General Science GK Questions with Answers – Page 94

In 1932 Chadwick bombarded beryllium with alpha particles and showed that the highly penetrating radiation given off consisted of neutral particles with almost the same mass as a proton.

In 1897 Thomson passed an electric discharge through a gas at very low pressure and showed that the cathode rays produced were a stream of identical negatively charged particles, far lighter than any atom and the same whatever gas or electrode was used.

The fossil of Archaeopteryx carries feathers and wings like a bird together with teeth in the jaws, claws on the wings and a long tail with bones, all reptilian features, so it stands as the standard example of a connecting link in the fossil record.

The same arrangement of bones, humerus, radius and ulna, carpals, metacarpals and phalanges, is used for walking in a man, for swimming in a whale, for flight in a bat and for running in a cheetah, which indicates descent from a common ancestor and is called divergent evolution.

He held that an organ used often becomes stronger and one left unused withers, and that characters so acquired in a lifetime are passed to the offspring, the giraffe's lengthening neck being his best known illustration.

Darwin set out in that book the theory of evolution by natural selection, drawing on observations made during his voyage on HMS Beagle, among them the finches of the Galapagos islands whose beaks differ with their diet.

A person with Down syndrome carries three copies of chromosome 21 instead of two, a condition called trisomy 21, so the total chromosome number is 47 rather than 46.

A human body cell has 46 chromosomes arranged in 23 pairs, of which 22 pairs are autosomes, the chromosomes that are alike in both sexes, and the remaining pair is of sex chromosomes, XX in a female and XY in a male.

RNA carries adenine, guanine, cytosine and uracil, and the uracil occupies the place that thymine holds in DNA, pairing with adenine in the same way.

James Watson and Francis Crick published the double helix model in 1953, with two strands running in opposite directions and bases paired on the inside, using the X-ray diffraction photographs produced by Rosalind Franklin and Maurice Wilkins; Watson, Crick and Wilkins shared the Nobel Prize in 1962.

The correct answer is B, Wilhelm Johannsen, the Danish botanist who gave the words gene, genotype and phenotype, distinguishing the hereditary constitution of an organism from its visible expression.

In a dihybrid cross two pairs of characters are followed together, for example seed shape and seed colour, and the appearance of all four combinations in the proportion nine to three to three to one shows that the inheritance of one pair does not depend on the inheritance of the…

When two heterozygous plants of the first generation are crossed, three quarters of the offspring show the dominant character and one quarter the recessive one, because the recessive appears only when both factors in the pair are recessive.

Mendel chose it because it breeds true, is easy to cross by hand, completes a generation in a single season and offers seven pairs of sharply contrasting characters such as tall against dwarf stem and round against wrinkled seed.

The pinna is the outer, visible flap of the ear, and its funnel shape collects sound from the surroundings. Sound gathered by the pinna travels down the ear canal to the tympanic membrane, or eardrum, which starts to vibrate.

The tiny pores on the surface of a leaf, found mostly on its lower side, are called stomata. Each stoma is a slit guarded by two bean shaped guard cells, which swell to open it and shrink to close it.

Methyl ethyl ketone has a methyl group on one side of the carbonyl and an ethyl group on the other, which makes four carbons in all with the carbonyl at the second position, so its IUPAC name is butan-2-one or 2-butanone.

A homogeneous mixture has the same composition and properties throughout and no visible boundary between its parts, so a true solution such as salt water qualifies, and so does brass, an alloy of copper and zinc, since alloys are solid solutions.

Gamma rays are electromagnetic waves of the highest frequency and shortest wavelength, given out by the nucleus of a radioactive atom and in nuclear reactions, and their energy lets them kill cancer cells in radiotherapy.

The principle says a body immersed wholly or partly in a fluid is pushed up by a force equal to the weight of the fluid it pushes aside, and that upward force is called buoyancy or upthrust.