Zadanie 7, Paper 2, maj 2022, TZ1, Biologia IB SL

(a) Ribose drawn as a pentagon and labelled. ✔

A labelled nitrogenous base joined to the 1′ position of ribose. ✔

A labelled phosphate group joined through the 5′ position. ✔

(b) In animals, mitosis produces somatic cells whereas meiosis produces cells of the sexual reproductive pathway. ✔

Mitosis has one division, meiosis two. ✔

Mitosis usually yields two daughter cells, meiosis four products. ✔

Mitosis generally preserves genetic identity, whereas meiosis generates variation. ✔

Mitosis supports growth and repair; meiosis supports sexual reproduction. ✔

Mitosis preserves chromosome number; meiosis halves it. ✔

Homologous chromosomes pair in meiosis but not ordinary mitosis. ✔

Crossing over is characteristic of meiosis, not ordinary mitosis. ✔

(c) An antibiotic kills or inhibits susceptible bacteria. ✔

Resistance varies among bacteria. ✔

Random mutation can generate resistance. ✔

Resistant bacteria are not killed by the antibiotic OR susceptible bacteria are killed. ✔

This gives a selective advantage or unequal reproductive success. ✔

Surviving resistant bacteria reproduce. ✔

The resistance allele is inherited by their descendants. ✔

Resistant variants become more frequent. ✔

The population has evolved increased resistance. ✔

Quality: the response is clear on first reading, concise and contains little repetition or irrelevant material. ✔

Part (a):1 per correctly drawn and labelled feature,maximum 3; if more than one nucleotide is drawn,maximum 2. “Sugar” without ribose is insufficient. Part (b):any 5 paired contrasts,maximum 5; no credit for unpaired statements. Part (c):any 7 points,maximum 7; cap at 6 if “pathogen” is used throughout without identifying bacteria. Award 1 independent communication-quality mark. Total 16.