Q4. Why do you think the zygote is dormant for some time in a fertilised ovule? (NCERT Exercise 12)
Most zygotes divide only after a certain amount of endosperm has formed. This is an adaptation to provide assured nutrition to the developing embryo (NCERT page 19).
Q5. Assertion: the white kernel of a coconut is cellular endosperm. Reason: in the common type of endosperm development, free nuclei form first and cell walls form later. Are both true, and does the reason explain the assertion?
Both are true, and the reason explains the assertion: the coconut water is the free-nuclear stage and the kernel round it has become cellular (NCERT page 19).
Q6. Which of these are false fruits: mango, apple, strawberry, guava, cashew?
Apple, strawberry and cashew, in which the thalamus also contributes to fruit formation (NCERT page 20). Beyond the NCERT text: in cashew the fleshy part grows from the swollen flower stalk (pedicel) and the receptacle (the thalamus) (Wikipedia, “Cashew”, facts in our words). Mango and guava are not false fruits in NCERT: it names them only as fleshy fruits (page 20), and its false fruits are apple, strawberry and cashew.
Q7. NCERT asks how many eggs there are in an embryo sac, embryo sacs in an ovule, ovules in an ovary and ovaries in a flower. Answer from the chapter, and say what this means for the number of seeds a tree can make.
One egg per embryo sac (NCERT page 11); generally one embryo sac per ovule (page 9); one ovule (wheat, paddy, mango) to many (papaya, water melon, orchids) per ovary (page 9); each pistil has one ovary, and a flower may have one pistil or several (page 8). Each fertilised ovule gives one seed and a tree bears many flowers, so one tree can make a very large number of seeds (reasoned from NCERT page 22).
Q8. Give three advantages of seeds to flowering plants.
Any three of: pollen-tube delivery makes fertilisation independent of an external water film for swimming sperm; seeds aid dispersal to new habitats; food reserves support many seedlings until they photosynthesise; the hard seed coat protects the embryo; as products of sexual reproduction they carry new genetic combinations (NCERT pages 21–22).