Explanation

• The fourth ventricle is a cerebrospinal fluid-filled cavity located between the pons and medulla oblongata in front and the cerebellum behind.
• It is part of the brain’s ventricular system.
• It is connected to the third ventricle through the cerebral aqueduct.
• The fourth ventricle continues into the central canal of the spinal cord and helps circulate cerebrospinal fluid (CSF).

Last verified on 27-10-2026

Explanation

• Glycolysis is the common initial stage of both aerobic and anaerobic respiration.
• It occurs in the cytoplasm and breaks one glucose molecule into two molecules of pyruvate, producing a net gain of 2 ATP and 2 NADH.
• In aerobic respiration, pyruvate is generally further broken down through aerobic pathways.
• In anaerobic conditions, it may undergo fermentation or other processes to regenerate NAD⁺.

Last verified on 27-10-2026

Explanation

• Ringworm is a fungal infection caused by dermatophytes, including Microsporum, Trichophyton, and Epidermophyton.
• Despite its name, ringworm is not caused by a worm.
• It often produces a circular, red, itchy rash on the skin.
• The infection may affect the scalp, body, feet, or groin, depending on the site of infection.

Last verified on 27-10-2026

Explanation

• Sergei Nawaschin discovered double fertilization in flowering plants (angiosperms) in 1898.
• In double fertilization, one male gamete fuses with the egg cell to form a diploid zygote (2n), while the other fuses with the two polar nuclei to form the triploid endosperm (3n) in typical angiosperms.
• The zygote develops into the embryo, while the endosperm provides nourishment to the developing embryo.

Last verified on 27-10-2026

Explanation

• The clitellum is a thickened, glandular band present in sexually mature earthworms.
• It secretes mucus during reproduction and produces material that forms the cocoon for eggs.
• Earthworms belong to the phylum Annelida and class Clitellata.

Last verified on 27-10-2026

Explanation

• The Stark effect is the splitting or shifting of spectral lines of atoms or molecules due to an external electric field.
• The Stark effect is named after German physicist Johannes Stark, who discovered it in 1913.

Additional information:

• The Zeeman effect is the splitting of spectral lines due to an external magnetic field.
• The Photoelectric effect occurs when light ejects electrons from a material.

Last verified on 27-10-2026

Explanation

• Methane (CH₄) has four C–H bonds arranged symmetrically in a tetrahedral shape.
• Each C–H bond has a small bond dipole, but the four bond dipoles cancel one another because of the molecule’s symmetrical geometry.
• Therefore, methane has a zero net dipole moment.

Last verified on 27-10-2026

Explanation

• Silicon has atomic number 14, with the electronic configuration 1s² 2s² 2p⁶ 3s² 3p².
• When two electrons are removed from silicon, they are removed from the 3p subshell, producing Si²⁺ with the configuration 1s² 2s² 2p⁶ 3s².
• The outermost occupied orbital is then the 3s orbital, which is spherical in shape.

Last verified on 27-10-2026

Explanation

• Aluminium chloride (AlCl₃) is trigonal planar in its monomeric form, with aluminium at the centre and three chlorine atoms around it.
• The central aluminium atom is described as sp²-hybridized, forming three sigma bonds arranged at approximately 120°.
• Aluminium chloride can also form a dimer, Al₂Cl₆, under certain conditions.
• In the dimer, bridging chlorine atoms change the bonding arrangement.

Last verified on 27-10-2026

Explanation

• The azimuthal quantum number (l) identifies the subshell: l=0 for s, l=1 for p, l=2 for d, and l=3 for f.
• The number of orbitals in a subshell is calculated using 2l+1.
• For l=2, the number of orbitals is 2(2)+1=5.
• These five d orbitals are degenerate in an isolated atom, meaning they have the same energy.

Last verified on 27-10-2026