Maharashtra State Textbook Bureau Solution for Class 10 Science Chapter 3 - Life Processes in Living Organisms Part - 2
Maharashtra State Textbook Bureau Solution for Class 10 Science Chapter 3 - Life Processes in Living Organisms Part - 2 Exercise
- In humans, sperm production occurs in the organ testis.
- In humans, Y chromosome is responsible for maleness.
- In male and female reproductive system of humans, _____________ gland is same. (There is no similar gland in male and female reproductive system. There may be some homologies but there is no similarity.)
- Implantation of embryo occurs in uterus.
- Asexual type of reproduction occurs without fusion of gametes.
- Body breaks up into several fragments and each fragment starts to live as a new individual. This is fragmentation type of reproduction.
- Pollen grains are formed by meiosis division in locules of anthers.
Growth of follicles present in the ovary occurs under the effect of follicle stimulating hormone. This follicle secretes estrogen. Ovarian follicle along with oocyte grows/regenerates under the effect of estrogen. Under the effect of luteinizing hormone, fully grown up follicle bursts, ovulation occurs and corpus luteum is formed from remaining part of the follicle. It secretes estrogen and progesterone. Under the effect of these hormones, glands of endometrium of uterus are activated and it becomes ready for implantation.
There are different methods of asexual reproduction in different unicellular animals.
(1) Binary fission: It is a process in which the parent cell divides to form two identical daughter cells. It takes place either by mitosis or amitosis. Unicellular organisms undergo binary fission under favourable conditions and abundant food supply. Prokaryotes, protists such as Amoeba and eukaryotic cell-organelles such as mitochondria and chloroplasts perform binary fission.
Based on the axis of fission, there are two sub-types of binary fission.
- Simple binary fission: The plane of division is not definite, it can be in any direction due to lack of specific shape as seen in Amoeba.
- Transverse binary fission: The plane of division is transverse, as seen in Paramoecium.
(2) Multiple fission: Amoeba reproduces through multiple fission under unfavourable conditions and lack of food supply. It forms a protective covering and becomes encysted. Inside the cyst, amoeba undergoes repeated nuclear division followed by cytoplasmic division. Several amoebulae are formed which remain dormant inside the cyst. On return of favourable conditions, they come out by breaking the cyst.
(3) Budding: Yeast is a unicellular fungus that reproduces through budding. The parent cell produces two daughter nuclei by mitotic division. A small bulging bud appears on the surface of the parent cell. One daughter nucleus enters the bud. It then grows and after maturation, separates from the parent cell to have an independent existence as a new yeast cell.
- IVF means In vitro Fertilization (IVF). It is a technique in modern medical science where childless couples can be blessed with their own child using sophisticated techniques.
- Childless couples with problems of low sperm count, obstacles in oviduct, absence of sperm motility often take help of IVF.
- The IVF technique involves the removal of oocyte from the mother followed by its artificial fertilisation by the sperms collected from the father.
- The entire process of fertilization is carried out in a test-tube. Hence, the baby born with this technique is called a test tube baby.
- The embryo so formed is then implanted in the uterus of the mother or a surrogate mother at an appropriate time to allow further development of the embryo.
Precautions to be followed to maintain reproductive health:
- Every individual should have scientific and authentic information concerning reproductive health.
- Cleanliness of the body as well as the mind is important to maintain good reproductive health.
- One should be careful about sexual relationship. Such relations should not be experimented in young age. Often, not being mindful in such cases can change one's sexual health forever.
- Cleaning of genitals and other private parts are important aspects of cleanliness and personal hygiene during menstruation.
- One should always stay away from cross-infections of venereal type while living in a society.
- Menstrual cycle is the event of cyclic changes that takes place at an interval of 28 to 30 days in a mature woman.
- Hormones from the pituitary - FSH (Follicle Stimulating Hormone) and LH (Luteinizing Hormone) and hormones from the ovary - estrogen and progesterone control the menstrual cycle.
- Under the influence of FSH, the ovarian follicle grows along with the oocyte present in it. This growing follicle produces estrogen.
- Under the influence of estrogen, the uterine inner layer called endometrium grows or regenerates. In the meantime, the development of follicle is completed.
- LH from the pituitary stimulates the bursting of the ovarian follicle and releases the mature oocyte out of the follicle and the ovarian wall. This process is called ovulation.
- The empty ovarian follicle after ovulation becomes corpus luteum. Corpus luteum produces the hormone progesterone.
- Under the influence of progesterone, the glands from the uterine endometrium begin their secretions. The oocyte, if fertilized, is implanted into the endometrium.
- If the oocyte is not fertilized, the corpus luteum becomes a degenerate body called corpus albicans. Corpus albicans cannot secrete estrogen and progesterone.
- Due to lack of these hormones, the endometrial layer of the uterus collapses. The tissue debris, along with unfertilized egg are removed through the vagina as menstrual flow. This results in bleeding for about 5 days.
- If the woman is not pregnant, the menstrual cycle keeps on repeating regularly.
- Sexual reproduction occurs due to the fusion of two opposite sex gametes.
- The male gamete is from the father while the female gamete is from the mother. Both these gametes are produced by the process of meiosis.
- When these gametes unite by the process of fertilization a diploid zygote is produced.
- This diploid zygote is formed by the combination of the haploid male and female gametes.
- As a result, the DNA of the new-born includes the DNA of both the parents.
- Therefore, in sexual reproduction the new-born shows similarities with respect to the characters of its parents.
Human male reproductive system
Human female reproductive system
Flower with its sexual reproductive organs
a. Hormones related with male reproductive system:
- Follicle stimulating hormone and ICSH or Luteinizing hormone secreted by pituitary gland
- Testosterone secreted by testis
b. Hormones secreted by ovary of female reproductive system:
c. Types of twins:
- Monozygotic twins
- Siamese twins
- Dizygotic twins
d. Any two sexual diseases:
e. Methods of family planning:
- Copper T
- Oral contraceptive pills
- In humans, males (XY) produce two different types of gametes, X and Y.
- The human female (XX) produces only one type of gamete containing X chromosomes.
- The sex of the baby is determined by the type of male gamete that fuses with the female gamete.
- If the fertilising sperm contains X chromosome, the baby produced will be a girl.
- If the fertilizing sperm contains Y chromosome, the baby produced will be a boy.
- Hence, it is a matter of chance that determines the sex of a baby. There is an equal probability of the fertilizing sperm being an X or Y chromosome.
- It is the genetic make-up of the sperm that determines the sex of the baby. Thus, gender of the child is determined by the male partner of the couple.
Asexual Reproduction in Plants:
- Vegetative propagation is a method of asexual reproduction in plants.
- It takes place with the help of vegetative parts like root, stem, leaf and bud.
- Potato, suran (Amorphophallus) and other tubers propagate with the help of 'eyes' called buds. These eyes are present on the stem tubers.
- In case of plants like sugarcane and grasses, buds present on nodes perform vegetative propagation.
- Plants like Bryophyllum perform vegetative propagation with the help of buds present on the leaf margin.
Some couples are not able to bear a child due to various problems either in the mother or in the father. In such cases modern techniques such as IVF, surrogacy and sperm bank are useful in conceiving a child.
- Surrogacy: In a woman, if there is a problem in the implantation of the embryo in the uterus, then help of another women is taken for development of the embryo. This women is called a surrogate mother. Oocyte from the real mother is taken out and fertilised with sperms collected from her husband. These gametes are fertilised outside in a test-tube and then the fertilised zygote is implanted in the surrogate mother. This technique is called surrogacy.
- In vitro fertilization (IVF): It is done when there are problems such as low sperm count or obstacles in the oviduct. In IVF, oocyte from the woman is taken out and fertilised with sperms collected from her husband. Fertilisation is done in a test-tube. The embryo formed is implanted in the uterus of the woman for further growth.
- Sperm bank: If the male partner has problems with sperm production, then the sperms are collected from the sperm bank. Sperm bank is a place where the donors donate the sperms and such sperms are stored under controlled environment. The donor has to be physically and medically fit in order to donate the sperms. The donor's identity is kept secret.
- Plants reproduce sexually with the help of flowers. Androecium and gynoecium are the male and female reproductive parts of the flowers respectively.
- In the carpel, the ovule undergoes meiosis and forms the embryo sac.
- A haploid egg cell and two haploid polar nuclei are present in each embryo sac.
- The pollen grains from the anther reach the stigma of the flower by the process of pollination.
- They germinate on the stigma and give rise to a long pollen tube and two male gametes.
- The pollen tube travels through the style of the flower and the male gametes present in the pollen tube are transferred to the embryo sac in the ovary.
- On reaching there, the tip of the pollen tube bursts releasing two male gametes in the embryo sac.
- One male gamete unites with the egg cell and forms a zygote. The other male gamete unites with the two polar nuclei forming the endosperm.
- Since there are two nuclei participating in this process, it is called double fertilisation.
- After fertilization, the ovule develops into seed and the ovary forms the fruit.
- The seed under favourable conditions germinates and can produce a new plant.