General Science Previous Year Questions (PYQ) with Answers – Page 58

Pollen first reaches the stigma, then the gametes fuse, the zygote divides to form an embryo, and the embryo inside the seed grows into a seedling.

A salamander is an amphibian, and amphibians have a heart with two atria and one ventricle. Heart chambers increase along the vertebrate groups.

Elephantiasis, or lymphatic filariasis, is an endemic disease: it stays steadily present in certain regions and develops slowly over years, rather than breaking out suddenly in a large number of people.

The spring constant is force divided by extension, so its SI unit is newton per metre. Hooke's law says that, within the elastic limit, the restoring force of a spring is proportional to how far it is stretched or compressed: F = −kx.

Of the four, ultraviolet lies furthest towards the short-wavelength, high-energy end of the electromagnetic spectrum. All electromagnetic waves travel at the speed of light in vacuum, but they differ in wavelength and frequency.

In aerobic tissues, where oxygen is available, glucose is broken down completely into carbon dioxide, water and energy. Aerobic respiration begins with glycolysis in the cytoplasm, which gives pyruvate.

After fertilisation, each ovule grows into a seed, and the ovary that holds the ovules grows into the fruit. In flowering plants, a pollen tube carries two male gametes to the ovule.

The breakdown of glucose into pyruvate, called glycolysis, takes place in the cytoplasm (cytosol) of the cell. Glycolysis is the first step of respiration in almost every living cell.

A simple periscope has two plane mirrors facing each other in parallel, each tilted at 45° to the tube. Light from the object enters the top opening and strikes the upper mirror, which is set at 45° and turns the light through 90° down the tube.

A plane mirror always forms a virtual image, one that cannot be caught on a screen, so calling it real is the false statement.

Tropolone is aromatic, but its seven-membered ring is made only of carbon atoms, so it is not heterocyclic. A heterocyclic compound has at least one atom other than carbon, such as oxygen, sulphur or nitrogen, inside its ring.

Natural chlorine is a mixture of two isotopes, and their weighted average is about 35.5 u. Chlorine has two stable isotopes: chlorine-35, which makes up about 75 per cent of natural chlorine, and chlorine-37, about 25 per cent.

Above the threshold, the kinetic energy of the ejected electrons rises as the frequency of the light rises, so the statement that it does not change is wrong.

The triple point is the single temperature and pressure at which the solid, liquid and vapour phases of a substance exist together in equilibrium.

Where oil meets water, the unequal pull of their molecules sets up a surface (interfacial) tension that keeps the two liquids as separate layers.

The de Broglie wavelength depends only on momentum, so equal wavelengths mean equal momenta. In 1924 Louis de Broglie proposed that every moving particle has a wave linked to it, with wavelength λ = h/p, where h is Planck's constant and p is the linear momentum.

X-rays are electromagnetic waves with no electric charge, so electric fields cannot deflect them. X-rays were discovered by Wilhelm Röntgen in 1895, who won the first Nobel Prize in Physics in 1901 for it.

Pitch is how high or low a sound seems to the ear, and it depends on the frequency of vibration: the higher the frequency, the higher the pitch.

Platelets, or thrombocytes, gather at a cut and start the process that forms a clot and stops bleeding. Platelets are tiny cell fragments without a nucleus, broken off from large cells called megakaryocytes in the bone marrow.

Chemical messengers called neurotransmitters are released from the nerve endings, the tips of the axon, into the synapse. A nerve impulse travels from the dendrites through the cell body and along the axon as an electrical signal.