How Do Organisms Reproduce — Karnataka (SSLC) Class 10 Science Solutions (Free)

Reproduction = process by which organisms produce offspring to ensure species survival. Asexual: one parent, no gamete fusion, genetically identical offspring (clones). Methods: binary fission (bacteria), budding (hydra), fragmentation (starfish). Sexual: two parents, gamete fusion (sperm + egg), genetically different offspring. Methods: in animals (internal/external fertilization), in plants (pollination, fertilization). Sexual reproduction increases genetic variation, important for evolution a…

Female reproductive system: 1) Ovaries: produce eggs (ova) by meiosis; release one egg monthly (ovulation). 2) Fallopian tube: carries egg from ovary; fertilization occurs here. 3) Uterus: muscular organ; fertilized egg implants here (develops into fetus). 4) Cervix: narrow opening of uterus. 5) Vagina: birth canal, receives sperm during intercourse. Menstrual cycle: ~28 days, phases are menstruation, follicular, ovulation, luteal. Hormones (FSH, LH, estrogen, progesterone) control cycle.

Male reproductive system: 1) Testes: produce sperm by meiosis; secrete testosterone (male hormone). 2) Epididymis: stores sperm, matures it. 3) Vas deferens: transports sperm from testes. 4) Seminal vesicles: secrete seminal fluid (nourishes sperm). 5) Prostate gland: adds fluid to semen. 6) Urethra: carries urine and semen; exits through penis. Sperm production: spermatogenesis takes ~74 days in seminiferous tubules. Semen contains 100+ million sperm per ml; only one fertilizes egg.

Menstrual cycle = ~28-day cyclical process preparing uterus for pregnancy. Four phases: 1) Menstruation (days 1-5): uterine lining sheds, bleeding occurs. 2) Follicular phase (days 1-13): FSH rises, ovary follicles develop, estrogen increases. 3) Ovulation (day 14): LH surge triggers egg release from ovary. 4) Luteal phase (days 15-28): corpus luteum produces progesterone, uterine lining thickens for implantation. If no fertilization, progesterone drops, cycle repeats. Irregular cycles possible …

Fertilization = fusion of sperm and egg nucleus to form zygote. Process: 1) Sperm enters vagina, swims through cervix, travels up fallopian tube. 2) Sperm penetrates egg's corona radiata and zona pellucida. 3) Sperm and egg nuclei fuse, combining 23 + 23 = 46 chromosomes. 4) Zygote forms; undergoes mitosis forming blastocyst. Location: fallopian tube, 12-24 hours after ovulation. Fertilized egg travels to uterus over 3-4 days, implants in uterine wall. Early division produces identical twins (bl…