Explanation

• The Sun is a star.
• There are lots of stars, but the Sun is the closest one to Earth.
• It is the center of our solar system.
• The Sun is a hot ball of glowing gases.
• The sun is composed of layers made up almost entirely of hydrogen and helium.

Last verified on 13-03-2026

Explanation

• Sound waves are mechanical waves that require a medium (air, water, or solid) to travel.
• They transport energy, not matter.
• Particles of the medium vibrate around their mean position but do not move along with the wave.
• Examples: Speaking, music, and alarms transfer energy through sound waves.

Last verified on 13-03-2026

Explanation

• Refraction: Bending of light when it passes from one medium to another.
• A prism bends light at different angles depending on wavelength.
• This separation of colors is called dispersion, forming a spectrum.
• Visible spectrum colors: Red, Orange, Yellow, Green, Blue, Indigo, Violet (ROYGBIV).

Last verified on 13-03-2026

Explanation

Thermal energy can be transferred through all three methods:

• Conduction: Direct transfer between particles in physical contact.
• Convection: Transfer through the movement of fluids.
• Radiation: Transfer through electromagnetic waves (e.g., light, radio waves).

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

• 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 same atomic number (Z) → same number of protons
• Different mass numbers → different number of neutrons

Explanation

• The spleen is not part of the digestive tract; it is part of the lymphatic system and helps in blood filtration and immune response.

Additional information:

Main components of human digestive tract:

• Mouth – ingestion and initial digestion
• Oesophagus – food passage
• Stomach – protein digestion
• Small intestine – nutrient absorption
• Large intestine / Colon – water absorption and feces formation

Last verified on 13-03-2026

Explanation

• Filtration is not part of digestion; it occurs mainly in the kidneys for removing waste from blood.

Additional information:

Main functions of the digestive system:

1. Ingestion – taking in food
2. Propulsion – swallowing and peristalsis
3. Mechanical processing – chewing and churning
4. Chemical digestion – breaking down molecules with enzymes
5. Absorption – nutrients absorbed into blood or lymph

Last verified on 13-03-2026