Multicellular life arose over a billion years ago

� Multicellular life arose over a billion years ago THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 1

KINGDOM ANIMALIA THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 2

What Is an Animal? �Animals �Are eukaryotic, multicellular, heterotrophic organisms that obtain nutrients by ingestion �Digest their food within their bodies THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 3

�Most animals reproduce sexually and then proceed through a series of developmental stages �Most animals have muscle cells and nerve cells that control the muscles Haploid Sperm Egg 2 1 Meiosis Fertilization Zygote (fertilized egg) Adult 3 Diploid Blastula (cross section) 7 Metamorphosis Digestive tract Outer cell layer Primitive (ectoderm) gut 6 4 5 Early gastrula Larva Inner cell layer (endoderm) THURSDAY 18 TH MARCH 2010 Later gastrula Opening Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 4

Early Animals and the Cambrian Explosion �Animals probably evolved from a colonial protist that lived in the Precambrian seas Digestive cavity Reproductive cells 1 Early colony of protists (aggregate of identical cells) 2 Hollow sphere THURSDAY 18 TH MARCH 2010 (shown in cross section) Somatic cells 3 Beginning of 4 Infolding cell specialization Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 5 Gastrula-like “protoanimal” Figure 17. 4 5

�At the beginning of the Cambrian period, 545 million years ago, animals underwent a rapid diversification THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 6

Animal Phylogeny �To reconstruct the evolutionary history of animal phyla, researchers must depend on clues from comparative anatomy and embryology �Four key evolutionary branch points have been hypothesized �The first branch point is defined by the presence of true tissues THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 7

Sponges Cnidarians Flatworms Roundworms Mollusks Annelids Arthropods Echinoderms Coelom from cell masses Chordates Coelom from digestive tube 4 Pseudocoelom No body cavity Radial symmetry 1 True coelom 3 Body cavities Bilateral 2 symmetry True tissues Multicellularity THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 8

�The second major evolutionary split is based partly on body symmetry (b) Bilateral symmetry (a) Radial symmetry THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 9

�Third, the evolution of body cavities led to more complex animals A body cavity � Is a fluid-filled space separating the digestive tract from the outer body wall � May be a pseudocoelom or a true coelom Body covering Tissue-filled (from ectoderm) region (from mesoderm) (a) No body cavity (e. g. , flatworm) Pseudocoelom Body covering (from ectoderm) Digestive tract (from endoderm) (b) Pseudocoelom (e. g. , roundworm) Coelom Digestive tract (from endoderm) Muscle layer (from mesoderm) Body covering (from ectoderm) Tissue layer lining coelom and suspending Digestive tract (from Mesentery internal organs (from endoderm) mesoderm) (c) True coelom (e. g. , annelid) THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 10

� Fourth, among animals with a true coelom, there are two main evolutionary branches, which differ in embryonic development THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 11

THE KINGDOM ANIMALIA � Divided into invertebrates and vertebrates � Invertebrates are animals without backbones and represent 95% of the animal kingdom THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 12

Invertebrates - Sponges �Phylum Porifera �Includes sessile animals once believed to be plants �Lack true tissues �The body of a sponge resembles a sac perforated with holes �Draws water into a central cavity, where food is collected THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 13

Choanocyte in contact with an amoebocyte Pores Water flow Skeleton fiber Central cavity Choanocyte Amoebocyte THURSDAY 18 TH MARCH 2010 Flagella Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 14

Invertebrates - Cnidarians �Phylum Cnidaria �Is characterized by organisms with radial symmetry and tentacles with stinging cells THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 15

�The basic body plan of a cnidarian �Is a sac with a gastrovascular cavity �Has two variations: the sessile polyp and the floating medusa Mouth/anus Tentacle Gastrovascular cavity Tentacle Mouth/anus THURSDAY 18 TH MARCH 2010 Polyp form Medusa form Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 16

�Examples of polyps are �Hydras, sea anemones, and coral animals THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 17

�The organisms we call jellies are medusas THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 18

�Cnidarians are carnivores that use tentacles armed with cnidocytes, or “stinging cells, ” to capture prey Coiled thread Tentacle “Trigger” Capsule Cnidocyte Discharge of thread Prey THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 19

Invertebrates - Flatworms �Phylum Platyhelminthes �Is represented by the simplest bilateral animals �Includes free-living forms such as planarians Digestive tract (gastrovascular cavity) Nerve cords Mouth Eyespots THURSDAY 18 TH MARCH 2010 Nervous tissue clusters Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 20

�Some flatworms are parasitic �Blood flukes are an example �Tapeworms parasitize many vertebrates, including humans Head Reproductive structures Hooks Sucker THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 21

Invertebrates - Roundworms �Phylum Nematoda �Includes the most diverse and widespread of all animals �Occurs in aquatic and moist terrestrial habitats THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 22

�Roundworms exhibit an important evolutionary adaptation, a digestive tube with two openings, a mouth and an anus �A complete digestive tract can process food and absorb nutrients efficiently THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 23

Invertebrates - Mollusks �Phylum Mollusca �Is represented by soft-bodied animals, but most are protected by a hard shell �Includes snails, slugs, clams, octopuses, and squids, to name a few THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 24

�The body of a mollusk has three main parts: a muscular foot, a visceral mass, and a mantle Visceral mass Coelom Mantle Kidney Reproductive organs Heart Digestive tract Mantle cavity Shell Radula Anus Gill Foot THURSDAY 18 TH MARCH 2010 Mouth Nerve cords Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU Mouth 25

�The three major classes of mollusks are 1. Gastropods, which are protected by a single, spiraled shell THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 26

2. Bivalves, protected by shells divided into two halves THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 27

3. Cephalopods, which may or may not have a shell THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 28

Invertebrates - Annelids �Phylum Annelida �Includes worms with body segmentation Anus Brain Coelom Digestive tract Segment walls Mouth Accessory hearts THURSDAY 18 TH MARCH 2010 Main heart Nerve cord Blood vessels Excretory organ Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 29

�There are three main classes of annelids 1. Earthworms, which eat their way through soil THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 30

2. Polychaetes, which burrow in the sea floor THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 31

3. Leeches, some of which are parasitic THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 32

Invertebrates - Arthropods �Phylum Arthropoda �Contains organisms named for their jointed appendages �Includes crustaceans, arachnids, and insects THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 33

General Characteristics of Arthropods �Arthropods are segmented animals with specialized segments and appendages Cephalothorax Abdomen Thorax Antennae (sensory reception) Head Swimming appendages Pincer (defense) THURSDAY 18 TH MARCH 2010 Walking legs Mouthparts (feeding) Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 34

�The body of an arthropod is completely covered by an exoskeleton THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 35

Arthropod Diversity �There are four main groups of arthropods 1. Arachnids, such as spiders, scorpions, ticks, and mites THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 36

2. Crustaceans, such as crabs, lobsters, crayfish, shrimps, and barnacles THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 37

3. Millipedes and centipedes THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 38

4. Insects, most of which have a three-part body Head Thorax Abdomen Hawk moth Antenna Forewing Eye Mosquito Paper wasp Mouthparts Hindwing Grasshopper Damselfly THURSDAY 18 TH MARCH 2010 Water strider Ground Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU beetle 39

�Many insects undergo metamorphosis in their development (a) Larva (caterpillar) (b) Pupa (c) Pupa (d) Emerging adult THURSDAY 18 TH MARCH 2010 (e) Adult Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 40

Invertebrates - Echinoderms �Phylum Echinodermata �Is named for the spiny surfaces of the organisms �Includes sea stars, sand dollars, sea urchins, and sea cucumbers THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 41

�Echinoderms �Are all marine �Lack body segments �Usually have an endoskeleton �Have a water vascular system that facilitates gas exchange and waste disposal THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 42

THE VERTEBRATE GENEALOGY �Vertebrates �Are represented by mammals, birds, reptiles, amphibians, and fishes �Have unique features, including the cranium and backbone THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 43

Characteristics of Chordates �Phylum Chordata �Includes the subphylum of vertebrates THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 44

�Other subphyla include the lancelets and tunicates, which share four key chordate characteristics THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 45

�The four chordate hallmarks are �A dorsal, hollow nerve cord �A notochord �Pharyngeal slits �A post-anal tail THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 46

Notochord Dorsal, hollow nerve cord Brain Muscle segments Mouth Anus Post-anal tail THURSDAY 18 TH MARCH 2010 Pharyngeal slits Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 47

�An overview of chordate and vertebrate evolution THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 48

THURSDAY 18 TH MARCH 2010 Precambrian Cambrian Paleozoic Triassic Tertiary Cenozoic Lancelets Tunicates Cretaceous Mesozoic Jurassic Agnatha (jawless vertebrates, such as lampreys) Permian Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU Mammalia (mammals) Aves (birds) Reptilia (reptiles) Amphibia (frogs and salamanders) Osteichthyes (bony fishes) Chondrichthyes (sharks and rays) Ordovician Silurian Devonian Carboniferous Eras Periods Chordates Vertebrates Tetrapods Amniotes Feathers Hair Amniotic egg Legs Lungs or lung derivatives Jaws Vertebrae Ancestral chordate 49

Fishes �The first vertebrates probably evolved during the early Cambrian period, about 540 million years ago �These early vertebrates, the agnathans, lacked jaws �Agnathans are represented today by lampreys THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 50

�The two major groups of living fishes are the classes �Chondrichthyes or cartilaginous fishes �Osteichthyes or bony fishes THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 51

�Cartilaginous fishes have a flexible skeleton made of cartilage �Sharks have a lateral line system sensitive to vibrations in the water THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 52

�Bony fishes �Have a skeleton reinforced by hard calcium salts �Have a lateral line system, a keen sense of smell, and excellent eyesight THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 53

Amphibians �Members of the class Amphibia �Exhibit a mixture of aquatic and terrestrial adaptations �Usually need water to reproduce THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 54

�Amphibians �Were the first vertebrates to colonize land �Descended from fishes that had lungs and fins with muscles Lobe-finned fish THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU Early amphibian Figure 17. 34 55

Reptiles �Class Reptilia �Includes snakes, lizards, turtles, crocodiles, and alligators �Can live totally on land THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 56

�Adaptations for living on land include �Scales to prevent dehydration �Lungs for breathing �The amniotic egg THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 57

�Reptiles are ectotherms that obtain their body heat from the environment �Cold blooded �Reptiles diversified extensively during the Mesozoic Era THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 58

�Dinosaurs included the largest animals ever to live on land THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 59

Birds �Class Aves �Evolved during the great reptilian radiation of the Mesozoic era �Evolved the ability to fly THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 60

�Bird anatomy and physiology are modified for flight �Bones are honeycombed, which makes them lighter �Some specific organs are absent, which reduces weight �A warm, constant body temperature is maintained through endothermy THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 61

�A bird’s wings �Illustrate the same principles of aerodynamics as the wings of an airplane Ai rfo il THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 62

Mammals �Class Mammalia �Evolved from reptiles about 225 million years ago �Includes mostly terrestrial organisms �Two features are mammalian hallmarks �Hair �Mammary glands that produce milk and nourish the young THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 63

�There are three major groups of mammals �Monotremes, the egg-laying mammals, constitute the first group THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 64

�The second group of mammals, marsupials, are the so- called pouched mammals � Most mammals are born rather than hatched and are nurtured inside the mother by an organ called a placenta THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 65

�Eutherians are also called placental mammals � Their placentas provide more intimate and long-lasting association between the mother and her developing young than do marsupial placentas THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 66

The Evolution of Primates �Primate evolution �Provides a context for understanding human origins �Primates �Evolved from insect-eating mammals during the late Cretaceous period �Early primates �Were small, arboreal mammals THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 67

�The distinguishing characteristics of primates were shaped by the demands of living in trees �Limber shoulder joints �Eyes in front of the face �Excellent eye-hand coordination �Extensive parental care THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 68

�Apes, the closest relatives to humans THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 69

The Emergence of Humankind �Humans and apes have shared a common ancestry for all but the last 5– 7 million years THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 70

Anthropoids Prosimians Ancestral primate THURSDAY 18 TH MARCH Evolution from the start to the pinnacle DR. KOFI 2010 OWUSU-DAAKU Humans Chimpanzees Orangutans Gibbons Old World monkeys New World monkeys Prosimians (lemurs, lorises, pottos, and tarsiers) Gorillas Apes Monkeys 71

Some Common Misconceptions �Our ancestors were not chimpanzees or any other modern apes �Chimpanzees and humans represent two divergent branches of the anthropoid tree THURSDAY 18 TH MARCH 2010 Evolution from the start to the pinnacle DR. KOFI OWUSU-DAAKU 72