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19 Lecture Ppt


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19 Lecture Ppt

  1. 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 19 Evolution of Animals
  2. 2. Key Innovations Distinguish Invertebrate Groups 19-
  3. 3. 19.1 Animals have distinctive characteristics <ul><li>Animals are multicellular eukaryotes </li></ul><ul><ul><li>Chemoheterotrophs that acquire nutrients from an external source and digest it internally </li></ul></ul><ul><ul><li>Usually carry on sexual reproduction and begin life only as a fertilized diploid egg </li></ul></ul><ul><ul><li>Developmental stages to produce specialized tissues within organs with specific functions </li></ul></ul><ul><ul><li>Muscles and nerves characterize animals </li></ul></ul><ul><ul><ul><li>Allow animals to perform flexible movements </li></ul></ul></ul>19-
  4. 4. Figure 19.1 Developmental stages of a frog 19-
  5. 5. 19.2 Animals most likely have a protistan ancestor <ul><li>Two hypotheses on origin of animals </li></ul><ul><ul><li>Multinucleate Hypothesis </li></ul></ul><ul><ul><li>Animals arose from a ciliated protist in stages </li></ul></ul><ul><ul><ul><li>The ciliate would have acquired multiple nuclei, and then it would have become multicellular </li></ul></ul></ul><ul><ul><li>Colonial Flagellate Hypothesis </li></ul></ul><ul><ul><ul><li>Animals descended from an ancestor that resembled a spherical colony of flagellated cells </li></ul></ul></ul>19-
  6. 6. Figure 19.2 The colonial flagellate hypothesis 19-
  7. 7. Radial and Bilateral Symmetry 19-
  8. 8. 19.3 The traditional evolutionary tree of animals is based on seven key innovations (figure 19.3A) 19-
  9. 9. Animal Body Cavities <ul><li>Figure 19.3B Types of body cavity </li></ul>19-
  10. 10. APPLYING THE CONCEPTS—HOW SCIENCE PROGRESSES 19.4 Molecular data suggest a new evolutionary tree for animals <ul><li>In traditional tree, protostomes are restricted to three phyla, which have a coelom </li></ul><ul><ul><li>Arthropods, Annelids, and Molluscs </li></ul></ul><ul><li>Evolutionary tree based on molecular data suggests many more animal phyla should be designated protostomes because their rRNA sequences are so similar </li></ul><ul><ul><li>Segmentation doesn’t play a defining role in the evolutionary tree based on molecular data </li></ul></ul>19-
  11. 11. Figure 19.4A Proposed new evolutionary tree 19-
  12. 12. Figure 19.4B Roundworms and arthropods are molting animals 19-
  13. 13. 19.5 Some animal groups are invertebrates and some are vertebrates <ul><li>For convenience, the animal phyla have been divided into </li></ul><ul><ul><li>Invertebrates - those that do not have an endoskeleton of cartilage and bone </li></ul></ul><ul><ul><li>Vertebrates - those that do have an endoskeleton </li></ul></ul><ul><li>Animals evolved in the sea and most animals still live in the water </li></ul><ul><ul><li>Among the invertebrates only the molluscs, annelids, and arthropods have terrestrial representatives </li></ul></ul>19-
  14. 14. 19-
  15. 15. 19.6 Sponges are multicellular invertebrates <ul><li>Only animal without true tissue, organized at cellular level </li></ul><ul><li>Body of Sponges - phylum Porifera because their bodies are perforated by pores </li></ul><ul><ul><li>Filter feeder , also called a suspension feeder, because it filters suspended particles from water </li></ul></ul><ul><li>Endoskeleton </li></ul><ul><ul><li>Have fibers of spongin, a modified form of collagen </li></ul></ul><ul><ul><li>Typically have an endoskeleton also with spicules, small, needle-shaped structures with one to six rays </li></ul></ul><ul><li>Reproduction </li></ul><ul><ul><li>Reproduce asexually by budding </li></ul></ul><ul><ul><li>Reproduce sexually as egg and sperm are released into central cavity </li></ul></ul><ul><ul><ul><li>Zygote develops into a flagellated larva that may swim to a new location </li></ul></ul></ul>19-
  16. 16. Figure 19.6 Sponge anatomy 19-
  17. 17. 19.7 Cnidarians have true tissues <ul><li>Cnidarians (phylum Cnidaria) - an ancient group of invertebrates </li></ul><ul><ul><li>Most in the sea, but a few freshwater species </li></ul></ul><ul><li>Radially symmetrical and capture their prey with a ring of tentacles that have specialized stinging cells, cnidocytes </li></ul><ul><ul><li>Each cnidocyte has a capsule called a nematocyst , containing a long, spirally coiled, hollow thread </li></ul></ul><ul><li>Two basic body forms </li></ul><ul><ul><li>Polyp - mouth is directed upward from the substrate </li></ul></ul><ul><ul><li>Medusa - mouth is directed downward </li></ul></ul><ul><li>Cnidarians - a sac body plan with only one opening </li></ul>19-
  18. 18. Figure 19.7A Cnidarian diversity 19-
  19. 19. Figure 19.7B Anatomy of Hydra , a polyp 19-
  20. 20. 19.8 Free-living flatworms have bilateral symmetry <ul><li>Flatworms (phylum Platyhelminthes) </li></ul><ul><ul><li>First phylum with bilateral symmetry </li></ul></ul><ul><li>Have three germ layers </li></ul><ul><ul><li>Ectoderm from which body wall develops </li></ul></ul><ul><ul><li>Endoderm from which digestive cavity develops </li></ul></ul><ul><ul><li>Mesoderm which contributes to organ formation </li></ul></ul><ul><li>Have no coelum and are called acoelomates </li></ul><ul><li>Planarians have several body systems </li></ul><ul><ul><li>Digestive System - pharynx leads to gastrovascular cavity </li></ul></ul><ul><ul><li>Excretory System - a series of interconnecting canals </li></ul></ul><ul><ul><li>Reproductive System - Hermaphrodites (both male and female sex organs) and perform cross-fertilization </li></ul></ul><ul><ul><li>Nervous System - brain and two lateral nerve cords are joined by cross-branches called transverse nerves </li></ul></ul>19-
  21. 21. Figure 19.8 Planarian anatomy 19-
  22. 22. 19.9 Some flatworms are parasitic <ul><li>Tapeworms </li></ul><ul><ul><li>Endoparasites (internal parasites) of various vertebrates, including humans </li></ul></ul><ul><ul><ul><li>Vary in length from a few millimeters to 20 meters </li></ul></ul></ul><ul><ul><li>Tough body covering resistant to the host’s digestive juices </li></ul></ul><ul><ul><li>Scolex bears hooks and suckers for attachment to the intestinal wall of the host </li></ul></ul><ul><li>Flukes </li></ul><ul><ul><li>Endoparasites of various vertebrates </li></ul></ul><ul><ul><li>Anterior end of the animal has an oral sucker and at least one other sucker used for attachment to the host </li></ul></ul><ul><ul><li>Nearly 800,000 persons die each year from an infection called schistosomiasis </li></ul></ul>19-
  23. 23. Figure 19.9A Tapeworm ( Taenia solium ) anatomy and life cycle 19-
  24. 24. Figure 19.9B Sexual portion of blood fluke ( Schistosoma spp.) life cycle 19-
  25. 25. 19.10 Roundworms have a pseudocoelom and a complete digestive tract <ul><li>Roundworms (phylum Nematoda) possess two anatomic features not previously seen </li></ul><ul><ul><li>body cavity - pseudocoelom and is incompletely lined with mesoderm </li></ul></ul><ul><ul><li>complete digestive tract - it has both a mouth and an anus </li></ul></ul><ul><li>Nonsegmented, meaning that they have a smooth outside body wall </li></ul><ul><li>Ascaris </li></ul><ul><ul><li>Humans are infected with a roundworm called Ascaris when eggs enter the body via uncooked vegetables </li></ul></ul><ul><li>Other Roundworm Parasites </li></ul><ul><ul><li>Trichinosis - serious human infection acquired when humans eat meat that contains encysted larvae </li></ul></ul><ul><ul><li>Elephantiasis is caused by a roundworm called a filarial worm, </li></ul></ul><ul><ul><li>which utilizes mosquitoes as a secondary host </li></ul></ul>19-
  26. 26. <ul><li>Figure 19.10A Ascaris Figure 19.10b Encysted Trichinella larva </li></ul>19-
  27. 27. Figure 19.10C Elephantiasis 19-
  28. 28. 19.11 A coelom gives complex animal groups certain advantages <ul><li>Coelom - body cavity completely lined by mesoderm </li></ul><ul><li>Two groups </li></ul><ul><ul><li>Protostomes - Molluscs, annelids, and arthropods </li></ul></ul><ul><ul><li>Deuterostomes - echinoderms and chordates </li></ul></ul><ul><li>Two major events can be used to distinguish protostomes from deuterostomes </li></ul><ul><ul><li>Blastopore - protostomes: mouth appears near blastopore; deuterostomes: anus appears near blastopore </li></ul></ul><ul><ul><li>Coelom formation - protostomes: splitting produces the coelom; deuterostomes: the coelom arises as a pair of mesodermal pouches from the gut wall </li></ul></ul><ul><li>Advantages of a Coelom </li></ul><ul><ul><li>Body movements are freer because outer wall can move independently of the enclosed organs </li></ul></ul><ul><ul><li>Ample space of a coelom allows complex organs and organ systems to develop </li></ul></ul>19-
  29. 29. Figure 19.11 Protostomes compared to deuterostomes 19-
  30. 30. 19.12 Molluscs have a three-part body plan <ul><li>All molluscs (phylum Mollusca) have a body composed of at least three distinct parts </li></ul><ul><ul><li>The foot - strong, muscular portion used for locomotion </li></ul></ul><ul><ul><li>Visceral Mass - soft-bodied portion that contains internal organs </li></ul></ul><ul><ul><li>The mantle - covering that envelops the visceral mass </li></ul></ul><ul><ul><ul><li>The mantle may secrete an exoskeleton called a shell </li></ul></ul></ul><ul><li>Gastropods (meaning stomach-footed) including snails and nudibranchs </li></ul><ul><ul><li>Animal moves by muscle contractions that pass along its ventrally flattened foot </li></ul></ul><ul><li>Cephalopods (meaning head-footed) including octopuses, squids, and nautiluses </li></ul><ul><ul><li>The foot has evolved into tentacles about the head </li></ul></ul><ul><li>Bivalves (shells have two part) including clams, oysters, scallops, and mussels </li></ul><ul><ul><li>The clam is a filter feeder and food particles and water enter the mantle cavity by way of a siphon </li></ul></ul>19-
  31. 31. Figure 19.12A Body plan of a typical mollusc 19-
  32. 32. Figure 19.12B Three groups of molluscs 19-
  33. 33. 19.13 Annelids are the segmented worms <ul><li>Annelids (phylum Annelida) are segmented, as can be seen externally by the rings that encircle the body </li></ul><ul><ul><li>Partitions called septa divide the well-developed, fluid-filled coelom, which is used as a hydrostatic skeleton </li></ul></ul><ul><ul><li>Excretory system consists of nephridia, tubules that collect waste material and excrete it through an opening in the body wall </li></ul></ul><ul><li>Oligochaetes </li></ul><ul><ul><li>Earthworm is an oligochaete because it has few setae, bristles that anchor the worm </li></ul></ul><ul><li>Polychaetes </li></ul><ul><ul><li>Most annelids are polychaetes (having many setae per segment) that live in marine environments </li></ul></ul><ul><li>Leeches </li></ul><ul><ul><li>Have no setae, but have the same body plan as other annelids </li></ul></ul><ul><ul><li>Blood suckers that are able to keep blood flowing and prevent clotting </li></ul></ul>19-
  34. 34. Figure 19.13A Earthworm anatomy 19-
  35. 35. Figure 19.13B Other annelids 19-
  36. 36. 19.14 Arthropods have jointed appendages <ul><li>Arthropods (phylum Arthropoda) are extremely diverse </li></ul><ul><ul><li>More than one million species have been discovered </li></ul></ul><ul><li>Six characteristics </li></ul><ul><ul><li>Jointed appendages </li></ul></ul><ul><ul><li>Exoskeleton </li></ul></ul><ul><ul><li>Segmentation </li></ul></ul><ul><ul><li>Well-developed nervous system </li></ul></ul><ul><ul><li>Variety of respiratory organs </li></ul></ul><ul><ul><li>Reduced competition through metamorphosis </li></ul></ul>19-
  37. 37. Figure 19.14A Exoskeleton and jointed appendages of a crayfish, an arthropod 19-
  38. 38. Figure 19.14B Monarch butterfly metamorphosis 19-
  39. 39. 19.15 Well-known arthropods other than insects <ul><li>Crustaceans - name derived from their hard, crusty exoskeleton </li></ul><ul><ul><li>Largely marine arthropods that include crabs, barnacles, shrimps, and crayfish </li></ul></ul><ul><ul><li>Head usually bears a pair of compound eyes and five pairs of appendages </li></ul></ul><ul><li>Arachnids include spiders, scorpions, ticks, mites, and harvestmen </li></ul><ul><ul><li>Spiders have a narrow waist that separates the cephalothorax, with four pairs of legs, from the abdomen </li></ul></ul>19-
  40. 40. Figure 19.15A Crustacean diversity 19-
  41. 41. Figure 19.15B Centipede and millipede 19-
  42. 42. Figure 19.15C Spider and relatives 19-
  43. 43. 19.16 Insects, the largest group of arthropods, are adapted to living on land <ul><li>Insects - so numerous (>one million species) and diverse that the study of this one group is a major specialty in biology called entomology </li></ul><ul><li>Adapted to a life on land </li></ul><ul><ul><li>Body is divided into head, thorax, and abdomen </li></ul></ul><ul><ul><li>Mouthparts adapted to each species’ way of life </li></ul></ul><ul><ul><li>Wings enhance an insect’s ability to survive </li></ul></ul><ul><ul><ul><li>way of escaping enemies, finding food, facilitating mating, and dispersing offspring </li></ul></ul></ul>19-
  44. 44. Figure 19.16 Insect diversity 19-
  45. 45. 19.17 Echinoderms are radially symmetrical as adults <ul><li>Echinoderms (phylum Echinodermata) lack chordate features, but are related to because they are deuterostomes </li></ul><ul><ul><li>Radially, not bilaterally, symmetrical as adults </li></ul></ul><ul><ul><ul><li>Their larva is a bilaterally symmetrical filter feeder </li></ul></ul></ul><ul><ul><li>Adult echinoderms do not have a head, brain, or segmentation </li></ul></ul><ul><ul><ul><li>Their nervous system consists of nerves in a ring around the mouth extending outward radially </li></ul></ul></ul><ul><li>Locomotion by a water vascular system that pumps water into many tube feet, expanding them </li></ul><ul><li>No complex respiratory, excretory, or circulatory system </li></ul><ul><ul><li>Fluids within the coelomic cavity and the water vascular system carry out many of these functions </li></ul></ul><ul><li>In ecosystems, most feed on organic matter in the sea or substratum </li></ul><ul><ul><li>Sea stars prey upon crustaceans, molluscs, and other invertebrates </li></ul></ul>19-
  46. 46. Figure 19.17 Echinoderm structure and diversity 19-
  47. 47. Further Innovations Allowed Vertebrates to Invade the Land Environment 19-
  48. 48. 19.18 Four features characterize chordates <ul><li>Dorsal supporting rod (notochord) extends the length of the body </li></ul><ul><li>Dorsal tubular nerve cord contains a canal filled with fluid </li></ul><ul><li>Pharyngeal pouches only during embryonic development in most vertebrates </li></ul><ul><li>A postanal tail extends beyond the anus </li></ul>19-
  49. 49. Figure 19.18 The four chordate characteristics 19-
  50. 50. 19.19 Invertebrate chordates have a notochord as adults <ul><li>A few of the invertebrate chordates never replace the notochord with the vertebrae </li></ul><ul><ul><li>Tunicates (subphylum Urochordata) live on the ocean floor as filter feeders </li></ul></ul><ul><ul><ul><li>Larva is bilaterally symmetrical and has the four chordate characteristics </li></ul></ul></ul><ul><ul><ul><li>Metamorphosis produces the sessile adult </li></ul></ul></ul><ul><ul><li>Lancelets (subphylum Cephalochordata) marine chordates only a few centimeters long </li></ul></ul><ul><ul><ul><li>Lancelets retain the four chordate characteristics as adults </li></ul></ul></ul>19-
  51. 51. Figure 19.19 The invertebrate chordates 19-
  52. 52. 19.20 The evolutionary tree of vertebrates is based on five key features <ul><li>Vertebrates </li></ul><ul><ul><li>Fishes, amphibians, reptiles, birds, and mammals </li></ul></ul><ul><ul><li>Vertebrae are most obvious feature </li></ul></ul><ul><ul><li>Vertebral column is flexible because vertebrae are separated by disks, which cushion the vertebrae </li></ul></ul><ul><ul><ul><li>The soft center of a disk presses on the spinal cord </li></ul></ul></ul><ul><ul><li>Derived Characters Among Vertebrates </li></ul></ul><ul><ul><ul><li>Jaws, Lungs, Jointed Limbs, and Amniotic Eggs </li></ul></ul></ul>19-
  53. 53. Figure 19.20 Evolutionary tree of the chordates 19-
  54. 54. 19.21 Jaws and lungs evolved among the fishes <ul><li>Jawless Fishes (Class Agnatha) </li></ul><ul><ul><li>Cylindrical and up to a meter long </li></ul></ul><ul><ul><li>Smooth, scaleless skin, no jaws or paired fins </li></ul></ul><ul><li>Cartilaginous Fishes (Class Chondrichthyes) includes sharks, the rays, and the skates </li></ul><ul><ul><li>Skeletons of cartilage, instead of bone </li></ul></ul><ul><ul><li>Shark senses </li></ul></ul><ul><ul><ul><li>Able to sense electric currents in water </li></ul></ul></ul><ul><ul><ul><li>Lateral line system senses pressure waves caused by fish </li></ul></ul></ul><ul><ul><ul><li>Keen sense of smell </li></ul></ul></ul><ul><li>Bony Fishes (Class Osteichthyes) most numerous and diverse of all vertebrates </li></ul><ul><ul><li>Ray-finned fishes - use their fins to balance and propel body </li></ul></ul><ul><ul><ul><li>Have a swim bladder, which usually serves as a buoyancy organ </li></ul></ul></ul><ul><ul><ul><li>Bony scales that protect body but do not prevent water loss </li></ul></ul></ul>19-
  55. 55. Figure 19.21A Evolution of jaws 19-
  56. 56. Figure 19.21B Diversity of fishes 19-
  57. 57. Figure 19.21C This transitional form links the lobes of the lobe-finned fishes to the limbs of ancestral amphibians 19-
  58. 58. 19.22 Amphibians are tetrapods that can move on land <ul><li>Amphibians (class Amphibia) means living on both land and in the water, represented by frogs, toads, newts, and salamanders </li></ul><ul><li>Characteristics </li></ul><ul><ul><li>Adults have small lungs - air enters the mouth by way of nostrils </li></ul></ul><ul><ul><li>Respiration is supplemented by gas exchange through the smooth, moist, skin </li></ul></ul><ul><li>Most members lead an amphibious life </li></ul><ul><ul><li>Larval stage lives in water, and adult stage is on land </li></ul></ul>19-
  59. 59. Figure 19.22 Frogs and salamanders are well-known amphibians 19-
  60. 60. 19.23 Reptiles have an amniotic egg and can reproduce on land <ul><li>Reptiles (class Reptilia) diversified and most abundant between 245 and 66 MYA </li></ul><ul><li>The reptiles living today are mainly alligators, crocodiles, turtles, snakes, lizards, and tuataras </li></ul><ul><li>Body is covered with hard, keratinized scales, which protect animal from desiccation and from predators </li></ul><ul><li>Fertilization is internal, and the female lays leathery, flexible, shelled eggs </li></ul><ul><ul><li>Amniotic egg made development on land possible and eliminated the need for a swimming larval stage </li></ul></ul><ul><li>Fishes, amphibians, and reptiles are ectotherms </li></ul><ul><ul><li>Body temperature matches the temperature of their environment </li></ul></ul>19-
  61. 61. Amniotic Egg 19-
  62. 62. Figure 19.23 Reptilian diversity 19-
  63. 63. 19.24 Birds have feathers and are endotherms <ul><li>Birds (class Aves) are characterized by the presence of feathers </li></ul><ul><ul><li>Lay a hard-shelled amniotic egg </li></ul></ul><ul><ul><ul><li>Data suggests birds are related to bipedal dinosaurs and should be classified as such </li></ul></ul></ul><ul><ul><li>Birds are adapted to fly </li></ul></ul><ul><ul><ul><li>Forelimbs are modified as wings </li></ul></ul></ul><ul><ul><ul><li>Hollow, light bones </li></ul></ul></ul><ul><ul><ul><li>Horny beak has replaced jaws with teeth </li></ul></ul></ul><ul><ul><li>Birds are endotherms and generate internal heat </li></ul></ul><ul><ul><ul><li>May be associated with efficient nervous, respiratory, and circulatory systems </li></ul></ul></ul><ul><ul><li>Seasonal migration of many species over very long distances </li></ul></ul><ul><ul><ul><li>Navigate by day and night, whether it’s sunny or cloudy, by using the sun and stars and even the Earth’s magnetic field to guide them </li></ul></ul></ul>19-
  64. 64. Figure 19.24A Bird flight 19-
  65. 65. Figure 19.24B Types of bird beaks 19-
  66. 66. 19.25 Mammals have hair and mammary glands <ul><li>Mammals (class Mammalia) evolved during Mesozoic from reptiles called therapsids </li></ul><ul><li>Two chief characteristics </li></ul><ul><ul><li>Hair: Mammals are endotherms, and hair aids temperature control </li></ul></ul><ul><ul><li>Milk-producing mammary glands: enable females to feed (nurse) their young without leaving them to find food </li></ul></ul>19-
  67. 67. Monotremes and Marsupials <ul><li>Monotremes - mammals that have a cloaca , a terminal region of the digestive tract serving as a common chamber for feces, excretory wastes, and sex cells </li></ul><ul><ul><li>Also lay hard-shelled amniotic eggs </li></ul></ul><ul><li>Marsupials - begin their development inside the female’s body, but they are born in a very immature condition </li></ul><ul><ul><li>Newborns crawl up into a pouch on their mother’s abdomen </li></ul></ul>19-
  68. 68. Figure 19.25A Monotremes and marsupials 19-
  69. 69. Placental Mammals <ul><li>Placental mammals - extraembryonic membranes of the reptilian egg are modified for internal development within the uterus of the female </li></ul><ul><ul><li>Chorion contributes to the fetal portion of the placenta, while a part of the uterine wall contributes to the maternal portion </li></ul></ul><ul><ul><li>Nutrients, oxygen, and waste exchanged between fetal and maternal blood </li></ul></ul><ul><li>Distinguished by their mode of locomotion </li></ul><ul><ul><li>Bats have membranous wings supported by digits </li></ul></ul><ul><ul><li>Horses have long, hoofed legs; and whales have paddlelike forelimbs </li></ul></ul><ul><li>Distinguished by the way of obtaining food </li></ul><ul><ul><li>Mice have continuously growing incisors </li></ul></ul><ul><ul><li>Horses have large, grinding molars </li></ul></ul><ul><ul><li>Dogs have long canine teeth </li></ul></ul>19-
  70. 70. Figure 19.25B Placental mammals 19-
  71. 71. APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 19.26 Many vertebrates provide medical treatments for humans <ul><li>Hundreds of pharmaceutical products come from vertebrates </li></ul><ul><ul><li>Animals that produce poisons and toxins give us medicines that benefit us </li></ul></ul><ul><ul><li>Some produce proteins similar to human proteins to be used in medical treatment </li></ul></ul><ul><li>Powerful applications of genetic engineering found in development of drugs and therapies for human diseases </li></ul><ul><ul><li>Xenotransplantation, transplantation of vertebrate tissues and organs into human beings </li></ul></ul><ul><ul><li>Use of transgenic vertebrates for medical purposes does raise health and ethical concerns </li></ul></ul>19-
  72. 72. Figure 19.26 Vertebrates used for medical purposes 19-
  73. 73. Connecting the Concepts: Chapter 19 <ul><li>As terrestrial mammals, humans might assume that terrestrial species are more successful than aquatic ones </li></ul><ul><ul><li>If not for the myriad types of terrestrial insects, there would be more aquatic species than terrestrial ones on Earth </li></ul></ul><ul><li>Adaptative radiation of mammals has taken place on land, and this might seem impressive to some </li></ul><ul><ul><li>Actually, the number of mammalian species (4,800) is small compared to the molluscs (110,000 species) </li></ul></ul><ul><li>Size and complexity of the brain is also sometimes cited as a criterion by which vertebrates are more successful than other living things </li></ul><ul><ul><li>This characteristic has been linked to others that make an animal prone to extinction </li></ul></ul><ul><ul><li>Long life span, slow to mature, have few offspring, expend much energy caring for their offspring, and tend to become extinct if their normal way of life is destroyed </li></ul></ul>19-