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COPPERBELT COLLEGE OF EDUCATION MODULE 3 BIO 261: Diversity, Form and Function of Organisms MODULE 3 Copperbelt College of Education Kitwe- Zambia Science Department Copyright © Copperbelt College of Education 2011 No part of this module may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without permission in writing from the publisher Copperbelt College of Education science Department p.o box 29382 Kitwe Zambia Phone:+260212239003 E-mail:[email protected] Acknowledgements The COPPER BELT COLLEGE OF EDUCATION SCIENCE DEPARTMENT wishes to thank those below for their contribution to this BIO 261 MODULE 3: MUMA A (Mr) CBUC CHANGWE P.B (Ms) CBUC KAPONGOLO E.L (Mr) CBUC BIO 261: Diversity, Form and Function of Organisms Contents About this [DOCUMENT TYPE] 1 How this [DOCUMENT TYPE] is structured .................................................................. 1 Course overview 3 Welcome to [Add course title here] [Course sub-title] ..................................................... 3 [Add course title here] [Course sub-title]—is this course for you? .................................. 3 Course outcomes ............................................................................................................... 3 Timeframe ......................................................................................................................... 4 Study skills ........................................................................................................................ 4 Need help? ........................................................................................................................ 6 Assignments ...................................................................................................................... 7 Assessments ...................................................................................................................... 8 Getting around this [DOCUMENT TYPE] 9 Margin icons ..................................................................................................................... 9 Unit 1 11 [Add unit title here]......................................................................................................... 11 Introduction ........................................................................................................... 11 [First topic heading] .............................................................................................. 13 [Second topic heading] .......................................................................................... 15 Unit summary ................................................................................................................. 22 Assignment ......................................................................Error! Bookmark not defined. Assessment.......................................................................Error! Bookmark not defined. Unit 2 23 [Add unit title here]..........................................................Error! Bookmark not defined. Introduction ........................................................................................................... 23 [First topic heading] ...............................................Error! Bookmark not defined. [Second topic heading] ...........................................Error! Bookmark not defined. Unit summary ................................................................................................................. 32 Assignment ......................................................................Error! Bookmark not defined. Assessment...................................................................................................................... 32 Unit 3 33 [Add unit title here]..........................................................Error! Bookmark not defined. Introduction ........................................................................................................... 33 [First topic heading] ...............................................Error! Bookmark not defined. [Second topic heading] ...........................................Error! Bookmark not defined. ii Contents Unit summary ................................................................................................................. 39 Assignment ..................................................................................................................... 39 Assessment...................................................................................................................... 40 Unit 4 41 [Add unit title here]..........................................................Error! Bookmark not defined. Introduction ........................................................................................................... 41 [First topic heading] ...............................................Error! Bookmark not defined. [Second topic heading] ...........................................Error! Bookmark not defined. Unit summary ................................................................................................................. 54 Assignment ..................................................................................................................... 54 Assessment...................................................................................................................... 54 BIO 261: Diversity, Form and Function of Organisms About this Module Diversity, Form and Function of Organisms Module 3 has been produced by Copper belt College of Education All modules produced by Copper belt College of Education are structured in the same way, as outlined below. How this Module 3 is structured The course overview The course overview gives you a general introduction to the course. Information contained in the course overview will help you determine: If the course is suitable for you. What you will already need to know. What you can expect from the course. How much time you will need to invest to complete the course. The overview also provides guidance on: Study skills. Where to get help. Course assignments and assessments. Activity icons. Units. We strongly recommend that you read the overview carefully before starting your study. The course content The course is broken down into units. Each unit comprises: An introduction to the unit content. 1 About this Module PHYLUM: CHORDATA Unit outcomes. New terminology. Core content of the unit with a variety of learning activities. A unit summary. Assignments and/or assessments, as applicable. Resources For those interested in learning more on this subject, we provide you with a list of additional resources at the end of this module; these may be books, articles or web sites. Your comments After completing Module 3 we would appreciate it if you would take a few moments to give us your feedback on any aspect of this course. Your feedback might include comments on: Course content and structure. Course reading materials and resources. Course assignments. Course assessments. Course duration. Course support (assigned tutors, technical help, etc.) Your constructive feedback will help us to improve and enhance this course. 2 BIO 261: Diversity, Form and Function of Organisms Course overview Welcome to Module 3 You will be introduced to higher animals. Higher animals are animals that bear back bones. In other words, they are known as vertebrates. Vertebrates comprise fishes, amphibians, reptiles, birds and mammals. This module is broken down into four units. You will look at protochordates in unit 1, fishes in unit 2, amphibians and reptiles in unit 3 then birds and mammals in unit 4. As a teacher, you may find some ideas familiar, but you are still encouraged to take up this module seriously. We have made the concepts in the module as understandable as possible. Diversity, Form and Function of Organisms Module 3—is this course for you? This course is intended for people who had studied and passed BIO 110 at first year and has also done module 1of this course. Course outcomes Upon completion of MODULE 3 you will be able to: 3 Course overview PHYLUM: CHORDATA Identify major morphological and anatomical features of vertebrates. Outcomes including Compare and contrast the morphological and anatomical features of representative taxa among animals. Describe the life cycle of important representative taxa among animals. Describe the classification of animal representative taxa. Discuss the diversity of vertebrates. Timeframe This module is expected to take you a minimum of 80 hours. This time should be spent on studying the module and doing the activities. How long? Study skills As an adult learner your approach to learning will be different to that from your school days: you will choose what you want to study, you will have professional and/or personal motivation for doing so and you will most likely be fitting your study activities around other professional or domestic responsibilities. Essentially you will be taking control of your learning environment. As a consequence, you will need to consider performance issues related to time management, goal setting, stress management, etc. Perhaps you will also need to reacquaint yourself in areas such as essay planning, coping with exams and using the web as a learning resource. Your most significant considerations will be time and space i.e. the time you dedicate to your learning and the environment in which you engage in that learning. 4 BIO 261: Diversity, Form and Function of Organisms We recommend that you take time now—before starting your selfstudy—to familiarize yourself with these issues. There are a number of excellent resources on the web. A few suggested links are: http://www.how-to-study.com/ The “How to study” web site is dedicated to study skills resources. You will find links to study preparation (a list of nine essentials for a good study place), taking notes, strategies for reading text books, using reference sources, test anxiety. http://www.ucc.vt.edu/stdysk/stdyhlp.html This is the web site of the Virginia Tech, Division of Student Affairs. You will find links to time scheduling (including a “where does time go?” link), a study skill checklist, basic concentration techniques, control of the study environment, note taking, how to read essays for analysis, memory skills (“remembering”). http://www.howtostudy.org/resources.php Another “How to study” web site with useful links to time management, efficient reading, questioning/listening/observing skills, getting the most out of doing (“hands-on” learning), memory building, tips for staying motivated, developing a learning plan. The above links are our suggestions to start you on your way. At the time of writing these web links were active. If you want to look for more go to www.google.com and type “self-study basics”, “self-study tips”, “self-study skills” or similar. 5 Course overview PHYLUM: CHORDATA Need help? Your course lectures are Help Ms P. B. Changwe 0976 876396 or 0969 913824 Mr. E. L. Kapongolo 0979 488913 During Residential School you will have access to the college library. 6 BIO 261: Diversity, Form and Function of Organisms Assignments In this course you will be expected to write a total of three assignments. One assignment will be written after each module. For example, you will be given an assignment based on module 3. Assignments All written assignment to be sent to The Director, Copper belt College of Education, P.O BOX 20382, KITWE. You are expected to submit assignments in the order in which the modules are given to you. 7 Course overview PHYLUM: CHORDATA Assessments At the end of each unit, you will find self-marked activities. These activities are for your own practice Assessments You will also write a Tutor Marked Assessment for this module. It is important that you do all the self-marked activities and Tutor Marked Assessment because these will help you check your progress. We recommend you discuss the contents of the learning journal with your Tutor. 8 BIO 261: Diversity, Form and Function of Organisms Getting around this module 3 Margin icons While working through this MODULE 3 you will notice the frequent use of margin icons. These icons serve to “signpost” a particular piece of text, a new task or change in activity; they have been included to help you to find your way around this MODULE3. A complete icon set is shown below. We suggest that you familiarize yourself with the icons and their meaning before starting your study. Activity Assessment Assignment Case study Discussion Group activity Help Note it! Outcomes Reading Reflection Study skills Summary Terminology Time Tip 9 BIO 261: Diversity, Form and Function of Organisms Unit 1 PHYLUM: CHORDATA 1.0 Introduction HELLO! Welcome to unit I of module 3. In this unit you will be introduced to phylum Chordata.To start with, if I may ask you a question. What are higher animals? I am sure you will agree with me that the best term we could use to describe higher animals is the word chordates. Chordates belong to phylum Chordata. How would you identify chordates? Of course, by looking at their general characteristics. What are the major characteristics of a Chordate? All chordates have a notochord: this is a slender rod-like structure on the dorsal side of an animal for muscle attachment and support. Notochord may not be present in animals throughout the life stages. pharyngeal region: this could be slits or gills of which at some stage in their life cycle may disappear. a post anal tail: this is a representation of some structures forming a chain or a tail which serves for locomotion especially in lower vertebrates. a dorsal nerve chord: this leads to a distinct brain. In other words it forms the central nerves system (CNS). Besides these four major characteristics of chordates, general body plan is another aspect. This plan can be cut into various segements; head, trunk and the tail. Associated with this plan, there is concept of symmetry known as bilateral symmetry. Meaning that animals can be cut into halves whereby one half looks like the other from the head to tail. Now move with me to the issue of classification. The phylum chordata is classified into subphyla, super classes and classes. There are five subphyla namely; Urochordata or Tunicata 11 Unit 1 PHYLUM: CHORDATA Hermichordata Cephalochordata Agnatha Gnathostomata Urochordata , Hermichordata and cephalochordata together form what is called protochordata while Agnatha and Gnathostomata form another second group known as vertabrata (true vertebrates). Are we together? Furthermore, phylum chordata includes the well known vertebrates and these are fishes, amphibians, reptiles and mammals. The vertebrates and hagfishes together comprise the taxon craniata. The remaining Chordates are Tunicates (Urochordata), Lancelets (Cephalochordata) and possibly some odd extinct groups. Chordates are well represented in marine, fresh water and terrestrial habitats from equator to the high northern and southern lattitudes. Having listed down the sub phyla , you will now be introduced to each of them in details starting with Urochordata. Upon completion of this unit you will be able to: Describe the characteristics of chordates. Identify the structural features of Tunicates, Acorn worms, Amphioxus, lampreys and hangfish. Outcomes Classify the chordates of representative taxa. Discuss the diversity of protochordates. Acraniata: Animals without a well developed head region (skull) Craniata: Animals whose head is well developed with central nerves system (CNS) Vertebrates: Animals with a backbone Terminology Adding extra rows to the Table graphicRemoving rows from the table graphic 12 BIO 261: Diversity, Form and Function of Organisms 1.1 Sub phylum: Urochordata This sub phylum is also known as Tunicata. 1.1.1 Classification of Urochordata Subphylum: Urochordata Class: Acidiaceae Class: Larvaceae Class: Thaliaceae There are three classes under phylum Urochordata which in certain characteristics. However the common characteristics among this phylum are explained below. 1.1.2 General characteristics for sub phylum Urochordata 13 Unit 1 PHYLUM: CHORDATA Fig 1.1 Structure of common tunicate Digestive system: a tunicate siphons water in itself and releases it through excurrent. This is refered to as filter feeding. Filter feeding is a primitive method of nutrition. Digestion and absorption occurs in the stomach. For respiratory system, the heart is responsible for circulating blood. Neural system is also functional in tunicates. 14 BIO 261: Diversity, Form and Function of Organisms Reproduction system: tunicates are hermaphrodites meaning that their sexes are not separated (monoecious). Fertilization occurs externally. The early stage (larva stage) is motile but as it develops it changes to its structural appearance. It becomes sessile. The most prominent feature is the notochord. The notochord gives support to the entire animal. Now, move on to sub phylum Hermichordata. 1.2 Sub phylum: Hermichrdata This is also known as Acorn worm 1.2.1 Classification of sub phylum Hermichordata Sub phylum Hermichordata consists of two classes Pterobranchia and Enteropneusta. Fig 1.2 An acorn worm represents the internal part namely; A. represents the external part B. The body is divided into proboscis, collar and trunk. Buccal diverticula is posterior part of proboscis. 15 Unit 1 PHYLUM: CHORDATA 1.2.3 Characteristics of subphylum Hermichordata Digestive system is complete. Nervous system: chemoreception Sensory neurons in proboscis functions in Respiratory system: respiratory system consists of gill slits connected to the pharynx with external environment. A single glomerulus connected to blood vessels may have excretoryl function and is considered a metanephridium. Reproductive system: colonies are formed by asexual budding in Pterobranchs. Asexual reproduction by fragmentation in Enteropneusta. Circulatory system is composed of dorsal and ventral vessels and dorsal heart. Feeding habits: Many Acorn worms are deposit feeders extracting the organic components of sediments. Others are suspension feeders capturing plankton and detritus. The muscular proboscis is the active part of the animal collecting food in mucous strands on its surface. Look at the next sub phylum. 1.3 Subphylum: Cephalochordata Animals under subphylum Cephalochordata are also refered to as Amphioxus. 1.3.1 Classification subphylum Cephalochordata Sub phylum Cephalochordata consists of class leptocardi 16 BIO 261: Diversity, Form and Function of Organisms Fig 1.3 Anatomy of amphioxus The appearance of Amphioxus is of fish like or larva like. The posterial region is not fully developed. There is no clear separation between the head and the trunk. Meanwhile the prominent features are pharyngeal region which constitutes a bigger region of the trunk , the gut shows no stomach, gonads develop below the pharynx and on the dorsal side is the notochord which persist throughout life span. The notochord is the major supporting structure of the animal amphioxus. The skin is very thin and does permit exchange of gases between the environment and animal. There is poor specialization of organization in amphioxus. Amphioxus tends to have a segemented body and muscles running from the notochord. These features are similar to invertebrates. There is poor cephalization (low development of CNS). However the notochord is present through out the life cycle. 1.3.3 Characteristics of Amphioxus Habitat: amphioxus live in marine environmental bottom areas, burrowing in the sands or mud areas. Excretory system in the ampioxus is poorly developed. There are special cells called flame cells responsible for excretion. These cells remove excretes from internal area to the outside. The evolutionary features of amphioxus show that they are primitive chordates closer to the invertebrates. Feeding: the common method of feeding in amphioxus is filter feeding methods. 17 Unit 1 PHYLUM: CHORDATA Respiratory system: there is absence of respiratory pigments and lack of well defined heart. ACTIVITY 1.1 1. Why are the amphioxus among the chordates and associated with vertebrates? ……………………………………………………………………. ……………………………………………………………………. ……………………………………………………………………. 2. What is the type of feeding found in tunicates? ......................................................................................................... ........................................................................................................ End of activity 1.4 Sub phylum Agnatha Agnatha are fish like in appearance. They lack appendages and jaws. 1.4.1 Classification of Agnatha Phylum: Chordata Sub phylum: Agnatha Class: Ostracoderm Class: Cyclostomata Order: Petromyzonitida Order: Myxinitida Class: Ostracoderm is extinct and made up of species whose head had exoskeleton but without developed endoskeleton. They were marine and filter feeders. Class: Cyclostomata. ‘Cyclo’ means circular (round) and ‘stoma’ means mouth. Therefore Cyclostomata means round mouth. 18 BIO 261: Diversity, Form and Function of Organisms 1.4.2 Characteristics of Agnatha The body is cylindrical (eel shaped), long and slender. The notochord is very prominent and persists throughout life span. Just like all pisces, the heart is two(2) chambered (1 auricle and I ventricle). They are poikilotherms (cold blooded). Unlike other species appendages are not paired, has no rib cage, has circular mouth and lack jaws. Class Cyclostomata is divided into two (2) orders myxinitida and petromyzonitida. Myxinitida consists of hagfish. Look at the structure of hagfish below. Fig 1.4 Atlantic hagfish The mouth of hagfish tend to be highly terminal. Their gill slits are any number from one to sixteen(1 - 16). Hagfish are completely marine. 19 Unit 1 PHYLUM: CHORDATA Petromyzonitida consists of lampreys. Fig 1.5 Sea Lamprey (Petromyzon marinus) Lampreys have seven(7) gill slits.The mouth part is funnel shaped and tend to point downwards. Lampreys are found in both fresh and marine waters. They live as adults in marine environment hence have to adjust osmotic potential. Digestive system: the mouth of agnatha lacks the true jaws but the cartilage structures are able to piece through the food and get the food.. the oesophagus is present. There is no well defined stomach almost no existence. Oesophagus end up with the small interstine hence they have to keep on feeding. Circulatory system: there is a ventral heart with two chambers on the ventral side circulatory system is pumped forward. Oxygenated blood is first supplied to the brain. On the dorsal side circulatory system is directed backwards. Respiratory system: oxygen in waters trapped less efficient, water enters and comes out through gill slits. It is a primitive way. Excretory system: Agnatha has pairs of kidneys with a tubular structure along the system. Reproductive system: fertilization in agnatha is external and sexes are separate (dioecious). 1.4.3 Economic importance 20 BIO 261: Diversity, Form and Function of Organisms Lampreys tend to attack other species especially those caught by fishermen. They lower the value of the catch. 1.4.4 Differences agnatha has from other chordates. Lacks jaws and paired appendages, Lacks pelvic girdle, The ribcage is absent, The notochord is present throughout its life span. 1.5 Subphylum: Gnathostomata Gnathostomata is a subphylum of true vertebrates. It consists of two supper classes: Pisces (fishes) and Tetrapoda. Supper class pisces consists of the following classes: placoderms (exitinct), chondrichthyes (sharks and cartilage fish) and osteichthyes (bony fish). Super class pisces will be discussed in details inunit 2. Super class:tetrapoda is associated with four legged animals. It consists of the following: Amphibian, Reptilia, Aves (birds) and Mammalia. Super class tetrapoda will be discussed in details in units 3 and 4 of this module. Stop for a while and reflect on what you have learnt in unit 1 by attempting the questions below. ACTIVITY 1.2 1. Name five subphyla of the phylum chordata ............................................................................................................ ............................................................................................................ 2. Briefly define the type of symmetry associated with vertebrates ............................................................................................................ ............................................................................................................ 3. Identify at least three differences between hagfish and lamprey .................................................................................................................... 21 Unit 1 PHYLUM: CHORDATA .................................................................................................................... .................................................................................................................... Unit summary Summary In this unit you learned about phylum chordata. It was very interesting to learn about the characteristics of chordates. In this unit you also learnt about the five sub phyla under phylum chordate. Sub phyla: urochordata, hermichordata, cephalochordata and agnatha were discussed in details while subphylum gnathostomata was not because it will be covered in the next unit. Just a quick reminder! All chordates are expected to have four major characteristics: notochord, pharyngeal region, post anal metametrical segment and dorsal tubular central nerves system. 22 BIO 261: Diversity, Form and Function of Organisms Unit 2 PISCES (FISHES) 2.0 Introduction Pisces is a super class. It is also known as fishes. It comprises classes: chondrichthyes and osteichthyes.. We shall look at chondrichthyes first and then osteichthyes later in details. Upon completion of this unit you will be able to: Compare and contrast the morphological and anatomical features between chondrichthyes and osteichthyes. Outcomes Identify the structural features chondrichthyes and osteichthyes. representative taxa of Describe the characteristics of fishes. Anadromous: Animals which live as adults in marine water or environment. Catadromous: Animals which spend their time in fresh water but marine for breeding only. Oviparous: A type of development in which the young hatch from eggs laid outside the mother’s body Ovoviviparous: A type of development in which the young hatch from eggs incubated inside the mother’s body Terminology 23 Unit 2 PISCES (FISHES) 2.1 Class: Chondrichthyes Chondrichthyes are the first true vertebrates. Chondri means have no true bones but have cartilagous bones as a skeleton system (cartilage). Ichthyes means fishes. Therefore it means that chondrichthyes are fishes comprising cartilage bones. 2.1 Classification of chondrichthyes Sub phylum: Gnathostomata Class: Chondrichthyes Sub class: Elasmobranchii Order: Cladoselanchii (extinct) Order: Pleuracanthedii (extinct) Order: Selanchii (Sharks) Order: Batoidea Sub class: Holocephali Order: Chimaerforms There are two sub classes which have four orders. The first two orders exist only in fossil records (extinct). Selanchii (order) is the most popular and is used to represent the sub class elasmobranchii. The other sub class holocephali has one order chimaerforms. 2.1.1 Characteristics of Chondrichthyes The skin is fairly tough and covered with placoid scales ( very tiny pointed scales).The skin is well supplied with mucus glands to make the fish slippery and move efficiently. Mucus reduces the resistance of environment when moving. They are marine but order pleuracanthedii lived in fresh water. They have ventral mouth (underside of the body) and supported with sharp teeth. Nostril is not connected in any way to the pharyngeal of the animal neither to the mouth. They have the mouth supported by jaws on both upper and lower. The skeletal 24 BIO 261: Diversity, Form and Function of Organisms system is entirely cartilageous. It enables us to consinder it as evolutionary primitive since the skeleton is cartilageous. Notochord is present and exists throughout its life cycle. They have paired fins that are pectorial and pelvic fins. Circulatory system consists of two chambered heart and a single circulatory system and moves in one direction of which ventral side is forward while dorsal side is backward. They are poikilotherm (cold blooded animals ). They do not require a lot of self generating energy to maintain and regulate body temperature. Fig 2.1 Male spiny dogfish shark Having looked at a picture above, you will agree the fact that Primitive features associated with chondrichthyes are that they have no typical oesophagus, the tongue is flat and is found at the base of the mouth and does not protrude. In addition intestines are not coiled. Circulatory system: chondrichtyes have the same plan as cyclostoma they have two chambered heart. Circulated fluid passes through the gill slits where it is oxygenated. An improvement is that water enters the mouth and comes out through the gills slits as compaired to Agnatha. Reproductive system: They have separate sexes .This is an advanced type. Internal fertilization through cloaca is exihibited, individual offsprings are similar to the parents and breeding takes place at a particular time and specific areas. Feeding of the young is separated from the old to avoid feeding competition among the fishes. 2.1.2 Economic Importance 25 Unit 2 PISCES (FISHES) Chondrichthyes are food for other animals They sting and attack the divers They destroy fishermen’s catches and reducing their values. 2.2 Class: Osteichthyes This class is also called bony fishes. There is over 20 000 various fishes. Half vertebrates species are osteichthyes. It is the most abundant class among the chordata. They exhibit an adaptive diversity. They have a variety of habitats; open water system, deep water layers, shore areas and others survive below the water in the sea. 2.2.1 Characteristics of Osteichthyes Fig 2.2 Anatomy of a freshwater fish They consist of a skin and mucous glands. The scales may not be present in some species. Some have dermal scales (the circular) and this is the majority of the group. Others have placoid scales but few. The mouths of the fishes tend to be terminal with developed jaws. Depending on the feeding behaviour eg predators (tiger fish, bubble fish) have very strong jaws. 26 BIO 261: Diversity, Form and Function of Organisms Those which feed on the vegetation and have mouth like filter feeding, mouths are structured to suit the feeding habits. Skeletal structure (system) is made of actual (true) bones. It consists of endoskeleton and exoskeleton on the head of bubble fish. Notochord is on the dorsal side and persists. Circulatory system consists of the heart with two chambers. Respiration system comprises the use of gills. The water enters the mouth and is released behind the operculum hence the efficience of absorbing oxygen from water. The gills in some fishes are modified into a lung eg bubble fish. This is some steps towards evolution. Others are lung fish whose lungs are to absorb atmospheric air (oxygen) to withstand the adverse environment . Concerning body temperature, all fishes are called cold blooded animals. The fishes are stream lined to move effectively in water but others are elongated eg eels. Others the body shape is compressed. The body shapes vary to suit the habitat. They have paired appendages. They have swim (air) bladder. This is an organ used for the movement of the fish to adjust the level in water. Gonads in females have well defined shapes which suits the breeding activity. When you press and the milky stick stuff comes out then it is a female. The females have a wide and long gonad and the outside shape of gonads is different from the male one. The standard length of a fish is considered from mouth to the posteriol end boadering the caudal fin. The size of fish varies from species to species and depends on the age. Fishes do not cease to grow unlike in mammals they continue growing throughout their life. There are several ways of describing and identifying fish species; the shape of caudal fin and covering of scales. Others are covered with scales on the trunk and tail only. Some are covered the whole body. Some are spotted. 27 Unit 2 PISCES (FISHES) Fig 2.3 various types of caudal fins You will also learn that there are evolutionary categories of fishes and these are sarcrotegii and actinoptergii. SARCROTEGII It has long fresh lobed fins. It has cosmoid scales (very small and thin scales ) and nostrils joined to the buccal cavity. ACTINOPTERGII This type of fish has common fins associated with a solid shape. They are red fins because of the spines present. The number of spines on dorsal fins suggest the type of fish (help in identifying fish). This is refered to as dorsal formula. Have a short break! During this break could you look at the question below to help you reflect on what you have just read. ACTIVITY 2.1 In what aspects is the class chondrichthyes more advanced to the class osteichthyes? ....................................................................................................... ........................................................................................................ ........................................................................................................ 2. Name two types of skeleton systems found in vertebrates ......................................................................................................... 28 BIO 261: Diversity, Form and Function of Organisms ......................................................................................................... 2.3 Some of the Fish Groups from Primitive to highly Evolved/ Advanced 2.3.1 Family: Protoptrinidae Eg Protopterus anniecters (African lungfish).They are able to gulp atmospheric oxygen and can live out of water for long periods of time. Their dorsal fin is jointed together with caudal fin. This type of fish is found in lower Zambenzi. 2.3.2 Family: Mormyridae Eg Mormyrus larade, Mormyrus longrastris and Marcusenius masolepdites These type of fish have very long extended snout or bottled nose. They have very tiny scales covering mainly the trunk. They tend to have darkish colour and have extended caudal region. they are found in the middle Zambenzi. 2.3.3 family: Anguillidae Eg Anguilla mossambiquous and Anguilla bincolar They are eel (shark like structures). There are four species in the middle Zambezi. In the past they were confined to the middle Zambezi but now are confined to the lower Zambezi. They are catadrous (migrate to the sea and spent their adult life there). 2.3.4 Family: Clupeidae Eg Limnothrissa miodo and stolothrissa tanganicae Clupeide is locally called kapenta. They are very small fish, found in open water environment. They feed on minute organisms. They are identified by a silvery band along the laterial line. 2.3.5 family: Cyprinidae Eg Barbus paeichii, Labeo altivelis and Cyprinus carpio They are identified by stream lined body. They lack teeth but have tubular structure for sucking plankton material. Jaws are poorly developed. They do not have true stomarch and lack adipose fin. They are common in lower Zambezi and Luangwa rivers. 2.3 6 Family: Characidae 29 Unit 2 PISCES (FISHES) Eg Bryanus lateralis, bryanus limber and Hydrocynus vittatus (tiger fish) They have sharp pointed teeth in the buccal cavity and have scales apart from the head. They are common in Zambezi river. Hydro means water and cynus means dog therefore hydrocyrus is one of the strong preditors. It has forked fin. 2.3.7 Family: Hepsetide Eg Hepsetus odoe It is called the Kafue pike and has very nice olive brown colour. 2.3.8.Family: Claride Eg Clarias gariepinus (barbel fish) It has a bony cover (exoskeleton). It has projections (spike like structures) on the body. There are no scales on the trunk. Henterablandlus longifilis (giant cat fish) This fish plays a significant role. It is a very good hunter invading streams. One of its gills is modified into a lung and can survive many hours out of water provided the place it is in is moist. Hence traders can transport this fish to far places and remain flesh. It has a lot of proteins. 2.3.9 Family: Malapterundae Eg Malepterus electricus This fish is able to create current. It has an inorganic battery which it uses to electrocute its prey. The dorsal fin is reduced to vestigial structure. 2.3.10 Family: Mochokidae Eg Synodontis sp {zambenzis) This fish has no scales. It has bony helment (cover), very strong spins and very short trunk. 2.3.11 Family Cichlidae Eg Oreochromis andersoni, Oreochromis macrochir, Oreochromis niloticus, Tilapia rendalli, Tilapia spermnii, Serranochromis angustica, serranochromis macrocepteris and Haplochromis giardis. 30 BIO 261: Diversity, Form and Function of Organisms 2.3.11.1 Characteristics of Cichlidae The Cichlidae are referred to as breams.They are covered by the scales on the trunk, head and gill covers. Dorsal fin is identified with o black sport (Tilapia spot). It disappears as the fish grows. Oreochromis andersoni is identified with prominent 3 spots on the trunk. It is known as ‘three spotted bream’. It is one of the common fishes in many places in Zambia. It is referred for fish farming because of its fast growth. Oreochromis macrochir has a green colour on the head region.it is called ‘green headed bream’ as a common name. Compared to O. andersoni growth rate is slow but grows very big hence farmers are reluctant to grow it. Oreochromis niloticus does not exist elsewhere but in Nile and lake Tanganyika and some rivers in West Africa. It is known as ‘Nile tilapia’. It is identified with Tilapia spot which does not disappear. Its caudal fin has the lines which cross each other. Tilapia rendalli has a red covering on the anterior part hence the name ‘red breasted bream’. It is very famous for feeding on acquatic miroplanktons in relation to biological control method. Tilapia spermanii is a very small bream roughly 30cm. it has greenish bandy running across the trunk. Seranchromis angustica, Seranchromis macrocepteris and haplochromis giardi are predators. They have red spots on the pelvic fin. 2.3.12 Economical importance of bony fish It provides fishing industry and employment to fishermen and traders. Fish can be farmed. Fish farming is the fastest food growing production. It also provides recreation and as an ornament (aquarium fisheries). Government earns income through licensing. It is used in biological control methods to control weeds. Species Haplochromis giardi feeds on snails hence used to control bilhazia. They feed on mosquito larva and control the spread of malaria. ACTIVITY 2.2 1. Briefly list three characteristics that make osteichthyes suitable for life in their habitats ………………………………………….. 31 Unit 2 PISCES (FISHES) …………………………………………………………………… …………………………………………………………………… ……………………………………………………………………. Unit summary Summary In this unit you learned two classes under superclass pisces or fishes. Thes two classes are chondrichthyes and osteichthyes. Condrichthyes are cartilage fishes while osteichthyes are bony fishes. Assessment What are the variations and adaptations of respiratory organs in super class pisces? Assessment 32 BIO 261: Diversity, Form and Function of Organisms Unit 3 AMPHIBIANS AND REPTILES Introduction Amphibians are the only living vertebrates that have transition from water to land in both their organismal development (ontogeny) and evolutionary history (phylogeny). Some examples of amphibians are frogs, toads and salamanders. Frogs and toads belong to the order Anura (have no tails in adults). Salamanders and newts, on the other hand, belong to the order Urodela (have tails even in adults). True toads belong to the family Bufonidae. The members of this family have short legs, stout bodies and thick skins with permanent warts. Reptiles are organisms whose body is entirely covered with scales. Reptiles are found both on land and in water. This means that some reptiles are found in water for example crocodiles while others are found on land for example snakes Upon completion of this unit you will be able to: describe the characteristics of amphibians. describe the characteristics of reptiles. Outcomes differentiate between amphibians and reptiles. state at least two examples of each group. 33 Unit 3 AMPHIBIANS AND REPTILES Terminology ontogeny: Organismal development phylogeny: Evolutionary history [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] General characteristics of amphibians Amphibians are organisms that live both in water and on land. Some of the features that qualify an organism to be an amphibian are that they have skeleton that is mostly bony. The limbs are usually four (quadrupedal); the heart has two atria but has only one ventricle. The skin is smooth, moist and glandular; respiration is through the skin and in some forms by gills and/or lungs. The presence of gills and lungs varies among species and by developmental stage of some species. Amphibians are ectothermic. The excretory system consists of mesonephric or opisonephric kidneys. The main nitrogenous waste or excretory product is urea. The ear has an eardrum or tympanic membrane and stapes for transmitting sound. The cornea is used for vision while the eyelids and lachrymal glands protect and wash the eye respectively. The mouth is usually large with small teeth in the lower and upper jaws. The nostrils are paired and open into a nasal cavity lined with olfactory epithelium at anterior (front) part of the mouth. Amphibians have ten pairs of cranial nerves. 34 BIO 261: Diversity, Form and Function of Organisms Reproduction Amphibians reproduce by laying eggs. The sexes are separate and fertilization is mostly external in frogs and toads but internal via a spermatophore in most salamanders. Eggs hatch into tadpole having a long tail. In addition the tadpoles have both internal and external gills. Tadpoles and salamander larvae are carnivorous. Most larger frogs are solitary except during breeding season. During the breeding season, most males are very noisy Protection from prey Snakes, aquatic birds, turtles and humans prey on adult frogs. Fish preys on tadpoles. Most adult frogs defend themselves by feigning death (they pretend that they are dead). When disturbed along the margin of a pond, a frog usually remains quite still. If they sense danger, it jumps into the grass cover. In addition, when held, a frog puts its captor off guard by ceasing to struggle. Then it leaps suddenly while releasing urine. In most amphibians, the ability to leap as well as use of poison glands is best method of protection Activity 3.1 1. In which habitat are amphibians mostly found? ……………………………………………………………… ……………………………………………………………… 2. State at least four characteristics of amphibians. ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… 35 Unit 3 AMPHIBIANS AND REPTILES ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… …………………………………………………………….. 3. How do amphibians reproduce? ……………………………………………………………… ……………………………………………………………… 4. List three types o amphibians. ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… 5. Explain how amphibians protect themselves from predators. 36 BIO 261: Diversity, Form and Function of Organisms General characteristics of Reptiles Reptiles are organisms with bodies that are covered with epidermal scales and sometimes bony dermal scales, integument with few glands. Reptiles have two pairs of limbs with five toes. The limbs are adapted for climbing, running or paddling. However, in reptiles such as snakes and some lizards, the limbs are vestigial. Apart from snakes, the skeleton of the rest of the reptiles is ossified and also have ribs. The skull has one occipital condyle. Respiration in reptiles is mainly through lungs which have a large surface area. However some reptiles use the cloaca, pharynx or skin for respiration. The circulatory system is divided into systemic and pulmonary circulation. Reptiles are ectothermic. The kidneys are metanephric and are paired. The main excretory product is uric acid. They have a nervous system with optic lobes on the dorsal side of the brain. There are 12 pairs of cranial nerves. The sexes are separate and fertilization is internal. The eggs are covered with calcareous or leathery shells. Extraembronic membranes (amnion, chorion, yolksac and allantois) are present during embryonic life Activity 3.2 1. In which habitat are reptiles mostly found? ……………………………………………………………… ……………………………………………………………… 2. State at least four characteristics of reptiles. ……………………………………………………………… ……………………………………………………………… 37 Unit 3 AMPHIBIANS AND REPTILES ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… …………………………………………………………….. 3. How do reptiles reproduce? ……………………………………………………………… ……………………………………………………………… Tortoises and turtles Tortoises and turtles are enclosed in shells consisting of a dorsal carapace and a ventral plastron (breastplate). The shell is fused to the thoracic vertebrae and ribs. The shell protects the head and appendages (limbs).the limbs can be retracted inside. Turtles do not breathe by expanding their chest because of the shell; instead, they use abdominal muscles. Turtles have poor vision and are mute. However, they have good sense of smell color vision. Reproduction is by laying eggs. Fertilization is internal. The eggs are buried in the ground. Nest temperature determines the sex of the hatchlings. In turtles low temperatures produce males while high temperatures produce females. Lizards and snakes These belong to the order Squamata. Lizards belong to suborder Sauria. Lizards are a diverse group some of which are terrestrial, burrowing, arboreal and aerial. They have movable eyelids. Examples of lizards are geckos, iguanas, monitors and chameleons. Lizards are ectothermic and they have an external ear. However hearing is not very important in most lizards except for geckos because the males are strongly vocal to announce their territory 38 BIO 261: Diversity, Form and Function of Organisms Snakes belong to suborder Serpentes. Snakes do not have limbs. Snakes’ eyes are permanently covered Crocodiles and alligators [Add topic text here] Unit summary In this unit you learned [Add summary text here - you may wish to use the unit outcomes to write this text] Summary [Continue your body text here] Assignment [Add assignment text here] Assignment [Continue your body text here] 39 Unit 3 AMPHIBIANS AND REPTILES Assessment [Add assessment text here] Assessment [Continue your body text here] 40 BIO 261: Diversity, Form and Function of Organisms Unit 4 AVES (BIRDS) AND MAMMALS Introduction Birds are organisms whose bodies are covered by feathers. They have beaks and scales on their feet. Birds reproduce by laying eggs. There are different types of bird some birds are nocturnal eg. The owl while others are not Upon completion of this unit you will be able to: [verb] [complete the sentence]. [verb] [complete the sentence]. Outcomes [verb] [complete the sentence]. Mention at least four mammalian orders. [verb] [complete the sentence]. [verb] [complete the sentence]. Terminology [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] [Term]: [Term description] 41 42 Unit 4 AVES (BIRDS) AND MAMMALS General characteristics of aves (birds) The aves or simply birds have very interesting characteristics or features that are unique to them. I am very sure that you are able to distinguish birds from animals like amphibians and reptiles that you learnt in unit 1 and unit 2 respectively. So can you write at least two features that distinguish birds from other animals? 1) …………………………………………………………………… …………………………………………………………………… ……………………………………………………………………. 2) …………………………………………………………………… …………………………………………………………………… …………………………………………………………………… Okay, that’s good! Now let us look at the features or characteristics of birds in detail. Generally birds have four divisions or parts. The four parts are head, neck, trunk and tail. The neck is disproportionately long for balancing and for food gathering. They have two pairs of limbs namely forelimbs (front limbs) and posterior limbs (hind limbs). The forelimbs are usually modified for flying while the posterior limbs are adapted for perching, walking and swimming. The body is covered with feathers and leg scales. Aves do not sweat glands, oil or green gland at the base of tail. Birds have a skeleton which is ossified with air cavities. The front part of the head has a beak but there are no teeth. The nervous system is well developed. In addition to the nervous system, birds also have a circulatory system. The heart has four chambers. This is not the first time you are coming across a four chambered heart. Can you name another organism that has a four chambered heart? Did you say human being? Very good, that’s correct! A human being has a four chambered heart. Aves are endothermic organisms. Do have any idea what that means? Well, it simply means that birds are warmblooded. 42 BIO 261: Diversity, Form and Function of Organisms Feathers These possess remarkable toughness and tensile strength. Most feathers are contour feathers. Each contour feather consists of a hollow quill or calamus and shaft or rachis. The shaft has numerous barbs. Barbs are arranged in closely parallel fashion and spread diagonally outward from both sides of the central shaft to form a flat, expansive DIAGRAM OF CONTOUR FEATHER ON PG 380 Fig 4.0 43 44 Unit 4 AVES (BIRDS) AND MAMMALS Classification Birds are divided into two main groups. Guess what! The groups are based on whether the birds are able to fly or not. Aves that are able to fly belong to the group Neognathae. This group of birds escapes from predators by simply flying away. The ones that are not able to fly belong to the group Paleognathae. Can you guess how such birds escape from predators? Did you say by this flying? Of course not! Try again. Did you say by hiding? OOh! You can do better than that. Ok, I will tell you. It’s by running very fast away from predators. Examples of flightless birds are Ostriches and Kiwis. Skeleton A major requirement for flight is a light skeleton. The bones of flying birds are therefore light, delicate and have air cavities. The bones are said to be pneumatized. Pneumatized bones are nevertheless strong. In addition the bird’s skull is built lightly and fused in one piece. 44 BIO 261: Diversity, Form and Function of Organisms Digestive system Birds do not have teeth hence foods that require grinding are reduced in the gizzard. Salivary glands are poorly developed and mainly secrete mucus for lubricating food and the tongue. The pharynx is short and leads into the relatively long muscular esophagus which extends into the stomach. A n enlargement called the crop is found at the end of the esophagus and serves as a food storage chamber. In birds like pigeons, parrots and doves the crop produces a lipid and protein rich milk. In order to grind food, birds swallow gritty objects or pebbles which lodge in the gizzard. The cloaca is found at the terminal end of the digestive system. It serves as both reproductive part as well as for taking out waste matter. Beaks of birds are adapted to specialized food habits. Some beaks are chisel shaped while others are sharp and pointed. The following diagrams show different beaks of variety of adaptations. Fig 4.2 Reproductive System Males birds do not have a penis but only have testes and these appear very tiny and have a bean shape. During the mating or the breeding season, the testes however enlarge. During copulation the male touches his cloaca against that of a female. The sperms are released into the female cloaca. These sperms remain alive for main days after a single mating. 45 46 Unit 4 AVES (BIRDS) AND MAMMALS Females only have one ovary, the left ovary and oviduct. Female birds tend to lose the right ovary, that is the ovary and oviduct on the right side become vestigial structures. Now this is interesting! What reason can you give for this kind of adaptation in females? The ovary releases the eggs which pass down the oviduct. At this point fertilization takes place. The fertilized egg continues moving down the oviduct. Special glands secrete albumin, or egg white, which is added to the egg. Later on in the oviduct shell membrane, shell and shell pigments are secreted around the egg. Diagram of female reproductive system 46 BIO 261: Diversity, Form and Function of Organisms Care for young All birds lay eggs that must be incubated by one or both parents. Most birds build some form of nest in which to rear their young ones. Some young ones hatch naked, blind and are unable to walk. Such are referred to as altricial birds. Others, however, are able to walk and see soon after hatching. In addition they are covered with down feathers. Such birds are referred to as precocial birds. Fig 4.4 47 48 Unit 4 AVES (BIRDS) AND MAMMALS Activity 4.1 1. State at least four characteristics of aves (birds). ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… …………………………………………………………….. 2. How do birds reproduce? ……………………………………………………………… ……………………………………………………………… Origin and Evolution of mammals Present day mammals are descendent of organisms of the Paleozoic era particularly the synapsids. Synapsids have openings in the temporal region of the skull associated with attachment of mandibular muscles. The earliest synapsids were pelycosaurs (which were herbivorous) and therapsids which were carnivorous). Pelycosaurs diversified extensively and evolved changes in jaws, teeth and body form. Evolution continued and gave rise cynodonts from which modern mammals come from. General characteristics of mammals Modern living mammals differ from each other on the basis of reproduction. There are three types or patterns of reproduction 48 BIO 261: Diversity, Form and Function of Organisms among mammals and classification is based on the type of reproduction. Monotremes are egg-laying mammals, marsupials are pouched mammals and placental mammals. There are at least 29 recognized placental mammalian orders. In this module, only seven orders will be discussed. The orders are Primates, Chiroptera, Rodentia, Proboscidea, Lagomorpha, Perissodactyla and Artiodactyla. We will look at each of these orders later in this unit. We will also briefly look at marsupials and monotremes. This group of animals is a very interesting one. Can you think of the reason why it’s interesting? Of course one of the reasons is that that is where we, as human beings, belong! Now that makes it even easier for you. What are some of the features of a human being? What about features of a cow? You know cattle are mammals too. I suppose stating that having hair or fur was amongst the many things that you thought about. You are absolutely correct! Humans have hairs on their skin while cattle have fur. Perhaps the most interesting feature is that all mammals have breasts or mammary glands. Activity 4. 1. Which organism are ancestors of mammals? …………………………………………………………………….. 2. Mention the three types of modern mammals a) …………………………………………………………………… b) …………………………………………………………………… c) …………………………………………………………………… 3. List at least five orders found in class mammalian. a) …………………………………………………………………… 49 50 Unit 4 AVES (BIRDS) AND MAMMALS b) …………………………………………………………………… c) …………………………………………………………………… d) …………………………………………………………………… e) …………………………………………………………………… The body of most mammals is mostly covered with fur. Of course humans and pigs are an exception in that their skin is covered with hairs. Depending on the type of mammal integument glands could be either sweat, scent sebaceous or mammary glands. The skull has two occipital condyles. The nasal cavity is present too. This is true because animals breathe through their nostrils or simply through he nose. The outer ear is fleshy while the middle ear has three small bones and most of them have seven cervical vertebrae. In addition the pelvic bones are fused. Some mammals like human beings which have two sets of teeth are said to be diphyodont. The milk teeth are replaced by permanent teeth. Most have mammals have heterodont teeth which vary in structure and function. The eyelids are movable The circulatory system consists of four chambered heart with a persistent left aortic arch. Respiratory system composed of lungs with alveoli. There is muscular diaphragm for gaseous exchange. The excretory system consisting of metanephric kidneys and ureters that usually opens into a bladder. The brain is highly developed and 12 pairs of cranial nerves are present. Some mammals are endothermic while others are homeothermic. Mammals have separate sexes and fertilization is internal. The young ones are fed on milk Activity 4.2 50 BIO 261: Diversity, Form and Function of Organisms 1. In which habitat are mammals mostly found? ……………………………………………………………… ……………………………………………………………… 2. State at least four characteristics of mammals. ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… ……………………………………………………………… …………………………………………………………….. 3. How do mammals reproduce? ……………………………………………………………… ……………………………………………………………… Care for the young All mammals have mammary glands. Therefore one of the ways in which most mammals care for the young ones is by feeding them on milk. Marsupials These mammals have pouches. They do not have a true placenta. They have a special type of placenta called yolk sac placenta. Embryos of marsupials are encapsulated by shell membranes. After hatching the embryos do not in plant in the uterus. Instead they make shallow depressions in the uterine wall in which they lie and absorb nutrients. Gestation period is very brief but lactation period is prolonged. An example of a marsupial is a kangaroo 51 52 Unit 4 AVES (BIRDS) AND MAMMALS Monotremes These are mammals that lay eggs. An example is the duck-billed platypus. The gestation period is about 10-12 days. After hatching, the young feed on milk from the mother. However, the young do not suck the milk instead they lap the milk secreted onto the mother’s belly. Why do think the young do not suck? Well, it is because monotremes have no nipples! Order: Primates Primates have a large cerebral cortex and because of this primates come first in brain development in the animal kingdom. Most species have large eyes in two occipital condyles. Order: Chiroptera These are mammals which are able to fly because their fore limbs are modified into wings. An example of this order are bats. Bats are mostly nocturnal, that is they are active at twilight and at night. Bats navigate by echolocation. They therefore are able to fly quickly, while avoiding obstacles, even in absolute darkness. In addition bats are able to locate and catch insects with precision as well as finding their way deep into the caves. When in flight, a bat emits short impulses 5 to 10 m/sec in duration Order: Rodentia These are mammals which are able to fly because their fore limbs are modified into wings. Order: Proboscidea These are mammals which are able to fly because their fore limbs are modified into wings. 52 BIO 261: Diversity, Form and Function of Organisms Order: Lagomorpha These are mammals which are able to fly because their fore limbs are modified into wings. Order: Perissodactyla Order: Artiodactyla Order: Primates Glands Mammals have the greatest variety of integumentary glands. There are four classes of glands namely sweat, scent, sebaceous and mammary glands. Sweat glands are tubular, highly coiled glands that occur over much of the body surface. There two kinds of sweat glands: eccrine and apocrine. Eccrine glands secrete a watery fluid that cools the skin when it evaporates. Apocrine glands are larger than eccrine glands and have longer and more convoluted ducts. Apocrine glands always open into a hair follicle. In addition apocrine glands develop near sexual puberty and are restricted (in humans) to the arm pits (axillae), mons pubis (pubic area), breasts, prepuce, scrotum and external auditory canals. Sebaceous glands- are associated with hair follicles. These glands produce sebum into the hair follicle. 53 54 Unit 4 AVES (BIRDS) AND MAMMALS Unit summary Summary In this unit you learned aves and mammals. You learned that birds reproduce by laying eggs. Females only have one ovary, the left ovary. Mammals are of three types and these are monotremes, marsupials and placental mammals. [Continue your body text here] [Continue your body text here] Assignment [Add assignment text here] Assignment [Continue your body text here] Assessment [Add assessment text here] Assessment 54 BIO 261: Diversity, Form and Function of Organisms [Continue your body text here] Answers to activities in this module Activity 1.1 1. presence of the notochord, Presence of pharyngeal region, Presence of central nerves system though poorly developed and Cephalization though poorly developed. 2. Filter feeding. Activity 1.2 1. Urochordata, Hermichordata, Cephalochodata, Agnatha and Gnathostomata. 2. Bilateral symmetry 3. lampreys have seven gill slits while hagfish have varying number between one and sixteen The mouth of lampreys tends to point downwards while that of hagfish is highly terminal. Lampreys are fresh and marine water living while hagfish are completely marine. Activity 2.1 1. Chodrichthyes exhibit internal fertilization, At birth individual offsprings are similar to the adults Parents provide parental care, Young ones feed separetly on special food. 2. cartilage and True bones 55 56 Unit 4 AVES (BIRDS) AND MAMMALS Activity 2.2 Their skin contain mucus glands for little resistance with media Their bodies are streamlined to enable easy penetration and locomotion They have a swim bladder that aids with bouyance. 56