🔬 To Observe Disease-Causing Organisms: Ascaris, Entamoeba, Plasmodium & Ringworm (Permanent Slides) | Class 12 Biology Practical

     Studying microorganisms under the microscope is a crucial part of Class 12 Biology practicals. In this activity, students observe disease-causing organisms such as Ascaris, Entamoeba, Plasmodium, and Ringworm using permanent slides. These organisms are responsible for common human diseases, and understanding their structure helps us learn how infections spread and how they can be prevented.

Aim

To observe the disease-causing organisms like Ascaris, Entamoeba, Plasmodium and Ringworm through permanent slides.

Materials Required

Preserved slides or specimens of disease-causing organisms like Ascaris, Entamoeba, Plasmodium and Ringworm.

Procedure

Observe the specimens or slides and identify the organism on the basis of its features.

Observations

Ascaris

Phylum: Aschelminthes

Class: Nematoda

Type: Ascaris lumbricoides

Ascaris exhibits the following characteristic features:

• It has a long, cylindrical and unsegmented body.
• The male and female organisms are separate.
• It bears a mouth at the anterior end surrounded by three lips.
• There is an excretory pore on the ventral surface slightly behind the anterior end.
• A pair of penial spicules are present in the male worms close to the cloacal opening.
• The female genitals are present at about one-third distance from the anterior end.
• Ascariasis is the disease caused by Ascaris lumbricoides or roundworm.

Symptoms:

• Abdominal cramping
• Abdominal swelling
• Nausea
• Vomiting
• Fever

Entamoeba

Phylum: Protozoa

Class: Rhizopoda

Type: Entamoeba hystolytica

Following are the characteristic features of Entamoeba:

• It is a unicellular organism with an irregular shape.
• It consists of a few food vacuoles. The contractile vacuole is absent.
• Cysts with four nuclei are present.
• It consists of a nucleus located eccentrically in the cell.
• Entamoeba histolytica is an organism found in the intestines of humans that is responsible for causing amoebic dysentery.

Symptoms:

• Abdominal pain
• Watery diarrhoea with mucus, blood and pus
• Fatigue
• Fever
• Nausea
• Vomiting
• Plasmodium

Phylum: Protozoa

Class: Sporozoa

Type: Plasmodium vivax

Plasmodium can be identified by the following characteristic features:

• It is a unicellular endoparasite found within the red blood cells of the diseased person.
• The parasite is mostly diagnosed at the “signet ring” stage where the parasite appears as a round body.
• There is a big vacuole present inside the cell. The cytoplasm is accumulated at one place and contains the nucleus.
• Plasmodium vivax is a protozoan parasite that causes malaria in humans. The infected female anopheles bites a healthy person and transmits the sporozoite into the peripheral blood vessels of humans, thereby, causing malaria.

Symptoms:

• High fever
• Shaking chills from moderate to severe.
• Headache
• Vomiting
• Nausea
• Ringworm

Kingdom: Fungi

Class: Deuteromycetes

Type: Trichophyton rubrum

Trichophyton or ringworm fungus has the following characteristic features:

• This fungus feeds on the keratin of the skin of human beings.
• The hyphae are waxy and can be smooth or cotton-like.
• Hyphae that are not stained are yellowish-brown, reddish-brown or white in colour.
• Ringworm is a communicable fungal infection of the skin.

Symptoms:

• Scaly, itchy skin
• Red and raised patches
• They are redder at the periphery than at the centre and forms a ring-like appearance.

This Class 12 Biology practical focuses on the isolation of DNA from easily available plant materials such as spinach leaves, green pea seeds, papaya, or banana. The activity helps students understand the basic structure and extraction process of deoxyribonucleic acid (DNA), the genetic material responsible for inheritance.

In this practical, plant tissues are first crushed and mixed with a detergent solution to break cell membranes. Salt is added to separate proteins, and the mixture is filtered. Cold alcohol, usually chilled ethanol, is then gently poured, causing DNA to precipitate as white, thread-like strands. Students can observe this DNA using a glass rod or toothpick.

This experiment is simple, safe, and highly effective for demonstrating molecular biology concepts. It strengthens understanding of DNA structure, nucleic acids, and genetic material. This practical is important for CBSE Class 12 exams and enhances practical record writing and viva preparation.

AIM :- Isolate DNA from available plant material such as spinach, green pea seeds, papaya, banana etc.

REQUIREMENTS

Plant material (such as spinach leaves, green pea seeds or green papaya), mortar and pestle, beakers, test tubes, liquid detergent, non-iodised sodium chloride, distilled water, meat tenderizer or papain solution/juice of papaya/pine apple juice, 95% ethanol, spool etc.

PREPARATION OF SOLUTIONS

1. Detergent salt solution is prepared by adding 10 ml liquid detergent and 10 g of non-iodised sodium chloride to 90 mL of distilled water.

2. Meat tenderizer solution is  prepared by adding 5g of tenderizer to 95ml of distilled water.

3.  5% NaCI solution is prepared by dissolving 5 g of non-iodised sodium chloride in 100 ml of distilled water.

4. Chilling of ethanol must be done by keeping 95%, ethanol in plastic bottle in the freezer over night.

PROCEDURE

1. Take 5g of the Plant tissue (spinach leaf/green pea seed/green papaya) and grind it in the mortar by adding 10 ml detergent, salt solution and filter it through muslin cloth.

2. Take 10 ml of the filtrate, add 3-4 ml tenderizer/papaya juice and swirl the test tube by holding the tube between the two hands to mix the contents.

3. Pour 10 mL chilled ethanol carefully down the side of test tube to form a layer on the top of the content; let it stand undisturbed for about 3 minutes.

4. Using the glass rod stir gently through interface of the two layers to collect the precipitate of DNA and place it in a test tube with 5% NaCl or distilled water.

The quantity of DNA present in the given plant material can be estimated through spectrophotometer. 

OBSERVATION

The addition of ethanol to the solution causes DNA to precipitation. The DNA fibres appears as white precipitate of very fine threads on the glass spool.

PRECAUTIONS

1. The plant material should be washed thoroughly with distilled water to remove any dust and dried by blotting before weighing

2. All the glass wares used must be thoroughly cleaned and dried,

3. The chemicals and enzymes used for the experiment must be of standard quality which should be manufactured by standard pharmaceuticals.

This Class 12 Biology Practical focuses on studying different types of symbiotic associations found in nature. Students observe root nodules in leguminous plants to understand nitrogen-fixing bacteria like Rhizobium. The practical also includes examining Cuscuta (dodder), a parasitic plant that derives nutrition from its host, and studying lichens as a perfect example of mutualism between algae and fungi. This activity helps learners identify the structure, function, and ecological importance of these associations. It strengthens practical knowledge, supports exam preparation, and builds clear concepts for board exams and competitive exams. Ideal for CBSE and other boards.

Aim

To study symbiotic association in root nodules of leguminous plants, Cuscuta on host, lichens.

Observation

1) Symbiotic association in root nodules of leguminous plants

• Root nodules are commonly found in the roots of leguminous plants
• They are formed due to association with a nitrogen fixing bacteria,Rhizobium
• Rhizobium is gram - ve bacteria
• Root nodules contains pink oolour leghaemoglobin pigment
• It also contains enzyme nitrogenase which helps in the formation of Ammonia

2) Cuscuta on host

• Cuscuta commonly called dodder /amberal live as stem ectoparasite on other plants.
• Stem of Cuscuta is thin and slender shaped without cholorophyll.
• It winds around the stem of host plant.
• Stem of cuscuta fixes with the host plant by the special structure called Haustoria.
• Haustoria direct connection with host plant and withdraw water ,carbohydrates and other solutes.
• Cuscuta can weaken or kill host plant and reduce crop yield.

3. Lichens

• Lichens are composite organisms representing a symbiotic association between fungus and algae
• The algal component is phycobiont and the fungal component is myoobiont
• They grow on land, rocks, tree trunks and walls of houses.
• Algae prepares food for fungi and Fungi provides shelter and absorbs minerals nutrients and water to algae.
• Main three different types are crustose, foliose, fructicose

This Class 12 Biology Practical focuses on the study of prepared pedigree charts to understand the inheritance of common genetic traits. Students learn how traits like tongue rolling, blood groups (A, B, AB, O), widow’s peak, and colour blindness are passed from one generation to the next. By analysing pedigree symbols and patterns, learners can identify dominant, recessive and sex-linked traits. This practical helps build strong concepts of genetics, supports exam preparation, and improves scientific interpretation skills. Ideal for CBSE and all state boards, this activity is an essential part of the Class 12 Biology practical file.

AIM: To Study of prepared pedigree charts of genetic traits such as rolling of tongue, blood groups, widow's peak and colour blindness.

REQUIREMENTS:

Questionnaire about a particular disorder, a family with genetic disorder for more than one generation, paper, pencil, etc.

PROCEDURE:

The careful examination of chart would suggest whether the gene for the character is

i. A. Autosome-linked dominant or recessive

ii. X-chromosome linked dominant or recessive

iii. Y-chromosome linked or not.

Explanation of Each Trait

A. Autosome Linked Dominant Traits

i. The encoding gene of this trait is present on any one of the autosomes.

ii. The mutant allele is dominant and the wild type allele is recessive for such traits

iii. In this pedigree chart, the female being interviewed is exhibiting the trait and is indicated by an arrow mark in the chart.

iv. Transmission of trait occurs from any of the parent. 

v. Male and female are equaly affected. e.g., Widow' Peak.

Widow's Peak

It is a 'V'-shaped hairline across the forehead. it is a dominant trait. Thus, both homozygous dominant(A) and heterozygous (Aa) individuals have widow's peak, while homozygous recessive (aa) individuals have a straight hairline.

B. Autosome Recessive Traits

i. In this, mutant allele is recessive to its wild type allele,

ii. These traits occur in equal proportions in male and female siblings, whose parents are carriers of the allele, i.e., they have only a single copy of the allele and therefore they are normal.

iii. The siblings are homozygous for the defective allele, but their parents, though some may appearnormal are obviously heterozygous, i.e, are merely carriers of the trait.

iv. The marriage between man and woman genetically related with each other, occasionally results in the appearance of such traits, e.g, albinism and rolling of tongue

The Rolling of Tongue

Some persons are able to roll their tongue in U-shape. The inability to roll the tongue is caused by autosomal recessive allele "a', Thus, both homozygous dominant (AA) and heterozygous (Aa individuals are able to roll the tongue, while homozygous recessive (aa) individuals are unable to rol their tongue in this way.

x- Linked Recessive Traits

i. These are the traits whose encoding gene is present on the X-chromosome and its mutant allele is recessive to its wild type allele.,

ii. The females expresses the trait only when they are homozygous for the mutant allele whereas, males does so even when they are hemizygous for it.

iii. About half of the sons of the carier (heterozygous for the trait) females are affectecd.

iv. In case of homozygous females showing the trait, 50% of her daughters and all of her sons are likely to be affected. Therefore, it can be concluded that males are most affected population in this category.

v. Affected persons are related to one another through the maternal side of their family.

vi. Any evidence of male to male transmission of the trait rules out the X-linked inheritance.

vii. Examples are haemophilla and red-green colour blindness

Colour blindness

The colour blindness is a sex-linked recessive disorder of humans. In this, the affected individual is unable to differentiate between red and green colours. It results in the absence or malfunctioning of one or more of the three types of cone cell responsible for colour vision.

Pedigree analysis of colour blindness

Blood group inheritance

i. Blood group inheritance is independent of sex of organism.

ii. The ABO blood groups are controlled by gene I which have three alleles I⁰,Iª,Ib,I

iii. Iª and Ib are completely dominant over I⁰,Iª,Ib are dominant

OBSERVATIONS:

The integrated families showed the characteristics symptoms of the genetic disorder inferred in studies undertaken for the pedigree analysis

RESULT:

The families studied showed the transmission of traits responsible for genetic diseases in the successive generationsin each category.

Class 12 Biology Lab Manual – Final Practicals | Complete Lab Experiment File

A. List of Experiments

1. Prepare a temporary mount to observe pollen germination.

2. Study the plant population density by quadrat method.

3. Study the plant population frequency by quadrat method.

4. Prepare a temporary mount of onion root tip to study mitosis.

5. Isolate DNA from available plant material such as spinach, green

pea seeds, papaya, banana etc.

B. Study and observe the following (Spotting):

1. Flowers adapted to pollination by different agencies (wind, insects, birds).

2. Pollen germination on stigma through a permanent slide or scanning electron 

micrograph.

3. Identification of stages of gamete development, i.e., T.S. of testis and T.S. of

ovary through permanent slides (from grasshopper/mice).

4. Meiosis in onion bud cell or grasshopper testis through permanent slides.

5. T.S. of blastula through permanent slides (Mammalian).

6. Mendelian inheritance using seeds of different colour/sizes of any plant.

7. Prepared pedigree charts of any one of the genetic traits such as rolling of tongue, 

blood groups, ear lobes, widow's peak and colour blindness.

8. Controlled pollination - emasculation, tagging and bagging.

9. Common disease causing organisms like Ascaris, Entamoeba, Plasmodium, any

fungus causing  ringworm through permanent slides, models or virtual images or 

specimens. Comment on symptoms of diseases that they cause.

10. Models specimens showing symbiotic association in lichens, root nodules of 

leguminous plants, and parasitic mode of nutrition shown by Cuscuta on host.

11. Flash cards / models showing examples of homologous and analogous organs.

Class

This Class 12 Biology Practical focuses on studying meiosis in onion bud cells using a permanent slide. Students observe different stages of meiotic cell division, including prophase I, metaphase I, anaphase I, telophase I and the stages of meiosis II. This activity helps learners understand reduction division, formation of haploid cells and its importance in sexual reproduction. By identifying clear slide observations, students strengthen their concepts of genetics and heredity. This practical is essential for CBSE and state board exam preparation, enhancing diagram skills and practical file records. Perfect for Class 12 Biology practical learning.

Aim:-  To study meiosis in onion bud cells through permanent slide.

REQUIREMENTS

Permanent slide of different stages of meiosis in onion bud cells, microscope,

PROCEDURE

1. Fix the permanent slide under the microscope.

2. First observe the slide under the low power and then under high power of the microscope.

OBSERVATIONS

Under the high power of microscope following stages of meiosis are distinctly observed:

A. Meiosis I

1. Prophase I. It is of long duration and has five sub stages:

(a) Leptotene

(i) Chromatin fibres condense and form thick thread like structures called chromosomes.

(ii) Nuclear envelop and nucleolus are distinct.

(b) Zygotene

(i) Homologous chromosomes form pairs called bivalent. This pairing is called synapsis.

(ii) The individual of a pair are similar in length and in position of their centromere.

(c) Pachytene

(i) 'The two chromatids of each chromosome become visible, so that a bivalent becomes a tetrad.

(i) Crossing over (exchange of chromatid segments between homologous chromosomes) takes place between non- -sister chromatids of homologous chromosomes.

(d Diplotene

The two chromosomes each bivalent move away and homologues are held together at one or more points called chiasmata.

(e) Diakinesis

(i) Homologous chromosomes appear thick and ring shaped,

(ii) Nucleolus and nuclear envelope disappear and spindle begins to be formed.

2. Metaphase I

(i) The bivalent (homologous chromosomes) arrange themselves at the equator of the

spindle.

(ii) The spindle get attached to the centromere of the chromosome.

3. Anaphase I

(i) 'The two chromosomes of each bivalent move to the opposite pole.

(ii) Each pole has half the number of chromosomes with two chromatids each.

4. Telophase I

(i) The chromosome at each pole uncoil, and nucleolus and nuclear envelope reappear

(ii) Cytokinesis occurs to form two haploid daughter cells.

Interkinesis

A very short interphase may intervene between meiosis I and meiosis II.

B. Meiosis II

It includes following four stages:

1. Prophase II

(i) The chromosomes of daughter cell begin to condense and become thick

(ii) Nuclear envelope and nucleolus begin to disappear.

2 Metaphase II

(i) The chromosomes are aranged on the equator of the spindle.

(ii) Each chromosome held by the spindle at the centromere to both the poles.

3. Anaphase II

(i) The sister chromatids (daughter chromosomes) of each chromosomes separate and

migrate towards the opposite poles

(ii) Each pole, thus receives haploid number of chromosomes,

Telophase II

(i) The chromosomes begin to uncoil and become thin,

(ii) The nuclear envelope and nucleolus are reconstituted.

Cytokinesis occurs and four daughter cells are formed, each with haploid number of

chromosomes.

PRECAUTIONS

1. Floral buds should be fixed between 8 to 10 A.M.

2. Slide should be warmed gently to avoid over heating.

Class 12 Biology Lab Manual – Final Practicals | Complete Lab Experiment File

A. List of Experiments

1. Prepare a temporary mount to observe pollen germination.

2. Study the plant population density by quadrat method.

3. Study the plant population frequency by quadrat method.

4. Prepare a temporary mount of onion root tip to study mitosis.

5. Isolate DNA from available plant material such as spinach, green

pea seeds, papaya, banana etc.

B. Study and observe the following (Spotting):

1. Flowers adapted to pollination by different agencies (wind, insects, birds).

2. Pollen germination on stigma through a permanent slide or scanning electron 

micrograph.

3. Identification of stages of gamete development, i.e., T.S. of testis and T.S. of

ovary through permanent slides (from grasshopper/mice).

4. Meiosis in onion bud cell or grasshopper testis through permanent slides.

5. T.S. of blastula through permanent slides (Mammalian).

6. Mendelian inheritance using seeds of different colour/sizes of any plant.

7. Prepared pedigree charts of any one of the genetic traits such as rolling of tongue, 

blood groups, ear lobes, widow's peak and colour blindness.

8. Controlled pollination - emasculation, tagging and bagging.

9. Common disease causing organisms like Ascaris, Entamoeba, Plasmodium, any

fungus causing  ringworm through permanent slides, models or virtual images or 

specimens. Comment on symptoms of diseases that they cause.

10. Models specimens showing symbiotic association in lichens, root nodules of 

leguminous plants, and parasitic mode of nutrition shown by Cuscuta on host.

11. Flash cards / models showing examples of homologous and analogous organs.

Class