How Are Diseases Classified? Understanding Causes, Types & Prevention
The concept of diseases is essential in biology and helps explain real-world biological processes, health issues, and exam-level questions effectively.
Understanding Diseases
Diseases refer to any harmful deviation from the normal state or functioning of a living organism, usually shown by specific signs or symptoms. This concept is important in areas like disease classification, causes and prevention, and communicable versus non-communicable diseases. Understanding diseases is vital for both board exams and real-life health awareness.
Types and Classification of Diseases
There are many ways to classify diseases, but the most common categorisation is:
- Communicable Diseases: Spread from one person to another (e.g., malaria, tuberculosis, chickenpox).
- Non-communicable Diseases: Do not spread between people (e.g., diabetes, cancer, hypertension).
Other important disease types include deficiency diseases, degenerative diseases, genetic diseases, vector-borne diseases, and allergies.
Here’s a helpful table to understand disease classification better:
Disease Classification Table
| Type | Description | Examples |
|---|---|---|
| Communicable Diseases | Caused by pathogens and spread from person to person | Tuberculosis, Influenza, Malaria |
| Non-communicable Diseases | Not spread; depend on genes, nutrition, or lifestyle | Diabetes, Cancer, Asthma |
| Deficiency Diseases | Caused by lack of essential nutrients or vitamins | Beriberi, Rickets, Scurvy |
| Degenerative Diseases | Caused by aging or wear of tissues/organs | Osteoporosis, Alzheimer’s |
| Genetic Diseases | Result from changes in genes or chromosomes | Down Syndrome, Thalassemia |
| Vector-borne Diseases | Transmitted by vectors like mosquitoes or ticks | Dengue, Lyme Disease |
| Allergies | Immune system overreacts to harmless substances | Asthma, Hay Fever |
Common Causes of Diseases
The major causes of diseases are:
- Infectious agents (bacteria, viruses, fungi, protozoa)
- Deficiency of nutrients (vitamins, minerals, proteins)
- Genetic disorders (mutations, inherited factors)
- Environmental factors (pollution, toxins, climate)
- Lifestyle factors (diet, lack of exercise, stress)
- Vectors (insects like mosquitoes, ticks, bed bugs)
System-wise Examples of Diseases
Diseases often affect specific body systems. Here are some examples:
| System | Common Diseases |
|---|---|
| Digestive System | Diarrhoea, Food Poisoning, Gastroenteritis |
| Nervous System | Meningitis, Epilepsy, Alzheimer’s |
| Respiratory System | Asthma, Pneumonia, Tuberculosis |
| Circulatory System | Hypertension, Heart Attack, Stroke |
Notable Disease Lists – For Exams and Quizzes
Knowing the most common and important diseases is helpful for quick revision. Here are sample lists:
- Diabetes
- Hypertension (High blood pressure)
- Tuberculosis
- Malaria
- Dengue
- Cancer
- Asthma
- HIV/AIDS
- Cholera
- Polio
- COVID-19
- Hepatitis (A, B, C)
- Leprosy
- Pneumonia
- Goitre
- Rickets
- Kwashiorkor
- Measles
- Ringworm
- Chickenpox
Full lists, including rare and historical diseases, can be found in standard textbooks and health websites.
Common Symptoms and Prevention of Diseases
- Symptoms: Fever, cough, headache, tiredness, pain, swelling, rashes, itchiness, and more, depending on the disease.
- Prevention: Vaccination, proper nutrition, hygiene, safe drinking water, mosquito nets, regular exercise, and avoiding contact with infected people or vectors.
Quick Reference: Diseases List A–Z
| Disease Name | System/Type | Main Cause |
|---|---|---|
| Anemia | Blood/Deficiency | Iron deficiency |
| Asthma | Respiratory/Allergic | Allergens, Pollution |
| Beriberi | Deficiency | Vitamin B1 lack |
| Cholera | Digestive/Infectious | Bacteria (Vibrio cholerae) |
| Diabetes | Metabolic/Non-communicable | Hormonal, Genetic |
| Hepatitis | Liver/Infectious | Viruses (A, B, C, E) |
| Malaria | Vector-borne/Infectious | Mosquito (Plasmodium) |
| Polio | Nervous/Infectious | Poliovirus |
| Rickets | Deficiency | Vitamin D lack |
| Tuberculosis | Lungs/Infectious | Bacteria (Mycobacterium tuberculosis) |
Common Mistakes to Avoid
- Confusing diseases with symptoms or disorders.
- Mixing up causes (bacteria vs virus vs deficiency).
- Assuming all infectious diseases are contagious.
Real-World Applications
The concept of diseases is used in fields like medicine, agriculture, biotechnology, public health, and environmental science. Understanding diseases helps in designing vaccines, new medicines, health policies, and spreading awareness. Vedantu helps students relate such topics to practical examples faced in everyday life and exam questions.
In this article, we explored diseases, their types, causes, symptoms, and importance in daily life and exams. For more detailed examples and confidence building, keep practicing with Vedantu’s biology resources and revision lists.
Explore Related Topics on Vedantu
- Microbes and Diseases
- Symptoms of Various Diseases
- Disease and Its Causes
- Immunity
- Viral Diseases
- Bacterial Diseases in Humans
- Vector-Borne Diseases
- Deficiency Diseases
- Health and Hygiene
- Health Diseases
- Difference Between Epidemic and Pandemic
FAQs on Diseases in Biology: Types, Causes, and Key Examples Explained
1. What is a disease?
A disease is any condition that causes a disruption or damage to the normal functioning of the body's cells, tissues, or organs. It leads to abnormal signs and symptoms which can affect the overall health of an individual.
2. What are the different types of diseases?
Diseases are broadly classified into two main types: communicable diseases, which spread from one person to another and are caused by pathogens like bacteria, viruses, fungi, and parasites; and non-communicable diseases, which do not spread and are caused by factors like genetics, lifestyle, or nutritional deficiencies. Examples include infectious diseases such as malaria and non-infectious diseases such as diabetes.
3. What are the top 20 diseases?
The top 20 common diseases include both infectious and non-infectious diseases such as malaria, tuberculosis, HIV/AIDS, diabetes, cancer, hypertension, asthma, hepatitis, influenza, pneumonia, Alzheimer's disease, arthritis, stroke, chronic obstructive pulmonary disease (COPD), diarrhoea, measles, dengue, typhoid, anaemia, and heart diseases. Knowing these helps in exam preparation and understanding health challenges.
4. What are examples of viral diseases?
Viral diseases are caused by viruses and include diseases such as chickenpox, influenza, hepatitis (A, B, C), human immunodeficiency virus (HIV/AIDS), dengue, measles, mumps, and COVID-19. These diseases spread through various modes like air droplets, bodily fluids, or vectors like mosquitoes.
5. What causes diseases in humans?
Diseases are caused by multiple factors: infectious agents such as bacteria, viruses, fungi, protozoa, and parasites; genetic defects inherited from parents; nutritional deficiencies like lack of vitamins or minerals; and environmental factors including pollution, toxins, and lifestyle habits. Vector-borne diseases caused by organisms like ticks and mosquitoes are also common.
6. What diseases are caused by ticks or mosquitoes?
Diseases transmitted by ticks and mosquitoes are classified as vector-borne diseases. Examples caused by ticks include Lyme disease and tick-borne encephalitis. Mosquito-borne diseases include malaria, dengue fever, chikungunya, yellow fever, and Zika virus infection. These are common in tropical and subtropical regions.
7. Why do some diseases cause symptoms in only one system?
Some diseases affect only one specific organ system because they target particular cells or tissues. For example, asthma directly affects the respiratory system causing breathing difficulties, while hepatitis affects the liver. The specificity is due to the pathogen's nature or disease mechanism impacting only certain organs.
8. Why are vector-borne diseases common in some regions?
Vector-borne diseases are more common in regions with favorable conditions for vectors like temperature, humidity, and presence of water bodies. Tropical and subtropical climates support mosquitoes and ticks that transmit diseases such as malaria and dengue. Poor sanitation and stagnant water also increase vector breeding.
9. Why do students confuse infectious and non-infectious diseases?
Students often confuse infectious (caused by pathogens and contagious) and non-infectious diseases (caused by genetic, lifestyle, or environmental factors) due to overlapping symptoms or lack of clarity about disease causes. Using clear examples and classification tables helps reduce this confusion.
10. Why is understanding disease classification important for the exam?
Understanding the classification of diseases helps students to organize concepts clearly, answer board exam questions accurately, and relate diseases to their causes, symptoms, and prevention strategies. It improves conceptual clarity, which is essential for scoring well in Biology.
11. Why aren’t all diseases preventable?
Not all diseases can be prevented due to factors beyond control such as genetic disorders, some chronic diseases, and certain infections. While lifestyle, vaccination, and hygiene can prevent many diseases, hereditary diseases or those caused by unknown factors may not have defined prevention methods.
12. Why do diseases lists differ in books vs. online resources?
Disease lists vary because of differing classification criteria, regional prevalence, syllabus focus, and updating frequency in books versus online resources. Some sources emphasize common diseases for education, while others provide exhaustive lists, causing differences in the number and types of diseases shown.
