Life processes in living organisms part 2
Q1 Explain how does sexual reproduction occurs in plants ?
ANS: 1) Flower is the structural unit of sexual reproduction in plants It consists of four whorls: calyx, corolla, androecium and gynoecium.
2) Calyx and corolla are the accessory whorls of the flower as they are responsible for protection of inner whorls.
3) Androecium and gynoecium are the essential whorls as they are responsible for reproduction.
4) Androecium is the male whorl and its members are called stamens.
Anther and filament are the members of stamens.
5) Gynoecium is the female whorl and its members are called carpels.
Stigma, style and ovary are the members of carpel.
6) Pollen grains from anther are transferred to the stigma. This is called pollination.
7) Stigma becomes sticky during pollination.
8) Pollens germinate when they fall upon such sticky stigma that is a long pollen tube and two male gametes are formed. The pollen tubes carry male gametes.
9) Pollen tube reaches the embryo sac via style.
10) Tip of the pollen tube bursts and two male gametes are released in embryo sac.
11) One male gamete unites with egg cell to form zygote. Second male gamete unites with two polar nuclei and endosperm is formed
12) As two nuclei participate in this process, it is called as double fertilization.
Q2 Why is there a need of rest along with special personal hygiene during menstruation ?
Ans: 1) Menstrual cycle is a natural process in which unfertilized ovum along with the lining of endometrium is discharged through the vagina.
2) During menstruation, bleeding occurs continuously for approximately five days.
3) Severe pain and weakness is felt due to heavy bleeding.
4) There is higher possibility of infections during this period.
Q3 State the difference between asexual reproduction and sexual reproduction.
Asexual reproduction :-
1) Reproduction that occurs with the help of somatic cells is called as asexual reproduction.
2) This is uniparental reproduction, thus both male and female parent is not necessary.
3) This reproduction occurs with the help of mitosis only.
4) The new individual formed is exactly genetically similar to the parent.
5) Binary fission, multiple fission, budding, fragmentation, regeneration, vegetative propagation, spore formation are the various methods in asexual reproduction.
Sexual reproduction :-
1) Reproduction that occurs with the help of two germ cells is called sexual reproduction.
2) Male and female parent is necessary for sexual reproduction.
3) This reproduction involves both mitosis and meiosis type of cell division.
4) New individual formed is genetically different from their parents.
5) In all individuals, sexual reproduction occurs by gamete formation and fertilization.
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