How do organisms reproduce

• Reproduction is the process by which a living organism produces new individuals of its own kind
• Reproduction is important for the existence and continuity of the species
• Reproduction involves the creation of DNA copy and additional cellular apparatus by the cell involved in the process
• The process of DNA copying during reproduction leads to variations, which is the basis for evolution
• Living organisms reproduce mainly through asexual reproduction and sexual reproduction
• Types of Asexual Reproduction in Unicellular Organisms:

  • Binary Fission: Seen in bacteria, protozoa like Amoeba, Paramecium
  • Multiple Fission: Seen in Plasmodium
  • Budding: Seen in Yeast
  • Fragmentation: Seen in multicellular organisms like Spirogyra
  • Regeneration: Ability of organisms to develop lost parts
  • Spore Formation: Seen in Rhizopus
  • Vegetative Propagation: Method by which plants reproduce by their vegetative parts such as roots, stems, and leaves
• Importance of Vegetative Propagation:

  • Plants can bear flowers and fruits earlier
  • Plants which have lost the ability to produce viable seeds can also reproduce
  • All plants are genetically almost similar to the parent plant
  • Seedless varieties can be obtained
  • Used by horticulturists in developing methods like layering, grafting
• Tissue Culture: Technique of developing new plants from a cell or tissue in a nutrient medium under aseptic conditions
• Sexual Reproduction involves two individuals of two different sexes, male and female
• Sexual Reproduction in Flowering Plants:

  • Reproductive parts present in the flower
  • Parts of the flower: sepals, petals, stamens, and carpels
  • Pollination: transfer of pollen grains from anther to stigma
  • Fertilization: fusion of male and female gamete to form a zygote
  • Post-fertilization changes in the flower
• Seed and its parts:

  • Seed has two parts: Cotyledons and Embryo
  • Embryo has two parts: plumule and radicle
  • Germination: process of development of a seedling from the embryo under appropriate conditions
• Reproduction in Human Beings:

  • Male parent produces male gametes called sperms
  • Female parent produces female gametes called ova
  • Sperms are motile and produced in large numbers in the testes
  • Ova are non-motile and only one ovary produces one ovum in one month
  • Both gametes are microscopic unicellular and have half the number of chromosomes as body cells
  • Human beings become reproductively active from the onset of puberty
• Puberty is the period during adolescence when the rate of general body growth begins to slow down and reproductive tissues begin to mature
• Onset of puberty in human males is between 11 to 13 years of age, while in human females is between 10 to 12 years of age
• Puberty is associated with physical, mental, emotional, and psychological changes in boys and girls, known as secondary sexual characters
• In boys:

  • Beard and mustache start appearing
  • Voice begins to crack
  • Reproductive organs develop and start producing and releasing sperms
• In girls:

  • Breast size begins to increase
  • Skin of the nipples darkens
  • Menstruation starts
• Male reproductive system consists of:

  • 1 pair of testes
  • A system of ducts: Epididymis, Vas deferens or the sperm duct, Urethra
  • A system of glands: Seminal vesicles, Prostate gland, Cowper’s gland
  • A copulatory organ called a penis
• Functions of testes:

  • To produce male gametes (sperms)
  • To produce a male reproductive hormone called testosterone
• Functions of the vas-deferens:

  • Meant for the passage of sperms in the male body
• Functions of the glands:

  • Produce secretions which provide nutrition and medium for locomotion to the sperms
  • Secretions of the three glands along with the sperms form semen
• Function of the urethra:

  • Common passage for both semen and urine from the body to the outside
• Female reproductive system consists of:

  • 1 pair of ovaries
  • 1 pair of fallopian tubes or oviducts
  • A uterus/womb
  • A vagina/birth canal
• Functions of ovary:

  • To produce and release ova
  • To produce female reproductive hormones: estrogen and progesterone
• Function of the fallopian tubes:

  • Site of fertilization between the male and female gametes and formation of the zygote (early embryo)
• Function of the uterus:

  • Embryo formed in the fallopian tube gets attached to the endometrium and develops till delivery
• Menstruation:

  • Loss of blood, mucous, unfertilized ovum, and ruptured cells and tissues of the endometrium through the vagina
  • A 28-day cycle that occurs in every reproductively active female
  • Flow of blood continues for 2 to 8 days
• Reproductive Health:

  • Sexually transmitted diseases and birth control methods
• Birth control measures:

  • Mechanical, chemical, and surgical methods
• Mechanical methods:

  • Use of condoms to prevent the passage of semen
  • Diaphragm fitted over the cervix
  • Intra Uterine Contraceptive Device (IUCD) or loop inserted in the uterus
• Chemical methods:

  • Use of spermicides
  • Oral contraceptive pills
• Surgical methods:

  • Vasectomy in males
  • Tubectomy in females
• Medical termination of pregnancy (MTP) or abortions can be carried out to eliminate the developing embryo