# Human Health and Disease Notes, Class 12 Biology | SwaVid Human Health and Disease, NCERT Class 12 Biology: notes with key ideas, key terms, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-12/biology/chapter/human-health-and-disease Source: https://www.swavid.com/cbse/class-12/biology/chapter/human-health-and-disease # Human Health and Disease ## Key terms ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 12 Biology on SwaVid ### Health and common infectious diseases ### Innate and acquired immunity ### Active, passive immunity and allergies ### Structure of the immune system ### AIDS and cancer ### Drugs and alcohol abuse ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 12 › Biology › Human Health and Disease Notes written by SwaVid from the NCERT textbook. Class 12 Biology, Chapter 7. Key ideas, formulas and common mistakes. CBSE prints 12 marks for Unit VIII, not for this chapter alone. Short answer. This chapter explains common infectious diseases, immunity mechanisms, AIDS, cancer, and the abuse of drugs and alcohol. It shows how pathogens cause illness and how the immune system defends the human body. Source: NCERT Biology (Reprint 2026-27) , Chapter 7, Human Health and Disease Health is a state of complete physical, mental, and social well-being, not merely the absence of disease. Pathogens like bacteria, viruses, fungi, protozoans, and helminths cause diseases such as typhoid, pneumonia, common cold, malaria, amoebiasis, ascariasis, and ringworm. Innate immunity provides non-specific defence through physical, physiological, cellular, and cytokine barriers. Acquired immunity is pathogen-specific, characterized by memory, and mediated by B-lymphocytes producing antibodies and T-lymphocytes providing cell-mediated immunity. Active immunity develops when a host produces antibodies after exposure to antigens, while passive immunity involves ready-made antibodies, such as colostrum containing IgA. Allergy is an exaggerated immune response to foreign antigens, mediated by IgE antibodies and histamine released from mast cells. Primary lymphoid organs like bone marrow and thymus are sites where lymphocytes mature and differentiate. Secondary lymphoid organs like the spleen, lymph nodes, and MALT provide sites for lymphocytes to interact with antigens and proliferate. AIDS is caused by the human immunodeficiency virus (HIV), a retrovirus that attacks helper T-lymphocytes. Cancer involves uncontrolled cell division and metastasis, caused by physical, chemical, or biological carcinogens that activate oncogenes. Opioids, cannabinoids, and coca alkaloids interfere with normal neurotransmission and cause addiction and dependence. Chronic abuse harms the nervous system, liver, and other vital organs, leading to severe withdrawal syndromes upon sudden stoppage. Try each question first. Then tap it to see the answer. Plasmodium multiplies within liver cells and then attacks red blood cells. Rupture of red blood cells releases a specific toxic chemical. This chemical triggers the cyclic chill and high fever every 3 to 4 days. Haemozoin Allergies are exaggerated immune responses to environmental antigens. The immunoglobulin class produced in response to allergens is IgE. Mast cells release inflammatory chemicals upon stimulation. IgE antibodies; histamine and serotonin HIV is classified as a retrovirus. Retroviruses possess an RNA genome enclosed in an envelope. The viral genome copies itself into DNA using a specific viral enzyme. RNA genome; reverse transcriptase Microbes in Human Welfare . Biotechnology and its Applications . Reproductive Health . The 13 chapters of Class 12 Biology . CBSE does not give marks to one chapter. It prints 12 marks for Unit VIII, Biology and Human Welfare, which includes Human Health and Disease. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Microbes in Human Welfare. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 7 NCERT book - 12 marks, Unit VIII - 3 quick checks - Confusing the causative agents of the common cold and pneumonia . Remember that pneumonia infects the alveoli of the lungs and is caused by bacteria like Streptococcus pneumoniae, while the common cold infects the nose and respiratory passage without affecting the lungs and is caused by rhinoviruses. - Classifying colostrum or antivenom as active immunity . Identify whether the body produces its own antibodies or receives pre-formed ones. Colostrum contains ready-made IgA and antivenom contains ready-made antibodies against snake venom, making both examples of passive immunity. - Confusing the site of maturation of B-cells and T-cells . Both B-lymphocytes and T-lymphocytes originate in the bone marrow, but B-cells mature in the bone marrow while T-cells mature in the thymus. - Writing that HIV destroys red blood cells directly . State clearly that HIV enters macrophages and helper T-lymphocytes (CD4 cells), replicating via reverse transcriptase to deplete helper T-cell populations, not erythrocytes. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 12](https://www.swavid.com/cbse/class-12) - [Biology](https://www.swavid.com/cbse/class-12/biology/chapters) - [Start free →](https://www.swavid.com/signup) - [All 13 chapters](https://www.swavid.com/cbse/class-12/biology/chapters) - [NCERT Biology (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-12/biology/chapter/microbes-in-human-welfare) - [Open notes](https://www.swavid.com/cbse/class-12/biology/chapter/biotechnology-and-its-applications) - [Open notes](https://www.swavid.com/cbse/class-12/biology/chapter/reproductive-health) - [Class 12 Biology](https://www.swavid.com/cbse/class-12/biology/chapters) - [Start free →](https://www.swavid.com/signup)