Explanation

• Birds have hollow (pneumatic) bones to make their skeleton lighter, aiding flight efficiency.
• Hollow bones reduce overall body weight without sacrificing strength.
• This adaptation is crucial for sustained flying and gliding.

Last verified on 09-02-2026

Explanation

• The ozone layer absorbs and blocks the majority of the Sun’s harmful ultraviolet (UV) radiation.
• This protection helps prevent skin cancer, cataracts, and damage to ecosystems.

Last verified on 09-02-2026

Explanation

• Data collection and analysis rely on accurate observations and measurements.
• If proper observations are not made, the experiment’s results will be unreliable.
• Other steps like hypothesis generation or reasoning depend on this data for validation.

Last verified on 09-02-2026

Explanation

• Endothermic reactions absorb heat from the surroundings (e.g., photosynthesis, melting ice).
• Exothermic reactions release heat to the surroundings (e.g., burning fuel, respiration).
• The key difference is heat flow direction between the system and environment.

Additional information:

• Endothermic → feels cold to touch
• Exothermic → feels hot to touch
• Examples help remember: Ice melting (endo), Fire burning (exo)

Last verified on 09-02-2026

Explanation

• Endothermic reactions absorb heat from the surroundings.

Examples:

• Photosynthesis → plants absorb sunlight to make glucose
• Melting of ice → absorbs heat to change solid → liquid
• Dissolving ammonium nitrate in water → absorbs heat, feels cold

Burning of fuel is exothermic, releasing heat and light.

Last verified on 09-02-2026

Explanation

• Chemical changes produce new substances with different properties.

Examples:

• Cooking of food → new substances formed
• Burning of paper → produces ash and gases
• Rusting of iron → iron reacts with oxygen to form rust

Melting of ice is a physical change, only changing state from solid to liquid, no new substance is formed.

Last verified on 09-02-2026

Explanation

• Oxygenated blood from the lungs returns to the left atrium of the heart via the pulmonary veins.
• From the left atrium, blood moves to the left ventricle, which then pumps it to the whole body.

Additional information:

• The right atrium receives deoxygenated blood from the body.

Last verified on 09-02-2026

Explanation

• Proteins are the most abundant biomolecules in a typical cell’s dry mass.
• They perform structural, enzymatic, transport, and signaling functions in cells.
• Comprise roughly 50–60% of a cell’s dry weight more than others.

Last verified on 09-02-2026

Explanation

• The equilibrium constant (Kc) measures the ratio of product concentrations to reactant concentrations at chemical equilibrium.
• It is expressed in terms of molar concentrations (moles per liter, M).
• Used in chemical reactions in solution to predict the direction and extent of reactions.

Last verified on 09-02-2026

Explanation

• A hypothesis is a proposed explanation or prediction that can be tested through research or experiments.
• The statement about interfamily marriages increasing genetic disorders is a testable prediction, not yet proven.
• If tested and supported by data, it may contribute to a scientific theory later.

Last verified on 09-02-2026