Science · World of living · chapter 6 of 13

Class 10 Science Chapter 6: Control and Coordination case study question with answers

One case-based question of the kind the board asks in Section E: a passage and a table, then 3 parts worth 4 marks in all, with the answer and the marking scheme for each. Written from the NCERT chapter.

Case study · 4 marks

Ishita grew maize seedlings in three pots for five days. Pot A stood in open sunlight. Pot B was kept inside a cardboard box with a single opening on its left side. Pot C was laid on its side in a dark cupboard. In Pot B the stems curved towards the opening. In Pot C the stem tips turned upwards and the root tips turned downwards. Ishita then measured cells just below the stem tip in Pot B.

Side of the stem in Pot B	Average cell length
facing the opening	0.08 mm
away from the opening	0.12 mm

Part 1 · 1 mark

The curving of the stems in Pot B is an example of

(a) geotropism(b) phototropism(c) chemotropism(d) hydrotropism

Show answer

Answer: (b) phototropism

Shoots bend towards light; growth in response to light is phototropism.

Part 2 · 1 mark

Name the response shown by the stem and root tips in Pot C, and say which part grows away from the earth.

Answer and marking scheme

Geotropism, growth in response to the pull of gravity; the shoot grows upwards, away from the earth, and the root downwards.

geotropism; the shoot grows away from the earth (1)

Part 3 · 2 marks

From the table, which side of the stem in Pot B grew faster, and on which side must the growth hormone made at the shoot tip have collected? Name the hormone.

Answer and marking scheme

The cells on the side away from the opening are longer (0.12 mm against 0.08 mm), so that shaded side grew faster and the hormone must have collected there. The hormone is auxin, made at the shoot tip, which helps cells grow longer.

side away from the opening (shaded) grew faster, so the hormone collected there (1)
auxin (1)

The maize in Pot A later forms cobs whose seeds develop by rapid cell division. Name the hormone found in high concentration in these seeds, and one hormone that, like auxin, helps the stem grow.

Answer and marking scheme

Cytokinin, which promotes cell division and is concentrated in fruits and seeds. Gibberellin, which like auxin helps in the growth of the stem.

cytokinin in the seeds (1)
gibberellin helps stem growth (1)

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