1.At what step of mitosis do chromosome replicate to form daughter chromatid
2.After fertilization of an ovule Develops into a testa and develops into endosperm
3.state the difference between the composition of maternal blood entering the placenta
4.After four months of pregnancy the ovaries can be removed without terminating pregnancy.However during the first four months of pregnancy the ovaries must remain intact if pregnancy is to be maintained.Explain the following observation
5.Name the mechanism that prevents self pollination in flowers that have both male and female parts
6.State three characteristics that ensure cross pollination takes place in flowering plants
7.Explain why sexual reproduction is important in organism
8.What is meant by the terms:
Epigynous flower
Staminate flower
b.How are the male parts of wind pollinated flowers adapted to their function
9.Name the part of a flower that developed into seed
fruit
10.Explain the two processes which occur during anaphase of mitosis
b.What is the significance of meiosis
1. Chromosome replication occurs during the S phase of interphase, which is before the start of mitosis. In mitosis, the replicated chromosomes are then separated into daughter chromatids during the anaphase stage.
2. After fertilization of an ovule, the ovule develops into a seed coat (testa) and the fertilized ovule develops into endosperm. The endosperm is a nutrient-rich tissue that nourishes the developing embryo.
3. Maternal blood entering the placenta contains oxygen, nutrients, hormones, and waste products (such as carbon dioxide) from the mother's body. The composition of maternal blood can vary depending on the stage of pregnancy and the specific needs of the developing fetus.
4. During the first four months of pregnancy, the ovaries must remain intact because they produce hormones (such as estrogen and progesterone) that are crucial for maintaining the pregnancy. These hormones help support the growth of the uterus lining and prevent menstruation. After four months, the placenta takes over the production of these hormones, so the ovaries are no longer necessary for the maintenance of pregnancy.
5. The mechanism that prevents self-pollination in flowers that have both male and female parts is called self-incompatibility. This mechanism ensures that the flower is not fertilized by its own pollen, promoting genetic diversity and cross-pollination.
6. Three characteristics that ensure cross-pollination takes place in flowering plants are:
- Production of male and female reproductive structures (stamens and pistils) in separate flowers or in separate parts of the same flower.
- Presence of mechanisms to prevent self-pollination, such as self-incompatibility or physical separation of reproductive structures.
- Utilization of pollinating agents, such as insects, birds, or wind, to transfer pollen between different flowers or plants.
7. Sexual reproduction is important in organisms because it promotes genetic diversity. During sexual reproduction, genetic material from two parents is combined to create offspring with unique genetic traits. This genetic diversity provides a better chance for survival in changing environments, helps in adaptation to new conditions, and reduces the risk of genetic diseases.
8. a) Epigynous flower refers to a flower in which the female reproductive structures (such as stigma, style, and ovary) are located above the attachment point of the other flower parts (such as sepals, petals, and stamens).
b) Staminate flower refers to a flower that only contains male reproductive structures (stamens) and lacks female reproductive structures (pistil).
9. The part of a flower that develops into a seed is the ovule. The ovule contains the embryo sac, which houses the female gametes (eggs) and develops into a seed after fertilization.
10. During anaphase of mitosis, two processes occur:
a) Anaphase A: The sister chromatids of each chromosome separate and move towards opposite poles of the cell. This is facilitated by the shortening of microtubules in the spindle fibers, which pull the chromatids apart.
b) Anaphase B: The two poles of the cell move further apart, elongating the cell to prepare for cell division. This is achieved by the lengthening of microtubules in the spindle fibers and the force generated by motor proteins.
b) The significance of meiosis is that it ensures genetic diversity and the formation of haploid gametes. Meiosis involves two rounds of cell division, resulting in the halving of the chromosome number. This enables the exchange and reshuffling of genetic material between homologous chromosomes during crossing over, leading to genetic variation in the offspring. Meiosis is essential for sexual reproduction and the production of genetically diverse individuals.