Lower Invertebrates Powerpoint PDF

THE ANIMAL KINGDOM Lower Invertebrates PHYLUM PORIFERA – THE SPONGES 4 5  PHYLUM PORIFERA – THE SPONGES  About 9000 species, are marine, most are warm water, grow on rocks (are sessile).  Sponges come in many shapes and are asymmetrical; most are vase-shaped.  Thes...

THE ANIMAL KINGDOM Lower Invertebrates PHYLUM PORIFERA – THE SPONGES 4 5  PHYLUM PORIFERA – THE SPONGES  About 9000 species, are marine, most are warm water, grow on rocks (are sessile).  Sponges come in many shapes and are asymmetrical; most are vase-shaped.  These are the simplest multicellular animals; sponges do not have true tissue.  The sponge body is composed of 3 layers. 6  Sponges  The outer layer is the epidermis, and is pierced by numerous pores, which allow water, dissolved oxygen, and microscopic food particles to enter the sponge.  The pores are surrounded by porocytes, that regulate the size of the pores.  The inner layer which lines the central cavity is made up of specialized cells called collar cells or choanocytes.  Each collar cell has a flagellum.  As the flagella beat, water is drawn into the pores of the sponge, and out through the opening at the top called the osculum.  As water passes through the sponge, food particles are captured and digested by the collar cells. 7  Sponges  The middle layer, or mesohyl, is jellylike and contains amoebocytes.  Amoebocytes are important because they produce spicules.  Spicules provide support and give shape to the sponge.  Sponges are classified according to their type of spicule.  Some are composed of calcium carbonate (chalk sponges), some of silicon (glass sponges), & some of a protein called spongin (fibrous sponges).  In the past, sponges with skeletons of spongin were used as household sponges. 8  Sponges  Sponges are capable of regeneration, the replacement of lost parts.  Sponges reproduce both sexually and asexually.  Asexual reproduction occurs by budding, or fragmentation: buds break off and form new individuals.  Sexually, while each sponge has both sperm and eggs (hermaphroditic), they do not self fertilize.  Sperm released by a sponge are drawn into the pores of other sponges and fertilize the eggs which are in the jelly-like mesohyl.  The zygote becomes a ciliated larvae which leaves the mother and attaches itself to a solid object on the ocean floor. 9 10  Copyright © The McGraw-Hill Companies, Inc. 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Osculum Fig. 32.05(TE Amoebocyte Art) Pore Epithelial wall Water Pore Spicule Spongin Choanocyte Flagellum Collar Choanocyte Nucleus 11 12 PHYLUM CNIDARIA - THE CNIDARIANS 14  PHYLUM CNIDARIA – THE CNIDARIANS  This phylum was formerly called Coelenterata.  They are more complex than the sponges, they have the tissue level of organization.  About 10,000 species; this phylum includes hydras, jellyfish, corals, and sea anemones.  Most are salt water, with the exception of the hydras. 15  CNIDARIANS  There are two layers of cells, the outer epidermis, and the inner gastrodermis, which are separated by a jellylike material called mesoglea.  Cnidarians have specialized stinging cells called cnidocytes, which contain nematocysts, a coiled, hollow thread that is discharged when the stinging cell is stimulated.  Some nematocysts contain poison, which is injected into the prey and paralyzes it.  Once the prey is captured, the tentacles stuff it into the mouth. 16  CNIDARIANS  Cnidarians are radially symmetrical - they are a hollow sac with a single opening surrounded by tentacles.  There are 2 general body forms:  The polyp form is sessile and has a cylindrical body with a mouth and tentacles at the upper free end.  The other body form is the medusa, which is shaped like an upside-down bowl, with the mouth and tentacles facing downward, and are usually free-swimming.  Cnidarians reproduce either asexually or sexually.  They have a free-swimming ciliated larvae called a planula. 17  Copyright © The McGraw-Hill Companies, Inc. 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Fig. 32.06(TE Art) Gastrovascular cavity Epidermis Mesoglea Medusa Gastrodermis Tentacles Mouth Gastrovascular Polyp cavity 18 19 20  CLASS HYDROZOA – The Hydroids  Hydras - are freshwater and are found attached to rocks and plants.  They are a one-quarter inch long polyp.  They are capable of movement by somersaulting.  They have a nervous system called a nerve net, the nerve cells form an irregular network throughout the mesoglea.  The network connects special receptor cells with muscle cells; there is no brain.  When a tentacle comes in contact with a food item, impulses travel through the entire hydra, & in response the animal stretches toward the food, and the tentacles work to capture the food and stuff it into the mouth.  The food then moves into the gastrovascular cavity where enzymes are secreted that digest the food.  Wastes are carried out through the mouth by water currents. 21  Hydroids  Portuguese Man-of-War - is a colony of polyps that is suspended from a large medusa.  It has a bluish gas-filled bladder, and its nematocysts trail along, which can kill humans. 22 23  CLASS SCYPHOZOA - The Jellyfish  Thereare many forms of jellyfish, both harmless & harmful. 24 25 26 27  CLASS ANTHOZOA – Sea Anemones & Corals  Sea anemones are polyps that look like brightly colored flowers.  Some are mutualistic on hermit crabs.  Corals are also polyps, but grow in colonies.  They are surrounded by a hard calcium- containing skeleton (calcium carbonate, CaCO3).  In warm, shallow parts of the ocean, islands and coral reefs are formed by massive colonies of corals (10mm - 200mm/year). 28 29  PHYLUM CTENOPHORA – THE COMB JELLIES  About 100 species, are marine, transparent, are composed of 8 comblike plates made of cilia.  Many are bioluminescent & glow at night when a boat or swimmer passes by.  "Largest animal to use cilia for locomotion." 30 31 32 33  PHYLUM PLATYHELMINTHES - THE FLATWORMS 35  PHYLUM PLATYHELMINTHES - THE FLATWORMS  About 20,000 species, have flattened bodies, the simplest animals with a head and tail, have bilateral symmetry, have 3 germ layers, and are nonsegmented.  They are acoelomate (do not have a coelom), and have a sac plan with only one opening, and have organs.  They have the simplest of all excretory systems - have flame cells, which excrete wastes.  There are 3 classes of flatworms: one is free- living and 2 are parasites. 36  CLASS TURBELLARIA  These are free-living flatworms, are best known by the Planaria.  Planaria are found in freshwater streams and pond bottoms.  They are gray or black, about ½ inch long.  They have a triangular head that contains a pair of crossed eyes called eyespots, which are sensitive to light, and two auricles.  They glide along using microscopic cilia (a piece of liver in the water will be covered with them in a few hours).  They have a digestive system, but no skeletal, respiratory, or circulatory systems (oxygen & CO2 diffuse). 37  CLASS TURBELLARIA  Planarians are hermaphroditic (they have both testes & ovaries).  They do not self-fertilize, but rather exchange sperm with each other.  Eggs are laid which hatch into tiny worms.  They can reproduce asexually by fission & are capable of regeneration (cut off head & the tail will grown a new head).  Planarians have been used in memory experiments. In these experiments, planarians were trained to swim mazes & then were cut up & fed to untrained planaria. When the cannibals were taught the same task, they learned faster than the first set. 38 39  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 32.13(TE Art) Intestinal diverticulum Intestine Eyespot Epidermis Circular muscles Testis Intestine Longitudinal muscles Parenchymal Protruding Nerve Sperm muscle pharynx cord duct Oviduct Opening to pharynx 40 CLASS TREMATODA - PARASITIC FLUKES  Flukes are covered with a protective cuticle, which protects them from the digestive enzymes of their host.  They attach by means of suckers.  Flukes have a reduced digestive system because they get food that has already been broken down by their host.  Flukes can be blood flukes, liver flukes, lung flukes, etc.  Most are between 1mm & 8 centimeters.  Chinese liver flukes enter humans when uncooked fish is eaten. 41  PARASITIC FLUKES  Schistosomiasis - is the disease from the Schistosoma blood fluke.  After the larvae enter a human (primary host) by boring through the skin, they mature in the blood and reproduce (large numbers of eggs & larvae cause bleeding ulcers in the intestines & bladder).  The eggs are passed out of the body with digestive wastes.  In the water, their eggs hatch into a larva called a miracidium.  The larvae then enter snails (secondary host), undergo further development, & become cercaria, which leave the snails, and infect streams, rice paddies, etc., & then bore into human skin.  They cause loss of blood, diarrhea, and much pain. 42 43 44  Copyright © The McGraw-Hill Companies, Inc. 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Raw, infected fish is Fig. 32.15(TE Art) consumed by humans or other mammals Liver Metacercarial cysts in fish Bile duct Adult fluke muscle Egg containing miracidium Miracidium Cercaria hatches after being eaten by snail Redia Sporocyst 45 46 47  CLASS CESTODA – PARASITIC TAPEWORMS  Are long, 4-20+ meters in length, and are ribbon-like.  They live in human intestines where they are attached by means of a scolex - which has hooks and suckers.  Their body consists of segments called proglottids. 48  PARASITIC TAPEWORMS  Beef tapeworm - if cattle or pigs eat food that is contaminated with eggs (eggs came from human feces), the eggs develop into larvae in the cow's or pig's intestine, and eventually burrow into the muscle where they form a dormant capsule.  Human become infected when they eat undercooked beef or pork.  The capsule releases the larvae and they attach to the intestine.  They can grow in there for 10 years and to 50 feet.  Proglottids contain sperm and eggs and occasionally a piece containing fertilized eggs breaks off and passes out of the host.  They cause illness by absorbing needed nutrients through their body walls, and may actually obstruct the passage of food through the intestine. 49  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Solid worms are bilaterally symmetrical Tapeworms are parasites that attach Fig. 32.14(TE Art) acoelomates. Their bodies are composed of solid layers of tissues surrounding a central gut. The body of many flatworms is soft and by their heads to the intestinal wall of a host organism. The body of a mature tapeworm may reach 10 flattened, like a piece of tape or ribbon. meters in length—longer than a truck. Hooks Scolex attached to intestinal wall Sucker Each proglottid Scolex segment contains Reproductive Repeated proglottid organs. When segments segments of a worm pass out of Uterus humans in feces, embryos may be Most solid worms have ingested by cattle a highly branched gut or another human, that brings food near transmitting the all tissues for parasite to a new absorption directly host. Embryos of across the body wall. the tapeworms are Tapeworms are a released through a Proglottid special case in that single genital pore Genital they have solid bodies on each proglottid pore that lack a digestive segment. cavity. 50 51 52  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 32.14c(TE Art) Scolex attached to intestinal wall Repeated proglottid segments 53 PHYLUM NEMATODA - THE ROUNDWORMS 55  THE ROUNDWORMS  About 12,000 species, are round instead of flat, tapered at both ends, have a tough cuticle, range in length from 1mm to 1 meter, and are bilaterally symmetrical.  Some forms are parasitic in hosts, most are free-living in the soil and fresh & salt water.  One shovel full of garden soil has more than one million nematodes.  "If the earth would disappear, its general contour would be outlined in nematodes."  They have a tube within a tube body plan, food goes in through a mouth and wastes are passed out through a posterior anus.  They do not have a true skeleton, but rather a hydrostatic skeleton, a fluid-filled interior that supports them. 56  Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig. 32.18(TE Art) Intestine Uterus Anus Ovary Pharynx Mouth The pseudocoel of a nematode Genital pore separates the endoderm-lined gut from Excretory pore the rest of the body. The digestive tract is one-way: food enters the mouth at one end of the worm and leaves Roundworms are through the anus at the other end. bilaterally symmetrical, cylindrical, Intestine unsegmented worms. Muscle Most nematodes are very small, less than a Pseudocoel Nematodes have Excretory excretory ducts that millimeter long— duct hundreds of permit them to thousands may live in Oviduct Uterus conserve water and a handful of fertile soil. live on land. Other Cuticle Ovary roundworms possess Nerve cord excretory cells called flame cells. An adult nematode consists of very few cells. Caenorhabditis Elegans has exactly 959 The nematode's body is covered with a flexible, cells and is the only thick cuticle that is shed as the worm grows. animal whose complete Muscles extend along the length of the body rather cellular anatomy is than encircling it, which allows the worm to flex its known. body to move through the soil. 57  THE ROUNDWORMS  Ascaris - the larvae live in the soil in warm areas, especially in the southern United States.  Should they be eaten (unwashed fruit & vegetables, dirty hands), they break out of their protective covering, burrow through the intestine wall, then move to the organs: liver, heart, and finally the lungs.  In the lungs they molt, swim up to the throat, and are then swallowed, pass back to the intestines, mate, and eggs pass out with feces. 58 59  THE ROUNDWORMS  Hookworms - enter humans in warm climates who walk barefoot, especially in the southern United States.  Hookworm life cycle: larvae bore through feet  circulatory system lungs  coughed up  swallowed  small intestine  suck blood.  Importance of proper sanitation and thorough cooking of food. 60  THE ROUNDWORMS  Trichinella - causes the disease trichinosis, is 1mm in length.  They enter humans as cysts in rare pork.  Once in humans, the larva is released and develop in the intestine.  The adults move through the bloodstream and muscles, their movement in the muscles causes intense pain and muscle damage.  Since humans are not normally eaten, the larvae do not leave.  However should pigs eat infected pig or rat meat, they will become infected. 61 62 63  THE ROUNDWORMS  Pinworms - Enterobius - are a very common parasitic roundworm, especially among children.  Adults lay eggs in the anal region, which causes itching.  Children scratch the area and some eggs get under their fingernails.  Children reinfect themselves when they put their fingers in their mouths. 64 65 66  THE ROUNDWORMS  Elephantiasis - is a disease caused by the Filaria worm.  These worms are carried by a tropical mosquito, which spreads the worm when it bites humans.  The worms then invade lymph tissue, blocking lymph vessels, causing fluid to accumulate.  The affected area of the body becomes abnormally enlarged and the tissues become badly damaged.  Mosquitoes become infected when they bite an infected person. 67 PHYLUM ROTIFERA - THE ROTIFERS  THE ROTIFERS  About 2000 species in this phylum.  Rotifer is Latin for "wheel bearer", because they have a crown of cilia that draws water into the mouth.  They are microscopic, inhabiting freshwater and damp soil.  Their bodies are covered with chitin (polysaccharide of insect shells & in fungi).  When rotifers retract their head, their segments telescope.  They have sexual reproduction.  Also, sometimes rotifers reproduce by parthenogenesis - females produce more females from unfertilized eggs. 69 70 71