Explanation

• Energy transfer in a food chain follows the 10% law.
• Only about 10% of energy passes to the next trophic level.
• About 90% of energy is lost as heat and metabolic activities.
• This loss limits the number of trophic levels in a food web.
• Therefore, energy decreases by approximately 90% at each step.

Last updated question 17-02-2026

Explanation

• DNA sequencing by Sanger method uses ddNTPs.
• ddNTPs lack the 3′-OH group on the sugar.
• Without 3′-OH, no further nucleotide can attach.
• This causes termination of the DNA chain.
• Different labeled ddNTPs help determine the DNA sequence.

Explanation

• T₃ (Triiodothyronine) and T₄ (Thyroxine) are thyroid hormones.
• They are produced in the thyroid gland.
• They are formed by iodination of the amino acid tyrosine.
• Iodinated tyrosine molecules (iodotyrosine) combine to form T₃ and T₄.
• Dopamine and GABA are neurotransmitters, not thyroid hormone precursors.

Last updated question 17-02-2026

Explanation

• The cell membrane is made of a phospholipid bilayer.
• Cholesterol is embedded between phospholipids.
• It regulates membrane fluidity at different temperatures.
• It prevents the membrane from becoming too rigid in cold conditions.
• It also prevents excessive fluidity in high temperature, maintaining stability.

Last updated question 17-02-2026

Explanation

 Tigers (Panthera tigris) are classified as endangered by IUCN.

 Indus River Dolphin (Platanista minor) is also endangered.

Tigers face threats from habitat loss and poaching.

Indus dolphins are threatened by river pollution, dams, and reduced water flow.

Last updated question 17-02-2026

Explanation

Protozoans that eat other organisms (solid food particles like bacteria or other microorganisms) are called Holozoic. 

Explanation

Lithium (Li) and Magnesium (Mg), Magnesium (Mg) and Aluminium (Al) show a diagonal relationship in the periodic table

Where elements in adjacent groups and periods have similar properties.

Explanation

The method by which an animal adapts to resemble or act like another species (or an object in its environment) to gain a survival advantage is generally called mimicry. 

Explanation

• Copper exhibits +2 oxidation in CuO and CuSO₄.
•  In Cu₂O, it shows +1 oxidation.
•  Cu²⁺ is common in compounds.
•  It forms stable salts with sulfate and oxide ions.
•  Essential in many biological enzymes.

Last updated question 17-02-2026

Explanation

•  Linoleic acid is an essential fatty acid.
•  Humans cannot synthesize it.
•  It must come from diet.
•  Important for cell membranes.
•  Found in vegetable oils and nuts.