Chapter 26: Animals – The Invertebrates
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Chapter 26: Animals – The Invertebrates General Characteristics of Animals Multicelled In most cases cells form tissues that become arranged as organs and organ systems Body cells of nearly all species have diploid chromosome number Heterotrophs Require oxygen for aerobic respiration Reproduce sexually and asexually Most animals are motile during at least part of their life cycle Stages of embryonic development Embryonic cells give rise to primary tissue layers ectoderm, endoderm, and mesoderm Diversity in Body Plans Vertebrates – animals with backbone Invertebrates – no backbone Animals are radial or bilateral Radial Symmetry – body parts arranged regularly around a central axis Bilateral Symmetry – right and left halves are mirror images of each other. Gut – a tubular or saclike region in the body in which food is digested then absorbed. Saclike guts - have one opening (mouth) for taking in food and expelling wastes Tubelike guts - have 2 openings (mouth and anus) a complete digestive system Body cavity – between gut and body wall Coelom – unique tissue lining called peritoneum This lining also encloses organs and helps hold them in place (diaphragm) Some invertebrates don’t have a body cavity and tissues fill this region Pseudocoel (false coelom) – a body cavity with no peritoneum Segmented animals have a repeating series of body units They may or may not be similar to one another Puzzles About Origins Animals originated between 1.2 billion and 670 million years ago Probably evolved from protistans Sponges – Success in Simplicity Sponges (Porifera) – animals with no symmetry tissues or organs Most live in marine Body of a sponge is not symmetrical Made of spongin - a protein and the sharp glasslike spicules are made of calcium carbonate or silica Water flows into the sponge body through microscopic pores and chambers Collar cells – line inner body and beat flagella to move water through. Food particles get trapped in microvilli Reproduce sexually Release sperm into water Some reproduce asexually Fragmentation – small fragments break away from the parent Cnidarians – Tissues Emerge Cnidarians – tentacled, radial animals Most live in seas Nematocysts – capsules that house dischargeable tubular, threads Some deliver toxins Some deliver a sticky ooze to entangle prey Body Plans Medusae Float Look like bells or upside-down saucers Mouth centered under bell May have extensions to help with feeding and capture prey Polyps Tubelike body with a tentacle-fringed mouth at one end Other end attached to substrate Epithelium – a tissue having a free surface that faces the environment Nerve cells – in epithelium and these cells receive signals to detect changes in surroundings Contractile cells – carry out response by shortening Hydrostatic Skeleton – any fluid-filled cavity or cell mass against which contractile cells can act. Various Stages in Cnidarian Life Cycles Some species, Obelia, Physalia, etc, include both polyp and medusa body forms Medusa is the sexual stage Has gonads – primary reproductive organs Releases gametes by rupturing (lysis) Planulas – a zygote that is a swimming or creeping larva Forms into a polyp Comb Jellies Radial symmetry Weak – swimming predators in plankton communities Eight rows of comblike structures made of thick fused cilia Do not produce nematocysts Acoelomate Animals – And The Simplest Organ Systems When we move beyond cnidarians in our survey, we find animals that range from flatworms to humans. All of these animals have simple or complex organs Organ – an association of one or more kinds of tissues arranged in particular proportions and patterns Organ System – two or more organs that are interacting efficiently in the performance of some task Flatworms (Platyhelminthes) Turbellarians, flukes, tapeworms Bilateral Simple organ systems in a flattened body Saclike gut Most are hermaphrodites – have female and male gonads Has a penis so two flatworms can reproduce sexually by exchanging sperm Tubellarians Live in seas, planarians live in freshwater Eat tiny animals or suck tissues from dead or wounded ones A planarian can divide in half and regenerate missing parts Reproduce asexually by transverse fission Flukes Parasitic worms Life cycle has sexual and asexual phases One to four hosts Tapeworms Parasitize intestines of vertebrates Scolex – attach to intestine wall and has suckers, hooks or both Ribbon Worms Bilateral Soft-bodied elongated predators Swallow or suck tissue fluids from small worms mollusks and crustaceans Shallow marine habitats Roundworms (Nematoda) Pseudocoelomate worms Thrive in nearly all environments Most abundant animals alive 20,000 known species bilateral cuticles – a tough, flexible body covering simplest animal with a complete digestive system parasitic species can severely damage their hosts, humans, cats, dogs, cows, sheep, soybeans help decompose and recycle nutrients Rotifers (Rotifera) bilateral false coelom most live in freshwater eat bacteria and microscopic algae have a pharynx, esophagus, digestive glands, stomach, intestine, anus a crown of cilia at the head end two “toes” Two Major Divergences Protostomes Spiral cleavage First infolding forms mouth Archenteron – is an internal cavity that the tissues split at sides to form coelum Ex. Mollusks, annelids, arthropods Deuterostome Radial cleavage First infolding forms anus Archenteron – an internal cavity that the outpouching forms coelum Ex. Echinoderms, chordates A Sampling of Molluscan Diversity Have fleshy soft bodies Bilateral Have a small coelom Most have a shell Mantle – Most mollusks have a fleshy foot Chitons – slow moving with dorsal shell divided into eight plates Bivalves – two shells, clams, oysters, mussels Cephalopods – squids, octopus Octopuses have a highly developed nervous system with a large complex brain Twisting and Detwisting of Soft Bodies Soft snail body Its anus dumps wastes near the mouth As the gastropod embryo develops a cavity between its mantle and shell twists Torsion – twisting of internal organs Hiding Out One Way or Another A shell is an advantage against predators Dig into sand to hide On the Cephalopod Need For Speed Cephalopods lost their thick external shell and became streamlined and active Nerves connect their brain to muscles that respond swiftly to food or danger Jet Propulsion – force a jet of water from mantle cavity and a funnel-shaped siphon Annelids – Segments Galore Bilateral and segmented Phylum name means “ringed forms” Setae – bristles on each side of segments Provide traction to move through dirt Earthworms (oligochaetes) have few setae Leeches have no setae Advantages of Segmentation Individual parts can undergo modification and become highly adapted for specific tasks Annelid Adaptations – A Case Study Earthworms Partitions divide their body into a series of coelomic chambers Gut extends through all chambers Has a cuticle but it is permeable to water as well as to gases (have to live in moist habitats) Scavengers Aerate soil and lift nutrients to surface Arthropod Trilobites (extinct) Chelicerates – spiders Crustaceans – barnacles and crabs Uniramians – centipedes, millipedes, insects Arthropod means jointed foot Adaptations of Insects and Other Arthropods Hardened exoskeleton Cuticle of chitin, proteins, surface waxes and calcium carbonate Exoskeleton – protective external skeleton Defense against predation Waxy surface restricts water evaporation Molting – periodic shedding of body structures that are too small, worn out or both Jointed Appendages Cuticle is thinner at joints for motility Led to appendages as diverse as wings, antennae and legs Fused and Modified Segments Many fused together segments are modified to perform more specialized functions Different segments fused to form 3 regions – head, thorax and abdomen Respiratory Structures Aquatic arthropods depend on gills Insect tracheas begin as pores on the body surface and branch into tubes that deliver oxygen directly to tissues Specialized Sensory Structures Many species have a wide angle of vision and can process visual information from many directions Division of Labor Many species divide the job of surviving and reproducing among different stages of development Juvenile – a miniaturized version of the adult Metamorphosis – body form changes from embryo to adult Adult stage specializes in dispersal and reproduction A Look At Spiders and Their Kin Chelicerates originated in shallow seas Marine species – mites, sea spiders, horseshoe crab Land species – spiders, scorpions, ticks, chigger mites (arachnids) Spiders and scorpions are predators Bites of ticks can transmit disease Mites are free-living scavengers Arachnids have segments fused into forebody and hindbody Forebody – 4 pairs of legs, 1 pair pedipalps (sensory), 1 pair of chelicerae that inflict wounds and discharge venom Hindbody – spin silk threads Open circulatory system – a heart that pumps blood into body tissues A Look At The Crustaceans Shrimp, lobsters, crabs, barnacles, pillbugs Have an exoskeleton Majority live in marine habitats Many have 16 – 20 segments 2 pairs of antennae 1 pair of jawlike appendages (mandibles) molt repeatedly How Many Legs millipedes have about 100 legs each segment has 2 pairs of legs scavenge decaying plants centipedes have 15-177 pairs of legs each segment has 1 pair of legs fast-moving aggressive predators outfitted with fangs and venom glands prey on insects earthworms snails A Look At Insect Diversity have a head, thorax, and abdomen 3 pairs of legs 2 pairs of wings usually most successful insects are… small in size great reproductive capacity are winged life cycle proceeds through stages that allows for exploitation of different resources nymphs – small versions of the adult larvae – maggots specialized for eating pupa (cocoon) – an enclosure metamorphosis – a dramatic change in body form our most aggressive competitors, they destroy crops, wool, paper, etc. The Puzzling Echinoderms feather star, sea urchin, sea cucumber, brittle stars, sea biscuits, sand dollars coelomate deuterostomes usually have a complete digestive tract adults are radial symmetry body wall bears a number of spines, plates made of calcium carbonate have no brain water-vascular system – system of canals that delivers water throughout the body. By redistributing water they can move Chapter 26: Animals – The Invertebrates General Characteristics of Animals In most cases cells form tissues that become arranged as organs and organ systems Body cells of nearly all species have __________ chromosome number Require oxygen for aerobic respiration Most animals are motile during at least part of their life cycle Embryonic cells give rise to primary tissue layers ectoderm, endoderm, and mesoderm Diversity in Body Plans Vertebrates – Invertebrates – Animals are radial or bilateral Radial Symmetry – Bilateral Symmetry – Gut – a tubular or saclike region in the body in which food is digested then absorbed. Saclike guts – Tubelike guts – Body cavity – Coelom – This lining also encloses organs and helps hold them in place (diaphragm) Some invertebrates don’t have a body cavity and tissues fill this region Pseudocoel (false coelom) – Segmented animals have a repeating series of body units They may or may not be similar to one another Puzzles About Origins Animals originated between 1.2 billion and 670 million years ago Probably evolved from ____________ Sponges – Success in Simplicity Sponges (Porifera) – Body of a sponge is not ______________ Made of spongin – Water flows into the sponge body through microscopic pores and chambers Collar cells – Reproduce sexually Some reproduce asexually Fragmentation – Cnidarians – Tissues Emerge Cnidarians – Most live in ________ Nematocysts – Some deliver __________ Some deliver a sticky ooze to entangle prey Body Plans Medusae Look like bells or upside-down saucers May have extensions to help with feeding and capture prey Polyps Other end attached to substrate Epithelium – Nerve cells – Contractile cells – Hydrostatic Skeleton – Various Stages in Cnidarian Life Cycles Some species, Obelia, Physalia, etc, include both polyp and medusa body forms Medusa is the sexual stage Has gonads – Releases gametes by rupturing (lysis) Planulas – Forms into a polyp Comb Jellies __________ symmetry Weak – Eight rows of comblike structures made of thick fused cilia Do not produce _______________ Acoelomate Animals – And The Simplest Organ Systems When we move beyond cnidarians in our survey, we find animals that range from flatworms to humans. All of these animals have simple or complex organs Organ – Organ System – Flatworms (Platyhelminthes) Turbellarians, flukes, tapeworms Simple organ systems in a flattened body Most are hermaphrodites – Has a penis so two flatworms can reproduce sexually by exchanging sperm Tubellarians Live in _______, planarians live in _______________ Eat tiny animals or suck tissues from dead or wounded ones A planarian can divide in half and _______________ missing parts Reproduce asexually by transverse fission Flukes Life cycle has sexual and asexual phases Tapeworms Scolex – Ribbon Worms Soft-bodied elongated predators Swallow or suck tissue fluids from small worms mollusks and crustaceans Roundworms (Nematoda) Thrive in nearly all environments Most abundant animals alive ___________ known species Cuticles – Simplest animal with a ____________ digestive system Parasitic species can severely damage their hosts, humans, cats, dogs, cows, sheep, soybeans Rotifers (Rotifera) Most live in ____________ Eat bacteria and microscopic algae Have a pharynx, esophagus, digestive glands, stomach, intestine, anus A crown of ________ at the head end Two Major Divergences Protostomes First infolding forms __________ Archenteron – Ex. Deuterostome First infolding forms __________ Archenteron – an internal cavity that the outpouching forms coelum Ex. A Sampling of Molluscan Diversity Have fleshy soft bodies Have a small ____________ Mantle – Most mollusks have a __________ __________ Chitons – Bivalves – Cephalopods – Octopuses have a highly developed nervous system with a large complex brain Twisting and Detwisting of Soft Bodies Soft snail body As the gastropod embryo develops a cavity between its mantle and shell twists Torsion – Hiding Out One Way or Another A shell is an advantage against predators Dig into sand to hide On the Cephalopod Need For Speed Cephalopods lost their thick external shell and became streamlined and active Nerves connect their brain to muscles that respond swiftly to food or danger Jet Propulsion – Annelids – Segments Galore Phylum name means ___________ ___________ Setae – Provide traction to move through dirt _______________ (oligochaetes) have few setae _______________ have no setae Advantages of Segmentation Individual parts can undergo modification and become highly adapted for specific tasks Annelid Adaptations – A Case Study Earthworms Partitions divide their body into a series of _______________ chambers Gut extends through all chambers Has a cuticle but it is permeable to water as well as to gases (have to live in moist habitats) Arthropod Trilobites (extinct) Chelicerates – Crustaceans – Uniramians – Arthropod means ____________ ____________ Adaptations of Insects and Other Arthropods Hardened exoskeleton Cuticle of __________, proteins, surface waxes and calcium carbonate Exoskeleton – Defense against predation Waxy surface restricts water evaporation Molting – Jointed Appendages Cuticle is thinner at joints for motility Led to appendages as diverse as ________, ____________ and ____________ Fused and Modified Segments Many fused together segments are modified to perform more specialized functions Different segments fused to form 3 regions – head, thorax and abdomen Respiratory Structures Aquatic arthropods depend on ________ Insect tracheas begin as pores on the body surface and branch into tubes that deliver oxygen directly to tissues Specialized Sensory Structures Many species have a wide angle of __________ and can process visual information from many directions Division of Labor Many species divide the job of surviving and reproducing among different stages of development Juvenile – Metamorphosis – Adult stage specializes in dispersal and reproduction A Look At Spiders and Their Kin Chelicerates originated in shallow seas Marine species – Land species – Spiders and scorpions are _______________ Bites of ticks can transmit disease Mites are free-living scavengers Arachnids have segments fused into ____________ and ____________ Forebody – 4 pairs of legs, 1 pair pedipalps (sensory), 1 pair of chelicerae that inflict wounds and discharge venom Hindbody – Open circulatory system – A Look At The Crustaceans Have an _______________ Majority live in marine habitats Many have 16 – 20 segments 2 pairs of _______________ 1 pair of jawlike appendages (mandibles) How Many Legs Millipedes Each segment has _____ pairs of legs Scavenge decaying plants Centipedes Each segment has _____ pair of legs Fast-moving aggressive predators outfitted with fangs and venom glands Prey on insects earthworms snails A Look At Insect Diversity Have a head, thorax, and abdomen _____ pairs of legs _____ pairs of wings usually Most successful insects are… Life cycle proceeds through stages that allows for exploitation of different resources Nymphs – Larvae – Pupa (cocoon) – Metamorphosis – a dramatic change in body form Our most aggressive competitors, they destroy crops, wool, paper, etc. The Puzzling Echinoderms Feather star, sea urchin, sea cucumber, brittle stars, sea biscuits, sand dollars Usually have a _______________ digestive tract Adults are ____________ symmetry Body wall bears a number of spines, plates made of calcium carbonate Water-vascular system –
