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Answer the following questions from your knowledge of sexual reproduction in flowering plants - Leaving Cert Biology - Question (b) - 2020
Question (b)
Answer the following questions from your knowledge of sexual reproduction in flowering plants. (i) Describe in detail: 1. The development of the pollen grain from a... show full transcript
Worked Solution & Example Answer:Answer the following questions from your knowledge of sexual reproduction in flowering plants - Leaving Cert Biology - Question (b) - 2020
Step 1
Describe in detail: The development of the pollen grain from a microspore mother cell.
Answer
The development of the pollen grain begins in the anther, where diploid microspore mother cells undergo meiosis to produce four haploid microspores. Each microspore then divides by mitosis to form a pollen grain, which consists of two haploid nuclei: the generative nucleus and the tube nucleus. The tube nucleus will later control the growth of the pollen tube, while the generative nucleus will eventually divide to form two sperm cells.
Step 2
Describe in detail: The events that happen to a mature pollen grain following pollination up to double fertilisation.
Answer
Upon pollination, the mature pollen grain lands on the stigma of a compatible flower. The pollen tube begins to grow down the style towards the ovary, a process guided by chemical signals. The generative nucleus then divides by mitosis to produce two haploid male gametes. As the pollen tube reaches the ovule, it enters through the micropyle, releasing the male gametes. One sperm cell fertilizes the egg cell, forming the diploid zygote, while the other fuses with the two polar nuclei to form triploid tissue known as the endosperm, which will nourish the developing embryo.
Step 3
Give two adaptations of wind-pollinated flowers that increase their chance of successful pollination.
Answer
- Wind-pollinated flowers often have large anthers that produce a substantial quantity of pollen grains to increase the likelihood of reaching another flower.
- These flowers typically have stigmas that are feathery or sticky, which allows them to capture airborne pollen more effectively.
Step 4
State two advantages of sexual reproduction versus asexual reproduction in plants.
Answer
- Sexual reproduction leads to genetic variation among offspring, which can enhance survival and adaptability to changing environments.
- It reduces the likelihood of accumulating harmful mutations, as the combination of genetic material from two parents promotes healthier and more resilient populations.