Biology Questions and Answers

Answer: A

Leghaemoglobin absorbs oxygen in the root nodule.

Nitrogenase, the enzyme that fixes nitrogen, is destroyed by oxygen, yet the bacteria need oxygen for their own respiration. Leghaemoglobin binds the oxygen and delivers it at a very low free concentration, protecting the enzyme while feeding the bacteria. It is what makes an active nodule pink inside.

Answer: B

Photosynthesis is fastest in white light, because it contains every wavelength chlorophyll can use.

Chlorophyll absorbs most strongly in the blue-violet and red, and the accessory pigments capture parts of the spectrum chlorophyll misses, so the full white spectrum drives the process harder than any single colour.

Answer: D

Bacterial replication begins with DNA replication.

The circular chromosome is copied from a single origin; the two copies then attach to the plasma membrane and are drawn apart as the cell grows, and only then does the membrane pinch inward and the daughter cells separate.

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

Deductive reasoning applies general principles to predict or explain specific cases.

Its conclusion follows necessarily from its premises: if the general rule is true, the particular consequence must be. Inductive reasoning runs the other way, from particular observations to a general rule.