Chapter 3 - Life Processes in Living Organisms Part – 2
Chapter 3 : Life Processes in Living Organisms Part – 2
Textbook Exercise Solutions
Q1)Complete the following chart:
Answer :
The completed comparison table distinguishing Asexual reproduction and Sexual reproduction is given below:
No.
Asexual Reproduction
Sexual Reproduction
1
Reproduction that occurs with the help of somatic cells without gamete fusion.
Reproduction that occurs due to the fertilization of male and female gametes.
2
Only a single parent is required.
Two parents (male and female) are necessary.
3
Occurs with the help of mitosis only.
Involves both meiosis (for gamete formation) and mitosis (for embryo development).
4
New individuals formed are genetically identical (clones) to the parent.
New individuals formed are genetically different from parents, showing genetic variations.
5
Occurs by binary fission, multiple fission, budding, fragmentation, regeneration, vegetative propagation, and spore formation.
Occurs through two essential steps: gamete formation by meiosis, followed by fertilization to produce a diploid zygote.
Q2)Fill in the blanks:
1. In humans, sperm production occurs in the organ ............
Answer :
In humans, sperm production occurs in the organ (b) testis (inside the seminiferous tubules).
2. In humans, ............. chromosome is responsible for maleness.
Answer :
In humans, (b) Y chromosome is responsible for maleness.
3. In male and female reproductive system of human, ............. gland is same.
Answer :
There is no common gland present in both systems; however, the bulbourethral (Cowper's) gland in males and Bartholin's gland in females are homologous accessory glands.
4. Implantation of embryo occurs in ............
Answer :
Implantation of embryo occurs in (c) uterus (on the endometrium wall).
5. ............ type of reproduction occurs without fusion of gametes.
Answer :
(a) Asexual type of reproduction occurs without fusion of gametes.
6. Body breaks up into several fragments and each fragment begins to live as a new individual. This is .......... type of reproduction.
Answer :
This is (b) fragmentation type of reproduction (seen in Spirogyra).
7. Pollen grains are formed by ............. division in locules of anthers.
Answer :
Pollen grains are formed by (a) meiosis division in locules of anthers.
Q3)Complete the paragraph with the help of words given in the bracket:
(Luteinizing hormone, endometrium of uterus, follicle stimulating hormone, estrogen, progesterone, corpus luteum)
Answer :
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 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.
Q4)Answer the following questions short:
1. Explain with examples types of asexual reproduction in unicellular organism.
Answer :
Binary Fission: A parent unicellular organism divides into two equal daughter cells under favourable conditions:
Simple binary fission: Occurs in any plane (e.g., Amoeba).
Multiple Fission: During harsh, unfavourable conditions, Amoeba secretes a hard protective wall around itself, called a cyst. The nucleus divides repeatedly by mitosis into many daughter nuclei. When favourable conditions return, the cyst breaks open, releasing numerous young amoebulae.
Budding: In unicellular yeast, a small bulb-like outgrowth called a bud forms on the parent cell. The parent nucleus divides by mitosis and one daughter nucleus enters the bud. The bud grows, develops, and eventually separates to lead an independent life.
2. Explain the concept of IVF.
Answer :
IVF (In Vitro Fertilization): It is an assisted reproductive technology in which fertilization of an ovum by sperm is carried out outside the woman's body in a laboratory glass dish or test tube.
It is helpful for couples facing infertility issues such as low sperm count, blocked fallopian tubes, or irregular ovulation.
Mature ova are collected from the mother and fertilized with sperms from the father under sterile laboratory conditions.
The resulting embryo is cultured for a few days and then implanted into the woman's uterus for normal pregnancy and delivery.
3. Which precautions will you follow to maintain the reproductive health?
Answer :
Maintain personal hygiene by regularly washing and keeping genital organs clean and dry to prevent bacterial and fungal infections.
During menstruation, female hygiene must be maintained using clean, sterile sanitary pads, changing them every 4 to 6 hours.
Avoid unsafe sexual contact and practice protected relations to prevent Sexually Transmitted Diseases (STDs) such as Syphilis, Gonorrhea, and HIV/AIDS.
Consume a healthy, balanced diet rich in iron, proteins, and vitamins to avoid anemia and nutritional deficiencies.
4. What is menstrual cycle? Describe it in brief.
Answer :
The menstrual cycle is a natural, repeating series of physiological changes occurring in the female reproductive system every 28 to 30 days from puberty to menopause.
It is controlled by four hormones: FSH and LH (from the pituitary gland), and Estrogen and Progesterone (from the ovary).
Follicular Phase (Days 1–13): Under FSH, an ovarian follicle matures and secretes estrogen, which repairs and thickens the uterine endometrium.
Ovulation (Day 14): A surge of LH causes the mature follicle to burst, releasing the mature egg (ovum) into the fallopian tube.
Luteal Phase (Days 15–28): The ruptured follicle transforms into the corpus luteum and secretes progesterone, preparing the endometrium for embryo implantation.
Menstruation: If fertilization does not occur, the corpus luteum degenerates into corpus albicans. Progesterone levels fall, causing the uterine lining and blood vessels to break down. This is discharged through the vagina as menstrual bleeding lasting 3 to 5 days.
Q5)In case of sexual reproduction, newborn show similarities about characters. Explain this statement with suitable examples:
Answer :
Sexual reproduction involves the union of two haploid gametes: the sperm from the father (23 chromosomes) and the ovum from the mother (23 chromosomes).
During fertilization, these gametes unite to form a diploid zygote with 46 chromosomes (23 pairs), receiving exactly 50% of its genetic material (DNA) from the father and 50% from the mother.
Because the newborn inherits the genes of both parents, it displays clear physical and biological similarities to both.
Examples: A child may inherit eye colour, facial features, or hair type from the mother, while inheriting height, ear lobe shape, or blood group from the father.
At the same time, crossing over during meiosis creates unique gene combinations, so the child is similar to both parents but never an exact carbon copy.
Endometrium becomes thick, vascular, and ready for implantation.
Q7)Give the names:
1. Hormones related with male reproductive system:
Answer :
Testosterone (secreted by Leydig cells of testis), along with FSH and ICSH / LH (secreted by the anterior pituitary gland).
2. Hormones secreted by ovary of female reproductive system:
Answer :
Estrogen (secreted by developing ovarian follicle) and Progesterone (secreted by corpus luteum).
3. Types of twins:
Answer :
Monozygotic twins (identical twins formed from a single zygote), Dizygotic twins (fraternal twins formed from two separate ova and sperms), and Siamese twins (conjoined monozygotic twins joined at birth).
4. Any two sexual diseases (STDs):
Answer :
Syphilis (caused by Treponema pallidum) and Gonorrhea (caused by Neisseria gonorrhoeae).
5. Methods of family planning:
Answer :
Barrier methods (condoms, diaphragms), intrauterine devices (Copper-T), hormonal oral contraceptive pills, and permanent surgical methods (Vasectomy in males and Tubectomy in females).
Q8)Gender of child is determined by the male partner of couple. Explain with reasons whether this statement is true or false:
Answer :
The statement is TRUE.
Scientific Explanation:
Humans have 23 pairs (46 chromosomes) in their diploid cells. Out of these, 22 pairs are autosomes and 1 pair consists of sex chromosomes.
Human females are homogametic: they have sex chromosomes XX (44 + XX). All ova produced by a female contain only the X chromosome (22 + X).
Human males are heterogametic: they have sex chromosomes XY (44 + XY). During meiosis, males produce two distinct types of sperms in equal numbers (50% each):
50% sperms carry an X chromosome (22 + X).
50% sperms carry a Y chromosome (22 + Y).
If an X-bearing sperm fertilizes the ovum (22+X + 22+X = 44+XX), the baby is a girl.
If a Y-bearing sperm fertilizes the ovum (22+Y + 22+X = 44+XY), the baby is a boy.
Since the mother contributes only X chromosomes, the sex of the child is entirely determined by whether the father's fertilizing sperm carries an X or a Y chromosome. Holding women responsible for giving birth to a girl child is scientifically baseless and wrong.
Q9)Explain asexual reproduction in plants:
Answer :
Asexual reproduction in plants occurs primarily through Vegetative Propagation, where new plants develop directly from vegetative parts like stems, roots, leaves, or buds without seeds or gametes:
By Stem Tubers: Potatoes have 'eyes' which are vegetative buds. When planted in soil, each eye germinates into a new potato plant.
By Stems and Nodes: Plants like sugarcane and grasses reproduce vegetatively from buds present at their stem nodes.
By Leaves: In Bryophyllum, vegetative buds develop along the notches of leaf margins. When these leaves fall on moist soil, the buds develop roots and grow into independent plants.
By Roots: Sweet potato, carrot, and radish use swollen tuberous roots to produce new plantlets.
Q10)Modern techniques like surrogate mother, sperm bank and IVF technique will help the human beings. Justify this statement:
Answer :
Infertility affects many couples due to physical, hormonal, or anatomical conditions. Modern reproductive technologies provide safe, medical solutions to have children:
In Vitro Fertilization (IVF): Used when there are issues like low sperm count or blocked fallopian tubes. Oocytes from the woman are fertilized by husband's sperms in a test-tube dish, and the resulting embryo is implanted into the uterus.
Surrogacy: If a woman has a medical condition preventing her uterus from carrying a pregnancy, ovum from the biological mother and sperm from the father are fertilized via IVF. The embryo is then implanted into the womb of another healthy woman (surrogate mother) who carries the child to birth.
Sperm Bank (Semen Bank): When the male partner has azoospermia (zero sperm count) or genetic disorders, semen is obtained from certified, medically screened donors and preserved in liquid nitrogen. The donor sperm is used to fertilize the female partner's ovum through artificial insemination or IVF, with full legal confidentiality.
Q11)Explain sexual reproduction in plants (Double Fertilization):
Answer :
The flower is the reproductive organ of angiosperm plants. Sexual reproduction in plants involves pollination followed by double fertilization:
Pollination: Pollen grains from the anther of the stamen are transferred to the sticky surface of the stigma by wind, water, insects, or birds.
Pollen Germination: On the stigma, the pollen grain absorbs moisture and germinates, producing a long pollen tube that grows down through the style into the ovary.
Entry of Male Gametes: The generative cell inside the pollen tube divides into two haploid male gametes. The pollen tube enters the ovule through the micropyle and bursts, releasing the two male gametes into the embryo sac.
Syngamy (First Fertilization): One male gamete (n) fuses with the haploid egg cell (n) to form a diploid zygote (2n), which develops into the future plant embryo.
Triple Fusion (Second Fertilization): The second male gamete (n) fuses with the two haploid polar nuclei (2n) in the center of the embryo sac to form a triploid Primary Endosperm Nucleus (3n), which develops into nutritive endosperm for the growing seed.
Because fertilization occurs twice within the same embryo sac, this process is called Double Fertilization. After fertilization, the ovule becomes a seed, and the ovary ripens into a fruit.
Chapter Overview: Life Processes in Living Organisms Part – 2
Class 10 Science 2 Chapter 3 covers asexual reproduction in unicellular organisms (binary fission, multiple fission, budding) and multicellular organisms (fragmentation, regeneration, vegetative propagation, spore formation), sexual reproduction in angiosperm plants with double fertilization, human male and female reproductive systems, gametogenesis, the 28-day hormonal menstrual cycle, gender determination, twins, reproductive health, and modern assisted reproductive techniques (IVF, surrogacy, and sperm banks).
Frequently Asked Questions (FAQs)
Q1. Why is the male partner responsible for the gender of the baby?
Females produce only X-bearing eggs, while males produce equal numbers of X-bearing and Y-bearing sperms. Fertilization by an X sperm produces a girl (XX), and fertilization by a Y sperm produces a boy (XY).
Q2. What is meant by Double Fertilization in plants?
It is the unique process in flowering plants where one male gamete fertilizes the egg cell to form a diploid zygote, and the second male gamete fuses with two polar nuclei to form triploid endosperm.
Q3. What is the difference between Monozygotic and Dizygotic twins?
Monozygotic twins develop from a single fertilized zygote that splits into two embryos (always of identical gender and appearance). Dizygotic twins develop from two separate ova fertilized by two separate sperms.
Related Study Topics
Class 10 Science 2 Chapter 3Asexual vs Sexual ReproductionDouble Fertilization in PlantsHuman Reproductive SystemMenstrual Cycle HormonesSex Determination in HumansIVF Surrogacy Sperm Bank