Chapter 3 – Life Processes in Living Organisms Part - 2
1. Complete the following chart.
| Asexual reproduction | Sexual reproduction |
|---|---|
1. Reproduction that occurs with the help
of somatic cells is called as asexual
reproduction. | 1. __________ |
2. __________ | 2. Male and female parent are necessary
for sexual reproduction. |
3. This reproduction occurs with the help
of mitosis only. | 3. __________ |
4. __________ | 4. New individual formed by this method is genetically different from parents. |
5. Asexual reproduction occurs in different
individuals by various methods like
binary fission, multiple fission,
budding, fragmentation, regeneration,
vegetative propagation, spore
production, etc. | 5. __________ |
Ans:
| Asexual reproduction | Sexual reproduction |
|---|---|
1. Reproduction that occurs with the help of somatic cells is called as asexual reproduction. | 1. Reproduction that occurs due to fertilization of gametes is called sexual reproduction. |
2. For asexual reproduction only one parent is necessary. | 2. Male and female parent are necessary
for sexual reproduction. |
3. This reproduction occurs with the help
of mitosis only. | 3. This reproduction occurs with the help of both mitosis and meiosis. |
4. New individual formed by this method is genetically identical with parents. | 4. New individual formed by this method is genetically different from parents. |
5. Asexual reproduction occurs in different
individuals by various methods like
binary fission, multiple fission,
budding, fragmentation, regeneration,
vegetative propagation, spore
production, etc. | 5. Sexual reproduction occurs in two steps: First formation of haploid gametes by meiosis and then fertilization of these haploid gametes to form diploid zygote. There are no subtypes in the sexual reproduction. |
2. Fill in the blanks.
a. In humans, sperm production occurs in the organ ______.
Ans: testes
b. In humans, ______ chromosome is responsible for maleness.
Ans: Y
c. In male and female reproductive system of human, ______ gland is same.
Ans: bulbourethral
d. Implantation of embryo occurs in ______.
Ans: uterus
e. ______ type of reproduction occurs without fusion of gametes.
Ans: Asexual
f. Body breaks up into several fragments and each fragment starts to live as a new individual. This is ______ type of reproduction.
Ans: fragmentation
g. Pollen grains are formed by ______ division in locules of anthers.
Ans: meiosis
3. Complete the paragraph with the help of words given in the bracket.
(Luteinizing hormone, endometrium of uterus, follicle stimulating hormone, estrogen, progesterone, corpus luteum)
Growth of follicles present in the ovary occurs under the effect of ______ This follicle secretes estrogen. ______ grows / regenerates under the effect of estrogen. Under the effect of ______, fully grown up follicle bursts, ovulation occurs and ______ is formed from the remaining part of the follicle. It secrets ______ and ______. Under the effect of these hormones, glands of ______ are activated and it becomes ready for implantation.
Ans: Growth of follicles present in the ovary occurs under the effect of follicle stimulating hormone. This follicle secretes estrogen. Endometrium of the uterus 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 the remaining part of the follicle. It secretes progesterone and estrogen. Under the effect of these hormones, glands of endometrium are activated and it becomes ready for implantation.
4. Answer the following questions in short.
a. Explain with examples types of asexual reproduction in unicellular organism.
Ans:
(1) Process of formation of new organisms by an organism of the same species without involvement of gametes is called as asexual reproduction.
(2) Types of asexual reproduction in unicellular organisms:
(a) Binary fission:
(i) In this process, the parent cell divides to form two similar daughter cells.
(ii) Binary fission occurs either by mitosis or amitosis.
e.g. Prokaryotes (bacteria), Protists (Amoeba).
(b) Multiple fission:
(i) Asexual reproduction by multiple fission is performed by Amoeba.
(ii) Amoeba stops the formation of pseudopodia whenever there is a lack of food.
(iii) It becomes rounded and forms protective covering around the plasma membrane. Such encysted Amoeba is called a cyst.
(iv) Many nuclei are formed by repeated nuclear division in the cyst.
(v) It is followed by cytoplasmic division and thus many amoebulae are formed.
(vi) They remain encysted till there are adverse conditions. Cyst breaks open on arrival of favourable conditions and many amoebulae are released.
(c) Budding:
(i) Sexual reproduction occurs by budding in yeast cells.
(ii) Yeast cells produce two daughter nuclei by mitotic division.
(iii) A small bulge appears on the surface of the parent cell. This is called bud.
(iv) One of the two daughter nuclei enters this bud.
(v) After sufficient growth, bud separates from the parent cell and starts to live independently as a daughter yeast cell.
b. Explain the concept of IVF.
Ans:
(i) IVF means In Vitro Fertilization (IVF).
(ii) This is the technique in the modern medical field where childless couples can be blessed by their own child.
(iii) IVF technique is used for childless couples who are faced with problems such as less sperm count, obstacles in oviduct, etc.
(iv) The IVF technique is done by removing the oocyte from the mother and artificially fertilizing by the sperms collected from the father. This fertilization is done in a test-tube. Thus it is also called test tube baby. The embryo formed is implanted in the uterus of the real mother or a surrogate mother at appropriate time.
c. Which precautions will you follow to maintain the reproductive health?
Ans:
(i) A person’s state of physical, mental and social strength is called health.
(ii) Bleeding occurs during the menstrual cycle. Due to this, private organs need to be cleaned from time to time otherwise problems regarding reproductive health may arise.
(iii) It is essential to maintain the cleanliness of genitals of both males and females.
(iv) Also, one should avoid unsafe sexual contact.
d. What is menstrual cycle? Describe it in brief.
Ans:
(i) Female reproductive system undergoes some changes at puberty and those changes repeat at the interval of every 28 to 30 days. These repetitive changes are called the menstrual cycle.
(ii) Menstrual cycle in a natural process controlled by four hormones. Follicle stimulating hormone (FSH), Luteinizing hormone (LH), estrogen and progesterone.
(iii) One of the several follicles in the ovary starts to develop along with the oocyte present in it, under the effect of follicle stimulating hormone. This developing follicle secrete estrogen.
(iv) Endometrium of the uterus starts to develop or regenerate under the effect of estrogen.
(v) Meanwhile, the developing follicle completes its development.
(vi) It bursts under the effect of luteinizing hormone and oocytes are released. This is called ovulation.
(vii) Remaining tissues of the burst follicle forms the corpus luteum. Corpus luteum starts to secrete progesterone.
(viii) Endometrial glands secrete their secretion under the effect of progesterone. Such endometrium is ready for implantation of embryos.
(ix) If oocytes are not fertilized within 24 hours, corpus luteum becomes inactive and transforms into corpus albicans.
(x) Endometrium starts to degenerate in absence of estrogen and progesterone.
(xi) Tissues of degenerating endometrium and unfertilized ovum are discarded out through vagina, accompanied by bleeding.
(xii) Bleeding continues approximately for 5 days. This is called menstruation.
5. In case of sexual reproduction, new-born show similarities about characters. Explain this statement with suitable examples.
Ans:
(i) Two parents i.e. male and female are involved in sexual type of reproduction.
(ii) In sexual reproduction fusion of male gamete and female gamete occurs.
(iii) Due to this, new individuals always have the recombined genes of both the parents.
(iv) Hence, the new individual shows similarities with the parents for some characters and also has characters different from both parents.
6. Sketch the labelled diagrams.
a. Human male reproductive system.
Ans:
b. Human female reproductive system.
Ans:
c. Flower with its sexual reproductive organs.
Ans:
d. Menstrual cycle.
Ans:
7. Give the names.
a. Hormones related with male reproductive system.
Ans: FSH (Follicle stimulating hormone), LH (Luteinizing hormone), testosterone.
b. Hormones secreted by ovary of female reproductive system.
Ans: Estrogen and progesterone.
c. Types of twins.
Ans: Monozygotic twins and dizygotic twins.
d. Any two sexual diseases.
Ans: Syphilis and gonorrhea.
e. Methods of family planning.
Ans: Intrauterine device, use of condoms.
8. Gender of child is determined by the male partner of couple. Explain with reasons whether this statement is true or false.
Ans:
(i) During zygote formation, man contributes either X or Y chromosome to the next generation.
(ii) But, females transfer only X-chromosome to the next generation.
(iii) At the time of fertilization, if the X-chromosome comes from male, the child will be a girl. And if Y-chromosome comes from the male then the child will be a boy.
(iv) Thus, the gender of the child is determined by the male partner of the couple.
(v) So, the above statement is true.
9. Explain asexual reproduction in plants.
Ans:
(i) Reproduction in plants with the help of vegetative parts like root, stem, leaf and bud is called as vegetative reproduction.
(ii) Vegetative propagation in potatoes is performed with the help of eyes present on tuber whereas in Bryophyllum, it is performed with the help of buds present on leaf margin.
(iii) In the case of plants like sugarcane and grasses, vegetative propagation occurs with the help of buds present on nodes.
(iv) Plants like carrots and radishes perform vegetative propagation with the help of roots.
(v) Plants like Spirogyra reproduce asexually by fragmentation.
(vi) When there is plenty of water and nutrients available to Spirogyra, its filaments grow very fast and break up into many small fragments. Each fragment starts to live independently as a new spirogyra fibre.
10. Modern techniques like surrogate mother, sperm bank and IVF technique will help human beings. Justify this statement.
Ans:
(i) Modern techniques like surrogacy, IVF and sperm bank have been boon to the childless couples
(ii) In IVF technique, fertilization is brought about in a test-tube and the embryo thus formed is implanted in the uterus of the woman.
(iii) Surrogacy is a boon to women who face issues with their uterus. In this technique, oocytes are collected from the mother and sperms are collected from the father.
(iv) They are fertilized in the test tube and the embryo is implanted in the uterus of some other woman having a normal uterus. This process is called surrogacy and the woman bearing the child is called a surrogate mother.
(v) Sperm Bank or semen bank has been a boon for males who face issues with sperm count or motility.
(vi) Sperm banks are similar to blood banks where semen from physically and medically fit individuals are collected and stored.
(vii) Thus modern techniques like IVF, surrogacy and sperm bank help human beings.
11. Explain sexual reproduction in plants.
Ans:
(i) A flower is the site of sexual reproduction in plants.
(ii) It consists of four floral whorls: calyx, corolla, androecium and gynoecium.
(iii) Androecium and gynoecium are called essential whorls.
(iv) Calyx and corolla are called accessory whorls.
(v) Androecium is male whorl and its members are called stamens, gynoecium is female whorl and its members are called carpels.
(vi) Ovary present at the basal end of carpel contains one or many ovules. A hollow style comes up from the ovary.
(vii) Embryo sac is formed in each ovule by meiosis and each embryo sac consists of a haploid egg cell and two haploid polar nuclei.
(viii) Pollen grains are transferred from anther to the stigma. This is called pollination.
(ix) When pollination occurs a long pollen tube carrying two male gametes is formed.
(x) Pollen tube reaches the embryo sac via style.
(xi) Pollen tube bursts and two male gametes are released in the embryo sac. One male gamete unites with egg cells to form zygote. This process is called fertilization.
(xii) The second male gamete unites with two polar nuclei and an endosperm is formed. This is called double fertilization.
(xiii) After fertilization the ovule develops into seed and ovary into fruit.
(xiv) Seeds fall upon the ground when fruits break up and they germinate in the soil under favourable conditions.
(xv) Zygote develops at the cost of food stored in the endosperm of seed and thus a new plantlet is formed. This is called seed germination.
