Topics to be learn
  • Introduction
  • Types of Reproduction
  • Modes of Asexual Reproduction
  • Sexual Reproduction (Sexual Reproduction in Plants)
  • Process of Seed Germination
  • Reproduction in Human Beings
  • Male Reproductive System
  • Female Reproductive System
  • Fertilisation of egg
  • Reproductive Health
  • Female Foeticides
Introduction
  • Reproduction: Process by which living organisms produce new individuals similar to themselves.
  • Ensures continuity of life on Earth.
  • Nucleus of the cell contains DNA (Deoxyribose Nucleic Acid), the hereditary material.
  • DNA replicates, forming new cells, causing variation. New cells are similar but not identical to the original cell.
  • Variations help in the survival of the individual and species over time and are the basis for evolution.

Types of Reproduction

Asexual Reproduction

  • Single individual gives rise to a new individual.
  • Gametes are not formed.
  • New individual is identical to parent.
  • Useful for rapid multiplication.
  • Adopted by lower organisms.

Sexual Reproduction

  • Two individuals (one male and one female) are needed to give rise to a new individual.
  • Gametes are formed.
  • New individual is genetically similar but not identical to parents.
  • Generates more variations in species.
  • Adopted by higher organisms.
Asexual Reproduction:
  • Definition: Creation of new generations from a single individual.
Modes of Reproduction Used by Single Organisms

Fission:

  • Definition: Unicellular organisms divide to form new individuals.
  • Examples:
    • Binary fission: Equal division into two cells (e.g., Amoeba).
    • Multiple fission: Division into many daughter cells simultaneously (e.g., Plasmodium).

 

 

Fragmentation:

  • Definition: Multi-cellular organisms like Spirogyra break into pieces that grow into new individuals.

Regeneration:

  • Definition: Ability of organisms to grow into new individuals from body parts.
  • Examples: Planaria and Hydra regenerate complete organisms from fragments.

 Budding:
  • Definition: Outgrowth develops into new individual, detaching from parent.
  • Example: Hydra reproduces by budding.

 

Vegetative Propagation:

  • Definition: Plants reproduce from parts (roots, stems, leaves) under suitable conditions.
  • Examples: Layering, grafting used in agriculture, Bryophyllum reproduces from leaf notches.

Tissue Culture:

  • Definition: Growing new plants from tissue or cell cultures.
  • Process: Cells divide in culture medium with hormones, developing into plantlets.
  • Application: Used for ornamental plants, disease-free propagation.

Spore Formation:

  • Definition: Formation of spores that develop into new individuals.
  • Example: Rhizopus forms spores (sporangia) that germinate under favorable conditions.
Sexual Reproduction

  • Definition: Requires involvement of two individuals (male and female) to create new offspring.

  • Significance:

    • Variation: Sexual reproduction introduces variations through genetic recombination, enhancing survival chances in changing environments.
    • Adaptation: Allows populations to adapt more quickly to environmental changes compared to asexual reproduction.
    • Genetic Diversity: Combining DNA from two individuals results in novel combinations of genetic traits.

  • Limitations of Asexual Reproduction:

    • Limited genetic diversity leading to vulnerability in changing environments.
    • Accumulation of harmful mutations over generations.

  • Mechanisms in Sexual Reproduction:

    • Meiosis: Specialized cell division reducing chromosome number by half, ensuring genetic stability across generations.
    • Gametes: Male (motile) and female (with stored food) gametes unite during fertilization to form a zygote.

  • Complexity in Organisms:

    • As organisms become more complex, germ cells specialize to support the growth and development of new individuals.

  • Sexual Differentiation:

    • Male and Female Gametes: Motile sperm (male) and nutrient-rich egg (female) cells play roles in sexual reproduction.
    • Reproductive Organs: Developed to accommodate production and fusion of gametes, showing structural differences in males and females.

Sexual Reproduction in Flowering Plants

Reproductive Parts of Flowering Plants
  • Located in the flower: sepals, petals, stamens, pistil
  • Stamens and pistil are reproductive parts containing germ-cells
  • Petals and sepals serve functions like protection and attraction
Types of Flowers
  • Unisexual: Contains either stamens or pistil (e.g., papaya, watermelon)
  • Bisexual: Contains both stamens and pistil (e.g., Hibiscus, mustard)

Stamen

  • Male reproductive part
  • Produces pollen grains (yellowish powder)

Pistil

  • Female reproductive part
  • Made of ovary, style, and stigma
  • Ovary contains ovules with egg cell

Pollination

  • Self-pollination: Transfer of pollen within the same flower
  • Cross-pollination: Transfer of pollen between different flowers
  • Agents: wind, water, animals
Fertilization
  • Pollen grain lands on stigma, grows a tube to reach ovary
  • Fusion of male pollen germ-cell with female gamete in ovule forms zygote

Seed Formation

  • Zygote develops into embryo within ovule
  • Ovule becomes seed with tough coat
  • Ovary ripens into fruit; other flower parts may wither

Germination

  • Seed contains embryo for future plant
  • Development into seedling under suitable conditions
Reproduction in Human Beings
  • Humans use sexual mode of reproduction
  • Process involves sexual maturation and development of reproductive organs

Puberty and Body Changes

  • General growth and sexual maturation occur during puberty
  • Changes include growth spurts, appearance of secondary sexual characteristics
  • Common changes: growth of thick hair in armpits, genital area, skin becoming oily

Sexual Maturation Differences

  • Girls: Breast development, menstruation
  • Boys: Facial hair growth, voice changes, erections

Timing and Variability

  • Changes occur over months to years, vary among individuals
  • Not all changes happen simultaneously or at the same age

Purpose of Sexual Maturation

  • Prepares body for sexual reproduction through maturation of reproductive tissues
  • Puberty marks the period when reproductive organs develop

Significance of Changes

  • Signals readiness for mating and reproduction
  • Special organs like penis for internal transfer of germ-cells in mammals
Male Reproductive System 
  • Testes: Located in scrotum, outside abdominal cavity for lower temperature required for sperm formation
  • Sperm Production: Occurs in testes; regulated by testosterone which also influences puberty changes

Path of Sperm

  • Vas Deferens: Transports sperms to urethra
  • Urethra: Common passage for sperms and urine
  • Accessory Glands: Prostate, seminal vesicles add secretions for sperm nutrition and motility

Structure of Sperm

  • Tiny bodies with genetic material and a tail for movement towards female germ-cell

Female Reproductive System

  • Ovaries: Produce eggs and hormones; contain immature eggs from birth
  • Oviducts (Fallopian Tubes): Carry egg from ovary to uterus

Uterus

  • Elastic bag-like structure where embryo implants and develops into fetus
  • Opens into vagina through cervix

Fertilization and Pregnancy
  • Sperms travel to oviduct; fertilization of egg (zygote) occurs
  • Zygote develops into embryo, implants in uterine lining
  • Placenta: Provides exchange of nutrients and waste between mother and embryo

Development and Birth

  • Development takes approximately nine months in uterus
  • Birth occurs through rhythmic contractions of uterine muscles
Unfertilised Egg
  • Egg lives for about one day if not fertilised
  • Uterus prepares for fertilised egg with thick, spongy lining
  • Menstruation: Lining breaks down, exits through vagina as blood and mucous
  • Cycle occurs roughly every month, lasts two to eight days

Reproductive Health

  • Sexual Maturation: Gradual process alongside general body growth
  • Readiness for sexual acts and responsibilities requires consideration of physical and mental preparedness

Sexually Transmitted Infections (STIs)

  • Intimate contact during sexual acts can transmit diseases like gonorrhoea, syphilis, warts, HIV-AIDS
  • Condoms help prevent transmission to some extent

Contraception

  • Mechanical Barriers: Condoms prevent sperm-egg interaction
  • Hormonal Methods: Alter body's hormone balance to prevent egg release and fertilisation
  • Devices: Copper-T, intrauterine devices prevent pregnancy; may cause side effects
  • Surgical Methods: Block vas deferens or fallopian tubes to prevent sperm-egg meeting
  • Surgical methods and procedures like abortion have their own risks and ethical considerations

Social Issues

  • Female Foeticide: Declines child sex ratio; illegal and problematic for society
  • Maintaining female-male sex ratio important for healthy society

Population Concerns

  • Population Growth: Impacts standard of living and societal resources
  • Inequality often a critical factor influencing living standards