Reproduction and Development

• In living species, reproduction is a distinctive feature. Over the years, all living species have survived and grown by way of reproduction. Living organisms reproduce and give rise to similar organisms of the same species. Different species have different reproduction methods and processes.
• Modes of Reproduction


  • Sexual reproduction
  • Asexual reproduction
• Sexual reproduction


  Requires two parents to give birth to the offspring
• Asexual reproduction


  Requires one single parent to give birth to the offspring
• Asexual reproduction is commonly seen in plants, but in the animal kingdom, it is less common.
• Types of Asexual Reproduction

  • Binary Fission
  • Budding
  • Fragmentation
  • Parthenogenesis
• Binary Fission


  The DNA of the parent bacteria replicates itself and the cell divides into two halves, each half having its own DNA. The parent cell divides into two identical daughter cells.
• Budding


  The offspring grow on the parent body from a bud-like structure. The buds fall off the parent body once large enough, and begin their independent life.
• Fragmentation


  The parent organism splits into several fragments or segments, where each of the fragments evolves into a new organism.
• Parthenogenesis


  The female organism generates eggs without fertilization, and the offspring emerge from that. This reproductive form is not seen in mammals.
• Types of asexual reproduction in plants

  • Vegetative propagation
• Vegetative propagation


  Asexual reproduction that takes place in the stems of certain plants from certain buds that emerge on their leaves or stems, giving rise to new plants.
• Sexual Reproduction


  Involves two separate parents that belong to the opposite sex. Both plants and animals exhibit this kind of reproduction.
• Parts of a Flower

  • Calyx
  • Corolla
  • Androecium
  • Gynoecium
• Calyx


  Green petal-like structures located right above the receptacle called the base of the flower. Their primary task is to safeguard the flower while it is still in the bud process.
• Corolla


  The collective colorful petals of the flower that attract the pollinating agents.
• Androecium


  The male reproductive section of a flower made up of a series of stamens, each consisting of a filament and anther that produce the male gamete-containing pollen.
• Gynoecium


  The female reproductive organ of the flower, composed of the ovary, style, and stigma.
• Pollination and Fertilization


  1. Pollen grains and ovules travel to reach the stigma

  2. Fertilization occurs after pollination and germination, where the male gametes (pollen) fuse with the female gametes (ovum) to form a diploid zygote
• Types of Fertilization


  • Porogamy
  • Chalazogamy
  • Mesogamy
• Porogamy

  The common type of fertilization carried out in all angiosperms or flowering plants, where the pollen tube enters the ovule through the micropyle.
• Chalazogamy


  The type of fertilization carried out on all Casuarina species of plants, where the pollen tube enters the ovule through the pollen tube.
• Mesogamy


  The type of fertilization seen in all Cucurbit plants, where the pollen tube enters the ovule through its middle part or through the integuments of the ovule.
• Double Fertilization


  A fertilization process characterized by the fusion of two male gametes with a female gametophyte, where one sperm cell fuses with the egg-producing zygote, and the other fuses to create the endosperm with the two polar nuclei.
• Reproduction in Human Beings

  Sexual reproduction in which both male and female gametes fertilize to give birth to a zygote that develops into an embryo. Fertilization takes place within the female's body, called Internal fertilization.
• Parts of the Male Reproductive System

  • Penis
  • Scrotum
  • Epididymis
  • Vas deferens
  • Seminal vesicles
  • Prostate gland
  • Bulbourethral (Cowper's) glands
• Penis


  The male organ for sexual intercourse and urination. Semen and urine leave the penis through the urethra.
• Scrotum


  A loose, pouch-like sack of skin that covers the testicles and hangs behind the penis. It has a protective role, including maintaining optimum temperatures for the survival and function of the sperm.
• Epididymis


  Located at the back of the testis, it binds to the vas deferens and functions to store sperm and carry it.
• Vas deferens


  Transports mature sperm to the urethra during ejaculation.
• Seminal vesicles


  Sac-like pouches that bind near the base of the bladder to the vas deferens, producing molecules that serve as energy sources for sperm.
• Prostate gland


  A walnut-sized organ in front of the rectum situated below the urinary bladder, adding extra fluid to the ejaculate to nourish the sperm.
• Bulbourethral (Cowper's) glands

  Pea-sized structures situated just below the prostate gland on the sides of the urethra, containing a slick, clear fluid that lubricates the urethra and neutralizes residual urine-related acidity.
• Parts of the Female Reproductive System

  • Uterus
  • Ovaries
  • Vagina
  • Fallopian tubes
  • Cervix
• Uterus


  Hosts the fetus that is developing, produces vaginal and uterine secretions, and passes the sperm through to the fallopian tubes.
• Ovaries


  Produce the eggs and secrete progesterone and estrogen.
• Vagina

  Contains the labia, clitoris, and urethra, and is connected via the cervix to the uterus.
• Fallopian tubes

  Attached to the ovaries, where fertilization generally occurs as the egg passes through.
• Cervix

  Connects the vagina to the uterus.
• Fertilization and early embryonic development

  1. Gametes (egg and sperm) fuse to form a zygote

  2. Zygote undergoes rapid cell division to form the blastula

  3. Blastula folds upon itself during gastrulation to form the three germ layers (ectoderm, mesoderm, endoderm)

  4. Organs form from the germ layers through differentiation during organogenesis