Principles Biology I Lab
Principles Biology I Lab BIO 101L
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BIOL 101L Principles ofBiology Fall 2008 Invertebrates s L s we heme 39 39 r L 39 39 39 39 39 quot While these h all L L L 39 39 39 39 L organisms u h 39ethey are L 439 39 L On czhll In A l 39c L s s L r s L y l deltlonally r M r recently ofboLh A h uwenn y W Y based on Lhelr evolutlonary hlstory Flg 1 Today we will focus on G1 Invertebrata a group chat includes 39 l k In m I equot an L L n L L me quotM L ofdiversity and biomass for example The Invertebrata includes about95 onhe known each ghoup ofanimals Porifera Cnidaria menophora Wee mamng m common skew appendages ances39lar Arthropoda bhnd gm 2 W Nematode cell lavevs new segmemallun Annel ida pleaeames melee gm Mollusca Romera 3 eeu We bllalevalsvmmelw Platyhelmmthes Echinodermata eeMemsMes Chordata Meme seem meme The sponges Phylum Porifera belong to a lineage that most closely resembles the rst animals These marine animals possess simple asymmetrical bodies comprised of loosely aggregated cells These animals lack true tissues and organs A second evolutionary lineage includes the cnidarians Phylum Cnidaria Cnidarians are characterized by radial symmetry and the presence of true tissues that are organized into two layers the diploblastic condition Cnidarians also possess stinging cells called cnidocytes The third major animal line contains most of the known phyla of animals Members of this lineage possess three layers of tissue ie they are triploblastic and bilateral symmetry Despite these two synapomorphies this lineage contains a great diversity of body plans Biologists further divide this lineage based on the presence of a body cavity coelom and the development of the digestive tract Some of these animals have bodies with just one outer opening that serves as both a mouth and an anus Others have two openings and the digestive tract forms a tube Those animals with a mouth and an anus referred to as protostomes or deuterstomes depending how the mouth and anus develop In protostomes the rst embryonic opening or blastopore develops into a mouth In deuterostomes the blastopore develops into the anus In this and the following laboratory exercise you will investigate body form and function in representatives of five major phyla Porifera Cindaria Platyhelminthes Annelida and Arthropoda The specific animals that you will study are the sponge hydra atworm earthworm and crayfish You will examine or dissect these organisms and relate their structures to their functions lifestyles and evolutionary history Some structures will appear repeatedly among these organisms while other structures will occur in only one or a few species Thus as you study each animal keep in mind the relationship between form and function the relationship between environment and lifestyle and the evolutionary history of the organism OBJECTIVES 0 Compare and contrast the anatomy of representative animals describing similarities and differences in organs and body form that allow the animal to carry out particular functions 0 Relate the morphology of the animals to function in their environment 0 Discuss how similarities and differences in morphology may indicate phylogenetic relationships 0 Identify characteristics that are indicative of major phylogenetic branching points 0 Know the bold structures listed for each organism as well as the Kingdom and Phylum Use your Photographic Atlas for the Biology Lab phot atlas to identify structures WHAT YOU WILL DO IN LAB To guide your investigation of form function and relationships among ve phyla You will record your ndings for each organism in the appropriate columns of Summary Table 1 near the back of this handout This information will be used to answer questions in the Applying Your Knowledge section Any information from these sections is fair game for next week s quiz and the lab practical If you want to read more material about each phylum look at chapters 31 and 32 of your text Life 12 CHARACTERISTICS YOU WILL EXAMINE IN EACH PHYLUM 1 Symmetry Determine whether the organism is 0 asymmetrical no apparent symmetry 0 radially symmetrical the arrangement of parts around a central axis or 0 bilaterally symmetrical right and left halves are mirror images 2 Tissue organization Investigate whether the cells of the organism are organized into well defined tissue layers and determine the number of distinct layers present 3 Openings into the digestive tract Determine where food enters the body and digestive waste exits Some animals have only one opening to the digestive tract that functions as both a mouth and anus Others have a tubular digestive tract a tube within a tube with two openings an anterior mouth and a posterior anus 4 Circulatory system Determine whether the animal has no respiratog system an Qpen or a closed circulatog system In an open circulatory system the blood ows through coelomic spaces in the tissue as well as in blood vessels In animals with closed circulation the blood ows entirely through vessels 5 Habitat Determine whether the organism is a terrestrial marine freshwater or parasitic Keep this in mind as you address characteristics 710 6 Type of locomotion Determine how the organism moves Does it swim crawl walk on legs burrow in the substrate or l Are specific cellular structures such as cilia used for locomotion 7 Organs for respiration gas exchange Determine how oxygen enters the body and carbon dioxide exits the body Some animals use their as the site of gas exchange Others have specialized organs including the of aquatic organisms and the lungs of terrestrial organisms Insects have a unique respiratory system with structures called spiracles and tracheae 8 Organs for excretion Determine how the animal eliminates nitrogenous waste from the body In many animals these wastes diffuse out of the body through the E In others there are specialized structures such as malphigl1ian tubules lateral excretog canals metanephridia and kidneys 9 Support systems Determine what type of support system the animal possesses An endoskeleton lies inside the epidermis or skin of the animal and an exoskeleton lies outside the body wall Some animals lack true skeletons but may be supported by uid Fluid within and between cells and within body chambers such as a gastrovascular cavity serve as a hydrostatic skeleton 10 Segmentation Determine whether the animal has linear repetition of similar body parts The repetition of similar units or segments is called segmentation Segments can be similar in appearance and function or they can be specialized in structure and function Other animals have no segmentation ll Appendages Determine whether appendages organs or parts attached to a trunk or outer body wall are present Note whether they are present all along the length of the body or are restricted to one area Are they all identical or are they specialized for different functions 12 Type of nervous system Determine the type of nervous system that the animal possesses Is there a distinct brain or nerve cord or is there a diffuse nervous system Is there a nerve cord If so where is this nerve cord located One the dorsal side or the ventral side of the body Are sensory organs present If so which ones Phylum P0 rifera Sponges Sponges are among the simplest of living animals The body of a sponge is a loose aggregation of cells that surrounds a water canal system You will observe the unique body structure of a sponge by first observing a preserved specimen and then a prepared slide of a longitudinal section of the marine sponge 1 Observe the sponges on display at the back of the room and examine their external characteristics with a dissecting microscope Compare your observations with Fig 75 in your photo atlas Note the vaselike shape of some sponges and the large opening at one end of the body This opening is called the osculum In contrast to what you might think the osculum is not a mouth Rather it serves as an outlet for the water that passes through the sponge s body Water enters the central cavity called the spongocoel from channels and pores in the body wall The spongocoel is neither a digestive tube nor a chamber because particles of food are absorbed by cells that line the body wall Note that the body wall consists of numerous folds and channels 2 Examine the prepared slides of the sponge body and examine it with the light microscope Using Fig 74 view the structure of the body wall making note of the manner in which the cells are organized Find the agellated collar cells choanocytes that line the central cavity The collective beating of the agella of these cells generates an inward current through the sponge body and the collar cells trap and digest small food particles from the water Needlelike spicules composed of calcium carbonate surround the osculum and protrude from the surface of the body These structures give support and protection to the sponge and prevent small animals from entering the sponge s internal cavity 3 Examine a slide of spicules under the light microscope Compare to Fig 76 4 Fill in the information about sponges in Table l Phylum Cnidaria HydrasI Jelly shI and Sea Anemones Cnidarians are the simplest animals that possess true tissues These animals have saclike bodies consisting of just two tissue layers The central digestive compartment the coelenteron gastrovascular cavity has a single opening that serves as both the mouth and the anus Fig 79 736 These carnivorous animals use tentacles arranged in a ring around the mouth to capture and ingest prey The tentacles possess a unique feeding cell type called cnidocytes which contain a stinging thread capsule called a J When quot 39 39 the J turns inside out of the cnidocyte with explosive force releasing a long thread that entangles prey Most cnidarians are marine however a few live in freshwater Included among the freshwater species is the microscopic solitary organism Hydra the specimen you will examine today Examination of Hydra 1 Using a dissecting microscope observe the Hydra s structure and compare with Fig 710 11 Note the symmetry of the Hydra body plan 0 Tap the edges of your Petri dish Observe and compare the rate of elongation and the rate of contraction of this organism 0 Find the mouth with its surrounding tentacles Watch to see if a hydra catches any prey In addition to their function in acquiring food the tentacles are used in a type of locomotion that resembles a handspring The hydra can attach its tentacles to the substrate and ip its body completely over reattaching the base to a new position 2 Study the prepared slides of hydra using the light microscope Compare the sections with Fig 71214 Find the bud basal disk gastrodermis and epidermis Observe the tissue organization of the hydra body Can you see two distinct tissue layers What are these layers Although you will not be able to see it hydra do have a simple nervous system The slow movements of Hydra are coordinated by a microscopic nerve net present in the body wall Cnidarians lack a brain and nerve cord 3 Think about how the body of the hydra is supported How might the gastrovascular cavity provide support Complete the characteristics of hydra in Table 1 Examination of sea anemone M em39dz39um senile is a common anemone in the northeastern United States and in northern Europe It inhabits shallow subtidal water and lives attached to rocks 1 Find the tentacles mouth pharynx gastrovacular cavity and pedal disk Fig 736 Phylum Platyhelminthes FlatwormsI FlukesI and Tapeworms Platyhelminths have bilaterally symmetrical bodies that are dorsoventrally attened These socalled flatworms have several evolutionary developments compared to cnidarians Along with the evolution of bilateral symmetry came moderate cephalization and the ability for unidirectional movement Flatworms also are triploblastic a condition that has contributed to the development of true muscle and several other organs that are not present in the radiata There are about 20000 species of atworms grouped into three classes Flatworms are freeliving carnivores found under rocks leaves and debris in freshwater ponds and creeks They move over these surfaces using a combination of muscles in their body wall and cilia on their ventral side 1 Using a dissecting microscope observe a live atworm and compare to Fig 74546Note the mode of locomotion through the water What does it do if you w it with the tip of a probe What does this indicate Shine light from a pen light or ashlight onto the planarian and describe its response Find the head eyespot and gastrovacular cavity Response to Touch Response to Light Examine a whole mount of Planaria using a light microscope and compare it with Fig 746 Examine the body for possible digestive tract openings How many openings to the digestive tract can you see The mouth is at the end of a muscular protrusible pharynx that extends from the middle of the ventral side of the planarian Find the pharynx and mouth The proximal end of the pharynx opens into a branched gastrovascular cavity The blunt end of the animal is the anterior or head region Look for the pair of pigmented eyespots on the dorsal side of the head These sensory organs are sensitive to light intensities and the direction of a light source but cannot form images Lateral to the eyespots are aps called auricles that function for smell Beneath the eyespots are two cerebral ganglia that serve as a simple brain Two ventral nerve cords extend posteriorly from the ganglia running the entire length of the body The two cords are connected by transverse nerves to form a ladder like nervous system 2 Examine the prepared slide of a whole mount and crosssection of Planaria Fig 745 The evolution of three well de ned embryonic tissue layers has enabled atworms to have a variety of tissues and organs including reproductive organs and excretory organs The mesodermallyderived excretory system consists of two lateral excretory canals and ame cells that move uid through the canals Respiratory circulatory and skeletal systems are lacking in the atworm How do you think the body of the worm is supported How and where do you think gas exchange takes place 3 Fill in the characteristics of the atworm in Table 1 Examination of tapeworms 1T aem39a Cestodes or tapeworms are highly specialized internal parasites and with few exceptions the adults inhabit the intestine of a vertebrate such as dogs The tapeworm body consists of an anterior headlike scolex and the trunk or strobila consisting of a linear series of segments or proglottids The scolex attaches the worm to the gut wall of the host 1 Using Fig 75862 nd the scolex suckers and proglottids Where is the mouth Phylum Annelida EarthwormsI TubewormsI and Leeches Annelids are a diverse group of animals that live in marine freshwater and moist terrestrial habitats One group the leeches comprises bloodsucking parasites Annelids range in size from microscopic to several meters in length These animals share a number of features with nematodes e g bilateral symmetry three distinct tissue layers a complete digestive tract but have several new adaptations EARTHWORM DISSECTION pp of your photo atlas 1 Examine the live earthworm Lumbricus terrestris and compare it with Fig 785 Earthworms burrow through rich organic soils As you observe these animals note features that are adaptations to the burrowing terrestrial lifestyle Identify the anterior end of the worm by locating the mouth The mouth is overhung by a eshy dorsal protuberance called the prostomium The anus at the posterior end lacks his protuberance A swollen glandular band the clitellum is located closer to the mouth than to the anus and also can be used to identify the anterior end Note the segmented appearance of the earthworm The posterior segments of the earthworm have four pairs of setae Rub your fingers along the outer surface of the worm to feel the setae What function might the setae have Think of how the earthworm moves 2 Your lab instructor will show you how to anesthetize you earthworm Afterward place your worm on a dissecting tray and pin the head and anus Carefully cut open the body wall moving from the head to the anus As you cut pin back the body wall to expose the intemal organs Examine the dissected earthworm and compare to Fig 78691 Locate the digestive tract and its many specialized regions the pharynx esophagus crop gizzard and intestine Using the dissecting microscope locate the longitudinal and circular muscle layers that line the body cavity What advantage will these two muscle layers provide for locomotion Look for the large blood vessel on the dorsal wall of the digestive tract You may be able to see the ve pairs of enlarged lateral blood vessels hearts around the anterior portion of the digestive tract These lateral vessels connect the dorsal vessel to another large ventral vessel and also pump blood through the circulatory system A pair of small white coiled tubes called metanephridia are located in body cavity of each segment of the worm s body These organs remove wastes from the blood and from uid within the body cavity Look for the small brain just behind the prostomium on the surface of the digestive tract Locate the two nerves that pass from the brain around the pharynx These nerve tracts fuse ventrally and continue posteriorly as a ventral nerve cord with segmented ganglia 3 Using a microscope observe a prepared slide of a crosssection of an earthworm Fig 972 Locate the thin cuticle lying outside the epidermis Speculate about its function in a terrestrial habitat Locate the ventral nerve cord usually lying embedded in muscle 4 Fill in the characteristics of the earthworm in Table l Phylum Arthropoda Insects Crustaceans Spiders Ticks and Mites Arthropods are segmented coelomates with jointed appendages and a rigid exoskeleton comprised of chitin Arthropods are the largest group of invertebrates as well as the most diverse group of organisms on Earth with over 1 million described species 2 out of every 3 described species on the planet is an arthropod Arthropods are found in almost every type of environment They show a greater degree of complexity than most other invertebrates including highly developed sensory and nervous systems a hard chitinous exoskeleton and specialization of groups of body segments and their associated appendages into multiple functions This process is known as tagmatz39zatz39on In addition arthropods are the only invertebrates to have evolved ight which is one of the adaptations that has allowed the insects to become the most speciose group of animals Arthropods also show some of most extensive cephalization of all the invertebrates The arthropods share many features of their annelid ancestors including segmentation As you will see arthropods have expanded on the segmented body plan evolving many specialized appendages What characteristic separates this phylum form the segmented worms such as the earthworm CRAYFISH DISSECTION pp 166168 of your photo atlas Examine the body plan of the crayfish including symmetry segmentation and arrangement of appendages As for the grasshopper the body of the cray sh can be divided into three main regions the head the thorax which is fused with the head cephalothorax and the abdomen The head is distinguishable by its two pairs of antennae a pair of eyes and the hard mandibles that are used for eating Four long pairs of walking legs are present on the thorax The abdomen is equipped with 5 pairs of small swimmerets and ends in a long jointed tail or uropod 1 Note the tough outer cuticle of the crayfish It is constructed from protein and the polysaccharide chitin Locate the large exoskeletal plate or carapace that covers the thorax What is the function of the tough outer cuticle of these organisms 2 Using a pair of scissors on a preserved specimen cut away a portion of the carapace on the left side of the animal Locate the feathery gills that lie just beneath the carapace What is the function of these structures in the cray sh 3 Again using your scissors remove the dorsal portion of the carapace to expose other organs of the head and thorax Starting at the posterior lateral edge of the carapace make two lateral cuts extending along each side of the thorax and forward over the head The cuts should meet just behind the eyes creating a dorsal ap in the carapace Carefully lift the ap by inserting a needle under it and separating the underlying tissues as you lift 4 Locate the heart It is a small angular structure located just under the carapace near the posterior portion of the thorax If you do not see it it may have been removed with the carapace Thin threadlike arteries that distribute blood around the body lead out of the heart No veins are present Instead blood collects in sinuses around the heart Small holes ostia in the heart open to allow the blood to seep back into the heart Try to locate these holes What is the name of this kind of circulation 5 Locate the large saclike stomach in the head region If it is not immediately obvious it may be hidden by the large creamy colored digestive gland that lls much of the body Leading posteriorly from the stomach is the intestine Follow the path of the intestine to the anus by making a longitudinal cut through the exoskeleton on each side of the dorsal midline of the abdomen Lift and remove the exoskeleton to View the intestine 6 Turning your attention back to the anterior region of the digestive tract pull the stomach posteriorly This will tear the esophagus and allow you to look inside the most anterior portion of the head Two compact green glands cream or orangy color are located in this region These are actually long tubular structures that resemble nephridia but are compacted into a glandular mass Waste materials and excess water pass from these glands to the outside of the body through pores at the base of antennae 7 Locate the brain or ganglion just dorsal and anterior to the green glands It lies in the midline and nerves extend posteriorly from it fusing to form the ventral nerve cord 8 Fill in the characteristics of the atworm in Table l APPLYING YOUR KNOWLEDGE 1 One of the major differences between cnidaria and the various worms examined in this exercise is radial versus bilateral symmetry What is the advantage of radial symmetry for sessile attached animals and bilateral symmetry for mobile animals What major evolutionary trend accompanies bilateral symmetry 2 What is the adaptive signi cance of an animal having two separate openings to the digestive tract as seen in annelids and arthropods 3 What anatomical features are adaptations to a parasitic lifestyle Which are adaptations to an aquatic lifestyle To a terrestrial lifestyle 4 A major new feature observed in the phylums Annelida and Arthropoda is a segmented body Speculate about the advantages provided by segmentation Table 1 0f 12 characteristics for Tissue Di estive Circulato Organism Symmetry Organiz ati0n opgenings Sys tem ry Habitat Locomotion of of Animalia Sponge Hydra Flatworm Earthworm Crayfish Excretory Respiratory Organism Support System Segmentation Sponge Hydra Flatworm Earthworm Crayfish Nervous System Appendages