RRB Group D GK Questions 2026

Flame cells, also called solenocytes, are specialised cells with a tuft of beating cilia that drives waste fluid into a system of tubules, and they handle both the removal of nitrogenous waste and the balance of water in animals such as Planaria, Taenia and Fasciola.

Starfishes, sea urchins, sea cucumbers, brittle stars and sea lilies are found only in the sea, and their water vascular system, which works by taking in sea water, is one reason they never colonised fresh water or land.

More than three-fourths of all described animal species are arthropods, that is insects, spiders, scorpions, centipedes, crabs and prawns. A hard chitinous exoskeleton, jointed appendages, small body size and, in insects, the power of flight allowed the group to spread into almost every habitat on earth.

These are the three places in a eukaryotic cell where DNA is found. The nucleus holds nearly all of a cell's DNA, packed with proteins into chromosomes.

A ribosome contains RNA, but it has no genes of its own; it reads messenger RNA sent from the DNA of the nucleus or an organelle.

Both carry their own DNA and ribosomes and can make some of their own proteins. Mitochondria, the powerhouses of the cell, and plastids such as chloroplasts each contain a small circular DNA molecule and 70S ribosomes, much like bacteria.

The plasma membrane is made of lipids and proteins and contains no DNA or RNA. The plasma membrane is the outer boundary of the cell.

Copper is less reactive than lead, so it cannot push lead out of its compound. In a displacement reaction, a more reactive metal takes the place of a less reactive metal in its salt solution.

Graphite has free electrons that can move through it, so it conducts electricity; diamond and fullerene do not conduct well.

In a short circuit the live and neutral wires touch, the resistance of the path falls almost to zero, and the current shoots up.

A leaf from a sunny day is full of starch made by photosynthesis, and iodine turns starch blue-black. This is the standard school test for starch in a leaf.

A body moving faster than sound outruns its own sound waves, which pile up into a shock wave heard on the ground as a sonic boom.

Xylem carries water along with the minerals dissolved in it from the roots up to the stem and leaves. Plants have two kinds of conducting tissue.

Bacteria have a cell wall and human cells do not, so a drug that attacks the cell wall harms only the bacteria.

Each nucleotide of DNA is made of these three parts, and many nucleotides joined together form the polynucleotide chain. In a DNA strand, the sugar of one nucleotide is linked to the phosphate of the next by a phosphodiester bond, making a sugar-phosphate backbone.

A magnesium atom sits at the centre of every chlorophyll molecule, so a plant cannot make chlorophyll without it. Chlorophyll is built around a ring-shaped structure called a porphyrin, with a single magnesium ion held at its centre.

A carbonate reacts with an acid at room temperature to give carbon dioxide, and only carbon dioxide turns limewater milky.

The body's weight stays the same, but standing puts it on the small area of the feet, so the pressure is greater.

Silver is the best conductor, nichrome is an alloy with high resistivity, and glass is an insulator with enormous resistivity.

During a hard sprint the muscles run short of oxygen and switch to anaerobic respiration, which leaves lactic acid behind.