General Awareness
Biology Guide & Practice
Master human diseases, their causes, symptoms, transmission modes, vitamins and deficiency diseases for SSC, Banking and Defence exams. Explore dynamic solver blueprints, master fundamental equations, examine step-by-step solved examples, and practice with real exam-grade mock test sets.
1. Fundamentals & Definitions
- Human Disease: A condition that involves the malfunctioning or improper functioning of various body parts. It can be caused by factors like hormonal imbalance, genetic disorders, or malfunctioning of the immune system.
- Pathogen: A biological agent (microorganism) that causes disease or illness to its host.
- Vector: A living organism that transmits an infectious pathogen to another living organism. Examples include arthropods (mosquitoes, ticks, fleas, sandflies) and vertebrates (dogs, bats).
- Communicable Disease: An infectious disease that is transmissible from one person to another, either directly or indirectly.
- Non-Communicable Disease (NCD): Also known as a chronic disease, it is a non-infectious medical condition that tends to be of long duration. NCDs are the result of a combination of genetic, physiological, environmental, and behavioral factors.
- Transmission: The passing of a pathogen causing communicable disease from an infected host to a particular individual. The main routes are:
- Air-borne Transmission: Pathogens remain suspended in the air (droplet nuclei) and are transmitted to individuals. Examples: Chickenpox, Influenza (Flu), Measles, Tuberculosis.
- Contact Transmission: Pathogens spread through person-to-person contact (touching, kissing, sexual contact) or via placenta/blood. Examples: Herpes, AIDS, Syphilis.
- Vehicle Transmission: Involves inanimate materials (fomites) like utensils, bedding, needles, food, or water that carry the pathogen. Examples: Cholera, Typhoid, Food Poisoning.
- Vector-Borne Transmission: A living organism (vector) transmits the pathogen. For example, flies carrying bacteria or mosquitoes transmitting parasites.
2. Core Concepts & Classifications
Diseases Caused by Microbes (Communicable)
Protozoan Diseases
| Disease Name | Protozoa | Location / Affected Organ | Transmission | Symptoms |
|---|---|---|---|---|
| Malaria | Plasmodium | Red Blood Cells (RBC) | Female Anopheles mosquito | Destroys RBC, high fever |
| Pyorrhoea | Entamoeba gingivalis | Gums | Direct Contact | Bleeding Gums |
| Sleeping Sickness | Trypanosoma | Brain, Cerebrospinal Fluid | Tsetse Fly | High Fever, Sleepiness |
| Dysentery (Amoebic) | Entamoeba histolytica | Intestines | Contaminated food/water | Vomit, Loose Motion, Stools with mucus |
| Kala-azar | Leishmania donovani | Liver, Spleen, Bone Marrow | Sandfly | Bone marrow affected, fever |
| Diarrhoea | Ascaris lumbricoides | Intestine | Contaminated food/water | Vomit, Loose Motions |
| Filariasis | Wuchereria bancrofti | Lymph vessels | Culex mosquito | Elephantiasis (swelling of feet/legs) |
Viral Diseases
| Disease Name | Virus | Location / Affected Organ | Symptoms |
|---|---|---|---|
| AIDS | HIV (Human Immunodeficiency Virus) | White Blood Cells (WBC) / Immune System | Immune System affected (WBC decrease) |
| Dengue | Dengue virus (Arbovirus) | Whole Body | Head & Joint Pain, fever |
| Measles | Morbillivirus | Whole Body | Redness on Body, fever, rash |
| Jaundice | Hepatitis virus | Liver | Yellowing of skin and eyes |
| Rabies | Rabies lyssavirus | Nervous System | Hydrophobia (fear of water), fever |
| Herpes | Herpes Simplex Virus | Skin | Skin Swelling, sores |
| Polio | Poliovirus | Whole-body (Nervous system) | Pain in body, paralysis |
| Influenza (Flu) | Myxovirus | Whole Body (Respiratory system) | Sneezing, fever, body ache |
| Chicken Pox | Varicella Zoster Virus | Whole Body | High fever & rash |
| Small Pox | Variola Virus | Whole Body | Light fever & rash |
Bacterial Diseases
| Disease Name | Bacteria | Location / Affected Organ | Symptoms |
|---|---|---|---|
| Tetanus | Clostridium tetani | Nervous System | Lockjaw, muscle spasms |
| Cholera | Vibrio cholerae | Intestine | Severe diarrhoea, dehydration |
| Trachoma | Chlamydia trachomatis | Cornea of Eye | Ache in Eyes, blindness |
| Typhoid | Salmonella typhi | Intestine | High fever, holes in intestines |
| Tuberculosis (TB) | Mycobacterium tuberculosis | Lungs | Breathing Issues, cough, fever |
| Diphtheria | Corynebacterium diphtheriae | Respiratory Tract | Suffocation, sore throat, fever |
| Whooping Cough | Bordetella pertussis | Respiratory System | Severe Cough |
| Bubonic Plague | Yersinia pestis | Red Blood Cells (RBC), Lymph nodes | Fever, Unconsciousness, swollen lymph nodes |
| Pneumonia | Diplococcus pneumoniae | Lungs | Fluid in lungs (Swelling), cough |
Fungal Diseases
| Disease Name | Fungi | Location / Affected Organ | Symptoms |
|---|---|---|---|
| Asthma | Aspergillus fumigatus | Lungs | Lung blockage, difficulty breathing |
| Athlete's foot | Tinea pedis | Skin (Feet) | Itching and swelling in feet |
| Scabies | Acarus scabies | Skin | Itching in body |
| Baldness | Tinea capitis | Scalp | Hair loss, bald patches |
| Ringworm | Trichophyton | Skin | Circular rashes on skin |
Non-Communicable Diseases
Genetic & Chromosomal Disorders
- Turner Syndrome: A chromosomal disorder (44 + X) in females where one X chromosome is missing or partially missing, leading to developmental issues and infertility.
- Klinefelter Syndrome: A genetic condition in males caused by an extra X chromosome (44 + XXY), resulting in underdeveloped testes and infertility.
- Down's Syndrome: Caused by a full or partial extra copy of chromosome 21 (Trisomy 21). It leads to developmental and intellectual delays.
- Patau's Syndrome: A serious genetic disorder caused by an extra copy of chromosome 13 (Trisomy 13). It causes severe intellectual disability and physical defects.
- Color Blindness: A genetic inability to distinguish between certain colors, most commonly red and green. The gene is located on the X chromosome, making it more common in males.
- Haemophilia: A hereditary genetic disorder that impairs the body's ability to make blood clots, a process needed to stop bleeding.
Cancer
- Definition: A group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body.
- Benign Tumor: A mass of cells that lacks the ability to invade neighboring tissue or metastasize. It is less harmful.
- Malignant Tumor (Cancer): Cells that grow uncontrollably and can spread from the original site (metastasize) to other parts of the body. It is more harmful.
- Leukemia: Cancer of blood-forming tissues, including bone marrow, resulting in a high number of abnormal white blood cells.
- Sarcoma: Cancer of connective tissues like bones, muscles, and cartilage.
- Oncology: The study and treatment of tumors (cancer).
Solved Examples
1Easy Example
Question: Tuberculosis is a common infectious disease that primarily affects the lungs. It is caused by which type of pathogen? (A) Virus (B) Bacteria (C) Fungus (D) Protozoa
2Moderate Example
Question: Malaria is a life-threatening disease. How is it primarily transmitted from one person to another? (A) By drinking contaminated water (B) Through airborne droplets from a cough or sneeze (C) By the bite of an infected female Anopheles mosquito (D) Through direct physical contact with an infected person
3Hard Example
Question: Kala-azar, also known as visceral leishmaniasis, is a severe parasitic disease. What is the specific causative agent (pathogen) and its corresponding vector? (A) Pathogen: Trypanosoma, Vector: Tsetse Fly (B) Pathogen: Wuchereria bancrofti, Vector: Culex mosquito (C) Pathogen: Plasmodium, Vector: Anopheles mosquito (D) Pathogen: Leishmania donovani, Vector: Sandfly