Biology Questions and Answers

Answer: D

A tree's age is estimated from the number of annual rings in its trunk.

Each ring is one year's growth: the pale wide band is spring wood and the dark narrow band summer wood. The technique is dendrochronology, and ring width also records the climate of each year.

Answer: B

Lenticels are involved in gaseous exchange.

They are loose patches of cells in the bark, visible as small raised pores, through which oxygen and carbon dioxide pass to and from the living tissues beneath. They take over the role of the stomata once a woody stem is covered by impermeable cork.

Answer: C

A successful experiment results only in the rejection of one or more hypotheses.

Evidence can disprove a hypothesis conclusively but can never prove one, since the next observation may contradict it. A hypothesis that survives repeated attempts to refute it is provisionally accepted, not proved.

Answer: C

Fungi account for the largest number of species among these.

About 100,000 have been described and the true number is estimated in the millions, against perhaps 40,000 algae, 20,000 lichens and 25,000 mosses and ferns. Fungi are second only to insects among all groups of organisms.

Answer: A

A baby born with a small tail shows atavism - the reappearance of an ancestral character that has been lost in the course of evolution.

The human embryo has a tail of about a dozen vertebrae in the sixth week, which normally regresses. Occasionally the regression fails, leaving a vestigial tail at birth.

Answer: C

Cyanobacteria live inside the vegetative part of Cycas.

Anabaena and Nostoc inhabit the coralloid roots - specialised roots that grow upward to the soil surface - and fix atmospheric nitrogen for the plant in exchange for shelter and carbohydrate.

Answer: B

Insect-pollinated flowers have pollen that is rough and sticky, often with spines or a sticky coating, so it clings to a visiting insect.

Wind-pollinated pollen is the opposite: small, smooth, dry and light, produced in enormous quantity so that a little of it reaches a stigma by chance.

Answer: D

Darwin set out his theory in On the Origin of Species, published on 24 November 1859.

The whole print run of 1,250 copies sold on the first day. 'Survival of the fittest' was Herbert Spencer's phrase, which Darwin adopted only in the fifth edition.

Answer: C

Homologous structures are different in different animals but are modifications of the same basic structure.

The forelimb of a man, a bat, a whale and a horse has the same bones in the same order, adapted to grasping, flying, swimming and running. That shared plan is what points to a shared ancestor.

Answer: A

Thomas Malthus wrote the essay on population that helped Darwin.

His Essay on the Principle of Population (1798) argued that populations grow geometrically while food supply grows arithmetically, so most individuals must die before reproducing. Darwin saw that this struggle would favour whichever variants happened to be better suited.