Biol 111 Comparative & Human Anatomy Lab 1: Introduction & Evolution of Vertebrates Spring 2014

Transcription

1 Biol 111 Comparative & Human Anatomy Lab 1: Introduction & Evolution of Vertebrates Spring 2014 Philip J. Bergmann Lab Objectives The laboratory portion of the course is designed to coincide as much as possible with the lecture. It aims to give you a hands-on, practical, and interactive experience, allowing you to better learn anatomy and to hone your dissecting skills. While the lecture emphasizes the evolution of anatomy, the lab emphasizes the anatomy itself (but still in an evolutionary context). The laboratory is an integral component of the course, needed to properly learn anatomy. The major objectives of the lab are: 1. To learn the basic anatomy of vertebrates in general. 2. To appreciate how the various anatomical systems are functionally integrated with one another. 3. To learn to do detailed, beautiful dissections. 4. To learn how to approach the dissection of anatomy so that you are able to study any part of the anatomy of any vertebrate. Lab Schedule The lab for Biol 111 is scheduled for three hours a week for 14 weeks. You will find that it is often necessary to spend more time during the week than three hours doing the dissections and studying the anatomy. To help you with this, there will be an open lab policy (see below) during weekdays. The lab schedule is as follows: Week of Topic January 14 Introduction, Evolution of Vertebrates: Protochordates & Agnathans January 21 Cranial Osteology January 28 Postcranial Osteology, Shark External Anatomy & Fin Musculature February 4 Myology: Shark Demo & Cat 1 February 11 Myology: Cat 1 February 18 Myology: Cat 3, Review February 25 Lab Exam 1 March 4-8 No lab Semester Break March 11 Shark Digestive, Respiratory & Urogenital Systems March 18 Cat Digestive, Respiratory & Urogenital Systems March 25 Shark Nervous System: Graded Dissection April 1 Circulatory System: Shark 1 April 8 Circulatory System: Shark 2, Cat 1 April 15 Circulatory System: Cat 2 April 22 Lab Exam 2 1

2 Lab Components The lab will be evaluated based on several components, worth 50% of the course grade: Lab Exam points 12% of total course grade February 26, 28 Lab Exam points 12% April 23, 25 Graded Dissection 100 points 10% March 26, 28 Lab Quizzes 60 points 6% Ongoing Course Participation 100 points 10% Ongoing Below is information about each component, also found in the course syllabus. Laboratory Exams There will be two lab exams during the semester. These lab exams will test your knowledge of material presented and available in lab. Because this is an anatomy lab, you will be expected to be able to identify anatomical structures and to know their functions and relationships to other structures. The lab exam format will consist of fill-in-the-blank questions, and some short answer (couple of sentences) questions. The exams will be in the form of stations with demo material about which you will be asked questions. The stations will be timed so that all students have a chance to see all of the material, and time will be available to return to stations you want to revisit at the end of each exam. Lab exams will not be cumulative. A term list will be provided with each exam that lists all terms that students are responsible for in alphabetical order (not by lab). Due to the nature of these exams, making up a missed exam is extremely difficult. Graded Dissection An important skill gained during this course is the ability to dissect vertebrates. You will spend a lot of time honing your dissection skills, and so it is only fair that part of the grade be determined by how well you learn to dissect. Students will have one week to dissect the shark brain and origins of the cranial nerves in late March and early April and will be graded on the quality of their dissections. A good quality dissection is one that has all structures undamaged, clearly visible and identifiable. Lab Quizzes During some labs, you will be given short (5-10 minute) quizzes on material either covered during the previous lab or during that week s lab. The primary purpose of these quizzes is to give students a gauge of how they are doing in the lab in terms of learning the material. There will be six quizzes, three before each of the lab exams. Course Participation Attending all labs is mandatory and contributes to the lab participation grade. This 10% of the course is also based on participation, completion of dissections and worksheets, and a good attitude during labs. At the beginning of each lab, students should show the TA their worksheet from the previous lab to get a check mark. The TA will also lead a discussion of the previous lab s questions at the beginning of lab. It is expected that students take part in the discussion by answering questions and contributing ideas. During the last lab before each lab exam, the instructors will also note the degree of completeness of the dissection up to that point of the course. This should be an easy 10% of the course, but really depends on you being engaged. Part of this grade is also for participation during lecture. 2

3 Using the Lab Handouts There is a handout associated with each lab session, available on the course website as a PDF. Each handout will help to guide you through each lab and is particularly important because it contains information about the material you should learn for each lab. Before studying from the purchased lab manual, refer to the lab handout to determine what you need to know. Each lab is presented in the same format. The Lab Objectives is a short section outlining what you should be doing and learning during each lab. The Material to Learn section contains information on which aspects of the anatomy you need to learn and those that you do not, and this is summarized as concisely as possible with a listing of figures and tables to learn and omit, all referenced to the lab manual, The Dissection of Vertebrates by De Iuliis and Pulera. This section also contains a list of terms that you need to learn. This is the definitive list that you can use as a study guide for each lab. There are a lot of terms and this list should help you manage learning them. Note that there are terms that appear in the lab manual figures that you do not need to know. A useful strategy is to go through the term list for each lab and put a small "x" beside the terms in the figures of the lab manual that you do not need to know. The Background & Instructions section tells you what you should be doing during each lab, and includes specific directions for doing the dissection for each lab. These instructions are crucial to getting started and completing each lab efficiently. Your TA and Dr. Bergmann will be available to further help in case of uncertainty ask them many questions. This section also contains key background information to learn. Finally, it contains questions for you to complete during and after the lab. These questions appear in bold and italics. Some time will be spent at the beginning of each lab discussing questions from the previous lab, so come prepared to participate in the discussion (participation points!). These questions will help put the anatomical material into a broader context, relate it to the lecture, and prepare you for exams. You will quickly realize that there is a lot of text to go through in the lab manual and you are expected to read each lab before coming to lab. Do not wait until lab to read the lab handouts and manual because there will not be enough time to complete the dissections. Please come prepared to each lab: read the entire lab before coming, and bring a print out of the lab handout and your lab manual. It is a good idea to bring past lab handouts as well, so that you can review material from previous weeks. Supplies Gloves, lab aprons, specimens and dissecting tools are available in the lab. If you wish, you may purchase your own dissecting kit this is the best way to ensure that your tools are in good condition. Bringing the lab manual and lab handout to each lab is critical to doing the lab. Specimen Preservation and Safety You will be handling preserved lamprey, shark and cat specimens extensively during each lab of the course. These specimens are fixed in 10% formaldehyde solution, called formalin, and stored in a less toxic holding solution. Formaldehyde is a carcinogen and quite pungent. It is the major health hazard in the lab. To mediate this hazard, when not in use, specimens are stored in a sealed refrigerator. The lab is also equipped with ventilation fans that easily maintain fumes at non-toxic levels. Despite these precautions, the fumes can be quite strong and protecting yourself is important: 1. Wear gloves whenever handling specimens. 2. Do not eat or drink in the lab (this is prohibited). 3. Step out of the lab for a couple minutes a few times a lab session to get some fresh air. 3

4 4. If you feel ill from the fumes, excuse yourself and step out of the lab. 5. If you are or may be pregnant, inform Dr. Bergmann and consult your physician. Another hazard in the lab is the use of sharp implements, including scalpels and scissors. Be careful when dissecting with these instruments. Always point the sharp and pointy ends away from yourself and others. Always report any accidents to the TA or Dr. Bergmann immediately. A first aid kit is available if needed. Open Lab Policy The instructors make every effort to open the lab outside of scheduled class time for students to facilitate completion of dissections, review and learning of the material, and studying for exams. Open lab must be requested by students, and agreed to by the TA or Dr. Bergmann. Students should arrange for open lab preferably at least 24 hours in advance. While the instructors are willing to open labs even on short notice, they also have other responsibilities and meeting or other plans may prevent them from being able to open lab if it is requested at the last moment. Lab can be opened during most times during the week, including the weekend. Weekend times must be arranged by the end of Thursday. There are a few times when lab will not be opened. Lab will not be open during the day prior to a lab exam, as this time is used to set up the exam. Lab will also be closed during the 45 minutes prior to the beginning of labs (so 12:40-1:25 on Tuesday and Thursday). Finally, open lab may also be unavailable if another class is using the lab space (such restriction is usually minimal). Other Lab Rules In addition to the safety rules discussed earlier, please follow these important rules: 1. Attend all labs and show up on time. TAs and Dr. Bergmann will have important information for you at the beginning of each lab session. 2. Keep the lab tidy. When you finish dissecting, put away your specimen, dispose of any biological waste in the appropriate place, wash and put away your dissecting tray and tools, and wipe down your lab bench. Leave the lab as clean or cleaner when you are done than when you started. 3. Be courteous and helpful to other students and instructors in the lab. 4. Treat the specimens with respect. Keep in mind that all of the animals that you are dissecting were once alive. Your opportunity to dissect them to learn anatomy is a privilege, so treat them with appreciation and respect. This means no playing with the specimens, scaring other students with the specimens, or making distasteful jokes about the specimens. Other students may have fishes or cats as pets and may be offended by such behavior. 5. Do not remove specimens from the lab. 6. Do not damage or monopolize demonstration material it should be available to all students. 4

5 Evolution of Vertebrates: Protochordates & Agnathans Lab Objectives 1. To learn the anatomical planes and directions so that you can read and talk anatomy. 2. To learn the 5 key chordate characteristics (what makes a chordate a chordate). 3. To be able to identify the chordate characteristics in the Urochordata, Cephalochodata, and lamprey. 4. To learn the difference between chordates and vertebrates. 5. To learn the anatomy of the lamprey, a primitive vertebrate, establishing a baseline for comparison to the shark and the cat. Material to Learn 1. Anatomical planes and directions: Figures 1 & 2 2. Chordate phylogeny and key characteristics: Figure 1.1 (Figure 1.2 is helpful for material covered in lecture) Text in sections on Vertebrate Relatives & Craniates and Vertebrates (pp. 4-8) 4. The chordate characteristics in Urochordates, Amphioxus and larval lamprey (see below) 5. Lamprey anatomy, Chapter 2: Know: Arcualia only in Fig. 2.1 Know: Fig. 2.2, 2.3, 2.4, 2.7, 2.8, 2.9 OMIT: Fig. 2.5, 2.6. Blood vessels, except dorsal aorta. Term List Intoduction Anterior Posterior Dorsal Ventral Medial Lateral Proximal Distal Sagittal Transverse Frontal Deep Superficial Combined terms (e.g., posteroventral, anterodorsal, anterolateral, posteromedial) Chapter 1 & Related Hemichordata Urochordata Chordata Cephalochordata Craniata Vertebrata Myxinoidea Petromyzontoidea Ammocoetes larva Gnathostomata Chondrichthyes Osteoichthyes Sarcopterygii Tetrapoda Pharyngeal slits Endostyle Dorsal, hollow nerve cord Notochord Post-anal tail Gill slits Thyroid gland Atriopore Adhesive papilla Sessile 5 Gill filaments Subpharyngeal gland Muscle Chapter 2 Anterior dorsal fin Anus Arcualia Brain Caudal fin Cloaca Dorsal aorta External Pharyngeal Slits Eye Horny Teeth Heart Intestine Lateral line pores Liver Mouth Myomeres Myoseta

6 Naris Notochord Olfactory sac Oral funnel Ovary Pharynx Pineal eye complex Posterior dorsal fin Spinal cord Tail Tongue Trunk Urogenital papilla Background & Instructions You will not be dissecting during today s lab, although you will get plenty of opportunity to dissect later during this course. Instead, there is demonstration material available for examination and study. On demonstration there is a series of microscope slides, and a number of specimens of the lamprey. The microscope slides are all of basal chordates: the Urochordata (sea squirts), Cephalochordata (Amphioxus), and the Ammocoetes larva (larval lamprey). Also, answer the questions throughout this lab after you have read the material and as you examine the demo material. All of the animals that you see today are chordates, and so they all have five key chordate characteristics at some point in their life cycles. Chordates are characterized by having pharyngeal slits, a dorsal hollow nerve cord, a notochord, an endostyle, and a post-anal tail. Throughout today's lab keep these characteristics in your mind and look for them in all of the specimens that you examine. Pharyngeal slits - are openings that evolved in the pharynx of chordates. The pharynx is the anterior end of the gut, immediately posterior to the mouth. In vertebrates, the pharyngeal slits become gill slits. In other forms, the slits are used for filter feeding, allowing water to pass through them, but being too narrow to let food through. Dorsal hollow nerve cord - is also called the spinal cord and, unsurprisingly, fills a nervous function, connecting the brain with the rest of the nervous system. Notochord - is a hydrostatic organ that acts as an endoskeleton it maintains the elongate shape of the animal, preventing the body from collapsing on itself. Generally, the notochord is dorsal in position and runs from anterior to posterior. It lies immediately ventral to the spinal cord. Endostyle - In basal chordates, the endostyle secretes mucous that is used to trap food particles. It is also involved in iodine metabolism, and is homologous to the thyroid gland of vertebrates. Typically, it is positioned ventral to the pharynx. Post-anal tail - is a muscular projection posterior to the anus. It is typically used in locomotion. Although some chordates (like humans) have lost the tail secondarily, it is present in most species. 6

7 1. Amphioxus whole mount microscope slide and whole specimen Amphioxus is a cephalochordate. Although it is more closely related to craniates than the Urochordata, we mention it first because it is a good example of a general chordate body plan, and structures are relatively easy to find on it. Examine the slide under a dissecting microscope. The slide is quite thick, so you will have to focus up and down through the animal to get a view of all of the structures. Also look at the whole specimens these are helpful because you can see what the actual animal looks like. Identify the five chordates characteristics: Pharyngeal slits - Look for the pharynx at the anterior end of the animal. The slits run from anterodorsal to posteroventral. During filter feeding, water enters through the mouth, passes through the pharyngeal slits, and exits through the atriopore. Dorsal hollow nerve cord This is a dark pink stripe that runs anterior to posterior along the dorsal side of the animal. Notochord This is a dark stripe that often stains a more orange color than the nerve cord. It also runs along the dorsal side of the animal, located immediately ventral to the nerve cord. It begins anterior to the nerve cord. Endostyle The endostyle is a structure that is difficult to see in the whole mount. It runs longitudinally along the ventral edge of the pharynx. In the whole mount, it may appear as a darker pink stripe. Post-anal tail Locate the anus, which is posterior to the atriopore and ventral on the animal. The part of the animal posterior to this is the post-anal tail. In examining the whole mount, but also the whole animal, note the myomeres, which are segmental muscles running more or less transversely along the animal. They form a fine chevron pattern. Use the remainder of this page to draw the amphioxus whole mount. Label all the structures that you identify. 7

8 What are five features that all chordates have? Do you have all of these five features? Which ones do you lack? What happened? Why are humans still considered chordates? 2. Urochordata larva and adult The urochordates, or sea squirts, are a clade of chordates, meaning that they have all five chordate characteristics. However, unlike the other animals on display, the urochordate larva differs tremendously from the adult. The larva does not feed and is motile, dispersing after hatching and finding an appropriate place to settle. Once it settles, it attaches to the substrate using its adhesive papillae, and metamorphoses into a sessile, feeding adult. Due to these differences, neither the larva nor the adult have all five chordate characteristics, but together they have all of them. Examine the slides of both larva and adult and consider which chordate characteristics you see in each. Use the remainder of this page to draw the larval and adult sea squirt. Label the structures that you identify. 8

9 Which key chordate characteristics does the urochordate larva have? How about the adult? 3. Ammocoete larva of the lamprey, whole mount and composite cross section slides The larval lamprey looks quite different from the adult, but quite similar to amphioxus. The lamprey is a chordate. It is also a vertebrate, containing small vertebral rudiments called arcualia around its notochord when adult (see below). It is a good example of how an embryonic animal can have a relatively generalized morphology and subsequently specialize for its adult life style. The ammocoete is a small filter feeder, while the adult lamprey is parasitic, opening wounds on fishes with its teeth and feeding on their bodily fluids. Use a dissecting scope to examine the whole mount of the ammocoete larva. Note how it looks very similar to amphioxus. Try to identify the five key chordate characteristics - they should be in the same place as you saw in amphioxus. Use a compound or dissecting microscope to examine the cross sections of the ammocoete larva. Identify the dorsal hollow nerve cord (a dorsal structure, now cut in cross section), and the notochord ventral to it. Identify a cross section through the pharyngeal area by noticing the feathery gill filaments that project laterally from the wall of the pharynx. The pharynx is the central space through which water and food pass. Ventral to the pharynx is a bilaterally symmetrical lobed organ called the subpharyngeal gland. This is a version of the endostyle. Switch to a posterior cross section through the ammocoete. Notice the nerve cord and notochord, which project all the way to the posterior end of the tail. A dorsal fin appears as a thin dorsal projection from the tail. The caudal fin is the ventral projection. Also notice the masses of muscle in the tail, which are used to generate forces for propulsion through the water. Use the remainder of this page to draw and label the ammocoete cross sections that you look at. 9

10 What are two differences between that amphioxus and ammocoete whole mounts that you can use to distinguish these animals? 4. Adult Lamprey specimens A number of adult lamprey specimens are available on demonstration. These are pre-dissected for you, so you do not need any dissecting tools other than a metal probe to use to point to structures. Wear gloves to handle these specimens, as they have been preserved in formalin. As you examine the adult lamprey, see if you can find all of the key chordate characteristics and consider how the animal is specialized for its lifestyle. The lamprey serves two important purposes in this lab. First, it shows how the key chordate characteristics appear in a large, non-microsopic animal. Second, it gives you an anatomical baseline of what a basal vertebrate looks like. It will serve as a good foundation to build knowledge upon as you dissect the shark and cat in upcoming labs. Examine the following: Whole lamprey specimen - Examine the external morphology, identifying the structures shown in Figures 2.2, 2.3 and the lower right of 2.4. Cross sectioned lamprey specimen - Identify the structures shown in Figures 2.7 & 2.9 that you are responsible for (see term list). Mid-sagittally sectioned lamprey specimen - Identify the structures shown in Figure 2.8. Although all views are important, this one shows the most. Again, consider only the structures that you are responsible for (you can omit many of the muscles, some cartilages, and the blood vessels, but know what the heart is). Describe the life style of the larval and adult lamprey. How do they differ? What are at least two specializations that the adult lamprey has for its lifestyle? How has the function of the pharyngeal structures changed from Amphioxus to a lamprey? 10