BIOLOGY CONCEPTS CONNECTIONS Fourth Edition Neil A Campbell
BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor CHAPTER 18 The Evolution of Animal Diversity Modules 18. 1 – 18. 4 From Power. Point® Lectures for Biology: Concepts & Connections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
What Am I? • Of some 1. 5 million species of organisms known to science, over two-thirds are animals • Humans have a long history of studying animal diversity – But do we always know what an animal is when we see one? Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Imagine you were the first person to encounter this duckbilled platypus • It has webbed feet, a bill, a furry body, mammary glands, and it lays eggs – With all of its varying characteristics, what would you think it is? Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Biologists often encounter classification problems when evolution creates organisms with similar characteristics – Marsupials, such as this Tasmanian tiger, are a good example Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
ANIMAL EVOLUTION AND DIVERSITY 18. 1 What is an animal? • Animals are eukaryotic, multicellular heterotrophs that ingest their food – They lack cell walls – They also have unique intercellular junctions Figure 18. 1 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Animals proceed through a welldefined life cycle sis ho tam orp 2 7 Adult Zygote (fertilized egg) 3 DIPLOID Larva Outer cell layer (ectoderm) Inner cell layer (endoderm) Opening Blastula (cross section) 4 5 Later gastrula (cross section) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Sperm Eggs 1 Digestive tract 6 Figure 18. 1 B HAPLOID Mei osis Me • Most animals are diploid except for haploid eggs and sperm Early gastrula (cross section)
18. 2 The animal kingdom probably originated from colonial protists • Cells in these protists gradually became more specialized and layered Digestive cavity Reproductive cells 1 Early colony of protists; aggregate of identical cells 2 Hollow sphere (shown in cross section) Somatic cells 3 Beginning of cell specialization (cross section) 4 Infolding (cross section) 5 Gastrula-like “protoanimal” (cross section) Figure 18. 2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Ecological, geologic, or genetic factors may have caused the Cambrian explosion in animal diversity • Cambrian fossils can be classified as ancient representatives of the familiar animal phyla Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
INVERTEBRATES 18. 3 Sponges have a relatively simple, porous body • Organisms in the phylum Porifera are among the simplest animals Central axis – Many sponges are radially symmetrical – Their parts are arranged around a central axis Figure 18. 3 A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Flagellated choanocytes filter food from the water passing through the porous body Choanocyte in contact with an amoebocyte Pores WATER FLOW Skeletal fiber Central cavity Choanocyte Amoebocyte Flagella Figure 18. 3 C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The sponge lineage arose very early – They probably evolved from multicellular choanoflagellates, the group that most likely gave rise to the animal kingdom Single cell Stalk Figure 18. 3 D, E Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 4 Cnidarians are radial animals with stinging threads • Cnidarians are the simplest animals with tissues • These animals exist in two radially symmetrical forms – Polyps, such as hydra, corals, and sea anemones Figure 18. 4 A, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– Medusas, the jellies Figure 18. 4 B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Cnidocytes on their tentacles sting prey – The tentacles, controlled by nerves, then push the food through the mouth into a gastrovascular cavity – In the cavity, the food is digested and then distributed – In cnidarians, only two cell layers are produced during gastrulation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Coiled thread Tentacle Capsule (nematocyst) “Trigger” Discharge of thread Prey CNIDOCYTE Figure 18. 4 D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 5 Most animals are bilaterally symmetrical • These animals have mirror-image right and left sides – They also have a head with sensory structures – They move headfirst through their environment Dorsal Posterior Anterior Ventral Figure 18. 5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 6 Flatworms are the simplest bilateral animals • Phylum Platyhelminthes – Planarians have a simple nervous system consisting of a brain, sense organs, and branching nerves – As in cnidarians, the mouth of a flatworm is the only opening for its gastrovascular cavity Digestive tract (gastrovascular cavity) Mouth Eyespots Nervous tissue clusters Figure 18. 6 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nerve cords Bilateral symmetry
• Flukes and tapeworms are parasitic flatworms with complex life cycles Mature flukes in blood vessels of intestine Male Human host Female 1 Sexual reproduction of flukes in human; fertilized eggs pass out in feces 6 Larva penetrates skin and blood vessels 2 Eggs hatch in water 5 Larva that infects human 3 Larva that infects snail 4 Figure 18. 6 B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Asexual reproduction of flukes in snail Snail host
• A tapeworm Units with reproductive structures Hooks Sucker Head Figure 18. 6 C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 7 Most animals have a body cavity • Sponges, cnidarians, and flatworms lack a body cavity Body covering (from ectoderm) Tissuefilled region (from mesoderm) Digestive tract (from endoderm) Figure 18. 7 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Nearly all other animals have a body cavity • This cavity is a fluid-filled space between the digestive tract and the body wall – The cavity aids in movement, cushions organs, and it may help in circulation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Body covering (from ectoderm) Pseudocoelom Muscle layer (from mesoderm) Digestive tract (from endoderm) Body covering (from ectoderm) Coelom Digestive tract (from endoderm) Tissue layer lining coelom and suspending internal organs (from mesoderm) Figure 18. 7 B, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 8 Roundworms have a pseudocoelom and a complete digestive tract • Nematodes have a body cavity not completely lined by mesoderm • Like most animals, they possess a complete digestive tract – This is a tube with a mouth and an anus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Many nematodes are free-living Trichinella juvenile Muscle tissue – Others are parasites Figure 18. 8 A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 9 Diverse mollusks are variations on a common body plan • Phylum Mollusca is a large and diverse phylum that includes – gastropods, such as snails and slugs Figure 18. 9 B, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– bivalves, such as clams and scallops Figure 18. 9 D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– cephalopods, such as squids and octopuses Figure 18. 9 E, F Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• All mollusks have a muscular foot and a mantle – The mantle may secrete a shell which encloses the visceral mass • Mollusks have a true coelom and a circulatory system – Many mollusks feed with a rasping radula Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
VISCERAL MASS Coelom Kidney Heart Reproductive organs Digestive tract MANTLE Shell Mantle cavity RADULA Radula Anus Gill Mouth FOOT Nerve cords Mouth Figure 18. 9 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 10 Many animals have a segmented body • Segmentation is the subdivision of some or most of the body into a series of repeated parts, or segments Anus Brain Main heart Coelom Digestive tract Segment walls Mouth Accessory heart Nerve cord Blood vessels Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Excretory organ Figure 18. 10 A
• Segmentation probably evolved as an adaptation for movement Figure 18. 10 B, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 11 Earthworms and other annelids are segmented worms • The segmented bodies of annelids (phylum Annelida) give them added mobility for swimming and burrowing – An earthworm eats its way through soil Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Polychaetes search for prey on the seafloor or live in tubes and filter food particles Figure 18. 11 A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Most leeches are free-living carnivores, but some suck blood Figure 18. 11 C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 12 Arthropods are the most numerous and widespread of all animals • Arthropods (phylum Arthropoda) are segmented animals with exoskeletons and jointed appendages Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Cephalothorax Abdomen Thorax Head Antennae (sensory reception) Swimming appendages Walking legs Pincer (defense) Mouthparts (feeding) Figure 18. 12 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• In terms of numbers, distribution, and diversity, they are the most successful phylum of animals – Horseshoe crabs are ancient marine arthropods Figure 18. 12 B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Most arachnids are terrestrial and carnivorous Figure 18. 12 C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Crustaceans are nearly all aquatic Figure 18. 12 D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Millipedes and centipedes make up a fourth group of arthropods Figure 18. 12 E Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 13 Insects are the most diverse group of organisms • Insects are the most numerous and successful arthropods • They have a three-part body consisting of – head, thorax, and abdomen – three sets of legs – wings (most, but not all insects) • The development of many insects includes metamorphosis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Head Antenna Thorax Abdomen Forewing Eye Hindwing Mouthparts Figure 18. 13 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The insects you see here undergo incomplete metamorphosis – Their young resemble adults, but are smaller with different body proportions Figure 18. 13 B, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The insects you see here undergo complete metamorphosis Figure 18. 13 D, E Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– They have larvae specialized for eating and growing – The larvae look very different from the adults – Adults are specialized for dispersal and reproduction Haltere Figure 18. 13 F, G Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 14 Echinoderms have spiny skin, an endoskeleton, and a water vascular system for movement • Phylum Echinodermata includes organisms such as sea stars and sea urchins – These organisms are radially symmetrical as adults Figure 18. 14 B, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
– The water vascular system has suction-cup-like tube feet used for respiration and locomotion Anus Spines Stomach TUBE FEET CANALS Figure 18. 14 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 15 Our own phylum, Chordata, is distinguished by four features • Organisms in this phylum are segmented animals with four distinctive features – Dorsal hollow nerve cord – Stiff notochord – Pharyngeal slits behind the mouth – Muscular post-anal tail Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The simplest chordates are tunicates and lancelets – These are marine invertebrates POST-ANAL TAIL DORSAL, HOLLOW NERVE CORD PHARYNGEAL SLITS Muscle segments Mouth NOTOCHORD LARVA Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 18. 15 A
• Lancelets Head NOTOCHORD DORSAL, HOLLOW NERVE CORD Mouth Pharynx PHARYNGEAL SLITS Digestive tract Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Water Anus exit Segmental muscles POST-ANAL TAIL Figure 18. 15 B
VERTEBRATES 18. 16 A skull and a backbone are hallmarks of vertebrates • Most chordates are vertebrates Vertebrae Backbone Skull – Their endoskeletons include a skull – Their backbone is composed of vertebrae Figure 18. 16 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 17 Most vertebrates have hinged jaws • Lampreys lack hinged jaws – They are classified as agnathans • Jaws evolved by the modification of skeletal supports of the gill slits Gill slits Skeletal rods Skull Mouth Figure 18. 17 A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 18 Fishes are jawed vertebrates with gills and paired fins • There are two classes of fish – Chondrichthyes, cartilaginous fishes such as sharks – Osteichthyes, bony fishes such as tuna and trout Figure 18. 18 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Bony fishes are more diverse and have – more mobile fins – operculi that move water over the gills – a buoyant swim bladder BONY SKELETON OPERCULUM Gills SWIM BLADDER Figure 18. 18 B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• There are three major classes of bony fishes – Ray-finned fishes Rainbow trout, a ray-fin – Lobe-finned fishes – Lungfishes Coelacanth, a lobe-fin Figure 18. 18 C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 19 Amphibians were the first land vertebrates • Class Amphibia is represented today by – frogs – toads – salamanders Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Amphibians were the first terrestrial vertebrates – Their limbs allow them to move on land – However, amphibian larvae must develop in water Figure 18. 19 A-C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Air-breathing lungfishes that developed skeleton-reinforced appendages probably gave rise to the first amphibians Bones supporting gills Typical tetrapod limb skeleton Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 18. 19 D
18. 20 Reptiles have more terrestrial adaptations than amphibians • Class Reptilia is able to live on land due to – waterproof scales – a shelled, amniotic egg • Modern reptiles are ectotherms – They warm their bodies by absorbing heat from the environment Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 18. 20 A, B
• Dinosaurs were the most diverse reptiles to inhabit land – This group included some of the largest land animals ever – They may have been endothermic, producing their own body heat Figure 18. 20 C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 21 Birds share many features with their reptilian ancestors • Like reptiles, class Aves has Teeth (like reptile) Wing claw (like reptile) – scales – amniotic eggs Feathers Long tail with many vertebrae (like reptile) Figure 18. 21 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Other bird characteristics include – wings – feathers – an endothermic metabolism – hollow bones – a highly efficient circulatory system Figure 18. 21 B, C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 22 Mammals also evolved from reptiles • Class Mammalia descended from reptiles • Mammals are endothermic • There are two unique mammalian characteristics – Hair, which insulates the body – Mammary glands, which produce milk that nourishes their young Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Most mammals give birth to young after a period of embryonic development inside the body of the mother – The embryo is nurtured by an organ called the placenta • A few mammals lay eggs – Monotremes Figure 18. 22 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Marsupials have a short gestation – The tiny offspring complete development attached to the mother’s nipple, usually inside a pouch – Example: kangaroos Figure 18. 22 B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• Most mammals are eutherians, also called placentals – They have a relatively long gestation – Complete embryonic development occurs within the mother Figure 18. 22 C Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
PHYLOGENY OF THE ANIMAL KINGDOM 18. 23 A phylogenetic tree gives animal diversity an evolutionary perspective • A traditional phylogenetic tree is based on patterns of embryonic development and some fundamental structures Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Porifera Platyhelminthes Cnidaria Mollusca Arthropoda Nematoda Annelida Pseudocoelom PROTOSTOMES No body cavity Coelom from cell masses Chordata Present day Echinodermata DEUTEROSTOMES Coelom from digestive tube True coelom Body cavity Radial symmetry No true tissues Bilateral symmetry True tissues Ancestral protists Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 18. 23 A
Lophotrochozoa No true tissues CHORDATA ECHINODERMATA Ecdysozoa Protostomes Radial symmetry ARTHROPODA NEMATODA ANNELIDA MOLLUSCA PLATYHELMINTHES CNIDARIA PORIFERA • A molecularbased tree has added two clades within the protostomes Deuterostomes Bilateral symmetry True tissues Ancestral colonial choanoflagellate Figure 18. 23 B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
18. 24 Connection: Humans threaten animal diversity by introducing non-native species • Introduced species are threatening Australia’s native animals Figure 18. 24 A-D Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
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