Explanation

Explanation

Explanation

Greenhouse gases trap heat primarily by absorbing and re-emitting infrared radiation emitted from the Earth's surface

Molecules with three or more atoms, such as CO2 and methane,

Allow them to absorb this longwave radiation and radiate it back towards the surface

Last updated question 25 feb 2026

Explanation

• The SA (sinoatrial) node initiates the heartbeat.
• It produces rhythmic electrical impulses automatically.
• It sets the normal heart rate, so it is called the natural pacemaker.
• Located in the right atrium
• It is the dominant pacemaker because its cells generate action potentials faster than other parts of the conduction system.

Explanation

Since none of the given options show features like cell specialization or permanent cell association

The transition to multicellularity is better supported by colonial organization and cell differentiation.

Contractile vacuole is used for osmoregulation 

Encystment is a survival mechanism to withstand unfavorable conditions

Binary fission is a type of asexual reproduction

Explanation

Nitrous Oxide is significantly more potent at trapping heat than methane and carbon dioxide

N2O absorbs infrared radiation very strongly and stays long in the atmosphere.

It has a GWP of approximately 265–298, making it nearly 300 times more potent than CO₂ per unit

Explanation

Humans have 22 pairs of autosomes and 1 pair of sex chromosomes.

Chromosome 21 is the smallest autosome in terms of base pairs.

Chromosome 1 is the largest autosome.

Chromosome 23 refers to sex chromosomes (X or Y), not autosomes.

Chromosome 21 is associated with Down syndrome when trisomic.

Last updated question 17-02-2026

Explanation

• The nephron is the functional unit of the kidney.
• Sodium reabsorption occurs at different parts of the nephron.
• Thick loop of Henle actively pumps out Na⁺ using ATP (active transport).
• Thin loop of Henle mainly allows passive movement of water and ions.
• Proximal tubule reabsorbs Na⁺ mainly by secondary active transport; collecting duct fine-tunes Na⁺ under hormonal control (aldosterone).

Last updated question 17-02-2026

Explanation

• Carolus Linnaeus gave the artificial system of classification. 
• He classified plants mainly based on the number and arrangement of stamens.
• known as the "Father of Taxonomy

Last updated question 17-02-2026

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