HKDSE 2013 Biology

Paper 2 Question 2 Comments on Candidates’ Performance

Q.2(a)(i)

• Poorly answered

• Q: An experiment was conducted to study the efefffectect ofof aciacidd rraiainn on the grgrowowtthh of bean seedlings plants in pots containing two different soils, eieittherher wwiitthh oror wwiitthouthout heavyheavy mmetetalal XX – Conclusion should be drawn on:

1. the effect of acid rain and heavy metal X

2. the effect of them on the growth (NOT average increase in fresh weight) of bean seedling

• Only a few candidates could conclude that growth is the slowest with the presence of both acid rain and heavy metal X

Q.2(a)(i)

Q.2(a)(i)

Q.2(a)(ii)

• Poorly answered

• Most could not realize that

– acid rain dissolves the heavy metal ion X in

the soil

– increase in amount of dissolved heavy metal

ion X causes a greater effect of inhibition on

the growth of bean seedling

• Some do not give explanation with reference to the results, but by guessing

– e.g. X damages the roots

Q.2(a)(ii)

Q.2(a)(ii)

Q.2(a)(iii)

• Well answered

• Some gave vague answers on the effect of air pollutants, e.g.

– poisonous

– erosion on skin

– get sick

Q.2(a)(iii)

Q.2(a)(iii)

Q.2(b)(i)

• Poorly answered

• Most did not recognize that these chemicals are fat-soluble

• Misconceptions:

– small molecular size

– indigestible

Q.2(b)(i)

Q.2(b)(ii)

• Well answered

• Some gave irrelevant answers like how pollutant Y is accumulated

Q.2(b)(iii)

• Fairly answered

• Q: With reference to the ffuunnccttiioonnaall rroollee of organisms in the ecosystem…

– Answer should refer to the functional role, not

just give the name of the organism group

• Bacteria / Plants x

• Decomposers / Producers .

Q.2(b)(iii)

Q.2(b)(iv)

• Well answered

• Some wrongly thought that toxic substances are transported to the liver for

storage / removal / excretion

General comments

• Read the question carefully

– Many answers from Level 1 students are not

related to the questions

• Misunderstanding of the question

• Use more accurate terms in the answers

– e.g. “affect growth” does not mean inhibit

growth