19 Lecture Ppt

Key Innovations Distinguish Invertebrate Groups 19-

19.1 Animals have distinctive characteristics Animals are multicellular eukaryotes Chemoheterotrophs that acquire nutrients from an external source and digest it internally Usually carry on sexual reproduction and begin life only as a fertilized diploid egg Developmental stages to produce specialized tissues within organs with specific functions Muscles and nerves characterize animals Allow animals to perform flexible movements 19-

Figure 19.1 Developmental stages of a frog 19-

19.2 Animals most likely have a protistan ancestor Two hypotheses on origin of animals Multinucleate Hypothesis Animals arose from a ciliated protist in stages The ciliate would have acquired multiple nuclei, and then it would have become multicellular Colonial Flagellate Hypothesis Animals descended from an ancestor that resembled a spherical colony of flagellated cells 19-

Figure 19.2 The colonial flagellate hypothesis 19-

Radial and Bilateral Symmetry 19-

19.3 The traditional evolutionary tree of animals is based on seven key innovations (figure 19.3A) 19-

Animal Body Cavities Figure 19.3B Types of body cavity 19-

APPLYING THE CONCEPTS—HOW SCIENCE PROGRESSES 19.4 Molecular data suggest a new evolutionary tree for animals In traditional tree, protostomes are restricted to three phyla, which have a coelom Arthropods, Annelids, and Molluscs Evolutionary tree based on molecular data suggests many more animal phyla should be designated protostomes because their rRNA sequences are so similar Segmentation doesn’t play a defining role in the evolutionary tree based on molecular data 19-

Figure 19.4A Proposed new evolutionary tree 19-

Figure 19.4B Roundworms and arthropods are molting animals 19-

19.5 Some animal groups are invertebrates and some are vertebrates For convenience, the animal phyla have been divided into Invertebrates - those that do not have an endoskeleton of cartilage and bone Vertebrates - those that do have an endoskeleton Animals evolved in the sea and most animals still live in the water Among the invertebrates only the molluscs, annelids, and arthropods have terrestrial representatives 19-

19.6 Sponges are multicellular invertebrates Only animal without true tissue, organized at cellular level Body of Sponges - phylum Porifera because their bodies are perforated by pores Filter feeder , also called a suspension feeder, because it filters suspended particles from water Endoskeleton Have fibers of spongin, a modified form of collagen Typically have an endoskeleton also with spicules, small, needle-shaped structures with one to six rays Reproduction Reproduce asexually by budding Reproduce sexually as egg and sperm are released into central cavity Zygote develops into a flagellated larva that may swim to a new location 19-

Figure 19.6 Sponge anatomy 19-

19.7 Cnidarians have true tissues Cnidarians (phylum Cnidaria) - an ancient group of invertebrates Most in the sea, but a few freshwater species Radially symmetrical and capture their prey with a ring of tentacles that have specialized stinging cells, cnidocytes Each cnidocyte has a capsule called a nematocyst , containing a long, spirally coiled, hollow thread Two basic body forms Polyp - mouth is directed upward from the substrate Medusa - mouth is directed downward Cnidarians - a sac body plan with only one opening 19-

Figure 19.7A Cnidarian diversity 19-

Figure 19.7B Anatomy of Hydra , a polyp 19-

19.8 Free-living flatworms have bilateral symmetry Flatworms (phylum Platyhelminthes) First phylum with bilateral symmetry Have three germ layers Ectoderm from which body wall develops Endoderm from which digestive cavity develops Mesoderm which contributes to organ formation Have no coelum and are called acoelomates Planarians have several body systems Digestive System - pharynx leads to gastrovascular cavity Excretory System - a series of interconnecting canals Reproductive System - Hermaphrodites (both male and female sex organs) and perform cross-fertilization Nervous System - brain and two lateral nerve cords are joined by cross-branches called transverse nerves 19-

Figure 19.8 Planarian anatomy 19-

19.9 Some flatworms are parasitic Tapeworms Endoparasites (internal parasites) of various vertebrates, including humans Vary in length from a few millimeters to 20 meters Tough body covering resistant to the host’s digestive juices Scolex bears hooks and suckers for attachment to the intestinal wall of the host Flukes Endoparasites of various vertebrates Anterior end of the animal has an oral sucker and at least one other sucker used for attachment to the host Nearly 800,000 persons die each year from an infection called schistosomiasis 19-

Figure 19.9A Tapeworm ( Taenia solium ) anatomy and life cycle 19-

Figure 19.9B Sexual portion of blood fluke ( Schistosoma spp.) life cycle 19-

19.10 Roundworms have a pseudocoelom and a complete digestive tract Roundworms (phylum Nematoda) possess two anatomic features not previously seen body cavity - pseudocoelom and is incompletely lined with mesoderm complete digestive tract - it has both a mouth and an anus Nonsegmented, meaning that they have a smooth outside body wall Ascaris Humans are infected with a roundworm called Ascaris when eggs enter the body via uncooked vegetables Other Roundworm Parasites Trichinosis - serious human infection acquired when humans eat meat that contains encysted larvae Elephantiasis is caused by a roundworm called a filarial worm, which utilizes mosquitoes as a secondary host 19-

Figure 19.10A Ascaris Figure 19.10b Encysted Trichinella larva 19-

Figure 19.10C Elephantiasis 19-

19.11 A coelom gives complex animal groups certain advantages Coelom - body cavity completely lined by mesoderm Two groups Protostomes - Molluscs, annelids, and arthropods Deuterostomes - echinoderms and chordates Two major events can be used to distinguish protostomes from deuterostomes Blastopore - protostomes: mouth appears near blastopore; deuterostomes: anus appears near blastopore Coelom formation - protostomes: splitting produces the coelom; deuterostomes: the coelom arises as a pair of mesodermal pouches from the gut wall Advantages of a Coelom Body movements are freer because outer wall can move independently of the enclosed organs Ample space of a coelom allows complex organs and organ systems to develop 19-

Figure 19.11 Protostomes compared to deuterostomes 19-

19.12 Molluscs have a three-part body plan All molluscs (phylum Mollusca) have a body composed of at least three distinct parts The foot - strong, muscular portion used for locomotion Visceral Mass - soft-bodied portion that contains internal organs The mantle - covering that envelops the visceral mass The mantle may secrete an exoskeleton called a shell Gastropods (meaning stomach-footed) including snails and nudibranchs Animal moves by muscle contractions that pass along its ventrally flattened foot Cephalopods (meaning head-footed) including octopuses, squids, and nautiluses The foot has evolved into tentacles about the head Bivalves (shells have two part) including clams, oysters, scallops, and mussels The clam is a filter feeder and food particles and water enter the mantle cavity by way of a siphon 19-

Figure 19.12A Body plan of a typical mollusc 19-

Figure 19.12B Three groups of molluscs 19-

19.13 Annelids are the segmented worms Annelids (phylum Annelida) are segmented, as can be seen externally by the rings that encircle the body Partitions called septa divide the well-developed, fluid-filled coelom, which is used as a hydrostatic skeleton Excretory system consists of nephridia, tubules that collect waste material and excrete it through an opening in the body wall Oligochaetes Earthworm is an oligochaete because it has few setae, bristles that anchor the worm Polychaetes Most annelids are polychaetes (having many setae per segment) that live in marine environments Leeches Have no setae, but have the same body plan as other annelids Blood suckers that are able to keep blood flowing and prevent clotting 19-

Figure 19.13A Earthworm anatomy 19-

Figure 19.13B Other annelids 19-

19.14 Arthropods have jointed appendages Arthropods (phylum Arthropoda) are extremely diverse More than one million species have been discovered Six characteristics Jointed appendages Exoskeleton Segmentation Well-developed nervous system Variety of respiratory organs Reduced competition through metamorphosis 19-

Figure 19.14A Exoskeleton and jointed appendages of a crayfish, an arthropod 19-

Figure 19.14B Monarch butterfly metamorphosis 19-

19.15 Well-known arthropods other than insects Crustaceans - name derived from their hard, crusty exoskeleton Largely marine arthropods that include crabs, barnacles, shrimps, and crayfish Head usually bears a pair of compound eyes and five pairs of appendages Arachnids include spiders, scorpions, ticks, mites, and harvestmen Spiders have a narrow waist that separates the cephalothorax, with four pairs of legs, from the abdomen 19-

Figure 19.15A Crustacean diversity 19-

Figure 19.15B Centipede and millipede 19-

Figure 19.15C Spider and relatives 19-

19.16 Insects, the largest group of arthropods, are adapted to living on land Insects - so numerous (>one million species) and diverse that the study of this one group is a major specialty in biology called entomology Adapted to a life on land Body is divided into head, thorax, and abdomen Mouthparts adapted to each species’ way of life Wings enhance an insect’s ability to survive way of escaping enemies, finding food, facilitating mating, and dispersing offspring 19-

Figure 19.16 Insect diversity 19-

19.17 Echinoderms are radially symmetrical as adults Echinoderms (phylum Echinodermata) lack chordate features, but are related to because they are deuterostomes Radially, not bilaterally, symmetrical as adults Their larva is a bilaterally symmetrical filter feeder Adult echinoderms do not have a head, brain, or segmentation Their nervous system consists of nerves in a ring around the mouth extending outward radially Locomotion by a water vascular system that pumps water into many tube feet, expanding them No complex respiratory, excretory, or circulatory system Fluids within the coelomic cavity and the water vascular system carry out many of these functions In ecosystems, most feed on organic matter in the sea or substratum Sea stars prey upon crustaceans, molluscs, and other invertebrates 19-

Figure 19.17 Echinoderm structure and diversity 19-

Further Innovations Allowed Vertebrates to Invade the Land Environment 19-

19.18 Four features characterize chordates Dorsal supporting rod (notochord) extends the length of the body Dorsal tubular nerve cord contains a canal filled with fluid Pharyngeal pouches only during embryonic development in most vertebrates A postanal tail extends beyond the anus 19-

Figure 19.18 The four chordate characteristics 19-

19.19 Invertebrate chordates have a notochord as adults A few of the invertebrate chordates never replace the notochord with the vertebrae Tunicates (subphylum Urochordata) live on the ocean floor as filter feeders Larva is bilaterally symmetrical and has the four chordate characteristics Metamorphosis produces the sessile adult Lancelets (subphylum Cephalochordata) marine chordates only a few centimeters long Lancelets retain the four chordate characteristics as adults 19-

Figure 19.19 The invertebrate chordates 19-

19.20 The evolutionary tree of vertebrates is based on five key features Vertebrates Fishes, amphibians, reptiles, birds, and mammals Vertebrae are most obvious feature Vertebral column is flexible because vertebrae are separated by disks, which cushion the vertebrae The soft center of a disk presses on the spinal cord Derived Characters Among Vertebrates Jaws, Lungs, Jointed Limbs, and Amniotic Eggs 19-

Figure 19.20 Evolutionary tree of the chordates 19-

19.21 Jaws and lungs evolved among the fishes Jawless Fishes (Class Agnatha) Cylindrical and up to a meter long Smooth, scaleless skin, no jaws or paired fins Cartilaginous Fishes (Class Chondrichthyes) includes sharks, the rays, and the skates Skeletons of cartilage, instead of bone Shark senses Able to sense electric currents in water Lateral line system senses pressure waves caused by fish Keen sense of smell Bony Fishes (Class Osteichthyes) most numerous and diverse of all vertebrates Ray-finned fishes - use their fins to balance and propel body Have a swim bladder, which usually serves as a buoyancy organ Bony scales that protect body but do not prevent water loss 19-

Figure 19.21A Evolution of jaws 19-

Figure 19.21B Diversity of fishes 19-

Figure 19.21C This transitional form links the lobes of the lobe-finned fishes to the limbs of ancestral amphibians 19-

19.22 Amphibians are tetrapods that can move on land Amphibians (class Amphibia) means living on both land and in the water, represented by frogs, toads, newts, and salamanders Characteristics Adults have small lungs - air enters the mouth by way of nostrils Respiration is supplemented by gas exchange through the smooth, moist, skin Most members lead an amphibious life Larval stage lives in water, and adult stage is on land 19-

Figure 19.22 Frogs and salamanders are well-known amphibians 19-

19.23 Reptiles have an amniotic egg and can reproduce on land Reptiles (class Reptilia) diversified and most abundant between 245 and 66 MYA The reptiles living today are mainly alligators, crocodiles, turtles, snakes, lizards, and tuataras Body is covered with hard, keratinized scales, which protect animal from desiccation and from predators Fertilization is internal, and the female lays leathery, flexible, shelled eggs Amniotic egg made development on land possible and eliminated the need for a swimming larval stage Fishes, amphibians, and reptiles are ectotherms Body temperature matches the temperature of their environment 19-

Figure 19.23 Reptilian diversity 19-

19.24 Birds have feathers and are endotherms Birds (class Aves) are characterized by the presence of feathers Lay a hard-shelled amniotic egg Data suggests birds are related to bipedal dinosaurs and should be classified as such Birds are adapted to fly Forelimbs are modified as wings Hollow, light bones Horny beak has replaced jaws with teeth Birds are endotherms and generate internal heat May be associated with efficient nervous, respiratory, and circulatory systems Seasonal migration of many species over very long distances 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 19-

Figure 19.24B Types of bird beaks 19-

19.25 Mammals have hair and mammary glands Mammals (class Mammalia) evolved during Mesozoic from reptiles called therapsids Two chief characteristics Hair: Mammals are endotherms, and hair aids temperature control Milk-producing mammary glands: enable females to feed (nurse) their young without leaving them to find food 19-

Monotremes and Marsupials 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 Also lay hard-shelled amniotic eggs Marsupials - begin their development inside the female’s body, but they are born in a very immature condition Newborns crawl up into a pouch on their mother’s abdomen 19-

Figure 19.25A Monotremes and marsupials 19-

Placental Mammals Placental mammals - extraembryonic membranes of the reptilian egg are modified for internal development within the uterus of the female Chorion contributes to the fetal portion of the placenta, while a part of the uterine wall contributes to the maternal portion Nutrients, oxygen, and waste exchanged between fetal and maternal blood Distinguished by their mode of locomotion Bats have membranous wings supported by digits Horses have long, hoofed legs; and whales have paddlelike forelimbs Distinguished by the way of obtaining food Mice have continuously growing incisors Horses have large, grinding molars Dogs have long canine teeth 19-

Figure 19.25B Placental mammals 19-

APPLYING THE CONCEPTS—HOW BIOLOGY IMPACTS OUR LIVES 19.26 Many vertebrates provide medical treatments for humans Hundreds of pharmaceutical products come from vertebrates Animals that produce poisons and toxins give us medicines that benefit us Some produce proteins similar to human proteins to be used in medical treatment Powerful applications of genetic engineering found in development of drugs and therapies for human diseases Xenotransplantation, transplantation of vertebrate tissues and organs into human beings Use of transgenic vertebrates for medical purposes does raise health and ethical concerns 19-

Figure 19.26 Vertebrates used for medical purposes 19-

Connecting the Concepts: Chapter 19 As terrestrial mammals, humans might assume that terrestrial species are more successful than aquatic ones If not for the myriad types of terrestrial insects, there would be more aquatic species than terrestrial ones on Earth Adaptative radiation of mammals has taken place on land, and this might seem impressive to some Actually, the number of mammalian species (4,800) is small compared to the molluscs (110,000 species) Size and complexity of the brain is also sometimes cited as a criterion by which vertebrates are more successful than other living things This characteristic has been linked to others that make an animal prone to extinction 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 19-

19 Lecture Ppt

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19 Lecture Ppt