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Biology and Human Welfare - Human Health and Diseases

Grade 12ICSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Health is defined by the WHO as a state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity.

Pathogens are disease-causing organisms. Examples include bacteria like Salmonella typhiSalmonella \ typhi (Typhoid) and Streptococcus pneumoniaeStreptococcus \ pneumoniae (Pneumonia).

Viral diseases include the Common Cold (Rhino viruses) and AIDS (Human Immunodeficiency Virus).

Protozoan diseases: Malaria is caused by PlasmodiumPlasmodium species (P. vivaxP. \ vivax, P. falciparumP. \ falciparum). The infectious stage is the sporozoite.

Immunity is the ability of the host to fight the disease-causing organisms. It is divided into Innate (non-specific) and Acquired (pathogen-specific) immunity.

The acquired immune response involves BlymphocytesB-lymphocytes (humoral) and TlymphocytesT-lymphocytes (cell-mediated).

Antibodies are specialized proteins produced by B-cells. The basic structure is represented as H2L2H_2L_2, consisting of two heavy and two light chains.

Active Immunity involves the host's own body producing antibodies (e.g., during infection), while Passive Immunity involves the transfer of pre-formed antibodies (e.g., IgAIgA in colostrum).

Autoimmunity is a condition where the body attacks its own cells (e.g., Rheumatoid arthritis).

AIDS is caused by HIV, a retrovirus with an RNARNA genome. It attacks helper TT-cells (THT_H cells), significantly reducing the CD4+CD_4^+ count.

Cancer involves uncontrolled cell division due to the loss of contact inhibition. Malignant tumors exhibit metastasis, spreading to distant sites via blood.

Drugs and alcohol abuse: Opioids (Heroin), Cannabinoids, and Alkaloids (Cocaine) interact with specific receptors in the Central Nervous System (CNS).

📐Formulae

H2L2 (Basic structure of an Antibody molecule)H_2L_2 \text{ (Basic structure of an Antibody molecule)}

CD4+ count<200 cells/mm3    Clinical AIDS diagnosis threshold\text{CD}_4^+ \text{ count} < 200 \text{ cells/mm}^3 \implies \text{Clinical AIDS diagnosis threshold}

BMI=mass (kg)height (m)2\text{BMI} = \frac{\text{mass (kg)}}{\text{height (m)}^2}

💡Examples

Problem 1:

Calculate the probability of a child inheriting a genetic disease if both parents are carriers of an autosomal recessive trait like Thalassemia.

Solution:

Using a Punnett square, let TT be the normal allele and tt be the recessive disease allele. The cross is Tt×TtTt \times Tt.

Explanation:

The offspring genotypes will be 1 TT:2 Tt:1 tt1 \ TT : 2 \ Tt : 1 \ tt. Therefore, the probability of a diseased child (tttt) is 25%25\%, and the probability of being a carrier (TtTt) is 50%50\%.

Problem 2:

Describe the diagnostic test used for Typhoid and the causative agent.

Solution:

Causative agent: Salmonella typhiSalmonella \ typhi. Diagnostic test: Widal Test.

Explanation:

The Widal test is a serological test that detects specific antibodies against the OO and HH antigens of Salmonella typhiSalmonella \ typhi in a patient's serum.

Problem 3:

Differentiate between Benign and Malignant tumors.

Solution:

Benign tumors remain localized; Malignant tumors invade surrounding tissues and show metastasis.

Explanation:

Malignant cells reach distant sites through circulatory systems and start a new tumor, a property known as metastasis, which is the most feared property of cancer.

Human Health and Diseases - Revision Notes & Key Diagrams | ICSE Class 12 Biology