Topics to be learn :

  • Reproduction: Asexual and Sexual reproduction
  • Reproduction and modern technology.
  • Reproductive health.
  • Population Explosion.

Life Processes in Living Organisms:

  • Nutrition, respiration, excretion, sensation & response (control & co-ordination) are crucial for survival.
  • Reproduction maintains species continuity but doesn't sustain individual life.

Energy Production Processes:

  • Respiration, circulation, and nutrition are vital for energy production.
  • Oxygen, supplied by respiratory and circulatory systems, aids in nutrient oxidation, releasing energy.

Types of Cell Division:

  • Mitosis maintains chromosome number, yielding two daughter cells.
  • Meiosis reduces chromosome number by half, yielding four daughter cells.

Role of Chromosomes:

  • Chromosomes carry DNA from parent to daughter cells.
  • They transmit hereditary traits to the next generation.

Reproduction: Asexual and Sexual:

Reproduction creates new offspring from existing parent organisms, crucial for species survival and evolution.

Maintenance of Species:

  • Ensures species continuity through successful reproduction, producing individuals of the same kind.
  • Offspring aren't genetically identical to parents due to genetic recombination during meiotic cell division.
  • Asexual reproduction yields identical offspring, while sexual reproduction results in genetic diversity.
  • Genetic recombination determines the similarity between parents and offspring, except in cases like monozygotic twins or asexual reproduction.

Relationship with Cell Division:

  • Reproduction involves chromosome division, leading to gamete formation, and subsequent union for offspring production.
  • Both sexual and asexual reproduction involve cell division.
  • Cell division also contributes to the growth of new organisms.

Two Main Types of Reproduction:

  1. Asexual Reproduction:
    • Uniparental reproduction without gamete formation.
    • Offspring are exact replicas of parent organisms.
    • Mitotic cell division facilitates asexual reproduction.
    • Demerit: Lack of genetic recombination.
    • Merit: Rapid reproduction process.

(A) Asexual Reproduction in Unicellular Organisms:

1. Binary Fission:

  • Process: Parent cell divides to form two similar daughter cells.
  • Methods: Occurs via mitosis or amitosis.
  • Initial Division: Nucleus and cytoplasm division.
  • Conditions: Favors abundance of food materials.
  • Performers: Prokaryotes, Protists, and certain eukaryotic cell-organelles (e.g., mitochondria, chloroplasts).

Subtypes Based on Axis of Fission:

  • Simple Binary Fission: Plane of division is indefinite, as seen in Amoeba.

  • Transverse Binary Fission: Division plane is transverse, as observed in Paramecium.

  • Longitudinal Binary Fission: Division plane is length-wise, as in Euglena.

2. Multiple Fission:

  • Occurs during unfavorable conditions, such as food scarcity.
  • Amoeba forms protective cyst.
  • Undergoes repeated nuclear and cytoplasmic divisions inside the cyst.
  • Produces multiple amoebulae, remaining dormant until favorable conditions return.
  • Amoebulae emerge upon cyst rupture in favorable conditions.

3. Budding:

  • Parent cell produces two daughter nuclei via mitotic division.
  • Results in a small bud on the parent cell's surface.
  • One daughter nucleus enters the bud, which grows and separates to form a new yeast cell.
  • Performer: Yeast, a unicellular fungus.

(B) Asexual Reproduction in Multicellular Organisms:

1. Fragmentation:

  • Definition: Parent organism's body breaks into fragments, each becoming an independent organism.
  • Examples:
  • Algae Spirogyra: Filaments break into fragments, each forming a new Spirogyra fiber.
  • Sponges like Sycon: Body fragments develop into new Sycon.

2. Regeneration:

  • Occurs in certain primitive organisms like Planaria.
  • Planaria breaks body into two parts.
  • Each part regenerates lost parts, forming two new Planaria.
  • In developed animals like wall lizards, regeneration restores lost parts such as tail or limbs.

3. Budding:

  • Demonstrated by multicellular organisms like Hydra.
  • Development of bud at specific body part during favorable period.
  • Bud formed through repeated divisions of regenerative cells.
  • Bud grows into a small Hydra, receiving nutrition from parent.
  • Upon sufficient growth, bud detaches to lead an independent life.

4. Vegetative Propagation:

  • Definition: Reproduction in plants using vegetative parts like root, stem, leaf, or bud.
  • Examples:
  • Potatoes: Using "eyes" present on tuber.
  • Bryophyllum: Utilizing buds on leaf margin.
  • Sugarcane & grasses: Propagation via buds on nodes.

5. Spore Formation:

  • Demonstrated by fungi like Mucor.
  • Filamentous body with sporangia.
  • Spores formed and released from burst sporangia.
  • Settlement in suitable places, germination, forming new fungal colonies.
  • Example: Fungal growth on wet bread or 'bhakari' in humid conditions.

Sexual Reproduction:

Definition: Reproduction involving male and female gametes, comprising gamete formation and fertilization.

1. Gamete Formation: Meiosis forms haploid gametes from diploid germ cells.

2. Fertilization:

  • Outcome: Union of haploid male and female gametes forms diploid zygote.
  • Development: Zygote undergoes mitotic divisions to form an embryo, leading to the creation of a new individual.

Parental Roles:

  • Male parent produces male gamete (sperm), while female parent produces female gamete (ovum).
  • Fusion of gametes forms a zygote with recombined genes from both parents, resulting in offspring with similarities and differences in parental characters.

Genetic Variation:

  • Importance: Genetic variation leads to diversity in living organisms.
  • Selection: Variations beneficial for environmental adaptation are retained, ensuring survival without extinction.

Note: Meiosis absence leads to diploid gametes, resulting in tetraploid zygotes with severe abnormalities and disrupted chromosome numbers.

Sexual Reproduction in Plants:

Flower Structure:

 

Four floral whorls:

  • Two accessory: Calyx (sepals) and corolla (petals), protective in nature.
  • Two essential: Androecium (male) and gynoecium (female), involved in sexual reproduction.

Androecium (Male Whorl):

  • Comprised of stamens, each with filament and anther.
  • Anther contains four locules where meiosis forms pollen grains.
  • Pollen grains released during suitable time.

Gynoecium (Female Whorl):

  • Composed of carpels, either separate or united.
  • Each carpel has ovary, style, and stigma.
  • Ovary contains one or multiple ovules.

Bisexual and Unisexual Flowers:

  • Bisexual: Both androecium and gynoecium present in the same flower (e.g., Hibiscus).
  • Unisexual: Either androecium or gynoecium present in separate male and female flowers (e.g., Papaya).

Process of Sexual Reproduction:

  • Ovule undergoes meiosis in the carpel, forming an embryo sac with haploid egg cell and two polar nuclei.
  • Pollen grains from anther reach stigma via pollination, germinating to form pollen tube and two male gametes.
  • Pollen tube travels through style, delivering male gametes to the embryo sac.
  • One male gamete fertilizes egg cell, forming zygote; other fertilizes polar nuclei, forming endosperm.
  • Double fertilization: Fusion of male gamete with egg and polar nuclei.
  • After fertilization, ovule develops into seed, and ovary forms fruit.
  • Favorable conditions enable seed germination, producing a new plant.

Pollination:

Definition: Transfer of pollen grains from anther to stigma.

Agents of Pollination:

  • Abiotic: Wind, water.
  • Biotic: Insects, birds, or other animals.

Types of Pollination:

  • Self-pollination: Involves one flower or two flowers on the same plant.
  • Cross-pollination: Involves two flowers on two plants of the same species.

Artificial Pollination: Scientists use brushes for pollination to create new high-yielding and resistant plant varieties.

Fertilization:

  • Pollen germinates on sticky stigma, forming a pollen tube and two male gametes.
  • Pollen tube carries male gametes to embryo sac.
  • Fertilization occurs: One male gamete fertilizes egg cell, while the other fertilizes two polar nuclei, forming endosperm.
  • Double fertilization involves two nuclei, resulting in zygote and endosperm formation.

Germination:

  • New plantlet development from zygote after fertilization.
  • Ovule develops into seed, ovary into fruit.
  • Seeds fallen on the ground germinate under favorable conditions, utilizing stored food in endosperm.

Sexual Reproduction in Human Beings:

Hormones:

  • Pituitary gland secretes FSH and LH.
  • LH (ICSH in males) regulates male reproductive functions.
  • Gonads secrete testosterone in males and estrogen/progesterone in females.
  • Testosterone: Masculinity and sperm production.
  • Estrogen: Female body changes for motherhood.

Human Male Reproductive System:

Location: Located inside the lower abdomen.


Organs:
  • Testes, duct systems, and glands.
  • Testes: Paired, located in the scrotum outside the abdominal cavity.
  • Seminiferous tubules in testes produce sperm via meiosis.
  • Sperm mature during travel, becoming capable of fertilization.
  • Sperm travel through duct system:
    • Rete testis → Vas efferentia → Epididymis → Vasa deferentia → Ejaculatory duct → Urethra.
Secretions:
  • Seminal vesicles (paired), prostate gland (single), Cowper’s glands (paired) secrete fluids.
  • Fluids combine with sperm to form semen.
Deposition: Penis deposits semen into the vagina during sexual intercourse.

Human Female Reproductive System:

Location: Located inside the lower abdomen.


Organs:

  • Pair of ovaries, Pair of fallopian ducts (oviducts), Single median uterus.
  • Uterus opens into vagina, Bartholin’s glands in vaginal walls.
  • Ovaries: Paired organs producing oocytes (eggs).
  • Fallopian Ducts:
    • Funnel-like end captures oocyte released during ovulation.
    • Cilia on inner surface push oocyte towards uterus.
    • Fertilization occurs in middle part of fallopian duct.
  • Uterus: Opens into vagina, Contractions during parturition (birth process).
  • Vagina: Birth canal, copulatory passage, and menstrual flow passage.

Formation of Gametes:

  • Sperm from father and ovum from mother are haploid gametes formed by meiosis.
  • Men can produce sperm from puberty till death, while women's reproductive function ceases at menopause.
  • Women release a single matured oocyte from the ovary every month.
  • Women can produce ova until around age 45, after which menopause occurs due to decreased secretion of female hormones.

Fertilization:

  • Union of sperm and ovum forming a zygote.
  • Internal fertilization in humans: Sperm deposited in vagina during intercourse, swim through uterus to fallopian ducts.
  • Women of advanced age have increased risk of conceiving abnormal children due to aging ova.

Development and Birth:

  • Fertilization occurs in fallopian duct, zygote undergoes mitotic divisions to form embryo.
  • Embryo travels to uterus, implants, and grows for about 40 weeks.
  • Placenta provides nutrition during pregnancy.
  • Hormone oxytocin initiates contractions of uterus for childbirth.

Sex Determination in Human Beings:

  • Gametes develop from diploid germ cells (44 autosomes + XX or XY sex chromosomes).
  • Germ cells undergo meiosis to form haploid gametes (22 + X or 22 + Y).
  • Sperms carry either (22 + X) or (22 + Y), while ova are all (22 + X).
  • Sperms complete meiosis before leaving male reproductive tract, while oocytes complete meiosis after ovulation.
  • Type of sperm determines child's sex: X-bearing sperm fertilizes oocyte = girl, Y-bearing sperm fertilizes oocyte = boy.
  • Female foeticide is unethical; girls are equal to boys in every aspect.

Menstrual Cycle:

Definition:

  • Naturally occurring repetitive changes in mature human females.
  • Controlled by four hormones: FSH, LH, estrogen, and progesterone.
  • FSH and LH secreted from pituitary, estrogen and progesterone from ovary.

Cycle Phases:

  • FSH stimulates ovarian follicle development, which secretes estrogen.
  • Estrogen prompts uterine endometrium development and oocyte growth.
  • LH triggers ovulation: bursting of follicle to release oocyte.
  • Corpus luteum forms from remaining follicle tissue, produces progesterone.
  • Progesterone readies endometrium for embryo implantation.
  • If oocyte fertilized, endometrium forms placenta along with developing fetus.
  • If not fertilized, corpus luteum degenerates into corpus albicans.
  • Corpus albicans stops estrogen and progesterone secretion, leading to endometrium degeneration.
  • Degenerating endometrium, unfertilized ovum, and blood discarded through vagina, causing menstruation.
  • Monthly cycle interrupted only by pregnancy; suspended during breastfeeding.
  • Menstruating women experience pain, weakness, susceptibility to infections, requiring rest and hygiene facilities.

Reproduction and Modern Technology:

Causes of Sterility:

  • Females: Irregular menstrual cycles, oocyte production difficulties, implantation issues, or oviduct obstacles.
  • Males: Absence of sperms in semen, slow sperm movement, or sperm anomalies.
Modern Reproductive Technologies:
 
1. In Vitro Fertilization (IVF):
  • Used for couples facing issues like low sperm count or oviduct obstacles.
  • Oocyte is removed from the mother, fertilized with sperm from the father in a test-tube, forming an embryo.
  • Embryo is implanted in the uterus of the mother or a surrogate.

2. Surrogacy:

  • Utilized when there are implantation problems in the uterus.
  • Another woman acts as the surrogate mother.
  • Oocyte from the biological mother fertilized with the father's sperm outside the body, then implanted into the surrogate.

3. Sperm Bank (IVF Semen Bank):

  • Helps men with sperm production issues.
  • Sperms donated by individuals are stored in a sperm bank.
  • Donor's identity kept confidential, and donors must be physically and medically fit.

Twins:

Twins are two embryos that develop simultaneously in the same uterus, resulting in two offspring.

Monozygotic Twins (Identical Twins):

  • Formed from a single embryo, these twins are exactly alike and of the same gender.
  • If embryonic cells divide into two groups within 8 days of zygote formation, monozygotic twins are formed.
  • Siamese twins, a subtype of monozygotic twins, occur when embryonic cells divide into two groups 8 days after zygote formation, resulting in conjoined twins with some body parts joined together.

Dizygotic Twins (Fraternal Twins):

  • Formed when two oocytes are released from the ovary and fertilized by two separate sperms.
  • These twins are genetically different and may be of the same or different genders.

Reproductive Health:

  • Definition: Refers to the physical, mental, and social well-being related to reproduction.
  • Challenges in India: Lack of awareness, social customs, traditions, illiteracy, and shyness contribute to the indifference towards reproductive health, particularly in women.
  • Practices for Reproductive Health: Maintaining genital hygiene is essential for reproductive health.
Sexually Transmitted Diseases (STDs):
  • Syphilis and gonorrhea are bacterial venereal diseases that affect many people.
  • Symptoms of syphilis include chancre occurrence, rashes, fever, joint inflammation, and alopecia.
  • Symptoms of gonorrhea include painful urination, pus discharge from the penis and vagina, inflammation of various body parts like the urinary tract, anus, throat, and eyes.

Population Explosion:

  • Definition: Excessive population growth within a short period.
  • Challenges in India: Population growth leads to issues like unemployment, declining per capita income, increasing loan burdens, and stress on natural resources.
  • Solution: Family planning is crucial for population control in India.