IGCSE Biology 2nd edition

Here you will find the answers to the 'in-text' questions which occur in IGCSE Biology (2nd edition) and GCSE Biology (3rd edition) by D. G. Mackean, published by Hodder Education, London, UK.

Chapters: | Index | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 |

Chapter 31. Micro-organisms


Page 286
1. Only cytoplasm and DNA are present in both bacterial cells and plant cells.
2. If the population of 5 bacteria doubles every 20 minutes, after 4 hours it will have reached 20480.
3. a The virus particle contains no cytoplasm, no cell membrane and no nucleus.
    b Viruses do not feed, respire, grow, excrete, move or respond to stimuli which are characteristics of living organisms. They do reproduce but only by rearranging their host’s cytoplasm. (See page 292).
4. In the bacterium, the nucleus divides and then the cytoplasm is shared between the two cells. In the virus there is no nucleus or cytoplasm. New virus particles are built by using the host’s cellular material.

Page 288
1. Fungal hyphae are growing in or on the material which is going mouldy. The hyphae are penetrating the tissue, digesting and absorbing the products of digestion.
2. Bread, wood and leather are derived from living organisms and contain materials which can be digested and used as food. Glass and plastic are man-made and do not contain any substances which could be used as nutrients.
3. Toadstools are the ‘fruiting bodies’ of fungi which are living in the soil. Fungi do not photosynthesize and so have no need of light. Green plants must have sufficient light in order to photosynthesize and grow.

Page 290
1. If the discs contain different antibiotics, the extent of the clear zone reflects the effectiveness of the antibiotic against that particular bacterium. If the discs contain different concentrations of the same antibiotic the clear zones show the effectiveness of the different concentrations. (In fact the former is the case).

Downloads
Download the answers in PDF format below
Section 1, Chapters 1-5
Section 2, Chapters 6-9
Section 3, Chapters 10-12
Section 3, Chapters 13-17
Section 3, Chapters 18-20
Section 4, Chapters 21-24
Section 5, Chapters 25-27
Section 5, Chapters 28-29
Section 6, Chapters 30-34
Section 6, Chapters 35-37
Section 7, Chapters 38-39
Section 8, Chapters 40-41


To contact me please email: DonMackean@biology-resources.com

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