Biology Questions and Answers

Answer: A

The condition is Myopia.

In myopia (short-sightedness), the eyeball is too long or the lens too strong, so light from distant objects focuses in front of the retina. Near objects are seen clearly but distant ones look blurred. It is corrected with a concave (diverging) lens.

Hyperopia (long-sightedness) is the reverse: distant objects are clear, near ones blurred. Astigmatism is blurring from an unevenly curved cornea, and presbyopia is the age-related loss of the ability to focus on near objects.

Answer: B

The one that is not an insect is the Spider.

A spider is an arachnid: it has eight legs, two body regions (cephalothorax and abdomen), no antennae and no wings.

Insects have six legs, three body regions (head, thorax and abdomen) and a pair of antennae. The mosquito and the house fly are true flies (Diptera) and the bed-bug is a true bug (Hemiptera), so all three are insects.

Answer: C

Proteins are digested in the stomach by pepsin.

The stomach's chief cells secrete pepsinogen, which hydrochloric acid converts into the active enzyme pepsin. Pepsin breaks proteins into smaller peptides in the acidic conditions of the stomach.

Amylase digests starch, lipase digests fats and maltase splits maltose, so none of them digests protein.

Digestion of protein is completed in the small intestine by trypsin and other enzymes from the pancreas, after pepsin has begun the process in the stomach.

Answer: C

Polycythemia is a disease of the blood.

Polycythemia means an abnormally high number of red blood cells, which makes the blood thicker. Polycythemia vera is a bone-marrow disorder, and secondary polycythemia can follow chronic low oxygen, as at high altitude.

It affects the heart and other organs only indirectly; it is classed as a blood disorder.

It can be detected by a raised haemoglobin or haematocrit in a routine blood test, and its main risk is clotting, because thicker blood flows more slowly.

Answer: B

The development described is CRISPR.

CRISPR-Cas9 is a gene-editing technique adapted from a bacterial immune defence. A guide RNA directs the Cas9 enzyme to a chosen DNA sequence, where it cuts the DNA so that genes can be disabled, corrected or replaced. It is cheap and precise enough to be used to correct genetic defects and improve crops, and it raises ethical questions, especially over editing human embryos. Its developers, Jennifer Doudna and Emmanuelle Charpentier, received the 2020 Nobel Prize in Chemistry.

DNA barcoding identifies species from a short standard gene region. p53 is a tumour-suppressor gene. 'Terminator' technology makes seeds sterile so they cannot be replanted. None of them edits genes at will.

Answer: B

The cells are mainly cells of gut microbes.

Alanna Collen's 10% Human (2015) is about the human microbiota, the bacteria and other microbes living on and in the body, most of them in the gut. Its title comes from the long-quoted estimate that microbial cells outnumber human cells by about nine to one, and its argument is that these microbes are central to digestion, immunity and even mood.

Later studies have revised the ratio closer to one to one, but the book's subject is unchanged. Junk DNA is non-coding DNA inside our own cells, stem cells are human cells, and CRISPR-modified cells are an engineering product, not a natural majority of the body.

Answer: A

The key gives Decrease in carbon monoxide.

Cigarette smoke carries carbon monoxide, which binds haemoglobin and reduces the oxygen the blood can carry. Within a day of quitting, the carbon monoxide level falls, the blood carries oxygen normally again and the lungs begin to recover. This is the answer the Commission fixed.

Be aware that the question is loosely worded. The airway lining also regenerates over months after quitting, so synthesis of new mucosa is a real part of healing, but it is the slower, structural change and the key does not use it. An increase in oxygen uptake is a result of the lower carbon monoxide, not its cause, and long-term inflammatory changes are damage, not healing.

Answer: C

Colchicine is obtained from glory lily.

Colchicine is an alkaloid extracted from the seeds and tubers of the glory lily, Gloriosa superba, as well as from the autumn crocus, Colchicum autumnale. It is used to treat gout, and in plant breeding it is used to double chromosome numbers and produce polyploids, because it stops spindle formation during cell division.

Opium poppy yields morphine and codeine, pyrethrum yields the insecticide pyrethrin, and sarpagandha (Rauvolfia serpentina) yields reserpine, used for high blood pressure.

Answer: D

All four statements are correct, so the answer is A, B, C and D.

The large intestine consists of the caecum, colon, rectum and anal canal (A). Its bacteria carry out the last stages of digestion, fermenting leftover material and producing some vitamins, such as vitamin K and some B vitamins (B). It absorbs water, ions such as sodium, and these vitamins, turning the remaining material into faeces (C).

Defecation, the elimination of faeces from the rectum, is a reflex triggered by the stretching of the rectal wall, aided by voluntary contraction of the diaphragm and abdominal muscles (D). Since all four hold, every option leaving one out is incomplete.

Answer: C

The breed indigenous to Karnataka is Amrit Mahal.

Amrit Mahal is a draught cattle breed of Karnataka, from the Chikkamagaluru, Hassan, Chitradurga and Tumakuru region. It was developed in the herds of the Mysore rulers, notably under Hyder Ali and Tipu Sultan, who used the fast, hardy bullocks to haul artillery.

Red Sindhi comes from Sindh, now in Pakistan, and Gir from the Gir hills of Gujarat; both are dairy breeds. Since Amrit Mahal fits, 'None of the above' is wrong.