A-Level A-Level Biology 2

Question 1

What is the Hardy-Weinberg principle?

Accepted Answer

A model stating that allele frequencies in a population remain constant from generation to generation in the absence of evolutionary influences

Answer

The Hardy-Weinberg principle states that allele and genotype frequencies remain constant in large, randomly mating populations with no mutation, migration, selection, or genetic drift. Equations: p + q = 1 and p² + 2pq + q² = 1.

Question 2

What is the role of restriction enzymes in genetic engineering?

Accepted Answer

To cut DNA at specific recognition sequences, producing fragments for cloning

Answer

Restriction endonucleases cut double-stranded DNA at specific palindromic recognition sequences (4–8 base pairs), often producing 'sticky ends' that allow fragments to be joined to vectors using DNA ligase.

Question 3

What is ecological succession?

Accepted Answer

The process by which communities of organisms change and develop over time in a habitat, from pioneer species to a climax community

Answer

Ecological succession is the directional change in a community over time. Primary succession starts on bare substrate (e.g., rock after a glacier). Species modify the habitat, allowing new species to establish, eventually reaching a stable climax community.

Question 4

What is the difference between Type I and Type II diabetes?

Accepted Answer

Type I is an autoimmune condition destroying beta cells; Type II is insulin resistance often linked to lifestyle

Answer

Type I (insulin-dependent) diabetes is autoimmune — the immune system destroys pancreatic beta cells, stopping insulin production. Type II develops when cells become resistant to insulin, often linked to obesity and lifestyle, though genetics plays a role.

Question 5

What is the function of the glomerulus in the nephron?

Accepted Answer

Ultrafiltration of blood under pressure to produce glomerular filtrate

Answer

The glomerulus is a knot of capillaries inside the Bowman's capsule. High hydrostatic pressure forces small molecules (water, urea, glucose, ions) out of the blood into the Bowman's capsule as filtrate. Large proteins and cells cannot pass.

A-Level Revision Practice Test

A-Level Revision Practice Test

A-Level A-Level Biology 2