Biology

Which one of the following is the correct sequence during sexual reproduction in Angiosperms ?

[amp_mcq option1=”Egg → zygote → embryo → seed” option2=”Embryo → egg → zygote → seed” option3=”Egg → embryo → zygote → seed” option4=”Egg → seed → zygote → embryo” correct=”option1″]

During sexual reproduction in Angiosperms (flowering plants), the sequence of development starting from the female gamete is as follows: The haploid egg cell fuses with a haploid sperm cell during fertilization to form a diploid zygote. The zygote undergoes mitotic divisions and differentiation to develop into a multicellular embryo. The embryo is contained within the seed, which develops from the ovule after fertilization. Therefore, the correct sequence is Egg → zygote → embryo → seed.

The developmental sequence after fertilization in flowering plants is Egg + Sperm → Zygote → Embryo → Seed.

The seed is a mature ovule, and the fruit is a mature ovary, both developing after fertilization and containing the embryo within the seed.

In flowering plants, DNA content of the parent plant gets halved during

[amp_mcq option1=”Seed germination” option2=”Fruit formation” option3=”Flower bud formation” option4=”Pollen formation” correct=”option4″]

In flowering plants, DNA content gets halved during meiosis. Meiosis is a type of cell division that produces gametes (sex cells) with half the number of chromosomes (and thus half the DNA content) of the parent cell. In flowering plants, pollen grains contain the male gametes (sperm), and their formation (microsporogenesis) involves meiosis. Similarly, the formation of the female gametophyte and egg cell (megasporogenesis) also involves meiosis, halving the DNA content. Seed germination, fruit formation, and flower bud formation involve mitotic division and growth, not the halving of DNA content for gamete production.

Meiosis reduces the chromosome number (and DNA content) by half to produce gametes. Pollen formation involves meiosis.

Fertilization, the fusion of male and female gametes, restores the diploid number of chromosomes (and doubles the DNA content compared to the gametes) in the zygote, which then develops into the embryo.

Relationship between a flower and honey-bee will help the flower for/in

[amp_mcq option1=”Faster development” option2=”Pollination” option3=”Quick germination of pollen” option4=”Increase in size” correct=”option2″]

Honey-bees are common pollinators. When a honey-bee visits a flower to collect nectar or pollen, it inadvertently picks up pollen grains on its body. As it visits other flowers of the same species, it transfers pollen to the stigma, facilitating pollination. Pollination is the transfer of pollen from the anther to the stigma, a necessary step for fertilization and subsequent seed and fruit development in many flowering plants.

The relationship between flowering plants and pollinators like honey-bees is a classic example of mutualism, where the flower benefits from pollination (leading to reproduction), and the bee benefits from food resources (nectar and pollen).

While successful pollination leads to seed/fruit development which is part of the plant’s life cycle, the direct benefit to the flower from the bee’s visit is the act of pollination itself. The bee’s visit does not directly cause faster flower development, quicker pollen germination (which happens after pollination on the stigma under favorable conditions), or increase in flower size.

In angiosperms, pollen grain germinates to produce two male gametes. Which one of the following functions is carried out by these gametes ?

[amp_mcq option1=”Both the gametes fuse with a single egg cell” option2=”Both the gametes fuse with two different egg cells” option3=”One gamete fuses with the egg cell and the other one eventually degenerate” option4=”One gamete fuses with the egg cell and the other one fuses with a diploid secondary nucleus” correct=”option4″]

In angiosperms, the pollen grain contains two male gametes. During double fertilization, one male gamete fuses with the egg cell to form the diploid zygote, which develops into the embryo. The other male gamete fuses with the diploid secondary nucleus (formed by the fusion of two polar nuclei) within the embryo sac to form the triploid primary endosperm nucleus (PEN), which develops into the nutritive tissue called endosperm. This process of fertilization of both the egg cell and the secondary nucleus is unique to angiosperms.

Double fertilization is a characteristic feature of angiosperms, involving two male gametes: one fertilizes the egg (forming the zygote), and the other fertilizes the secondary nucleus (forming the endosperm).

The pollen tube grows down the style and enters the ovule, releasing the two male gametes into the embryo sac. This ensures efficient delivery and participation of both gametes in the fertilization process.