This set of Class 12 Biology Chapter 2 Multiple Choice Questions & Answers (MCQs) focuses on “Reproduction in Flowering Plants – Double Fertilisation”.
1. Double fertilization is seen in _______
Explanation: Double fertilization is found in angiosperms only. In angiosperms, female gametophyte abruptly stops its growth at 8 nucleate stages. After the formation of the zygote and primary endosperm nucleus, further growth of embryo sac takes place.
2. In _______, female gametophytes stop their growth at 8 nucleate stages.
Explanation: Double fertilization occurs only in angiosperms. The female gametophyte in angiosperms abruptly stop their growth at 8 nucleate stages.
3. The further growth of embryo takes place when the ______ has been formed.
Explanation: Further growth of embryo sac occurs only when the zygote has been formed and primary endosperm nucleus has been created by triple fusion.
4. What initiates the formation of endosperms?
b) Triple fusion
d) Double fusion
Explanation: The triple fusion initiates the formation of endosperm by withdrawal of nourishment from the nucellus and parent plant.
5. Endosperm is formed only when it is needed.
Explanation: The need arises after fertilization because the endosperm provides nutrition for the simultaneously developing embryo. If fertilization fails, no endosperm will be formed.
6. Which 2 scientists stated that endosperms were for reduction of female gametophyte?
a) Chargaff and Franklin
b) Nirenburg and Khoranna
c) Watson and Crick
d) Brink and Cooper
Explanation: According to Brink and Cooper (1940), endosperm is a tissue developed to compensate for the extreme reduction of female gametophyte in angiosperms.
7. The growth of the pollen tube is directed by ______
Explanation: In the ovary the growth of the pollen tube is directed by another tissue called obturator. The pollen tube enters the ovule, either through its micropyle (porogamy e.g., Lily), chalaza (chalazogamy e.g., Betula, Casuarina, Juglans regia) or the sides after piercing through the integuments (mesogamy, e.g. Cucurbita, Populus, Pistacea).
8. Generative fertilization is also called _____
c) vegetative fertilization
Explanation: Generative fertilization is also called syngamy or true fertilization. Out of the two male gametes one fuses with egg or oosphere to perform generative fertilization.
9. Second fertilization is called ________
d) vegetative fertilization
Explanation: Second fertilization is called vegetative fertilization since as a consequence, a vegetative or nutritive tissue is formed to nourish the embryo. Vegetative fertilization is also called triple fusion since three nuclei get fused, two polar nuclei and one male gamete.
10. Pollen tube is attracted to the _____ end of the embryo sac.
Explanation: After entering the ovule, the pollen tube is attracted towards the micropylar end of the embryo sac. The attractants are secreted by synergids or help cells. The pollen tube pierces one of the two synergids and bursts open into it.
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