Biol0011 Lab Manual[1]

UNIVERSITY OF THE WEST INDIES (MONA)

DEPARTMENT OF LIFE SCIENCES

PRELIMINARY BIOLOGY (BIOL0011/BLO5A)

LABORATORY MANUAL

SEMESTER I Biological Chemistry, Cells, Variety of Life

BIOL0011 Preliminary Biology Laboratory Manual Page 2

Wk Dates PRACTICALS1 Chemical & Physical Phenomena 0 Introductions, Group Assignment

2 Water 1 Collection & Preservation of Data

3 Functional Groups4 Carbohydrates 2 Physical & Chemical Phenomena - I5 Lipids 3 Physical & Chemical Phenomena - II6 Proteins7 Nucleic Acids, Protein Synthesis 4 Characteristic reactions of compounds 8 Enzymes 5 Enzymes9 Enzymes

10 Cell Structure 6 Light Microscopy

11 Cell Membrane Transport 7 Cell StructureTEST #1 Theory lecture 1-9 [6%]

12 Cell Cycle, Mitosis, Meiosis 8 Mitosis13 Cell Cycle, Mitosis, Meiosis 9 Meiosis14 Mutation15 Human Reproduction 10 Mammalian Reproduction 16 Human Reproduction 11 Angiosperm Reproduction17 Plant Reproduction18 Plant Reproduction Heroes Day (Oct 19)

19 Mendelian Inheritance TEST #2 Practica l 1- 11 [12%]

20 Mendelian Inheritance

21Linkage & Chi-Square Test 12 Monohybrid & Dihybrid Crosses; Chi-

Square Test22 Natural Selection, Speciation 13 Natural Selection & Evolution

23 Natural Selection, Speciation

24 Taxonomy, Viruses14 Kingdom Protoctista: Algae, Protozoa;

Kingdom Fungi25 Bacteria, Fungi, Protoctista 15 Kingdom Plantae: Bryophytes,

26 Plants27 Plants 16 Kingdom Animalia: Porifera, Cnidaria28 Animal Features 17 Kingdom Animalia: Platyhelminthes,

Nematoda, Annelida and Mullusca

29 Porifera, Cnidaria, Platyhelminthes30 Nematoda, Annelida 18 Kingdom Animalia: Arthropoda31 Arthropoda & Mollusca 19 Kingdom Animalia: Echinodermata and

Chordata 32 Echinodermata, Protochordata33 Chordates (Vertebrates) 20 Kingdom Animalia: Chordata (Vertebrata)

34 Chordates (Vertebrates) TEST #3 Practica l 12-20 [12%]

35 Biodiversity & Conservation

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Review

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Nov 23-27

Nov 02-06

Nov 09-24

Nov 16- 27

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Oct 12-16

Oct 19-23

Oct 26-30

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Sep 21-25

Sep 28-Oct 02

Oct 05-09

BIOL0011 Pre l im inary Bio logy I. Course Tim etable Sept-Nov, 2009 LECTURES

1

2

Sep 07-11

Sep 14-18


BIOL0011 / BL05A— PRELIMINARY BIOLOGY I - COURSE OUTLINE

Level 0; Semester 1; Credits: 6 P

Aim: To equip students with a basic knowledge of biological principles and processes.

Objectives: The course will enable students to:

• describe the chemical and biological foundation of life • show understanding of the basic principles of evolution • show variations in plant and animal life

Pre-requisites: CSEC Biology or equivalent

Syllabus: Biological techniques, biological chemistry, chemicals of life, enzymes, cells and tissues, cell division, genetics, evolution, mechanisms of speciation and variety of life: bacteria, protist, fungi, plants and animals.

I. CHEMICAL & PHYSICAL PHENOMENA

Matter Atoms, molecules, ions, isotopes Elements & compounds, mixtures States of matter

Bonds (ionic, covalent, polar) Dispersion systems

Homogenous & heterogeneous dispersions Types of dispersions (Solutions, Colloids, Suspensions)

II. WATER Structure of water Properties of water

Solvent pH properties Temperature Regulation (Heat capacity, Heat of fusion, Heat of vaporization) Surface Tension Capillarity

III. FUNCTIONAL GROUPS Inorganic versus organic molecules Importance of the carbon in organic molecules Characteristics & chemistry of Carbon Functional Groups: -OH, -COH (aldehydes & ketones), -COOH, -NH2, -SH, -PO4. IV. CARBOHYDRATES (STRUCTURE AND FUNCTION) Structure and levels of organization

Monosaccharides e.g., glucose Disaccharides e.g., sucrose Polysaccharides e.g., starch, cellulose, glycogen

Isomerism – structural & stereoisomerism Role in energy transfer, structural frameworks, storage V. LIPIDS (STRUCTURE AND FUNCTION) Structure (components) & properties

Saturated and unsaturated fatty acids Phospholipids, micelles Steroids eg. cholesterol


VI. PROTEINS (STRUCTURE AND FUNCTION) Major roles in physiology & structural frameworks Structure

Amino acid Primary, Secondary, Tertiary and Quaternary levels of organization

Relation of structure to properties Major classes of proteins VII. ENZYMES Function as Biocatalysts Classification Mode of action (Lock & key hypothesis, Induced fit) Properties (relate to protein structure): effect of pH, temperature; concentration (enzyme & substrate). Interpretation of related graphs Competitive & non-competitive inhibition VIII. NUCLEI ACIDS, GENES, PROTEIN SYNTHESIS Nucleic acids Structure (components, H-bonding, base pairing) Functions of DNA & RNA DNA replication Gene concept Protein Synthesis IX. CELL STRUCTURE Cell Theory, endosymbiont theory Generalized cell structure

Prokaryote cells Eukaryote cells (plant and animal)

Structure of organelles The plasma membrane X. TRANSMEMBRANE TRANSPORT Mechanisms of transport

Passive (Diffusion, Facilitated Diffusion, Osmosis) Active (Carrier Protein mechanisms, Coupled channels Na/K pump) Bulk Transport (Endocytosis, Exocytosis)

XI. CELL CYCLE, CELL DIVISION Stages of the cell cycle Mitosis cell division

Principle (Conserve chromosome number and genetic variation) Purpose (Growth, Maintenance, Repair, Asexual Reproduction) Process of mitosis: stages

Meiosis Cell Division Principle (haploid/diploid, conserve chromosome number, increase genetic

variation) Purpose (Gametogenesis, Genetic recombination) Process of meiosis (stages, Crossing over, Independent Assortment)

Genetic variation further enhanced by random fertilization during sexual reproduction XII. MUTATION Gene Mutation: types Chromosomal Mutation: types XIII. HUMAN REPRODUCTION Male & female reproductive systems Gametogenesis (oogenesis, spermatogenesis) Structure & function of gamete Reproductive Endocrinology

Hormonal regulation of oogenesis and spermatogenesis The principle of negative feedback

Pregnancy & Development Fertilization Placenta: structure & function Foetal development & factors affecting it


XIV. PLANT REPRODUCTION Sexual & Asexual reproduction Flower structure & gametogenesis Pollination mechanisms Fertilization: self & cross pollination mechanisms Seed & fruit formation XV.MENDELIAN GENETICS Monohybrid Inheritance Dominance, Codominance, Incomplete Dominance Sex determination, sex linkage Dihybrid inheritance XVI. LINKAGE & CHI-SQUARE TESTING Accounting for disruptions in expected Mendelian ratios Application of the Chi-square test XVII. THE THEORY OF EVOLUTION Natural selection Evidence of evolution (Geographical distribution of animals, Comparative anatomy, Comparative biochemistry, Embryology, Paleontology) Variation Species Concepts (Morphological, Phylogenetic, Biological) Isolating mechanisms Speciation methods (Parapatric, Allopatric, Sympatric, Hybridization, Phyletic) XVIII. TAXONOMY (and DIVERSITY OF ORGANISMS) Introduction to Taxonomy & its importance Hierarchical nature of classification systems Construction & use of a dichotomous key Classification of organisms

Viruses Domains, Kingdoms (features)

XIX. PROKARYOTES Bacteria – Eukaryotic features

Eubacteria, Archaeobacteria

XX. KINGDOM PROTOCTISTA General features and structure

Algae (Chlorophyta, Phaetophyta, Rhodophyta) Protozoa (Rhizopoda, Mastigophora, Cilliophora) Slime Moulds

XXI. KINGDOM FUNGI Structure and general features including nutrition and biological importance

Higher fungi Lower fungi Lichens Mycorrhizae

XXII. KINGDOM PLANTAE Structure and general features Classification

Nonvascular Plants: Bryophyta (Hepaticae, Musci) Vascular Plants

o Ferns o Seed Plants

Conifers Flowering Plants


XXIII. KINGDOM ANIMALIA General features of animals Multicellularity (advantages) Animal Body Plan

• Body Symmetry (asymmetry, radial & bilateral symmetry) • Body layers (diploblastic, triploblastic) • Body Cavities (acoelomate, pseudocoelomate, coelomate) • Body Segmentation (advantages) • Embryonic development (protosomes, deuterosomes)

Classification and structure of animals • Porifera

o Histology o Types (asconoid, leuconoid, synconoid)

• Cnidaria o Body layers, Nutrition o Classification (Hydrozoa, Scphozoa, Anthozoa)

• Platyhelminthes o Symmetry, body layers, nutrition, habitats, locomotion o Classification (Turbellaria, Trematoda, Cestoda)

• Nematoda o Symmetry, body layers, body cavity, nutrition, locomotion o Classification

• Annelida o Symmetry, body layers, body cavity, segmentation, locomotion o Classification (Polychaeta, Oligochaeta, Hurudinea)

• Mollusca o Generalized Molluscs o Body Plan, symmetry, body layers, body cavity, segmentation o Classification ((Gastropoda, Cephalopoda, Bivalvia)

• Arthropoda o Symmetry, body layers, body cavity, segmentation o Classification (Subphylum Crustacea, Chelicerata, Uniramia [Class

Hexapoda, Chilopoda, Diplopoda] • Echinodermata

o Symmetry, body layers, body cavity, segmentation, locomotion, water vascular system

o Classification (Asteroidea, Ophiuroidea, Echinoidea) • Chordata

o Symmetry, body layers, body cavity o Four characteristic features o Invertebrate Chordates (Protochordata, Urochordata, Cephalochordata):

Classification and features o Vertebrate Chordates (Agnatha, Gnathostomata): Classification and

features Chondrichthyes Osteichthyes Amphibia – habitats, three chambered heart & double circulation,

integument, pentadactyl limb Reptilia – amniote condition, the heart & circulation, integument,

internal fertilization Aves– ectothermy, flight adaptations, care of young Mammalia – endothermy, increased cerebral capacity, diversity of

form, increased range/habitats, care of young XXIV. BIODIVERSITY Definition and Value of Biodiversity Species Status (endemic, endangered, threatened, extinct) Resources (renewable, non-renewable) Human Influence (hunting, habitat destruction, alien introductions) and conflicts of interest Preservation (methods, organizations)


Practical Work:

• Experiments demonstrating biochemical and biological processes and principles.

• Studies of fresh (living) and preserved organisms to demonstrate external variations in different life forms.

Evaluation:

• Course work — 40% consisting of: o Two in-course practical tests — 24% o One in-course theory test — 6% o Laboratory reports — 10%

• Final examination – 60% consisting of : o One 2-hour theory paper (I) — 30% o One 2-hour comprehensive paper — 30%

Note: The theory paper has essay questions. The comprehensive paper has a combination of multiple choice, fill in, matching, true

or false, short answer and labelling questions.


BIOL0011/ BLO5A TUTORIAL QUESTIONS SECTION A

1. State the importance of the properties of water in life processes. 2. Compare hydrophobic and hydrophilic colloidal dispersions. 3. Describe the structure of proteins [lipids, carbohydrates] 4. Describe three roles played by lipids [proteins, carbohydrates] in the bodies

of living organisms. 5. Using examples, describe the characteristics of enzymes. 6. Describe how an enzyme works 7. Outline the steps involved in the replication of DNA. 8. State the functions of the three types of RNA. 9. Distinguish between DNA replication, transcription and translation. 10. Explain why the structure of the plasma membrane is well suited for its many

and varied roles in living organisms. 11. Describe the generalized eukaryotic [prokaryotic] cell. 12. Using examples, explain what is meant by active transport. [diffusion,

osmosis] 13. Describe the process of mitosis [meiosis]. 14. Describe how genetic diversity is obtained in sexually reproducing organisms. 15. Define the term mutation and explain how gene [chromosomal] mutations

occur. 16. Describe the structure of the mammalian ovary [testis] and outline the

process of oogenesis [spermatogenesis]. 17. State the functions of the hormones involved in gametogenesis. 18. Outline the process of fertilization in Angiosperms. 19. Explain the laws of segregation and independent assortment. 20. In TV bugs, Cable (A) is dominant to rabbit ears (a) and Colour (B) is

dominant to black & white (b). Work Aholic crosses a completely homozygous Cable, black & white bug to a completely homozygous rabbit ear, Colour bug. Determine the F1 genotype and phenotype. When he crossed the F1 to get an F2 Work Aholic obtained 85 Cable Colour bugs, 32 Cable black & white, 26 rabbit ears Colour and 8 rabbit ears black & white progeny for a total of 8000 TV bugs. Determine if these results are significantly different from that expected.

SECTION B

21. Outline the theory of evolution by natural selection. 22. Outline the evidence that supports the modern theory of evolution.


23. Define the three concepts of species. 24. Outline the ways by which speciation can occur. 25. Explain what is meant by the binomial system of nomenclature. 26. Explain what is meant by the hierarchical taxa by which organisms are

classified. 27. Describe the characteristics that might lead you to the conclusion that an

organism is to be classified as a bacterium [virus, protist, fungi, plant, animal]. (Include how you distinguish it from the other groups).

28. What are the three main groups of Protoctists (Protists)? [any phyla] Using examples, explain why Protists are so difficult to classify.

29. State the biological importance of lichens and mycorrhizae. 30. Compare the morphology of algae and bryophytes. [any other groups] 31. Compare the ferns and the gymnosperms. [any other plant groups] 32. Using appropriate examples, distinguish between diploblastic and triplobastic

animals. 33. Illustrate the types of symmetry found in animals. 34. Describe the types of coelomic cavities. What is the function of the coelom. 35. Animals are distinguished by the ways in which the early embryo develops.

Explain how the Protostomes and Deuterostomes differ. 36. Describe the main features of the Porifera. [any other animal phyla] 37. Using examples from the Cnidarians, explain what is meant by

polymorphism. 38. Compare the methods of locomotion found in worms. 39. Comment on features possessed by the Arthropods which contribute to their

success in colonising a wide range of habitats. 40. Describe the ways in which amphibians are adapted to life on land, and in

what ways are they still restricted to a watery/moist environment. 41. Describe the adaptations of reptiles which allow them to live on dry, often

desert environments. 42. State the advantages of a coelomic cavity; complete digestive tract, bilateral

symmetry and cephalisation. 43. Describe the features that are unique to the class Mammalia. 44. Describe the human threats to biodiversity.


INTRODUCTION

These exercises are designed to introduce you to cells, bio-molecules, reproduction, patterns of inheritance and principles of classification in animals and plants. These sessions will be scheduled opportunities for you to examine live and preserved specimens as well as prepared slides in order to gain a better understanding of the Biological concepts dealt with in lecture and tutorials. Take full advantage of these practical classes in order to thoroughly familiarize yourself with the material available as well as acquire training in practical skills and the thought processes associated with the study of Science. Come prepared: Read this manual and lecture notes before you arrive for

your laboratory session. Always take this manual, your notes and text books to help with your labeling, comments and discussion.

Be punctual: Any additional information regarding the class or modifications of protocol will be announced at the beginning of the session. It is in your best interest not to be late!

Observe carefully: A Greek scholar once said, ‘It is more difficult to observe than to invent.’ Precise observation is essential in biology and an important aid to observation is the preparation of large, clear accurately labelled drawings.

Record accurately: Only the precise, up-to-date and detailed record book will be useful for reference and revision. It is essential, therefore, that drawings be made at the time of observation; copies of textbook illustrations are of little value to you and will not impress your examiners!

Think: You are the investigator. Try to solve problems and identify structures yourself before consulting the lecturer, teaching assistant or demonstrator. You may, however, request help when you are in difficulty.

Be tidy: Leave the benches clear after each lab. Replace the microscope and ensure it is covered. Turn off the electric lamps. Throw discarded material into the appropriate receptacles provided. Do not throw non-liquids substances into the sinks.

adapted from the Introductory Level 1 Biology Laboratory Manual


LABORATORY REPORTS The cover page for each report should include the following information:

Name: ID No.: BIOL0011 Stream No.: Lab No. & Title:

A typical experimental report is expected to have the following headings:

Title: Aim1: Materials and Methods2: Results3: Comments and conclusion4:

1 You should formulate an appropriate aim after reading through the experiment. 2You may or may not be required to record the methods and materials. If not, you may write “As in lab manual”. If required, the methods should be listed in past tense. Diagrams of apparatus may help your revision. 3Your results may include diagrams and tables; all should have appropriate titles. 4Explain your results; Refer to known theories and indicate sources of errors.

A typical page of illustration is expected to be as follows:

Title: Half-flower drawing of Cassia sp.

Kingdom: Phylum & Sub- phylum: Class: Genus & Species:

Exercises should be placed in sequence, stapled together and submitted at the end of each laboratory session.


Notes on Scientific Illustrations Observe the specimen carefully before starting to draw. Use the textbook, notes and picture in your lab manual to identify the main features. The aim of your drawing is to illustrate the main features of the specimen. DDoo nnoott ccooppyy ffrroomm bbooookkss oorr ootthheerr ssttuuddeennttss.. DDeevveelloopp tthhee eesssseennttiiaall sscciieennttiiffiicc hhoonneessttyy wwhhiicchh iiss rreeqquuiirreedd iinn hhiigghheerr ssttuuddiieess wwhheerree yyoouurr oobbsseerrvvaattiioonnss ccoouulldd bbeeccoommee aa ssoouurrccee ooff kknnoowwlleeddggee ffoorr ootthheerrss.. AAnn aaccccuurraattee ppeerrssoonnaall rreeccoorrdd wwiillll hheellpp yyoouu ttoo rreemmeemmbbeerr ffeeaattuurreess yyoouu oobbsseerrvveedd.. Illustrations A large, clear diagram which shows the specimen being studied in its proper form and proportion is required. Use plain paper. Draw on one side of the paper only. Do not make more than two drawings on a page. Your illustration should show the proper form and proportion of the specimen. The lines should be clear, continuous and of even thickness. Use dotted lines to show borders lying beneath structures. Do not shade or use inks. Use the stippling style, i.e. making small dots with the tip of the pencil at right angles to the paper. The density of dots should indicate darker or lighter areas. Titles, Labels, Annotations Each drawing should have an appropriate title, e.g. “T.S. of Rat Testis”. As far as possible, all the labels should be to the right of the drawing. The lines from the specimen to the label should be narrow and straight, should never cross each other and should end at the beginning of the label. Labels should form a vertical column and be parallel to each other, in small print so they do not detract from the drawing. AAnnnnoottaattee yyoouurr ddrraawwiinngg. To annotate means to add a bbrriieeff note to a label i.e. a simple phrase, not a sentence. The annotation should provide more information on the structure, or give the function, depending on the purpose of the drawing. Magnification Always state the magnification/ reduction of your drawing. Magnification = size of drawing/ size of actual specimen. For microscopic observations, also state the magnification at which the specimen was viewed. E.g. ‘T.S. of the Root of a Dicotyledonous Plant viewed at x100’. This is obtained by multiplying the power of the objective by the power of the eyepiece. A scale bar should also be placed on the drawing to show the actual measurement of an important region of the specimen.


PRACTICAL 1 COLLECTION AND PRESERVATION OF DATA One aspect of science is to collect and organize facts. These facts are then analyzed, conclusions are drawn, generalizations are made and predictions are tested. Information collected from the observations or experiments may be qualitative or quantitative. Qualitative data are those which do not lend themselves to precise numerical expression, while quantitative data are the result of measurement and can be expressed in some definite and precise form. 1. Collection and Preservation of Numerical Data As a means of extracting as much information as possible from quantitative data, these may be arranged in tables or graphs and subjected to statistical analysis. The data, arranged in a table, yields limited information. A further step is to represent the results in a graphical form, either to compare the size of different quantities or to represent functional relationships, or, in many cases, to estimate an unmeasured quantity based on the trend shown by the graph (extrapolation procedures). One way to graph data is to construct a histogram. This is constructed from a frequency distribution table where the data on the variable is sorted into classes. The height of each bar on the plot represents the number of individuals in each class. If a line is drawn through the top of the bars on a histogram connecting the midpoints of each category, the data can be shown as a line graph. Typically, graphs are used to illustrate the correlation between two variables. Here the graph is usually constructed by plotting relevant points from the data and either joining them by straight lines or drawing a smooth curve through them. When constructing graphs always bear the following points in mind: - The given or selected quantity (independent or basic variable) is always

shown on the horizontal axis (X-axis). While the observed or calculated quantity (dependent or derived variable) is shown on the vertical axis (Y-axis).

- Note the range of values of the quantities to be shown and select appropriate scales for each axis. Scales should be as large as possible and linear in nature.

- The intervals between values on the scales should be equal, representing the same number of units. (Only when graphs are drawn on an exponential scale should the intervals represent the logarithm of the number rather than the number itself).


- Write along each axis the name of the quantity represented and the units of measurement.

- Plot the points precisely according to the table of values. - Join the points with a straight line or a smooth curve according to the

nature of the data. A line of best fit may have to be used for data which in theory should generate a straight line but in reality gives a ‘near straight’ relationship.

- Write a title clearly at the top to signify what the graph represents. - Where several relationships are illustrated on the same graph use a

different plotting pattern for each relationship. A key should denote what each pattern represents.

1A. Hand Span of Students on Campus Materials: Metric rulers, people, graph paper or graphing software Procedure: Collect hand-span data from at least 25 persons

Spread the hand flat, stretching out the distance from the thumb to the little finger as far as possible the measure the distance from the tip of the thumb to the tip of the little finger.

Record hand span measurements (to the nearest mm) and gender.

Present the data in ascending numerical sequence. Present frequency tables for all students, males only and females only. Present a histogram to represent the hand spans of all students. Present another histogram which compares male & female hand spans.

o A frequency distribution table shows how often group of data points

appears in a given data set. Divide the numbers over which the data ranges into intervals of equal length and tally how many data points (hand spans) fall into each interval.

o Mean = Sum (frequency X midpoint value) / total sample – 1. o Mode =midpoint with highest frequency. o Median = middle midpoint /class (if there are an odd number of classes)

or the average of the two middle midpoints (if there are an even number of classes). You may also use the raw data for the calculations.

i. Identify sources of error and means of improving the data collection. ii. Is the hand span measurement discrete or continuous? iii. What is the mean, mode and median hand span for all students, for

males only and for females only? iv. What information does the histogram communicate?


1B. Class data on Reasons Students Study Preliminary Biology A pie chart is a circular graph showing the relative frequencies or percents of each class. Like the histogram, it is used for one variable. It allows comparison of one class with the whole.

Represent the data collected from the survey (to be done in class) as a pie chart

FPAS entry requirement ________ Environmental/ Conservation concerns ______ Hope to study Zoology ________ Hope to study Botany ________ Hope to study Veterinary Medicine _______ Hope to study Human Medicine ________ Other _______ Determine the percentage of each class from the total number of students. i. What advantage is obtained by presenting the data as a pie chart (over presenting the list)? 2. Collection of Morphological Data

Create and complete a data table on the external morphological features of the organism provided. Include diagrams, measurements and written descriptions of various body parts.

Use abbreviated writing, e.g. “skin covered with bony scales; body length 122mm”, instead of, “the skin is covered with scales which are bony and its body is 122mm long”. 3. Collection of Ecological Data

Write a description of the site indicated. Record site location, types of organisms present, abundance and any interactions observed.


PRACTICAL 2 PHYSICAL AND CHEMICAL PHENOMENA - PART 1 The physical sciences are widely used in experimental work on living organisms. Knowledge of certain fundamental facts of Physics and Chemistry are essential for the broad understanding of physiological processes. To understand the macroscopic or microscopic structures of living organisms and the processes responsible for the formation, modification or destruction of these structures, it is necessary to consider the nature and properties of those particles of which all matter is composed. Living organisms are made up of numerous different compounds, each of which is composed of molecules of specific chemical composition. These compounds owe their properties both to the kinds of molecules of which they are composed as well as to the arrangement of these molecules. Diffusion In order to understand more clearly what is happening when a substance diffuses from one area to another, imagine a large auditorium that contains a great number of balls bouncing around in all directions. A ball’s direction of movement will change only upon collision into a wall or another ball. The result is a zig-zag fluctuating movement and the room becomes filled with flying rubber balls. Similarly, any chamber becomes filled with gas molecules because of their inherent motion, and the average speed of the entire group will remain constant as long as the temperature and pressure do not change. Now if the wall between this auditorium and the adjacent one were removed, some of the balls would pass into the empty room because they would no longer be impeded. The random movement finally results in an equal number of balls in each room. At this point the number moving from the first room to the second and vice versa will be equal, a condition termed dynamic equilibrium. NB: Movement takes place in both directions and the concentrations in two areas are equal. Net Diffusion: Direction of movement of the greatest number of molecules, i.e. net diffusion of rubber balls was from the first room to the second. Net diffusion ceased at equilibrium, while diffusion continues even at equilibrium. Osmosis: One of the most important materials that enter cells is water. The term osmosis refers to the movement of water through a differentially permeable membrane from a region of high free energy to a region of low free energy of water. In a strict sense, osmosis refers to the movement of a solvent through a selectively permeable membrane, however, the only solvent involved in living cells is water, so the more restricted definition tends to be used. Osmosis is a special example of net diffusion.


Capillarity: If the tip of a tube of small diameter is immersed in water, the level of water in the tube will rise higher than the surface into which the tube was placed. Such a rise in tubes, termed capillary action, depends upon the cohesion of water molecules to each other and the adhesion of water molecules to the tube walls. The smaller the diameter of the tube, the higher will be the capillary rise. Cohesion: refers to the attraction of similar molecules to each other (e.g. water molecules). Adhesion: refers to the attraction between dissimilar molecules (e.g. water molecules to the tube wall). Carry out the following experiments and try to explain the results obtained. 1. Diffusion 1A. Half fill a test tube with water and stand it in a beaker of water. Leave for 10 minutes for temperature equilibration. Drop a small crystal of copper sulphate into the test tube. Leave the apparatus standing without any disturbance and examine it at half-hour intervals.

Record your aim, your observations and explanation. 1B. You are provided with three Petri dishes each containing a film of agar. During its preparation the agar was mixed with a few drops of potassium ferrocyanide (K4Fe(CN)6) solution.

Use a cork borer to punch a hole in the center of the agar in each of the three dishes.

Fill the holes (don’t overflow) with 0.05, 0.25 or 1.25% FeCl3 (ferric chloride) solution. Label the petri dishes accordingly.

Record the times at which FeCl3 was added and, at half hour intervals, measure the progress of the blue colour (prussian blue) around the hole in each dish.

Record your aim, your results (tabulate) and explanation.

4 FeCl3 + 3 K4Fe(CN)6 = Fe4[Fe(CN)6]3 + 12 KCl Ferric chloride + Potassium ferrocyanide = Prussian blue + Potassium chloride


2. Osmosis 2A. Examine the osmometer and comment on your observations.

Explain why coloured fluid rose up the tube. 2B. Solanum tuberosum (potato) slices were immersed in sucrose solutions for two hours. The initial and final weights are recorded in the table.

Table: Change in weight of potato slices placed in varying concentrations of sucrose.

Concentration of Sucrose (M)

Initial Weight of potato slices (g)

Final Weight of potato slices (g)

0.15 3.45 3.98 0.20 3.25 3.73 0.25 3.20 3.60 0.30 3.10 3.40 0.35 3.02 3.21 0.40 2.80 2.92 0.45 3.30 3.23 0.50 3.25 3.04 0.55 3.18 2.83 0.60 3.21 2.82

Plot the difference between initial and final weight against

concentration of sucrose. Explain the data in terms of the concentration of water and the

concentration of dissolved chemicals in potato slices. Also explain the significance of the point at which the line crosses the x-axis? Use terminology: hyper/hypo/isotonic, hyper/hypo/osmotic

2C. You are provided with a live slug (Phylum Mollusca, Class Gastropoda)

Sprinkle the slug with a small amount of NaCl (sodium chloride). Observe what happens and explain.

3. Capillarity. Select three capillary tubes with bores of different sizes. Stand them in a beaker half filled with water. Observe the extent of the rise of water in the three tubes.

Explain why water rises in the capillary tubes? Use terminology: Hydrogen bonds, adhesion, and cohesion.

Explain the relationship between the diameter of the bore and the height to which the water rises?


PRACTICAL 3 PHYSICAL AND CHEMICAL PHENOMENA - PART II 4. Surface tension of water. Half fill a small beaker with water. Carefully lower a razor blade (flatly) on to the surface of the water. Observe the razor. Repeat the process using soapy water (prepared with soap powder).

Record your observations and explain them in relation to surface tension forces. Refer to properties of soap and water. Use terminology: hydrogen bonds, cohesion, amphiphatic.

5. Colloids. Half fill two 10ml test tubes with distilled water. Add about a teaspoonful of clean sand to one tube and the same amount of clay (break up any clumps) to the other tube. Shake the tubes well and let them stand for about five minutes. Observe the level of sedimentation. Divide the supernatant liquid from the tube containing the clay into two equal parts. Use one part as control; while to the other add about 0.5g magnesium sulphate or solid calcium chloride. Shake both tubes and let them stand for about three minutes.

Comment on your observations of the extent of sedimentation. 6. Emulsions Place 2ml of water in a test tube and add five drops of vegetable oil. Shake well and let stand. Observe. Add five drops of 10% NaOH and two drops of oleic acid. Again shake well and observe.

Explain your results. Use terminology: hydrophobic colloids, saponification.

7. Adsorption. Half fill two 10ml test tubes with a dilute solution of methylene blue. To one test tube add a small amount of activated charcoal and shake well. Filter both solutions separately through filter papers.

Compare the colour of both filtrates and explain. 8. Coagulation and Denaturation. To about 1ml of 30% egg albumen solution add an equal volume of 95% ethyl alcohol and shake gently by inverting the tube repeatedly. Observe. Take another 1ml of the egg albumen solution in a clean test tube and heat in a water bath for 5-10 minutes. Observe.

Comment on the effects of heat and alcohol on proteins.


PRACTICAL 4 CHARACTERISTIC REACTIONS OF MACROMOLECULES Carbohydrates, fats, proteins and nucleic acids are the major macromolecules that occur in cells. Carbohydrates range from relatively simple molecules called sugars to the complex molecules of starches and cellulose. The simplest class of carbohydrates is represented by the monosaccharides, e.g. glucose and fructose. Disaccharides are formed by combining two monosaccharides. One of the most important disaccharides is sucrose, made by linking glucose with fructose. Polysaccharides such as starch and cellulose are made up of a large number of monosaccharides joined in long chains. The fats or lipids are a group of organic substances originating in living cells. They are composed of two main groups, fatty acid and glycerol. Protein molecules are of gigantic size made up of a large number of amino acids units connected one to another by peptide bonds. A significant portion of the protoplasm of plant and animal cells is made up of proteins. The nucleic acids are of two types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). DNA is the hereditary material of the cell, while RNA is important in protein synthesis.

Carry out the following tests which demonstrate some of the means by which the above mentioned compounds can be identified. 1. Detection of Carbohydrates (reducing sugars) 1A. Add 5ml of Benedict’s solution to 5ml of the each of the carbohydrate solutions provided. Immerse the tube in a boiling water bath for 5 minutes. Record the colour change and the relative amount of precipitate formed for each of carbohydrate tested. Explain the results. 1B. Label three test tubes. To tube 1 add about 5ml of 10% sucrose solution and then 2 drops dilute

hydrochloric acid (HCI). Place in water bath for about 2 minutes then add 5ml of Benedict’s solution.

To tube 2 add about 5ml of 10% sucrose solution then 5ml of Benedict’s solution

To tube 3 add 5ml water and 2 drops of dilute hydrochloric acid (HCI) Place all the tubes in a boiling water bath for 15 minutes then observe.


i. What was the point of heating Benedict’s solution with dilute HCI? ii. If a food sample contains sucrose as the only sugar, what two tests

would have to be carried out to show the presence of this sugar? 1C. Place about 1ml of the carbohydrate solution into a test tube and add a drop of iodine in potassium iodide solution (I2 in KI). Which of the carbohydrates gave a blue colour? Immerse the blue coloured solution in a beaker of boiling water and heat for 3 minutes then remove from the heat and cool under the tap. Record and explain the results. 2. Detection of Lipids To about 2mls of water in a test tube add 2mls of coconut oil followed by a few drops of Sudan III or Sudan IV solution. Shake the tube well then allow it to stand for 1 minute. Note the formation of two layers. Which layer is coloured red? Why? 3. Detection of Proteins The Biuret Test : In separate test tubes place 3mls of 1% egg albumen solution or gelatin, 1% starch solution, 10% glucose solution and water. Add 1ml 10% Sodium Hydroxide (NaOH) solution. (CAUSTIC). Mix thoroughly then slowly add drop by drop 1% copper sulphate, (CuSO4) solution. Note the colour changes. With which of the sample did the Biuret test give a purple colour?


PRACTICAL 5 ENZYMES

Enzymes are complex proteins which act as biological catalysts that regulate chemical reactions in the cell. Many of the characteristic reactions of cellular activity, when carried out in the test tube, will proceed only at temperatures, pressure and pH values that are incompatible with life. In living organisms, complex metabolic reactions proceed rapidly under physiological conditions since the organisms produce enzymes. Enzymes are effective in minute amounts and are usually unchanged by the chemical reactions they promote. Many enzymes are very specific in the reactions they effect. Enzyme activity is usually expressed in terms of the rate of the reaction catalyzed by the enzyme. The following experiments will help in obtaining information of some of the factors that affect enzyme-catalyzed reactions. 1. Effect of pH on enzyme activity. Diastase is an enzyme (or mixture of enzymes) that catalyzes the hydrolysis of starch with the production of dextrins, maltose and glucose. The disappearance of starch from the reaction mixture could be ascertained by the iodine test.

Collect a petri dish containing starch agar and mark crossed lines on the underside with wax pencil to divide the plate into four quadrants, A, B, C & D. Use a cork borer to make a central well in each quadrant. To well A add two drops of buffer solution pH4; well B, pH5; well C, pH6 and well D two drops pH7 buffer solution. Add two drops of diastase to each well; cover the dish and leave for 2 hours. Stain the agar with dilute iodine for two minutes. Pour off the excess iodine and measure the diameter of the clear zone around each well. Tabulate your results. Comment on the effect on pH on enzymes.

2. Effect of enzyme concentration on enzyme activity. Dehydrogenases are widely distributed throughout the plant and animal kingdoms. They transfer hydrogen from donor to acceptor molecules. In certain enzymatic reactions coenzyme I and II act as hydrogen carriers for the hydrogen atoms removed by the dehydrogenase. Under aerobic conditions oxygen will act as the final hydrogen acceptor causing the formation of water. In anaerobic conditions, other materials can serve as hydrogen acceptors from reduced coenzyme. Methylene blue can act as hydrogen acceptor becoming leucomethylene blue (colourless) when reduced. It can therefore be used as an indicator of the enzyme’s activity.


2A. Place 0.5mls of 0.02% methylene blue in three 5mls snap cap vials. Fill the first vial with fresh bottled milk; the second with bottled milk that has been left unrefridgerated for at least three days; and the third with milk that was left unrefrigerated then boiled. Close the tubes and leave at room temperature. Examine at twenty minute intervals for two hours. Tabulate your results.

i. Which milk sample became decolourised first? Which didn’t? Why?. ii. What is the source of the enzyme? iii. Uncork the tubes in which the milk has decolourised and blow gently

into it. Explain your observations.

2B. A methylene blue test was historically used to determine the quality of milk in terms of its bacterial population.

Repeat the test in 2A with the sample of box milk provided, this time incubating at 37°C. Record the time taken for complete decolourization of your sample. Rate the sample.

Time Taken For Milk Of Varying Quality To Decolorize Methylene Blue Time to Decolourize Methylene Blue Rating of Milk

Less than 20 minutes Highly contaminated 20 minutes to 2 hours Poor

2 to 5 ½ hours Fair 2½ to 8 hours Good

More than 8 hours Excellent 3. Effect of temperature of enzyme activity. Tyrosinase is an enzyme which occurs widely in plants and animals alike. It is responsible for the production of most of the dark brown and black pigments of animals. A crude extract of tyrosinase is prepared from potato tubers by breaking down potato slices in a blender then filtering the juice through a coarse filter. Tyrosinase is an oxidase. It catalyzes the removal of two hydrogen atoms and electrons from molecules of such compounds as catechol (colourless) to form benzoquinone (coloured). The hydrogen atoms are then passed on to oxygen to form water.


In each of three test tubes add 5ml of water and ten drops of the potato extract. Place the first tube in an ice-water bath, the second in a beaker of water at room temperature and the third in a hot-water bath. Allow five minutes for temperature equilibration. Add ten drops of catechol (POISON!) to each tube, shake the tube then replace it in the appropriate incubator. At five minute intervals, for the next 30 minutes, examine the tubes. (Ensure the temperatures are kept relatively constant throughout the 30 minutes). Compare the relative colour intensities. Present your results in a table. Comment on your results and explain the effect of temperature on enzymes.


PRACTICAL 6 USE AND CARE OF THE COMPOUND MICROSCOPE A microscope extends our vision beyond the limits of the eye. It allows us to see cells. It consists of two main parts: a stand, comprising the foot and limb and a tube, containing the optical system. Objects to be examined are commonly mounted on a glass slide and retained on the stage by a clamp. The object is illuminated from below the stage by light reflected from the mirror. The microscope is fitted with a sub-stage condenser, which focuses the parallel light rays reflected into the condenser so that the quality of light illuminating the object can be adjusted. The tube is a hollow cylinder with an eyepiece (ocular) lens system. At the base is a revolving nosepiece to which objectives of different magnifications are attached. Objects are brought into focus by the movement of the tube, controlled by the coarse adjustment and the fine adjustment knobs. To obtain the best results use the following procedure: 1. Place the microscope on the bench with the tube in a vertical position

facing a good light source (artificial or diffused daylight but not direct sunlight)

2. Move the condenser right up (in older models the condenser slides in a sleeve mounting) and using the low power (LP) objective obtain a full illumination of the field of view by adjustment of the mirror.

3. Mount the piece of material to be examined on a slide with a small drop of water or dilute glycerol (the latter will dry out much more slowly). Then using a needle, cautiously lower a cover slip on to the specimen so as to exclude air bubbles.

4. Place the slide on the stage with the specimen directly below the LP objective and bring it into focus by using the coarse adjustment. The focal length of the LP objective (the distance between lens and the objective when in focus) is about 9mm.

5. Re-adjust the condenser so that an object (e.g. a pencil) placed between the lamp and the mirror also appears in focus.

6. Adjust the iris diaphragm so that a satisfactory compromise is obtained between brightness and contrast.

7. To view an object under the high power (HP) objective, place it in the centre of the LP field and swing the nosepiece to bring the HP objective into position. The distance between the objective and the coverslip is very small, so bring it into focus using the fine adjustment only. The condenser will still be in focus on the specimen and will not require adjustment; the iris diaphragm will probably require some readjustment.

Develop the habit of cleaning the ocular and objective lenses after each use of the microscope. Use only lens tissue, never filter paper, towels or


any other material that may scratch the lens. Remember that the microscope is an expensive precision instrument: always handle with care. Magnification Eyepieces – usually x 6, x10 and x15 Objectives – LP magnifies X10; HP magnifies X40 or X45; Oil immersion magnifies X100 approximately Total magnification of the microscope is obtained by multiplying together the magnification for eyepiece and objective lenses. Measuring Microscopic Objects It is often important for the biologist to know the dimensions of the object he is observing under the microscope. To do this you will need to know the diameter of your microscope’s field of view at different magnifications. Determination of the diameter of the field of view 1. Place a short plastic scale (or strip of 1 mm graph paper) on the centre

stage so that the scale is visible through the eyepiece. 2. Line up an intersection of one of the vertical lines and a horizontal line

so that the point at which they meet is just visible at the left side of the circular field of view. The horizontal line should run across the diameter of your field of view.

3. Count the number of units (intersecting lines) included from one side of the field to the opposite side (i.e. left to right). If the right side of the field does not coincide with one of the lines, you will have to estimate the fraction of a unit.

4. Write down this value for the diameter of the LP (in micrometers) of our microscope and note the number of the microscope.

5. As the diameter of the HP field is less than 1 mm, it is more accurate to obtain the diameter of the HP from the following formula:

Diameter of HP field = diameter of LP field÷ magnification of HP objective

magnification of LP objective Write down this value for the diameter of both LP and HP (in micrometers) of your microscope and note the number of the microscope. You will need this information every time you use the microscope. Microscope #: _____ LP field diameter ________ HP field diameter _______ To find the length or width of an object under the microscope, estimate it in relation to the diameter of the field in view. This method is not accurate, but it will enable you to obtain estimates of the size of microscopic objects.


PRACTICAL 7 CELL STRUCTURE

You will be using the microscope to observe the structures of cells. Illustrate the structures by drawing 2-3 cells (refer to page 12 – scientific illustrations).

1A. Strip a small sheet of inner epidermis from the fleshy leaf of an onion (Allium cepa) bulb, and place in a drop of water on a clean side. Gently spread out or cut off any folds in the sheet and cover with a clean cover slip (lower the cover slip from one edge in order to exclude air bubbles). Illustrate the cell to show the cell walls, cytoplasm, nucleus and nucleolus. You may need to irrigate the mount with iodine solution to see the nucleus.

Prepare a fresh sheet of onion epidermis but irrigate with 0.4M sucrose solution. Illustrate. Annotate your drawing to show the differences between these cells and those mounted in water.

2. Mount a young leaf of Elodea sp. in distilled water. Examine and draw a group of cells near the edge of the leaf. 3. Examine and draw cells from very thin sections of the inside of a potato (Solanum tuberosum) tuber. Irrigate with a dilute solution of iodine. What effect does the iodine have on the cells? Illustrate. 4. Gently scrape the inside of your cheek with the broad end of a toothpick. Add a drop of water to a clean slide, and then spread the scraping from the toothpick in the water. Cover the preparation and examine with the microscope. Notice that the cells are either square or diamond–shaped (squamous epithelial cells). You may irrigate with methylene blue to observe more cellular details. 5. Examine a thin longitudinal section of an onions root tip. From LP draw a plan diagram to show the root cap, the region of cell division (meristem) and region of elongation. Illustrate and compare the cells from each of these regions.

Prepare a table comparing the cells from the onion bulb, onion elodea leaf, potato tuber and human cheek.


PRACTICAL 8 CELL DIVISION - PART 1: MITOSIS The cell cycle consists of interphase and mitosis. Interphase – Cell outline box-like, nucleus is round, and situated within a relatively small amount of cytoplasm. The nucleus is bounded by a membrane (the nuclear membrane). The granular material enclosed by the nuclear membrane is termed chromatin. The nucleus may also contain a small dense body (or bodies) known as the nucleolus (nucleoli). Mitosis is the basic form of cell division in somatic eukaryotic cells. Cell division actually involves two processes: karyokinesis (division of the chromosomes) and cytokinesis (division of the cytoplasm). The result is daughter cells with the same number of chromosomes as the parent. The stages which may be observed are: Prophase – This is the initial stage of cell division. At this stage, the

chromatin appears as diffuse thread-like structures, the chromosomes. The chromosomes have become visible because each chromatin fiber has undergone a coiling process which shortens its length while increasing its diameter. Each chromosome in prophase is constructed of two identical chromatids, held together at a region called the centromere. In some cells the individual chromatids are not visible at this stage.

Metaphase – The nuclear membrane has disappeared and the chromosomes are now lined up in a row across the middle of the cell. The imaginary line on which the chromosomes are arranged is the equatorial plate. Spindle fibres radiate away from the equatorial plate towards the opposite ends (poles) of the cell.

Anaphase – The centromeres holding pairs of chromatids together have divided and one chromatid now called a daughter chromosome, of each pair is now moving toward each pole. A spindle fibre appears to be attached to the centromere of each chromosome.

Telophase – The chromosomes are now grouped at opposite poles of the cell and a thin partition, the cell plate may be seen cutting across the mitotic spindle along the equatorial plate. At this stage the chromosomes uncoil and appear as chromatin and the nuclear membrane and nucleolus re-appear.

Cytokinesis – This final stage in the separation of the daughter cells is produced by completion of the cell plate in plant cells and cytoplasmic furrowing in animal cells.


1. Examine the meristematic zone of an onion root-tip (longitudinal section) under HP. Identify and illustrate cells which are in Interphase, Prophase, Metaphase, Anaphase and Telophase.

2. You are provided with the following pairs of chromosomes. The letters represent genes. Illustrate the chromosome as they would appear in a cell: a. after replication in the S phase of Interphase Mitosis b. Prophase c. Metaphase (remember that homologous chromosomes do not pair up in

mitosis so they attach to separate spindles). d. Anaphase e. Telophase and f. at the end of Cytokinesis.


PRACTICAL 9 CELL DIVISION - PART II: MEIOSIS Meiosis (reduction division) occurs only during the formation of gametes. There are two divisions. The first results in two daughter cells which each contain half of the chromosomal material of the parent cell. The second division usually results in the production of either four spermatozoa or an ovum and three polar bodies. Meiosis 1 begins with Prophase 1 in which the members of homologous pairs of chromosomes physically join. Crossing-over takes place. This is a process of genetic recombination during which homologous (non-sister) chromatids exchange segments of DNA strands. Homologous chromosomes appear on the spindle in Meiosis 1 as a pair. They are separated in Anaphase 1 so at the end of Meiosis 1 each nucleus contains the haploid number chromosomes each consisting of two chromatids. Chromatids of each chromosome are separated in Anaphase II so at the end of Meiosis II there is one chromatid in each daughter cell. 1. Examine prepared slides of Lilium anthers showing stages of meiosis in pollen mother cells. Make drawings to show as many stages of the process as possible. 2. Examine prepared slides of grasshopper testis. Illustrate chiasma. 3. You are provided with the following pairs of chromosomes. The letters represent genes. Illustrate the chromosome as they would appear in a cell: a. after chromosome replication Meiosis b. when the homologues pair up (prophase I), c. when a chiasma is formed (prophase I), d. at the end of crossing over (prophase I), e. Metaphase I, f. Anaphase I, g. Telophase I, h. Metaphase II, i. Anaphase II, j. Telophase II, and k. at the end of Cytokinesis.


PRACTICAL I0 MAMMALIAN REPRODUCTION – TESTIS & OVARY The survival of the species depends upon a consistent succession of new individuals. This is accomplished by a process called reproduction in which the organism produces a group of new offspring. Among animals, a variety of reproductive methods (sexual and asexual) and organs exist. Mammals utilize sexual reproduction. The Male Reproductive System. The male reproductive system comprises the testes, the ducts of the testes, the auxiliary glands associated with them (seminal vesicles, prostate gland) and the penis. The primary function of the male reproductive system is the production of spermatozoa. The testis is a double gland since functionally it is both exocrine and endocrine. It is suspended within the scrotum and is surrounded by the testicular capsule which is composed of three layers; the outer tunica vaginalis, the middle tunica albuginea and the innermost tunica vasculosa. The testes contain seminiferous tubules in which the process of spermatogenesis (sperm production) occurs. It starts in the germinal epithelium which is composed of a mobile set of proliferating and differentiating spermatogenic cells and a permanent set of supporting Sertoli’s cells. The main endocrine secretion of the testis is testosterone produced by the interstitial cells of Leydig after stimulation by Interstitial Cell Stimulating Hormone (ICSH) or Luteinizing hormone (LH).

Make a drawing from HP to show the details of a seminiferous tubule. The Female Reproductive System The female reproductive system consist of the ovaries, a system of genital ducts, (the uterine tubes, uterus, and vagina) and the external genitalia. The ovaries like the testes are classified as double glands since they produce both exocrine and endocrine secretions. They are slightly flattened ovoid bodies (about 4cm x 2cm x 1cm) lying on each side of uterus in the lateral wall of the pelvic cavity. In sections of the ovary two zones may be distinguished as an outer cortex and inner medulla.

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PRACTICAL 11 ANGIOSPERM REPRODUCTION Among plants, reproduction may take place in a variety of different ways. Angiosperms, however, most commonly use sexual reproduction; the reproductive organs being on the flower. 1a. Examine and record the features of the flower provided. The outer most whorl of floral parts make up the perianth. In many flowers the perianth is distinguishable into the calyx and the corolla. Typically, the calyx (sepal) is green and protective, although it may be coloured. The corolla (petal) lies inside the sepals and are often brightly coloured and serve to attract insects to pollinate the flowers. The two whorls of perianth usually alternate with one another.

Determine if the parts of each whorl are free from each other (polypetalous, polysepalous) or fused together (gamosepalous, gamopetalous.) Count the number of petals and sepals.

Note the positions of the perianth parts on the enlarged end of the

flower stalk, the receptacle. Using forceps, gently pull off the perianth parts. Find the stamens that surround the pistil. The stamens collectively form the androecium. Observe that the stamen is composed of two parts: the filament that is terminated by a sac like anther. The pistil (gynoecium) has an enlarged ovary and a stalk like style terminated by one or more stigmas.

Determine if the stamens grow directly from the receptacle, or from the petals (epipetalous). Determine if they are free or fused to one another.

Determine whether the flower is hypogynous (perianth below, ovary

superior), epigynous (ovary below perianth) or perigynous (ovary and perianth on the same level).

1b. Mount an anther in a drop of water, crush it with a needle, cover and observe the contents microscopically. A large number of pollen grains should be apparent. Draw a few pollen grains to show their characteristic shape. 1c. Use a razor blade to cut a transverse section of ovary and examine it microscopically. Note the immature seeds (ovules) and observe that they grow from swellings (placentas) on the inside of the ovary. Make a low power diagram.


1d. A Half Flower Drawing is a conventionalized longitudinal section through the flower. The flower should be cut through the vertical plane of symmetry. Represent the cut edges of the flower by double lines and draw, with single lines, the background of the uncut portions of the half flower. Use your magnifying glass or dissecting microscope to observe the longitudinal section of the ovary. Note carefully the shapes of the receptacle, ovules and pedicel.

Make a half-flower drawing of the flower provided. Figure: Half-flower diagram

2. Examine the prepared slide of (a) T. S. unripe and (b) T. S. dehisced anthers. Make low power diagrams to show the structure of the anther and to illustrate the method of dehiscence. 3. Examine the flowers provided. In each case, state the possible method of pollination, giving at least two reasons for your conclusion.


PRACTICAL 12 MONOHYBRID & DIHYBRID CROSSES 1. Monohybrid Cross

This involves two different alleles at a single locus. One locus may govern seed colour, another seed shape. Alleles are genes that govern variations of the same character (e.g. green versus yellow seed colour) and occupy corresponding loci on homologous chromosomes. Coloured beads will be randomly selected to simulate monohybrid inheritance. Beads drawn represent the genotype of the new progeny. A chi squared test will then be used to compare the difference between the observed and expected values to determine whether or not the difference is significant.

Collect two bags. To each bag add 20 red beads and 20 blue beads. Shake the bags, and then randomly select two beads, one from each bag. Record whether you picked two red beads (RR), a red and blue (RB) or two blue beads (BB). Replace the beads in their respective bags and repeat the process 99 times.

Calculate the chi-square value to determine whether the difference is

significant at 0.05 probability value. • Record the null hypothesis. • Total the observed (O) number of RR, RB, and BB beads. • On the basis of expected Mendelian ratios and probability, calculate

the expected (E) values. Then, complete the chi squared table. X2=∑ (o-e)2 e

The number of degrees of freedom = (number of classes -1) represents the number of independent classes that contribute to the calculated value of x2.

The 0.05 probability value is used as the significance level by statistical convention. At two degrees of freedom, if the calculated chi-square value is less than the table value of 5.991, (see Chi squared table) then the deviation is not significant and the difference could have arisen by chance. If the calculated x2 is equal to or greater than the table value then the deviation is considered significant and the likelihood of such a large discrepancy arising by chance is too low.

• Conclude whether or not the null hypothesis is accepted.

Phenotype O E O-E (O-E)2 (O-E)2/E Red Red Red Blue Blue Blue

∑ 100 ∑


2. Dihybrid Cross This involves different alleles at two loci. A homozygous black, short haired guinea pig (BBSS) and a homozygous brown long haired guinea pig (bbss) are mated.

Determine the parental gametes and the first filial genotype and phenotype.

F1 generation Record in the Punnet square the gametes produced in the F1. Remember that gametes are formed by segregation and independent assortment of alleles. The four kinds of gametes are produced with equal probability.

Determine the genotype and phenotype of the progeny. Also record the genotypic and phenotypic ratio.

F2 generation 3. In TV bugs, Cable (A) is dominant to rabbit ears (a) and Colour (B) is dominant to black & white (b). Work Aholic found two Cable Colour bugs and did test cross (cross with the homozygous recessive) to determine their genotypes.

For Cable Colour bug #1 he obtained 30 bugs, all Cable Colour. Explain why he obtained these results.

For Cable Colour bug #2 he obtained 11 Cable Colour bugs, 8 Cable

black & white, 8 rabbit ears Colour and 6 rabbit ears black & white progeny for a total of 33 TV bugs. Explain why he obtained these results. Determine if these results are significantly different from those expected.

Parental genotype BBSS bbss GametesF1 genotypeF1 phenotype

F1 gametes


PRACTICAL 13 NATURAL SELECTION & EVOLUTION The aim of the biological sciences is to understand life. Any coherent theory of biology must account for overarching features of the natural world. 1. The unity of life 2. The diversity of life 3. The existence of biological adaptations 4. The dynamic history of life on Earth The theory of evolution is the cornerstone of modern biology that seeks to explain these. It attempts to explain why millions of species exist. As a principle, evolution states simply that species change through time. New species of organisms emerge and older forms of life disappear. Charles Darwin was the person who brought the evidence together and by 1838 he had proposed a mechanism, natural selection, for evolution. His ideas are summarized in four points. 1. There is variation among individuals of most populations. 2. Some proportion of that variation is inherited. 3. Populations tend to produce more offspring than the environment can

support. 4. Those individuals whose traits are best adapted to the prevailing

environment will survive better and leave more offspring than those with less adaptive traits.

The weakest part of Darwin’s theory was his inability to explain how genetic variation arose and how it was maintained in populations, both of which were poorly understood at the time. With the entry of Gregor Mendel’s work into the mainstream of biological thinking in the early twentieth century, the broad principles of the relationships between genes and natural selection were elucidated. The combination of Darwin’s theory of evolution with the principles of Medelian genetics is known as the neo-Darwinian synthesis of the synthetic theory of evolution. During the past fifty years, the synthetic theory has dominated scientific thinking about the process of evolution and stimulated a great deal of investigation. Current controversies revolve primarily around the rate of macroevolutionary change and the role played by chance in determining the direction of evolution. They do not affect the basic principles of synthetic theory. The debate, however, promises to give us a more complete understanding of evolutionary mechanisms than we have at present.


VARIATIONS IN ANIMAL POPULATIONS 1. Sources of variation: Variations in a population arises from two primary sources, mutation and genetic recombination Mutations add new genes or alleles to the gene pool and thus supply the genetic foundation on which evolutionary forces operate. You are already familiar with the variation produced by sexual reproduction from your studies of genetics and your experience with families. 1. Researchers have estimated that there are one or two mutations per gamete but that these are usually inconsequential as sources of variation within a population. However, in asexual species, such as bacteria, mutation can be an adequate source of variation. Can you suggest one reason for this? 2. Variation is a fundamental attribute of the individuals of a population and the raw material for evolution. Variation includes behavioural and biochemical traits as well as the common visible (morphological) traits. Such variation must be genetically based to be significant to evolution.

Examine the sample of arthropod or mollusk individuals taken from a single population.

2a. Identify at least five morphological trait in which the individuals vary. Present your results in table which shows the feature and the number of individuals with each variation.

2b. Think about the variation in the population. Decide whether each morphological trait varies continuously or discontinuously and whether it is likely to be determined solely by genetic factors or also influenced by environmental factors. Suggest advantages and disadvantages that may be associated with different variations of each trait. 3. Comparison of Cytochrome C from Man and Seven Other Animals: An Exercise Using the Genetic Code Cytochrome c, or cyt c is a small, water soluble heme protein associated with the inner membrane of the mitochondrion. Each cytochrome c carries one electron between two different electron transport complexes (III and IV) embedded in the inner membrane. In doing this, cytochrome c repetitively undergoes either oxidation or reduction, but it does not bind oxygen. This electron transport chain drives the production of ATP.


Cytochrome c has been studied extensively because its small size (about 100 amino acids; molecular weight 12,000 daltons) and its water solubility permit researchers to isolate it from other mitochondrial proteins, which tend to be not only larger than cytochrome c but also fat soluble and embedded in the membrane. The amino acid sequences for the cytochrome c occurring in many organisms from yeast to humans have been determined. It is found universally in aerobic organisms. Comparison of amino acid sequences of the molecule in diverse species shows a great deal of similarity among organisms. This protein is highly conserved across the spectrum of species and so is useful in studies of evolutionary relatedness. Similarities in the amino acid sequences suggest a common ancestor that must have been using this protein even before basic divergences between plants and animals arose. The degree of similarities correlates closely with the apparent degree of relatedness. The sequences from monkeys and cattle are more similar than the sequences from monkeys and fish. Chickens and turkeys have the identical molecule (amino acid for amino acid) within their mitochondria, whereas ducks possess molecules differing by one amino acid. Similarly, both humans and chimpanzees have the identical molecule, while rhesus monkeys possess cytochromes differing by one amino acid. A sequence of thirteen amino acids, near the N-terminal end of cytochrome C from human tissue is:

gly-asp-val-glu-lys-gly-lys-lys-ileu-phe-ileu-met-lys The sequence, derived from the identical region of peptide chain of the cytchrome C of a number of other organisms (a-g) is as follows: a. gly-asp-val-ala-lys-gly-lys-lys-thr-phe-val-glu-lys b. gly-asp-pro-asp-ala-gly-ala-lys-ileu-phe-lys-thr-lys c. gly-asp-val-glu-lys-gly-lys-lys-ileu-phe-ileu-met-lys d. gly-asp-ileu-glu-lys-gly-lys-lys-ileu-phe-val-glu-lys e. gly-asp-ala-glu-asp-gly-lys-lys-ileu-phe-val-glu-arg f. gly-asp-val-glu-lys-gly-lys-lys-ileu-phe-val-glu-lys g. gly-ser-ala-lys-lys-gly-ala-thr-leu-phe-lys-thr-arg

For each of the sequences, calculate the least number of mutations that would be necessary if the sequence is to be changed to that found in man. (The least number of mutations as this is more likely to occur than a large number of mutations).

o You will need to compare each amino acid in the sequence with that in man’s sequence and, using the genetic code, determine

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Rank the following organisms in order of increasing ‘evolutionary distance’ from man: Silk moth, Tuna fish, Chicken, Rhesus monkey, Yeast, Wheat, Horse

Suggest which of the sequences a-g could belong to each organism.

Sequence No. mutations Organism Organism description 4A. Some persons find weak solutions of the chemical phenylthiourea (PTC) bitter and distasteful. Others are unable to taste it.

Place a piece of PTC paper on your tongue. Can you detect a bitter taste? Calculate the percentage of tasters and non-tasters in the class.

i. PTC is a harmless chemical but can you suggest a situation in the evolutionary history of humans in which the inability to taste a chemical might have had evolutionary consequences? 4B. Animals vary not only in their appearance but in their behaviour. For some behavioural variations, it is easy to suggest evolutionary or adaptive significance; for others, possible adaptive value is much harder to predict.

Check yourself for thumb and arm crossing and record the class data. Thumb crossing: Interlock fingers and check if left thumb is over or below the right thumb. The left thumb over is due to a dominant gene. Arm Crossing: Cross arms and check if left arm is over or below right arm. i. Can you suggest any adaptive significance for left or right dominance in thumb or arm crossing?


PRACTICAL14 PROKARYOTES; KINGDOM PROTISTA; KINGDOM FUNGI Nb. Refer to page 7 for hints on preparing illustrations. Remember to include the classification of each organism illustrated. 1. PROKARYOTES: Examine prepared slides to observe various bacterial shapes. 2. EUKARYOTES KINGDOM PROTISTA 2a. Algae Examine and draw, from fresh specimens and/or prepared slides, the following range of Algae.

Chlorophyta (green algae) i. Single celled eg. ii. Colonial eg. iii. Filamentous eg. iv. Thalloid eg.

Phaeophyta (brown algae) eg. Rhodophyta (red algae) eg.

Ulva sp Sargassum sp. 2b. Protozoa Examine and draw specimens from prepared slides. Annotate the labels relating to feeding and locomotory structures.

Amoebozoa/ Rhizopoda eg. Amoeba sp. – Locomotion is by means of pseudopodia.

Euglenophyta/ Mastigophora eg. Euglena sp. – Locomotion is by one or two anterior flagella (often difficult to see). This species also possesses


chloroplasts, and the cell surface is covered with a pellicle. There is no cellulose cell wall.

Euglenophyta. Volvox sp. is colonial. Colonial protist species are common (16 groups of protists contain colony-forming species) and colonies are often very difficult to distinguish from multicellular animals. Coloniality is favoured by biologist as the means by which multicellular animals evolved. Cells of Volvox are not differentiated into tissues and organs but show how the preliminary stages to such an evolutionary sequence may have occurred. In the slide you will be able to see the regular spacing of each cell, as well as the formation of new daughter colonies.

Ciliophora eg. Paramecium sp. – Characterized by the presence of cilia over the surface of the cell.

Place a drop of pond water on a slide with a coverslip and examine it under the microscope. Add a few drops of methyl cellulose to slow down the organisms if they move too quickly. Draw examples of the protists present. Identify each as amoeboid, flagellate, or ciliate.

Amoebozoa Ciliophora Euglenophyta Euglenophyta (colonial)


3. KINGDOM FUNGI Examine and draw from fresh specimens, preserved specimens and prepared slides, the following range of fungi.

Lower fungi: Hyphae are coencytic, sporangia contain indefinite number of spores. Identify hyphae, sporangiophore, sporangium, columella, sporangiospores and zygospores

Eg. Rhizopus sp. and Mucor sp.

Higher Fungi: Hyphae are septae. Eg. Aspergillus sp. and Penicillum sp. Examine and draw fruiting bodies: mushrooms and bracket fungi. Lower fungi Higher fungi Mushroom


PRACTICAL 15 KINGDOM PLANTAE (BRYOPHYTES, PTERIDOPHYTES & GYMNOSPERMS) 1. PHYLUM BRYOPHYTA

Examine and illustrate entire liverwort and moss plants, identifying the reproductive and vegetative portions.

Class Hepaticae (Liverworts). Eg. Marchantia sp. Note apical notch and gemma cup (asexual reproductive structures) on dorsal surface, antheridia and archegonia (sexual reproductive structures). Class Musci (Mosses). Eg. Polytrichum sp. Note the male plant with stem (axis), leaves and artheridial cup; the female plant with archegonial rosette and female plant with sporophyte .

Marchantia (female & male) Polytrichum (gametophyte with sporophyte) 2. PHYLUM PTERIDOPHYTA

Examine and draw the habit of heterosporous and homosporous peteridophytes.

Heterosporous Eg. Selaginella sp. Note different size leaves, fertile leaves forming cones. Draw spores from a squash of fertile leaves Homosporous eg. Eg. Nephrolepis sp. Illustrate the gametophyte. Illustrate the sporophyte noting circinnate vernation. On the leaf underside note the sori and indusium (covering sori).

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HOW TO CONSTRUCT AND USE DICOTOMOUS KEYS Biologists use taxonomic or identification keys to assist them in identifying organisms. Many identification keys are dichotomous; ie made up so that there are two choices. Each couplet had two leads. Choice of a lead directs the user to the possible identity of the organism or to another couplet. As a simple example to help you understand how an identification key works, let us examine a simple key to certain familiar animals: earthworm, grasshopper, dog, octopus, fish, snail, lobster, clam, alligator, bird and frog. As you proceed, especially note how the animals are grouped according to their similarities. Start at No. 1, examine your animal and select lead 1a or 1b. Follow to the next number as you are instructed and again select a or b. Proceed until you come to the name of the animal. Identification Key to Selected Animals. Couplet Characteristic Next move/Id 1a Animal with bony endoskeleton 2 1b Animal with exoskeleton or no skeleton 6 2a Fins present Fish 2b Fins absent 3 3a Oviparous 4 3b Viviparous Dog 4a Eggs laid on land 5 4b Eggs without shells laid in water Frog 5a Wings present Bird 5b Wings absent Alligator 6a Body soft, without external skeleton 7 6b Body covered with exoskeleton or shell 8 7a Body with eight arms (tentacles) Octopus 7b Body without arms Earthworm 8a Jointed exoskeleton present 9 8b Shell presented, not jointed 10 9a Six legs present Grasshopper 9b More than six legs present Lobster 10a Shell coiled Snail 10b Shell double and hinged Clam Preparing a dichotomous key.

You are provided with a collection of plants or animals. Prepare a dichotomous key to distinguish them. (See guide overleaf). In addition to your observations, use your notes and text to obtain information on the important features of the organisms.


NB. The key should be strictly dichotomous throughout. The leads in each couplet should be contrasting so that one fits the situation at hand while the other does not. For example:

a. Leaves opposite…………………. b. Leaves alternate………………….

The leads are usually in phrase form (not complete sentences), with each feature uniformly separated from one another by a semicolon. For example:

a. Leaves opposite; flowers blue; sepals 4………. b. Leaves alternate; flowers red; sepals 5………

Attempt to phrase leads to read as positive statements, especially the initial lead of the couplet. So, for example, use

a. Inflorescence an umbel………… b. Inflorescence a panicle………..

rather than a. Inflorescence an umbel………. b. Inflorescence not an umbel………

To avoid unnecessary confusion the initial word of each lead of the couplet should be identical. So, for example, use

a. Flowers blue; sepals 5………. b. Flowers red; sepals 4………...

rather than a. Flowers blue; sepals 5 b. Corolla red; calyx of 4 sepals…

Also, for clarity, two consecutive couplets should not each commence with the same word. So, for example, use

1a. Petals blue…………………….. 1b. Petals red……………………… 2a. Corolla actinomorphic (radially symmetrical)……… 2b. Corolla zygomorphic (bilateral or asymmetrical)……….

rather than 1a. Flowers blue…………………….. 1b. Flowers red………………… 2a. Flowers actinomorphic……… 2b. Flowers zygomorphic………..

Avoid the use of generalities or relative terms in contrasting leads of the couplet. So, for example, use

a. Petioles 2-3cm long; flowers 5-8 cm. in diameter…… b. Petioles 6-7cm long; flowers 0.5-1cm. in diameter…..

rather than a. Petioles short; flowers large and showy…………. b. Petioles long; flowers smaller and less conspicuous…….

Avoid using overlapping limits of variation. The following example is in poor form. Here, petiole length and flower color should be avoided. Other, more contrasting characters should be sought and embodied in the key.

a. Petioles 2-6cm long; flowers pink to red……… b. Petioles 3-8cm long; flowers red to purple……..

Use clearly discernible morphological characters whenever possible. Keys to dioecious plants should take into account both staminate and pistillate material. If vegetative parts do not display diagnostic features use both flowers and fruit. Within a single key, avoid switching from flower characters to fruit characters unless fruit and flowers are commonly present together – or unless sufficient supplemental characters are given to identify material in either condition.


PRACTICAL 16 KINGDOM ANIMALIA, PHYLA: PORIFERA AND CNIDARIA 1. PHYLUM PORIFERA The ciliate protists demonstrate the greatest complexity that has evolved in a unicellular organism. Further elaboration demands an increase in size and for this a multicellular structure has proved necessary. Sponges are the simplest multicellular animals. They have neither true tissues nor organs and their cells retain a considerable degree of independence. However unlike protists the various kinds of cells do not act entirely as individuals. The cells show a definite social organization with individual cells specialized for the functions of feeding, support or reproduction. Body Development Plan of Phylum Porifera: diploblastic, asymmetrical.

Examine and illustrate each type of sponge. Try to determine which are the inhalant and exhalent (osculum) openings.

Cut a small section of the sponge and treat it with bleach. Examine a drop of the digested material with the aid of a microscope. Observe and draw the spicules.

Illustrate the sponge Grantia from a prepared slide. Identify the spongeocoels (flagellated chambers) and the choanocyte cells.

Asconoid, Leuconoid and Synconoid sponges. Sponge spicules

2. PHYLUM CNIDARIA Body development plan of Phylum Cnidaria: diploblastic, radially symmetrical. The Cindaria show two advances in complexity over the sponges. They have an internal space for digestion, the gastrovascular cavity, which has a single extensible opening, the mouth. This allows them to feed on a


much greater range of food sizes than is possible for either the protists or the sponges. The body wall is composed of tissue layers, an outer ectoderm or epidermis, the middle non–cellular layer mesogloea and the inner endoderm or gastrodermis. Cnidarians are polymorphic, ie they have more than one body form. The “medusa” form is adapted for pelagic existence. It has the mouth and tentacles facing downwards. The “polyp” form is adapted for benthic existence with the mouth and tentacles facing upward. Cindaria are classified based on whether polyps or medusae are the dominant body form during the life cycle. Hydrozoa: polyps are generally more conspicuous than medusae.

Place a small section of the hydroid colony on a slide, with a cover slip, and examine it using the microscope. Look for the following features; hydranth, hydrotheca, tentacles, hypostome, mouth, gonotheca, blastostyle and stolon. Illustrate.

Observe live specimens in the lab if they are available. How does it feed? (include the role of cnidocytes)

Scyphozoa: the medusa is more conspicuous than the polyp.

Examine a preserved specimen of Aurelia (a jellyfish) using a hand lens. Illustrate the specimen. Label the oral arms, gastric pouch, gonads, circular canal, radial canals and tentacles.

Anthozoa: the dominant form is the polyp and there is apparently no medusae. They may be solitary or colonial.

Examine and illustrate a live specimen of Aiptasia (a local sea anemone).

Touch one of the tentacles with a T-pin and note the animal’s reaction. Present your anemone with small pieces of oyster flesh. Observe and

describe its feeding behaviour. Corals are colonies of polyps that feed by photosynthesis using mutualistic algae during the day. They also use their tentacles to catch small planktonic organisms at night. They have a calcium carbonate exoskeleton

Examine and Illustrate colonies of corals. Polyp and Medusa form Cnidarians.


Practical 17 KINGDOM ANIMALIA, PHYLA: PLATHYHELMINTHES, NEMATODA, ANNELIDA AND MULLUSCA

3. PHYLUM PLATYHELMINTHES (Flatworms) Body Development Plan of Phylum Platyhelminthes: bilateral symmetry, triploblastic, acoelomate. Flatworms show true bilateral symmetry; they have roughly mirror-image right and left halves, a head at the anterior end, a posterior tail end, an upper dorsal surface, and a lower ventral surface. They are triploblastic – in addition to the ectoderm (forms the epidermis) and endoderm (forms the gastrodermis) seen in the Cnidarians there is a third layer of tissue, the mesoderm. Flatworms are, however, acoelomate; the only body cavity is the gut which has a single opening. Platyhelminths also have their bodies dorso-ventrally flattened due to the dependence on diffusion for distribution of nutrients, gases and excretory products to and from tissues. They also have true organs - tissues are grouped into functional units.

Examine and illustrate Planaria sp. from a prepared whole mount slide or live Dugesia sp. Note the organs involved in feeding (muscular pharynx, central mouth and the intricately branched intestine).

Platyhelminthes: Dorsal of Dugesia sp.

4. PHYLUM NEMATODA (Roundworms) Roundworms show a major evolutionary advance over the flatworms: they possess a separate mouth and anus. This arrangement allows a more efficient, one-way passage of food through the digestive system. They have complex cuticle and their body walls contain only longitudinal muscles.

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PRACTICAL 8 KINGDOM ANIMALIA: PHYLUM ARTHROPODA 7. PHYLUM ARTHROPODA Arthropods are the dominant animals on earth, both in terms on number of

individuals and species. They have the following characteristics: Exoskeleton - an external skeleton that encloses the body like a suit of

armour. In places it is thin and flexible to allow movement of appendages.

Appendages - jointed to provide added flexibility. Segmentation - considered evidence of annelid ancestry; segments tend to

be reduced in number, fused, and for specialized functions. Cephalization – arthropods have well developed heads and sense organs. Body development plan of Phylum Arthropoda: Bilaterally symmetrical,

triploblastic, coelomate, protostome, segmented. Extant arthropods are classified into Crustacea, Uniramia or Chelicerata on the basis of the anatomy of their limbs, particularly those used for cutting and preparing food. Crustacea Crustacean appendages are all basically biramous (branched into two), with both sections normally being of different size and shape, often bearing further secondary branches. The appendages of the head comprise two pairs of antennae, one pair of mandibles and two pairs of maxillae.

Examine and illustrate the external features of the mangrove crab, Aratus sp. or the blue crab, Callinectes sp. (Class Malacostracea, Order Decapoda). Make one composite diagram, the left half showing the features of the dorsal surface and the right half showing the features of the ventral surface.

Note that the body consists of a large cephalothorax, with a smaller abdominal region folded underneath. Identify the various appendages, including the chelipeds (claws), walking legs, antennae, mouthparts and telson. Note the compound eyes on the stalks.

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Chelicerata The bodies of chelicerates are divided into an interior prosoma and a posterior opisthosoma. All have eight walking legs attached to the prosoma. Chelicerates include the spiders, ticks and scorpions. The spiders (class Arachnida, order Aranae) are the most numerous chelicerates. Their appendages are uniramous, the prosomal appendages comprising one pair of chelicerae, one pair of pedipalps and four pairs of walking legs, all attached near to the ventral mid line.

Examine and illustrate the external features of Argiope sp. Make one diagram, the left half showing the features of the dorsal surface and the right half showing the features of the ventral surface.

Note, on the ventral surface, the chelicerae, pedipalps, eyes and legs. On the dorsum, note the genital pore, spinnerets and openings to the book lungs. Chelicerata: Dorsal and Ventral of Argiope sp.


PRACTICAL 19 KINGDOM ANIMALIA: PHYLUM ECHINODERMATA AND CHORDATA 8. PHYLUM ECHINODERMATA Body Development Plan of Phylum Echinodermata: pentaradial symmetry, triploblastic, coelomate, deuterostomes, non-segmented. The major classes are Asteroidea (starfishes), Ophiuroidea (brittlestars) & Echinoidea (sea urchins). Asteroidea The spiny aboral (upper) surface has the madreporite (the external opening of the water vascular system) and the inconspicuous anus. The oral (lower) surface has the mouth and tube feet (located in the ambulacral grooves, and used in locomotion). The arms are not conspicuously separated from the central disc.

Examine and illustrate both surfaces of the starfish. Ophiuroidea These are the most highly mobile of all echinoderms. The arms are long and distinctly separate from the central disc. Tube feet are not located in ambulacral grooves. Ophiuroids do not use the tube feet as the principal method of locomotion, but instead use the arms directly, pulling with the anterior arms and pushing with the posterior arms. The oral surface has the mouth and madreporite.

Examine and illustrate both surfaces of the brittlestar. Echinoidea Sea urchins do not possess arms. The ossicles have become fused into a shell or test. Tube feet are located in ambulacral grooves. They have moveable spines, which are arranged in rows parallel to the ambulacral grooves. The oral surface has the mouth, with the Aristotle’s lantern (scraping organ used to remove algae from the substrate) inside.

Examine and illustrate the sea urchin. Pry the mouth open to view the Aristotle’s lantern.

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Pagee 60


9. PHYLUM CHORDATA Body Development Plan of Phylum Chordata: bilaterally symmetrical, triploblastic, coelomate, deuterostome, segmented. The Chordata, classified into three major subphyla, the Cephalochordata, Urochordata and Vertebrata, is extremely diverse but is characterized by four features, which all chordates possess at some stage of their lives. Notochord: a stiff but flexible rod running the length of the body and

providing an attachment site for muscles. Dorsal nerve cord: lying dorsal to the digestive tract, this hollow, nervous

structure develops a thickening at its anterior end which becomes the brain.

Pharyngeal gill grooves: located in the pharynx, these may form functional openings or may appear only as grooves during an early stage of development.

Post-anal tail: an extension of the body past the anus. Subphylum Cephalochordata: These chordates are acraniate but have a head and segmented muscle. All the typical chordate features are present in the adult organism.

Examine and illustrate the lancet Branchiostoma sp, a small fish-like animal that lives half-buried in sand on the sea floor. It is also called Amphioxus. Note all the chordate features in the adult.

View the demonstration of the transverse section of the lancet. Cephalochordata: lateral view and T.S. of Branchiostoma sp.


Subphylum Urochordata: The chordates are also acraniate. No head or segmentation is present. The larvae have all the chordate features but adults have only the pharynx; other features degenerate during metamorphosis. Adult sea squirts (tunicates) are sessile, filter-feeding and vase-shaped. Their ability to move is limited to a forceful contraction of the saclike body. The larvae are active swimmers that possess all the chordate features.

Examine and illustrate the tunicate provided. Place the specimen on a black tile to increase visibility of internal organs.

Note the inhalant and exhalent siphons, the perforated pharynx, stomach and heart. Urochordata: features of a sea squirt Subphylum Vertebrata In vertebrates, the embryonic notochord is replaced during development by a vertebral column, composed of cartilage or bone. This structure provides support for the body, a site of attachment for muscles and protection for the delicate nerve cord and brain. The vertebral column is part of a living endoskeleton, capable of growth and self-repair. It has allowed vertebrates to achieve great size and mobility. Examine the skeletons of various vertebrate organisms displayed in the laboratory. They will also be present at the next practical session. The subphylum vertebrata contains the superclasses Agnatha and Gnathostomata (with classes Chondrichthytes, Osteichthyes, Amphibia Reptilia, Aves and Mammalia). The Agnathans are jawless while the Gnathostomathans have jaws. The Agnathans, Chondrichthyes and Osteichthyes are fishes and they have a two chambered heart.


Superclass Agnatha (jawless fishes) These are regarded as the most primitive living vertebrates. Superficially they are fishlike but without scales, jaws and paired fins.

Examine and illustrate the lamprey. Note the dorso-ventral fins, gill openings, sucker and epidermal “teeth”. How does the lamprey feed?

Agnatha: External features and mouthparts of a lamprey


PRACTICAL 20 KINGDOM ANIMALIA, PHYLUM CHORDATA II Superclass Gnathostomata Class Chondrichthyes (cartilaginous fishes) This class includes the sharks, skates and rays. They have skeletons formed entirely of cartilage. The body is protected by a leathery skin with tiny tooth-like, placoderm scales.

Examine and illustrate a shark. Note the presence of paired pelvic and pectoral fins, the heterocercal tail fin and the rigid dorsal fin.

Class Osteichthyes (bony fishes) This class has fishes with skeletons made of bone. They have a swim bladder that allows the fish to float effortlessly at any depth. Osteichthyes includes sardines, tuna, eels luminescent deep-sea forms. The group is enormously successful and has spread to nearly every possible watery habitat, both freshwater and marine. They have paired fins and some groups have modified fleshy fins that could be used (in an emergency) as legs, dragging the fish from a drying puddle to a deeper pool.

Examine and illustrate a bony fish. Note the fins, lateral line, eyes, teeth and scales.

Class Amphibia The organisms in this class straddle the boundary between aquatic and terrestrial existence. They include the frogs, toads and salamanders. The limbs show varying degrees of adaptation to movement on land, from the crawl of salamanders to the efficient leap of frogs. Lungs replace gills in most adult amphibians, but the skin must remain moist, since it serves as an additional respiratory organ. A three chambered heart circulates blood more efficiently than in fishes.

Examine and illustrate the external features of either the toad, Bufo marinus (Order Anura) or a salamander (Order Urodela).

Class Reptillia This class includes the lizards, snakes, turtles, crocodiles and the extinct dinosaurs. Some reptiles live in an aquatic environment and lay eggs on land while others have achieved complete independence from their aquatic origin. Adaptations for terrestrial life include: presence of a dry, tough, scaly skin that resists water loss. internal fertilization.


shelled amniotic egg (which can be buried in sand or dirt, far from water) with an internal membrane, the amnion, which encloses the embryo in the watery environment all animals require.

efficient lungs. three-chambered heart with a septum in the ventricle to improve

separation of oxygenated and deoxygenated blood modified limbs and skeleton to provide better support and more efficient

movement on land.

Examine and illustrate the external features of the crocodile (Order Crocodila) or lizard (Order Squamata).

Class Aves This class contains the birds. The important features of this group are the presence of feathers on the skin and wings which allow flight. Adaptations for flight include: elevated body temperature to allow both muscles and metabolic

processes to operate at peak efficiency, supplying power and energy. four chambered heart that completely separates oxygenated and

deoxygenated blood. respiratory system supplemented by air sacs that supply oxygenated air

to the lungs even as the bird exhales. feathers to protect and insulate the body; to form lightweight extensions

to the wings and tail for lift-off and control hollow bones to keep the skeleton light weight.

Examine and illustrate the external features of a bird. Note

Chordate and Avian features. Class Mammalia This class contains all animals with mammary glands and hair/fur on their skin, including rats, goats, cats, dogs, monkeys, bats, elephants, seals and whales. Mammals are homeotherms, with four-chambered hearts and high metabolic rates. They show great diversity of form and live in a wide range of habitats, aerial, terrestrial (on or below ground) and aquatic.

Examine and illustrate the external features of an egg laying mammal (Sub-class Protheria), the platypus (Order Monotremata).

Examine and illustrate the external features of a pouch mammal (Subclass Metatheria), the kangaroo (Order Diprotodontia).

Examine and illustrate the external features of a placental mammal (Subclass Eutheria), the monkey (Order Primates).

In each case note Chordate and Mammalian and subclass features.


Chondrichthyes: External features of a shark

Osteichthyes: External features and skeleton of a bony fish

BIOL00

Amphibia: S Reptilia: Sk

11 Prelimina

Skeleton of a

keleton of a L

ary Biology

Toad

izard

Laboratory Manual Page 667


Aves: External features and skeleton of a bird.

BIOL00

Mammali

11 Prelimina

ia: Skeleton

ary Biology

n of a man

Laboratory Manual Page 669

Documents

Biol0011 Lab Manual[1]