Guide to STPM Pratical Third Term

1© Oxford Fajar Sdn. Bhd. (008974-T) 2013

Construction of a Dichotomous Key Using Local Specimens

This experiment enables students to: 1. Identify the external features (morphology) of an organism to be grouped into a phylum or a

class2. Increasetheirknowledgeinthefieldoftaxonomy 3. To use a dichotomous key to identify unknown plants or animals.

Organisms such as Amoeba sp. (slide), Hydra sp. (slide), ant, snail (garden snail), shrimp, Marchantia sp. (moss), Dryopteris sp. (with sori on the undersides of the fronds) and grass were examined under the microscope or using a magnifying glass (× 10). The opposing features, which clearly differentiate the organisms from one another, were noted down. A dichotomous key for this group of organisms was then constructed up to the category of phylum and class.

Characteristics of organisms noted:

Organism CharacteristicsGrass Green,containingchlorophyll;doesnotproduce spores;hasflowers, roots,

stems and leavesDryopteris sp. Containing chlorophyll; produces spores; fronds sub-divided into pinnae and

pinnules bearing sori on undersides Marchantia sp. Containing chlorophyll; produces spores; thalloid body with rhizoids;

has gemma cups, antheridiophores and archegoniophores as reproductive structures

Amoeba sp. Organism without chlorophyll; unicellular.

Hydra sp. Multicellular; soft cylindrical body without exoskeleton; body wall comprises oftwolayersofcells−ectodermandendoderm;hastentacles,agutcavityanda mouth

Snail Multicellular; with exoskeleton; has soft muscular foot and calcareous shell

Ant Invertebrate with jointed legs; body divided into head, thorax and abdomen;has three pairs of legs; wingless

Shrimp Invertebrate; body divided into cephalothorax and abdomen; has two pairs of antennaeandfivepairsofjointedlegs

From the above observations, it can be inferred that, Marchantia sp. is able to live successfully in highlands and damp areas due to its special rhizoids. The structural differences between Marchantia and Dryopteris are that Marchantia has a thalloid body and gemmae cups whereas Dryopteris has roots, stems, and leaves with the presence of sori on the underside of its fronds.Ant and shrimp share the same phylum, Arthropoda as both have segmented body with exoskeleton and jointed legs. The structural differences between them can be seen in the table below:

Ant Shrimp(a) Segmented body with exoskeleton which is

divided into head, thorax and abdomenSegmented body with exoskeleton which is divided into cephalothorax and abdomen

(b) 3 pairs of jointed legs 5 pairs of jointed legs

(c) A pair of antennae 2 pairs of antennae

(d) Tracheal system for respiration Gills for respiration

Guide to STPM Practicals For Third Term

Practical guide STPM 2013 2nd.indd 1 2013/5/15 15:23:22

2 © Oxford Fajar Sdn. Bhd. (008974-T) 2013

A simple spider key, showing contrasting characteristics can be used to differentiate the organisms for the purpose of constructing a dichotomous key.

OrganismsOrganisms without chlorophyll

Amoeba, Hydra, ant, snail, shrimp

multicellular

Hydra, ant, snail, shrimp

with tentacles

HydraAnt, snail, shrimp

unicellular

Amoeba without tentacles

with leg without leg

Snail

Shrimp

ten legs

Ant

six legs

Grass

Organisms with chlorophyll

flowering/not producing spores

with archegonia and antheridiophores

MarchantiaDryopteris

Marchantia, Dryopteria

non-flowering/producing spores

Marchantia, Dryopteris, grass

Dichotomous keyA1 With chlorophyll refer to BA2 Without chlorophyll refer to DB1 Does not produce spores but has flowers, roots, stems and leaves Phylum Angiospermae (Grass)B2 Produces spores refer to CC1 Fronds sub-divided into pinnae and pinnules bearing sori on undersides Phylum Filicinophyta (Dryopteris)C2 Thalloid body, has gemma cups, antheridiophores and archegoniophores as reproductive structures Phylum Bryophyta (Marchantia) D1 Unicellular Phylum Protoctista (Amoeba)D2 Multicellular refer to E E1 Soft cylindrical body without exoskeleton. Body wall comprises of ectoderm and endoderm. Tentacles, gut cavity and mouth present Phylum Cnidaria (Hydra)E2 With exoskeleton refer to FF1 Invertebrate with soft muscular foot and calcareous shell Class Mollusca (Snail) F2 Invertebrate with jointed legs refer to GG1 Invertebrate; body divided into head, thorax and abdomen. Has three pairs of legs; wingless Class Insecta (Ant) G2 Invertebrate; body divided into cephalothorax and abdomen. Has two pairs of antennae and five pairs of legs Class Crustacea (Shrimp)

Ant, shrimp

Without archegonia and antheridiophores

Practical guide STPM 2013 3rd.indd 2 2013/5/16 14:47:25


Preservation of Plant and Insect Specimens

This experiment enables students to: 1. Learn the skill of preservation of plants and insects prior to related experiments 2. Understand better the field of taxonomy 3. Identify the morphological features of plants and insects 4. Determine the phylum, class and order of the preserved plants and insects

Below are some of the plants and insects that can be preserved by dry or wet preservation techniques using FAA solution or 70% ethanol as preservative. Both these techniques can cause the colour of the specimens to fade and therefore their original colour should be noted before preserving them. Insects can be killed by squeezing their thorax or abdomen gently to block their air passages. Both the preservation techniques enable the plants and insects to be preserved for a long time. Gemma cups Male “umbrellas” Female “umbrellas”

Marchantia sp. is a liverwort commonly found in flowerpots in green houses, on moist bricks in gardens and on badly drained soils. On its thalloid body are small gemma cups with small oval pieces of tissue, which can be spread by raindrops and become new plants. This dioecious bryophyte can easily be identified by its male and female “umbrellas” which carry the male and female receptacles. Marchantia belongs to the division, Bryophyta and class, Hepaticae.

Dryopteris sp. which belongs to the division, Filicinophyta and class, Filicinae is a common fern found growing in dry open area. It is a hardy plant which reproduces rapidly and asexually by means of spores found in the sporangia that grow in clusters called sori on the underside of its fronds. The fern is also capable of reproducing sexually.

Both the housefly and the dragonfly or grasshopper (or locust) belongs to the phylum, Arthropoda which has the characteristics of segmented body, jointed legs in pairs, chitinous exoskeleton and open circulation. Both the animals belong to the class Insecta, which can be characterized by their bodies being divided into 3 distinct regions, that is, the head, thorax and abdomen. The head bears a pair of antennae, the thorax bears 3 pairs of jointed legs and the body is well supplied with respiratory tubes or trachea. The housefly belongs to the order Diptera, whereas the grasshopper/locust belongs to the order Orthoptera. Dragonflies, however belong to the order Odonata.

Guide to STPM Practicals

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Collection of Insects

This experiment enables students to: 1. Be aware of the diversity of insects in Malaysia 2. Learn the insects’ habitats, feeding and sexual behaviour, and their economic values3. Strengthentheirconceptandunderstandingofclassificationandnomenclature 4. Inculcate their love towards all living things and nature

Capturing of insects and preserving them 1. Insects can be captured by: (a) Sweeping small bushes with a net (b) Catchingflyinginsectslikebutterfliesdirectlywithanet (c) Using a light trap to catch nocturnal insects

2. The captured insects are then placed into the killing jar containing cotton wool soaked in concentrated ethanol. After the insects have been fully paralyzed, they are pinned on a piece of polystyrenetofixtheposition.

3. With suitable dissecting tools, the abdomen of the insect is slit open and the internal organs were removed. A wad of formalin-soaked cotton wool is then inserted into the abdominal cavity (see diagrams below).

4. Formalin is also injected into parts which are too small to be cut. The slit is then sealed.

5. The preserved insects are then clearly displayed and pinned onto a polystyrene. Each insect is labeled as follows:

Local name: Order: Location: Habitat: Date of collection: Collector’s name: (A total of 10 different species from ten different orders of insects are to be collected)

6. A suggested list of insects is given below. (a) Local name: Longhorn beetle Scientificname:Batocera davidis Order: Coleoptera (b) Local name: Brown spruce longhorn beetle Scientificname:Tetropium fuscum Order: Coleoptera


The abdomen of the insect is slit open and the internal organs are removed

A wad of formalin-soaked cotton wool is inserted into the abdominal cavity



(c) Local name: Titanic stag beetle Scientificname:Dorcus titanic Order: Coleoptera

(d) Local name: Elephant beetle Scientificname:Xylotrupes ulysses Order: Coleoptera

(e) Local name: Click Beetle Scientificname:Limonius canus Order: Coleoptera

(f) Local name: Sloe bug Scientificname:Dolycoris baccarum Order: Hemiptera

(g) Local name: Carpenter bee Scientificname:Xylocopa violacea Order: Hymenoptera

(h) Local name: Carpenter bee Scientificname:Xylocopa aruana Order: Hymenoptera

(i) Local name: Honey bee Scientificname:Vespa affinis Order: Hymenoptera

(j) Local name: Peacock pansy Scientificname:Junonia almana Order: Lepidoptera

(k) Local name: Striped albatross Scientificname:Appias libythea olferna Order: Lepidoptera

(l) Local name: Paper kite Scientificname:Idea leuconoe Order: Lepidoptera

(m) Localname:Greatorange-tipbutterfly Scientificname:Hebomoia glaucippe Order: Lepidoptera

(n) Local name: Pepatung merah Scientificname:Nannophya pygmaea Order: Odonata

(o) Localname:Rubymeadowhawkdragonfly Scientificname:Crocothemis servilia Order: Odonata

(p) Localname:Redgrasshawkdragonfly Scientificname:Neurothemis fluctuans Order: Odonata

(q) Local name: Common skimmer Scientificname:Neurothemis intermedia Order: Odonata

(r) Localname:Bluedragonfly Scientificname:Trithemis festiva Order: Odonata



(s) Localname:Commonfieldgrasshopper Scientificname:Chorthippus brunneus Order: Orthoptera

(t) Local name: Short horned grasshopper Scientificname:Chorthippus parallelus Order: Orthoptera

(u) Local name: Grasshopper Scientificname:Valanga nigricornis Order: Orthoptera

(v) Local name: Katydid Scientificname:Pterophylla camellifolia Order: Orthoptera

(w) Localname:Sawfly Scientificname:Arge humeralis Order: Hymenoptera

(x) Local name: Stick insect Scientificname:Phasma reinwarditi Order: Phasmida

(y) Local name: Cicada Scientificname:Cicadetta montana Order: Homoptera

7. Some interesting insects that are found around your neighbourhood.

Local name: The wood nymphOrder: Lepidoptera

Local name: Stick insectOrder: Phasmida

Local name: Stag beetleOrder: Coleoptera

Local name: Red dragonflyOrder: Odonata



Collection of Plants

This experiment enables students to: 1. Be aware of the plant diversity in Malaysia 2. Inculcate the love for plants and nature 3. Strengthen their understanding of classification of plants and nomenclature 4. Learn the economic values of Malaysian plants

Collection and preservation process 1. Plant specimen to be collected should not be too young or too old and cut to the size to fit a

tabloid newspaper. Only the leaf and stem (flowers if any) should be collected.

2. Specimens are pressed immediately after collection and put into the oven at 105 °C to rid them of water (see pictures below).

3. The dried specimen is then mounted onto drawing papers of size 6 in. × 10 in. or 13 in. × 8 in.

4. Each plant specimen is fully labelled as follows: Local name: Family: Location: Habitat: Date of collection: Collector’s name: (A total of 10 different species from ten different families of plants are to be collected)

5. A suggested list of plants that can be collected: (a) Local name: Asoka Scientific name: Saraca indica Family: Fabaceae

(b) Local name: Sial menaun Scientific name: Pternandra coerulescens Family: Melastomataceae

(c) Local name: Pandan jepun Scientific name: Pandanus amaryllifolius Family: Pandanaceae

(d) Local name: Ubi kayu Scientific name: Manihot utilissima Family: Euphorbiaceae


The selected specimen is pressed immediately after collection.

The specimen is then put into the oven at 105 °C to dry it.

Dried stems and leaves are then mounted.



(e) Local name: Angsana Scientificname:Pterocarpus indicus Family: Papilionaceae

(f) Local name: Tecoma Scientificname:Tabeayaia pentaphylla Family: Bignoniaceae

(g) Localname:Beringin/MalayanBanyan Scientificname:Ficus microcarpa (van nitida) Family: Moraceae

(h) Local name: Pulai Scientificname:Alstonia scholaris Family: Apocynaceae

(i) Local name: Kelat paya Scientificname:Eugena papilosa Family: Myrtaceae

(j) Local name: Gapis Scientificname:Saraca thaipingensis Family: Caesalpiniaceae

(k) Local name: Saga Scientificname:Adenanthera pavonina Family: Fabaceae

(l) Local name: Melinjau Scientificname:Gnetum gnemon Family: Gnetaceae

(m) Local name: Duku Scientificname:Lansium domesticum Family: Meliaceae

(n) Local name: Durian Scientificname:Durio zibethinus Family: Bombacaceae

(o) Local name: Gelam Scientificname:Melaleuca leucadendron Family: Myrtaceae

(p) Local name: Gaharu Scientificname:Aquilaria malaccensis Family: Thymelaeaceae

(q) Local name: Gajus Scientificname:Anacardium occidentale Family: Anacardiaceae

(r) Local name: Mango Scientificname:Mangifera indica Family: Anacardiaceae

(s) Local name: Cempedak Scientificname:Artocarpus champeden Family: Moraceae



(t) Local name: Berangan Scientificname:Castanopsis inermis Family: Fagaceae

(u) Local name: Penaga lilin Scientificname:Mesua ferrea Family: Clusiaceae

(v) Local name: Nangka Scientificname:Artocarpus heterophyllus Family: Moraceae

(w) Local name: Ixora Scientificname:Ixora javanica Family: Rubiaceae

(x) Local name: Kayu manis hutan Scientificname:Cinnamomum iners Family: Lauraceae

(y) Local name: Badam Scientificname:Prunus spp. Family: Rosaceae

6. Some interesting plants that can be collected.

Lidah buaya – Aloe vera Cekur – Kaempferia galanga Hempedu bumi – Andrographis paniculata



Ecological Study of a Terrestrial Ecosystem

This experiment enables students to: 1. Learn the basic principles of ecology through hands-on experience 2. Understand the biotic and abiotic elements of ecosystems3. Understandthedynamicrelationshipofelementsandenergyflowinanecosystem 4. Learn the simple instrumentations (improvised or otherwise) in ecological studies 5. Learn the methods of collecting and analysing ecological data 6. Write a systematic ecological study report 7. Inculcate the love for nature8. Inculcategoodmoralvalues,independenceandself-confidence

Some of the useful ecological tools that you may use in the course of your study.




Determination Of Plant Population Using A Quadrat Sampling Technique

1. Students may carry out this study in groups of 4 or 5 but individual report is required. 2. Each group should determine the area to be studied, the objectives, rough working plan, and the

techniques to be carried out. 3. The plant distribution of a terrestrial habitat can be determined by using quadrats. 4. The results can be tabulated (see tables and examples below) and calculations should be done

using the formulae given below. Quadrat sampling of plants in an open area

Formula:

(a) Species × frequency = no of quandrat containing the species x

total number of quandrats × 100

(b) Relative species × frequency = Species x frequency

Total frequency of all species × 100

(c) Species × density = Total number of the species x

(Total number of quadrat x area of each quadrat)

(d) Relative species × density = Species x density

Total density of all species × 100

(e) Species × coverage = Total area of coverage of species x

Total number of quandrat × 100

(f) Relative species × coverage = Species x coverage

Total coverage of all species × 100

An open area(Notice the laterite soil)

Quadrat size: 0.5 m2 (Random sampling)



Table 1: Presence of plant species

Plant species (x)

Quadrat Total number of quadrat containing species x

Species frequency (%)

Relative species frequency (%) 1 2 3 4 5 6 7 8 9 10

Acantha sp. 3 3 3 3 4 40 12.12Ischaemum sp. 3 3 3 3 3 3 3 3 3 9 90 27.27Imperata cylindrica 3 1 10 3.03

Lycopodium sp. 3 3 3 3 3 3 6 60 18.18Melastoma malabathricum 3 3 3 3 4 40 12.12

Eleucine sp. 3 3 3 3 3 5 50 15.15Polygala sp. 3 3 2 20 6.67Bryophyllum sp. 3 3 2 20 6.67

Total 33 330

Table 2: Number of plant species

Plant species Quadrat Total

number of species x

Species density (/m2)

Relative species density (%) 1 2 3 4 5 6 7 8 9 10

Acantha sp. 56 49 13 13 131 52.4 15.23Ischaemum sp. 15 55 50 5 60 32 28 26 30 301 120.4 35.00Imperata cylindrica

11 11 4.4 1.28

Lycopodium sp. 30 10 20 3 8 14 85 34.0 9.88Melastoma malabathricum 5 7 7 23

42 16.8 4.88

Eleucine sp. 70 98 55 20 10 253 101.2 29.42Polygala sp. 5 25 27 10.8 3.14Bryophyllum sp. 4 6 10 4.0 1.16

Total 860 344.0

Table 3: Area of coverage

Plant species

Quadrat (area covered by each spp, cm2) Total area of coverage of species x (cm2)

Species coverage (%)

Relative species coverage (%)

1 2 3 4 5 6 7 8 9 10

Acantha sp. 1000 900 100 100 2100 21000 12.61Ischaemum sp. 150 1000 1000 50 1200 640 560 520 600 5720 57200 34.35Imperata cylindrica 220 220 2200 1.32

Lycopodium sp. 600 200 400 30 80 280 1590 15900 9.55Melastoma malabathricum 90 70 70 460 690 6900 4.14

Eleucine sp. 980 2200 1500 400 200 5280 52800 31.71Polygala sp. 50 800 850 8500 5.11Bryophyllum sp. 80 120 200 2000 1.20

Total 16650 166500Theplantspeciesthatshowsthehighestspeciesfrequency/speciesdensity/speciescoverageisthe most dominant species in the habitat.



Soil Analysis

1. Soil sampling technique Metal cylinders or tin cans (improvised tools) are pressed or hammered into the soil to collect

the soil sample. The soil sample is taken back to the school science laboratory in the cylinder for further analysis (see picture below).

2. Determination of soil texture Students may use a soil sieve or measuring cylinder to determine the percentage of each soil

component as shown below.

Sieves of different mesh sizes are used to determine the amount of clay, silt and sand in the soil sample. A measuring cylinder (on the right) can also be used for the same purpose.

Calculation of the percentage of components of soil sample

FormulaPercentage of soil component

= height of soil componenttotal height of soil sample × 100% (using measuring cylinder method)

Working:Percentage of clay

= 5.559.30 × 100% = 59.67 %

Percentage of silt

= 1.879.30 × 100% = 20.11 %

Percentage of sand

= 1.889.30 × 100% = 20.22 %

Texture of soil Height (cm) % of soil componentclay 5.55 59.67silt 1.87 20.11sand 1.88 20.22Total 9.30 100.00

Soil sample in metal cylinder Laterite soil from open area Soil colour hints its content



3. Determine of soil sample pH A sample of soil is added to a test tube contain a spatula of barium sulphate which helps to

precipitate the clay particles in a soil sample suspension. The test tube is then 34 filledwith

water and shaken after adding 5-6 drops of Universal Indicator. A clear coloured liquid is formed above the soil which is noted and the pH recorded as shown in Table 4. The pH of the soil is then correlated to the plant species that is most suitable to live in this pH condition.

Table 4:

Soil sample Colour pH1 red 42 red 43 yellow 64 red 55 yellow 6

Average pH 5

The colour of the liquid above the soil sample is compared with the Universal Indicator Chart to determine the pH of the soil.

PER

CEN

T C

LAY

PERCENT SAND

PERC

ENT SILT



Use of the χ2 Test in Monohybrid and Dihybrid Genetic Crosses

Thisexperimentenablesstudentstousetheχ2 test to determine whether a set of experimental data obeysMendel’sfirstandsecondlaw. The monohybrid ratio 3:1 and dihybrid ratio 9:3:3:1 are hypothetical estimations based on dominant and recessive genes, segregation, independent assortment and random fertilisation whichmaybeinfluencedbychanceeventsandwillbesubjectedtonormaldeviation.Toassessa genetic hypothesis, a χ2testwasusedwhichcanchangethedeviationfromtheexpectedvalue/ratio to the probability that chance alone could be responsible for the deviation. This test takes into account the sample size and the number of parameters (degree of freedom). For most problems in genetics, the degree of freedom (df) is one less the number of classes of phenotypes (n). For example, in a monohybrid cross, where only one trait, that is, the colour of maize seed (purple which is dominant over yellow) is considered (n = 2), then the df is n – 1 = 2 – 1 = 1. In a dihybrid cross, where two traits, that is, the colour of maize seed (purple and yellow) and the conditions of maize seed (smooth which is dominant over wrinkled) are considered (n = 4), then the df is n – 1 = 4 – 1 = 3. In this experiment, the phenotypes of the maize seeds are counted from the ears of corn given as below and the results tabulated. 1. Ears of corns from monohybrid crosses (a) The phenotypes: purple and yellow seeds (b) The phenotypes: smooth and wrinkled seeds

2. Ears of corns from dihybrid cross Thephenotypes:purple/yellowandsmooth/wrinkledseeds.

From the results, the values of χ2 are calculated and compared with the values given in the table below.

χ2 = ∑(o – e)

2

(e)

o = observed value, that is, the actual number of seeds of a particular phenotype e = expected value, that is, the number of seeds of a particular phenotype calculated from the

monohybrid and dihybrid ratios

Purple seed

Yellow seed

Purple wrinkle seed

Purple smooth seed

Yellow wrinkle seed

Yellow smooth seed



χ2 table

df\p .99 .98 .95 .90 .80 .70 .50 .30 .20 .10 .05 .02 .011 .00016 .00063 .0039 .016 .064 .148 .455 1.074 1.642 2.706 3.841 5.412 6.6352 .0201 .0404 .103 .211 .446 .713 1.386 2.408 3.219 4.605 5.991 7.824 9.2103 .115 .185 .352 .584 1.005 1.424 2.366 3.665 4.642 6.251 7.815 9.837 11.3414 .297 .429 .711 1.064 1.649 2.195 3.357 4.878 5.989 7.779 9.488 11.668 13.277

p−Probabilitydf−Degreeoffreedom

Monohybridcross(Mendel’sfirstlaw)

Phenotype Expected ratio

Observation(o)

Expected number of count (e)

Divergence(o – e)

Divergence2

(o – e)2Divergence2/Expected no. of count(o – e)2/(e)

Yellow 1 79 72.75 6.25 39.0625 0.537Purple 3 212 218.25 6.25 39.0625 0.179

Total 291 0.716

χ2 = 0.716

Conclusion:The calculated χ2 value (0.716) is found to be lower than the value (3.841) given in the χ2 table(P0.05,df=1).ThereforethedeviationisnotsignificantandtheresultobeysMendel’sfirstlaw.

Dihybrid cross (Mendel’s second law)

Phenotype Expected ratio

Observation(o)

Expected number of count (e)

Divergence(o – e)

Divergence2

(o – e)2Divergence2/Expected no. of count(o – e)2/(e)

Purple smooth 9 669 675 –6 36 0.053

Yellow smooth 3 232 225 7 49 0.218

Purplewrinkled 3 231 225 6 36 0.160

Yellowwrinkled 1 68 75 –7 49 0.653

Total 1200 1.084

χ2 = 1.084

Conclusion:The calculated χ2 value (1.084) is found to be lower than the value (7.815) given in the χ2 table (P0.05,df=3).Thereforethedeviationisnotsignificant,thedihybridratioof9:3:3:1isacceptedand the result obeys Mendel’s second law.



Extraction of Plant DNA

This experiment enables students to:(a) To indicate the presence of DNA in living cells. (b) To describe the physical characteristics of DNA.

Deoxyribonucleic acid (DNA) is a nucleic acid that contains the entire genetic information of an organism is found in its nucleus. DNA is formed from nucleotide subunits namely thymine (T), adenine (A), guanine (G) and cytosine (C). In a cell, DNA exists in the form of double-stranded helix molecule of polynucleotide where there is base-pairing between A and T, and G and C. These two strands run in opposite directions to each other and are anti-parallel. A segment of DNA that carries the genetic information is called a gene. Inthisexperiment,studentswillusefinely-crushedonionsucculentleavesandaDNAExtractionKit (see below) to help them to extract DNA from the onion leaves following the instructions given. Theonion leavesmustfirstbehomogenized tobreakdownthecellwallas torelease theDNAfrom the plant cell. The isopropanol is used to precipitate the DNA extracted. In a proper forensic investigation, DNA in a solution can be visualized using the electrophoresis method.

At the end of the experiment, a whitish, sticky and slimy DNA is extracted and precipitated at the tip of a pooling stick.

A whitish, sticky and slimy DNA is extracted and preciptated at the end of a pooling stick.



Guide to STPM Pratical Third Term

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