Class 12 Biology Identification Disease Causing Organisms Symptoms Diseases Experiment

Not all organisms around the globe are beneficial for humans. Some are essentially harmful as they possess a grave threat to the optimal functioning of the human body including being potentially fatal too. These microbes that have the capacity to cause diseases are known as pathogens. Some common disease-causing organisms like Ascaris, Entamoeba, Plasmodium, and Ringworm exhibit some distinct features which help in their identification. The diseases caused by these organisms have particular symptoms as well.

Table of Contents

• Aim of the experiment

• Apparatus required

• Theory

• Procedure

• Observations

i) Characteristic features

ii) Systematic position

iii) Symptoms

• Results

• Precautions

• Lab manual questions

• Viva questions

• Practical based questions

• Summary

• Frequently Asked Questions (FAQs)

Aim

To observe and study permanent slides to identify the disease-causing organisms like Ascaris, Entamoeba, Plasmodium, and Ringworm and the symptoms of the disease.

Apparatus required

i) Permanent slides, Preserved specimens, or Photographs of Ascaris, Entamoeba, Plasmodium, and Ringworm

ii) Compound Microscope

Theory

The number of parasitic and pathogenic organisms (i.e. disease-causing) in humans is quite high. The human body is severely harmed by these organisms, bringing illnesses that often lead to diseases. These diseases may even be life-threatening. The external morphology of these organisms demonstrates distinct characteristics. The diseases they induce have particular symptoms as well.

Procedure

1. Carefully observe the features visible in a preserved specimen of Ascaris as it is of sufficient size to be visible to the naked eye. Note down the findings.

2. Observe the permanent slides of Entamoeba, Plasmodium, and Ringworm under the compound microscope as they are not easily visible to the naked eye. Initially, observe under low power magnification and then shift to high power magnification view. Write down the features visible.

3. Draw neat and clean diagrams of the pathogens and label them correctly.

Observations

Ascaris

i) Characteristic Features:

1. It has an unsegmented, long, and cylindrical body.

2. Sexes are separate and distinct. Females are longer than males in size.

3. The mouth is visible on the anterior end and it is encircled by three lips-like structures. These lips are not visible clearly to the naked eye and are viewed using a magnifying glass. One of the lips is located mid dorsally and the other two lips are present ventrolateral.

4. Both the posterior and anterior ends are pointed. The posterior tip in males is curved slightly.

5.  Along the length of the body, there are single longitudinal lines on the dorsal, ventral, and two lateral sides. In comparison to the other lines, the lateral lines are somewhat more defined and distinct.

6. There is an excretory pore on the ventral surface, just behind the anterior end.

7. The male worm possesses a pair of penial spicules right next to the cloacal aperture.

8. A female genital aperture can be seen in the female specimen mid-ventrally at about one-third of the distance from the anterior end.

Structure of a male ascaris 

ii) Systematic Position:

Phylum- Aschelminthes

Class-  Nematoda

Type- <i>Ascaris lumbricoides</i>

Disease caused by Ascaris lumbricoides or roundworms- Ascariasis

iii) Symptoms:

1. Abdominal discomfort and pain

2. Swelling in the abdominal region

3. Nausea and vomiting

4. Fatigue

Entamoeba

i)Characteristic Features:

1. It is unicellular with protruding finger-like structures called pseudopodia which is responsible for its irregular shape.

2. It consists of a single nucleus which is eccentrically positioned inside the cell. 

3. *A peripheral ring of nucleoprotein granules and a central karyosome can be seen in the nucleus. The remaining area of the nucleus appears to be empty.

4. In the cytoplasm, a few food vacuoles could be seen.

5. *There might be mature quadrinucleate cysts.

6. There are no contractile vacuoles.

*Distinctive feature of the pathogen

Structure of Entamoeba

ii) Systematic Position:

Phylum- Protozoa

Class- Rhizopoda

Type- Entamoeba histolytica

This is an intestinal parasite (a pathogen that resides in the intestines of humans). 

Disease caused by Entamoeba histolytica- Amoebic dysentery

iii) Symptoms:

1. Diarrhoea (Frequent, loose, mucous-filled watery stools)

2. Pain in the abdominal region

3. Spasms

4. Nausea and vomiting

Plasmodium

i) Characteristic Features:

1. It is a unicellular endoparasite and can be seen in the red blood cells of an infected person.

2. The signet ring stage of the parasite in the erythrocyte, where it manifests as a rounded body, is the most diagnostic.

3. The cell contains a sizable vacuole within and the nucleus is present where the cytoplasm is concentrated.

4. The parasite appears as a ring due to the aforementioned features.

ii) Systematic Position:

Phylum- Protozoa

Class- Sporozoa

Type- Plasmodium vivax

Disease caused by Plasmodium vivax- Malaria

Note: 

When a healthy individual gets bitten by the female anopheles mosquito, they develop a risk of infection to malaria. At that moment, the infected stage of the pathogen Plasmodium vivax, sporozoites, gets released into the peripheral blood vessels of the person and starts flowing through the bloodstream. The infective stage multiples repeatedly in the liver and erythrocytes.

iii) Symptoms:

1. Chills and a high temperature that periodically returns

2. Periods of excessive perspiration follow the chills

3. Headache and muscle ache

4. Fatigue

5. Nausea and vomiting

Ringworm

i) Characteristic Features:

1. It is a fungus that feeds on the keratin on the human skin.

2. Hyphae have a waxy, smooth, or cotton-like texture.

3. Unstained hyphae have distinct colours such as white, reddish-brown, or yellowish-brown.

ii) Systematic Position:

Kingdom- Fungi

Class- Deuteromycetes

Type- Trichophyton rubrum

Ringworm causes a fungal infection and it is communicable.

iii) Symptoms:

1. Skin is itchy and scaly (having sharp edges).

2. Red and raised patches are present in the infected areas of the skin.

3. The patches form a ring structure as they are redder in the periphery than in the centre.

Results

We can conclude that all disease-causing organisms have their distinctive external features. The symptoms of the diseases they cause are also specific.

Precautions

• Handle the specimens and slides with care to avoid breakage.

• Make sure the slides are placed in the correct position for observation under the microscope.

• To prevent contamination of the slides, always hold them by the sides and not in the middle.

• Always make sure to observe under low magnification at first and then move on to high magnification if it is not visible.

Lab Manual Questions

1. How long does Ascaris spend incubating outside of the human body?

Ans: The duration of incubation in Ascaris outside the human body is 6.

2. What is the genus of Plasmodium?

Ans: The genus of Plasmodium is Protozoans.

3. What is the kingdom of Ringworm?

Ans: The kingdom of Ringworm is Fungi.

Viva Questions

1. What is the infectious stage of plasmodium in the human host?

Ans:  The infectious stage of plasmodium in the human host is sporozoites.

2. What is a pathogen?

Ans: Pathogens are disease-causing microorganisms.

3. Are all microorganisms pathogenic?

Ans: No. Some microorganisms are helpful in our day-to-day life.

4. What is the location where Entamoeba histolytica stays in the human body?

Ans: They are located in the walls of large intestines.

5. What is the difference between a parasite and a pathogen?

Ans: A parasite is an organism that lives on or in another organism of a different species. An organism that lives on or in another organism of a different species is known as a parasite.

6. What is the common name of Ascaris lumbricoides?

Ans: The common name of Ascaris lumbricoides is roundworm.

7. What is the pathogen and carrier of malaria?

Ans: Plasmodium is the pathogen and the vector Anopheles stephensi (female) is the carrier of malaria.

8. What is the name of the disease caused by Entamoeba histolytica?

Ans: The disease caused by Entamoeba histolytica is Amoebic dysentery.

Practical-Based Questions

1. What is the correct method to hold prepared or permanent slides to avoid contamination?

1. Right in the middle

2. By the sides

3. Inverted

4. It does not matter which method is used to hold the slides.

Answer- B. By the sides

2. In the case of which of the following organisms, is there no need for a microscope to observe its features?

1. Ascaris

2. Entamoeba

3. Plasmodium

4. Ringworm

Answer- A. Ascaris

3. What does the body of Ascaris lumbricoides look like?

1. Long

2. Cylindrical

3. Unsegmented

4. All of the above

Answer- D. All of the above

4. Which sex among the Ascaris has the larger size?

1. Male

2. Female

3. Both have almost the same size

4. There are no different sexes

Answer- B. Female

5. What is the number of nuclei present in the cysts of Entamoeba?

1. Five

2. Three

3. Four

4. Two

Answer- C. Four

6. Which of the following best describes the appearance of a plasmodium parasite?

1. Ring

2. Flattened sac like

3. Cylindrical

4. String like

Answer- A. Ring

7. Which of the following gives a better description of the microbe nature of Ringworm?

1. Amoeba

2. Bacteria

3. Virus

4. Fungi

Answer- D. Fungi

8. In which of the following places Plasmodium is not found?

1. Latin America

2. Europe.

3. Asia

4. Some parts of Africa.

Answer- D. Some parts of Africa.

Summary

Several organisms are pathogenic (i.e., able to inflict sickness on people) and parasitic. These organisms seriously harm the human body and frequently cause diseases by infecting people with illnesses. These illnesses might be fatal. These species' outward morphology reveals various traits. They also cause illnesses that have specific symptoms.