IGCSE Biology 2nd edition GCSE Biology 3rd 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 16. Human reproduction


Page 142

1. Sperm cells are much smaller than ova. They have much less cytoplasm but they do have a
    long tail.
2. Epididymis, sperm duct, seminal vesicle and prostate gland, urethra.
3. Kidney, pelvic girdle, erectile tissue, foreskin, scrotum, rectum.
4. A zygote can give rise to any of the tissues in the body and can grow into a complete
    organism.

Page 144

1. a Ovulating once per month, a woman with a reproductive life of 37 years might release 12 x
    37 = 444 ova.
    b In the developed world only two or three ova are likely to be fertilized. It could be many
    more. In the developing world, the numbers could be 5 or more.
2. Vagina, cervix, uterus, oviduct.
3. At the moment of fertilization, the male nucleus (from the sperm cell) fuses with the female
    nucleus (of the ovum).
4. a Sperms retain the ability to fertilize an ovum for two or three days. So, fertilization is
    possible if mating occurs 2 days before ovulation.
    b If the ovum survives for only 24 hours, mating 2 days after ovulation is unlikely to lead to
    fertilization.

Page 146

1. The umbilical vein will contain less oxygen, glucose, amino acids and salts, and more carbon
    dioxide and urea (nitrogenous waste) than the umbilical artery.
2. The embryo receives all the oxygen it needs from the blood reaching it from the umbilical
    artery (via the placenta).
3. If the twin boys are formed from a single fertilized ovum they will be identical twins. If they
    arise from two, separate fertilized ova, they will be fraternal twins.

Page 149

1. a Developing manual skills, animal and crop husbandry, adapting to seasonal changes but also
    reading and mathematics will be essential in modern farming.
    b Reading and mathematics will be essential as well as manual skills.
2. The onset of ovulation means that the woman could conceive a child. Widening of the hips
    gives more space and support for a developing embryo. Enlargement of the uterus is in
    preparation for the developing embryo. The enlargement of the breasts is a result of the
    development of the mammary glands in preparation for breast-feeding.
3. Menstruation results from a breakdown of the uterine epithelium as a result of a failure of
    fertilization. If fertilization has taken place, the uterine lining will be retained and developed.

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


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