Explanation

• Fluoride is commonly added to drinking water in small amounts to prevent tooth decay (dental cavities).
• It strengthens tooth enamel and makes teeth more resistant to acid attacks from bacteria and sugars.
• Community water fluoridation began in 1945 in the United States as a public health measure.

Last verified on 15-03-2026

Explanation

• Mitochondria are cell organelles responsible for producing energy in the form of ATP (Adenosine Triphosphate) through cellular respiration. 
• They are called the “Powerhouse of the cell” because they provide the energy required for all cellular activities.
• Mitochondria have their own DNA and ribosomes, allowing them to replicate independently.

Last verified on 14-03-2026

Explanation

• The word ‘Scientia’ is derived from the Latin word Scientia which means ‘knowledge’.
• Science involves observation, experimentation, and analysis.
• The scientific method includes Hypothesis → Experiment → Observation → Conclusion.

Last verified on 13-03-2026

Explanation

• Tundra is a cold, treeless region found near the Arctic and Antarctic.
• Soil is often frozen (permafrost) throughout the year.
• Vegetation includes mosses, lichens, and low shrubs.
• Animals adapted: polar bears, arctic foxes, reindeer.

Last verified on 13-03-2026

Explanation

• Humans have 20 primary teeth (also known as deciduous or baby teeth).
• 32 permanent teeth (also known as adult teeth).

Explanation

• Respiration (breathing) is mainly controlled automatically by the brain’s respiratory center in the medulla oblongata.
• Normally, breathing occurs without conscious control, so it is an involuntary process.
• When a person cannot control breathing voluntarily (e.g., during sleep or unconsciousness), the body automatically continues respiration.

Last verified on 13-03-2026

Explanation

• Enamel is the hard, mineralized outer layer of teeth.
• It protects the inner parts of the tooth from damage and decay.
• Enamel is the hardest substance in the human body.
• It is mainly made of calcium phosphate.
  

Additional information:

• Incisors (8) – used for cutting food
• Canines (4) – used for tearing food
• Premolars (8) – help crush and grind food
• Molars (12) – grind food during chewing
• Total adult teeth = 32

Last verified on 13-03-2026

Explanation

• Digestion specifically means the mechanical and chemical breakdown of food into simpler substances.
• Mechanical digestion includes chewing and churning, while chemical digestion involves enzymes and acids.

Additional information:
Main 5 processes of the digestive system:

1. Ingestion – taking food into the body
2. Digestion – mechanical and chemical breakdown of food
3. Absorption – nutrients enter blood through the intestine
4. Assimilation – cells use absorbed nutrients
5. Egestion – removal of undigested waste

Last verified on 13-03-2026

Explanation

• The alimentary canal wall is made of four main tissue layers that help in digestion and movement of food.
• These layers include mucosa, submucosa, muscular layer, and serosa.
• Secretin is not a tissue layer; it is a digestive hormone released by the small intestine.

Last verified on 13-03-2026

Explanation

• The centrosome is a small non-membranous organelle found mainly in animal cells.
• It plays a key role in cell division (mitosis and meiosis) by organizing the spindle fibers.
• It contains two centrioles arranged at right angles.
• The centrosome ensures proper separation of chromosomes during cell division.

Last verified on 13-03-2026