair Long, keratin-rich filaments that extend from hair follicles Insulation, camouflage, sensory structure 1. Aves Other notable features of mammals Endothermy depends on higher metabolic rate 4-chambered heart Respiration using diaphragm Placenta in most mammals Specialized organ that brings fetal and maternal blood into close contact Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Uterus Chorion Umbilical cord Placenta Yolk sac Amnion 78 Mammary glands Females possess mammary glands that secrete milk 2. Crocodilia Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chondrichthyes 54 Class Mammalia Class Mammalia There are about 4,500 species of mammals Mixini – Lowest number among 5 vertebrate classes – 3200 species are rodents, bats, shrews, or moles 53 Fetus 81 53 54 9 55 The mammalian lineage also gave rise to several adaptations in some groups 1. Specialized teeth 56 Digestion of plants 2. Different types of teeth are highly specialized to match particular eating habits Contrast carnivore teeth to herbivore teeth Herbivorous mammals rely on mutualistic partnerships with bacteria for cellulose breakdown Hooves are specialized keratin pads Horns are bone surrounded by keratin Antlers are made of bone, not keratin Development of hooves and horns 3. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Grinding teeth Dog Ripping teeth Chiseling teeth Incisors Canine Premolars and molars Flying mammals: Bats 4. Only mammals capable of powered flight Wing is a leathery membrane of skin and muscle stretched over 4 finger bones Navigate in the dark by echolocation Deer Beaver 83 Elephant Human 55 56 57 58 History of Mammals 2 Subclasses of Mammals Mammals have been around since the time of the dinosaurs, about 220 MYA Tiny, shrewlike, insect-eating, tree-dwelling creatures May have been nocturnal – large eye sockets Prototheria (most primitive) 1. Lay shelled eggs Only living group is the monotremes Theria 2. Mammals reached their maximum diversity in the Tertiary period (65–2 MYA) Viviparous – young are born alive Two living groups Marsupials or pouched mammals Placental mammals After mass extinction of dinosaurs Decline in the total number of mammalian species over last 15 million years 57 58 59 60 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Monotremes Marsupials Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lay shelled eggs Like reptiles have single opening (cloaca) for feces, urine, and reproduction Lack well-developed nipples Only three living species Duck-billed platypus 2 echidna species Major difference is pattern of embryonic development Short-lived placenta After birth, it crawls into marsupial pouch, latches onto nipple, and continues to develop b. Kangaroo – isolation of Australia Opossum – only North American marsupial (top): © W. Perry Conway/Corbis; (bottom): © Volume 6/Corbis RF a. (top): © Dave Watts/Alamy; (bottom): © B.J Alcock/Visuals Unlimited 59 60 10 61 Placental Mammals 62 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Produce a true placenta that nourishes embryo throughout its development Forms from both fetal and maternal tissues Young undergo a considerable period of development before they are born c. Includes most living mammals © Juergen & Christine Sohns/Animals Animals - Earth Scenes 61 62 63 64 About 40 MYA, the earliest primates split into two groups 1. Prosimians Evolution of Primates Primates are the mammals that gave rise to our own species Evolved two features that allowed them to succeed in an arboreal environment 1. Grasping fingers and toes First digit (thumb) is opposable in many Only a few survive today Lemurs, lorises and tarsiers Large eyes with increased visual acuity Most are nocturnal 2. Anthropoids Include monkeys, apes, and humans Almost all diurnal Binocular vision Eyes are shifted toward the front of the face Lets brain judge distances precisely 2. Changes in eye design include color vision Expanded brain Live in groups with complex social interactions Care for young for extended period Long period of learning and brain development 63 64 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 65 66 Hominoids 30 MYA Paraphyletic group – some more closely related to hominids New World monkeys migrated to South America All arboreal; many have prehensile tail Old World monkeys and hominids remained in Africa 65 No prehensile tails Hominids Humans Soon after the gorilla lineage diverged, the common ancestor of all hominids split off from the chimpanzee line to begin the evolutionary journey leading to humans Hominids Chimpanzees Gorillas c. Gibbons b. Hominoids Gibbon, orangutan, gorilla, and chimpanzee Larger brains than monkeys and lack tails a: © J & C Sohns/agefotostock; b: © PhotoDisc/Getty Images RF; c (left): © Dynamic Graphics Group/IT Stock Free/Alamy RF; c (right): © Joe McDonald/Visuals Unlimited Anthropoids Old World monkeys a. Prosimians Apes New World monkeys Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Orangutans Hominoids include Tarsiers Lemurs and lorises Old World Monkeys 0 10 Millions of years ago New World Monkeys 20 30 40 50 97 66 11 67 68 Apes vs. Hominids Early Hominids The common ancestor of apes and hominids is thought to have been an arboreal climber Genus Homo Genus Australopithecus Hominids became bipedal, walking upright Apes evolved knuckle-walking Differences related to bipedal locomotion Human vertebral column is more curved Spinal cord exits from bottom of skull Humans carry much of the body’s weight on the lower limbs 67 3–7 species (depending) 7 species Older and smaller-brained Several even older lineages In every case where the fossils allow a determination, the hominids are bipedal, the hallmark of hominid evolution 68 69 70 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Australopithecus afarensis Australopithecus robustus Homo habilis Homo floresiensis Australopithecines Homo sapiens sapiens Homo sapiens sapiens Homo neanderthalensis Homo heidelbergensis Homo floresiensis Homo erectus Homo ergaster Weighed about 18 kg About 1 m tall Hominid dentition Brains no larger than those of apes Walked upright Homo habilis Australopithecus africanus Australopithecus afarensis Australopithecus anamensis Australopithecus boisei Ardipithecus ramidus Australopithecus robustus Sahelanthropus tchadensis 7.5 7 6.5 6 Our knowledge is based on hundreds of fossils found in Africa Characteristics 5.5 5 4.5 4 3.5 3 Millions of Years Ago (MYA) 2.5 2 1.5 1 0.5 69 0 70 71 72 Bipedalism 71 Genus Homo Seems to have evolved as australopithecines left forests for grasslands and open woodland African fossils demonstrate that bipedalism extended back 4 MYA Substantial brain expansion, on the other hand, did not appear until about 2 MYA Why bipedalism evolved is still a matter of controversy The first humans evolved from australopithecine ancestors about 2 MYA Thought to be Australopithecus afarensis In the 1960s, hominid bones were found near stone tools in Africa Early human was called Homo habilis It closely resembled Australopithecus, but had larger brain 72 12 73 74 Homo floresiensis Modern Humans In 2004, a new human species was discovered in the tiny Indonesian Island of Flores Youngest fossils only 15,000 years old! H. floresiensis had a diminutive stature Coexisted with and preyed on a miniature species of elephant (now extinct) Believed to be more closely related to H. erectus than to H. sapiens Modern humans first appeared in Africa about 600,000 years ago Three species are thought to have evolved Homo heidelbergensis (oldest) Coexisted with H. erectus Homo neanderthalensis Shorter and stockier than modern humans Homo sapiens (“wise man”) Some lump all 3 into H. sapiens Small size may be an example of “island dwarfism” Small size may be an example of island dwarfism 73 74 105 75 Homo sapiens Neanderthals, Homo neanderthalensis 76 Made diverse tools Took care of sick and buried dead First evidence of symbolic thinking They abruptly disappeared about 34,000 years ago Effective making and use of tools Refined and extended conceptual thought Use of symbolic language Suddenly replaced by Cro-Magnons Only surviving hominid Progressive increase in brain size 2 species did not interbreed Complex social organization Elaborate cave paintings Thought to have had full language capabilities Extensive cultural experience 75 We change and mold our world rather than change evolutionarily in response to the environment 76 77 78 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Human Races 77 Human beings differentiated in their traits as they have spread throughout the world All humans are capable of mating with one another and producing fertile offspring Humans are visually oriented; consequently, we have relied on visual cues – primarily skin color – to define races Constant gene flow has prevented subspecies of humans from forming Genetic Similarity a. Skin Pigmentation b. Groupings based on overall genetic similarity are different from those based on skin color or other visual features 78 13