Biology · 2016 · May · Paper 2 · SL · Markscheme

M16/4/BIOLO/SP2/ENG/TZ0/XX/M 13 pages Markscheme May 2016 Biology Standard level Paper 2 – 2 – M16/4/BIOLO/SP2/ENG/TZ0/XX/M Section A Question Answers Notes Total 1. a a. nerve cells increase the least OR control cells the most  2 max b. «endodermal and contr ol cells are the same at 48 hours» but the control cells increase exponentially/much more than endodermal cells by 96 hours OR last 48 hours/from 48 hours to 96 hours, constant «small» increase in cell numbers for nerve, but greater/incre ased change for control and endodermal  Do not accept numbers without distinguishing terms. Award [1 max] if all three (nerve, endodermal and control cells) not mentioned at some point in the answer as stem requires all three. c. from 48 to 96 hours much more increase in cell number in control than in endodermal  b cell differentiation slows down/retards/decreases population growth OR population growth is slower in differentiating/differentiated cell lines  Accept converse eg: nondifferentiation accelerates growth. 1 c a. the percentage of «cells in» G1 in nerve is greater than in control OR the S phase has greater «percentage of cells» in control than in nerve  2 b. G2 phase is similar in both OR least/lower percentage of cells of the phases in both lines  Do not accept numbers without distinguishing terms. d a. more cells in G1 «of cell lines/nerves» with slow population growth  Accept converse statements. 2 max b. more cells in S «of cell line/control» with fast population growth/«significantly» fewer cells in S in both slow growth lines/nerves and endodermal cells  c. G2 seems not to be related with pop growth as it is very similar in the three cell lines 