Reproduction in Plants and Animals (Humans) | General Awareness for SSC CGL PDF Download

Reproduction

• Asexual Reproduction: This type of reproduction does not involve the formation or fusion of gametes.
• Sexual Reproduction: This type of reproduction involves the formation and fusion of gametes.

Asexual Reproduction

• Major Type: Occurs predominantly under favorable conditions.

Modes of Asexual Reproduction in Plants and Animals

1. Fission:
   • Found in unicellular organisms.
   • The cell divides equally, e.g., Amoeba.
2. Fragmentation:
   • The body breaks into parts, each of which can generate a whole new body, e.g., Spirogyra, bryophytes.
3. Regeneration:
   • Any body part can form new parts, e.g., Hydra.
4. Budding:
   • A bud forms on the body and grows into a full organism, e.g., Hydra, yeast.
5. Vegetative Propagation:
   • Vegetative parts like roots, stems, and leaves develop new identical plants (clones), e.g., sugarcane, rose.
   • Can be carried out artificially by grafting, cutting, layering, and micropropagation (tissue culture). This can be practiced year-round.
6. Spore Formation:
   • Spores, condensed protoplasmic bodies containing genetic material, separate from the main body and germinate into new organisms, e.g., algae and fungi.

Sexual Reproduction

• Adverse Conditions: Often occurs in adverse conditions among lower organisms, while many higher plants and animals have adapted it as their main mode of reproduction.
• Gametes: Critical for sexual reproduction, they are formed in reproductive organs and protect genetic and protoplasmic material, transmitting it to a suitable place for fusion and formation of a new organism.

Sexual Reproduction in Plants (Angiosperms)

• Growth Phases: After germination, plants go through vegetative and reproductive phases, influenced by hormones like auxin, gibberellin, and abscisic acid.
• Flower: The reproductive organ of plants. Flowers with both male and female reproductive organs are bisexual, while those with only one type are unisexual.
  • Male Organ: Androecium
  • Female Organ: Gynoecium

Pollination Agents:

• Wind: Anemophily
• Water: Hydrophily
• Insects: Entomophily
• Birds: Ornithophily
• Bats: Chiropterophily
• Snails: Malacophily
• Ants: Myrmecophily

The fate of various parts of flower is given below :

Sexual Reproduction in Humans

In humans only sexual mode of reproduction is found. Males and females are different from each other externally as well as internally. Male reproductive system forms sperms (male gamete) while female reproductive system forms egg (female gamete)

Comparison between secondary sexual character of man and woman is given below:

Male Reproductive System:

• Function: Produces sperm.
• Spermatogenesis: Formation of sperm occurs in the testes, which are located outside the body in the scrotum because sperm formation requires lower temperatures.
• Sperm Pathway: Sperm are delivered through the vas deferens to the urethra, which serves as a common pathway for urine and sperm.
• Accessory Glands: Includes the prostate gland and seminal vesicles, which aid in reproduction. Sperm, after being formed in the seminal vesicle, are collected in the epididymis via the rete testis.

Sperm Pathway: Seminal vesicle → Rete testis → Vasa efferentia → Epididymis → Urethra

Female Reproductive System

The female reproductive system is responsible for producing eggs. Egg production occurs in the ovaries. When a girl is born, her ovaries contain thousands of immature eggs, which begin to mature after puberty, forming primary, secondary, and eventually tertiary follicles. The tertiary follicles transform into mature Graafian follicles in response to certain hormones, following a periodic cycle known as menstruation (approximately 28 days in humans). The egg travels from the ovary to the uterus via the oviduct, where fertilization with sperm occurs to form a zygote. The zygote then moves to the uterus and develops into a new baby. 

Fertilization leads to the formation of a zygote, which undergoes cleavage and soon reaches the three-layered stage called gastrula. The fate of the cells in these three primary germ layers is as follows:

Reproductive Health

Reproductive health refers to a state of physical, mental, and social well-being in all matters related to the reproductive system at all stages of life. Men and women should have access to safe, effective, affordable, and acceptable methods of family planning and appropriate health-care services to safely navigate pregnancy and childbirth.

Contraceptive Methods:

• Barrier Methods: Prevent sperm from entering the uterus and reaching the egg. These include male and female condoms, diaphragms, cervical caps, contraceptive sponges, and Lea’s shields. They are generally less effective but have fewer side effects than hormonal methods or IUDs.
• IUD (Intrauterine Device): A small plastic device containing copper or hormones inserted into the uterus by a medical professional. It changes cervical mucus to decrease fertilization probability and alters the uterine lining to prevent implantation.
• Abstinence: Voluntary refraining from sexual activity. It is the only 100% effective method to prevent pregnancy and sexually transmitted diseases (STDs).
• Withdrawal: Involves removing the erect penis from the vagina prior to ejaculation.
• Sterilization: Surgical closing of reproductive tubes. Female sterilization (tubal ligation or tubectomy) closes the Fallopian tubes, while male sterilization (vasectomy) closes the sperm-carrying tubes.
• Birth Control Pills: Daily hormone medications prescribed by a doctor containing manufactured forms of estrogen and/or progesterone.
• Amniocentesis: A medical procedure used in prenatal diagnosis to detect chromosomal abnormalities and fetal infections. A small amount of amniotic fluid, containing fetal tissues, is extracted and the fetal DNA is examined for genetic abnormalities.