3. LIFE PROCESS IN LIVING ORGANISM 2 (2)

Introduction

  • Reproduction: Formation of new organisms of the same species by earlier existing organisms.

    • Important characteristics of living organisms.

    • Responsible for the evolution of each species.

  • Methods of Reproduction:

    1. Asexual Reproduction

    2. Sexual Reproduction

Asexual Reproduction

  • Formation of new organisms by the same species without gametes.

    • New organism has exact genetic similarity with the parent organism.

    • Uniparental reproduction occurring via mitotic cell division.

    • Advantage: Fast process.

    • Disadvantage: Absence of genetic recombination.

Asexual Reproduction in Unicellular Organisms

  1. Binary Fission:

    • Parent cell divides to form two similar daughter cells.

    • Occurs by mitosis or amitosis.

    • Typically happens during favorable conditions (abundant food).

    • Division axis varies in different protists.

  2. Types of Binary Fission:

    • Simple Binary Fission: e.g., Amoeba divides in any plane.

    • Transverse Binary Fission: e.g., Paramecium divides transversely.

    • Longitudinal Binary Fission: e.g., Euglena divides longitudinally.

  3. Multiple Fission:

    • Performed by organisms like Amoeba when conditions are adverse.

    • Amoeba becomes encysted to form a protective covering (Cyst).

    • Undergoes repeated nuclear divisions to form multiple nuclei in the cyst.

    • Forms daughter amoebae when conditions improve.

  4. Budding:

    • Example: Yeast cell reproduces by budding.

    • Parent cell develops a bulge (bud) that matures into a new daughter cell.

Asexual Reproduction in Multicellular Organisms

  1. Fragmentation:

    • Parent organism breaks into fragments; each fragment grows independently.

    • Seen in organisms like Spirogyra and Sycon.

  2. Regeneration:

    • Example: Planaria can regenerate missing parts.

    • Specialized cells divide rapidly to produce new cells.

  3. Budding:

    • Organisms like Hydra produce buds that develop into new individuals.

  4. Vegetative Propagation:

    • Plant parts (roots, stems, leaves) develop into new plants under suitable conditions.

    • Used in agriculture (layering, grafting) and produces genetically similar plants.

    • Example: Bryophyllum produces new individuals from its leaves.

  5. Spore Formation:

    • Seen in certain multicellular organisms, like fungi (Rhizopus).

    • Sporangia produce spores that can develop into new individuals.

Sexual Reproduction

  • Involves two germ cells (male gamete and female gamete).

  • Consists of two main processes:

    1. Gamete Formation

    2. Fertilization

Gamete Formation

  • Produced by meiosis, reducing the chromosome number by half (haploid).

Fertilization

  • Zygote is formed by the union of haploid gametes.

  • The zygote is diploid and undergoes mitosis to develop into an embryo.

  • Genetic variation occurs due to the fusion of gametes, aiding adaptation.

Sexual Reproduction in Plants

Parts of Flower

  1. Accessory Whorls:

    • Non-reproductive parts: Sepals and Petals.

    • Sepals support the petals, while petals attract pollinators.

  2. Essential Whorls:

    • Involved in reproduction: Androecium (male) and Gynoecium (female).

    • Androecium produces pollen grains containing male gametes.

    • Gynoecium includes stigma (receives pollen), style (connects stigma and ovary), and ovary (contains ovules with egg cells).

Pollination

  • Transfer of pollen from anther to stigma.

    • Self-pollination: Same flower.

    • Cross-pollination: Different flowers.

    • Pollination may involve biotic and abiotic factors.

Fertilization Process

  • Fusion of male and female gametes.

  • Pollen germinates on sticky stigma, forming a pollen tube that carries gametes.

  • Double fertilization occurs (one sperm fertilizes the egg, the other fuses with polar nuclei to form endosperm).

Germination

  • Seed formed after fertilization develops into a plant.

  • Process dependent on soil and water conditions.

Sexual Reproduction in Humans

Changes in Puberty

  • Defined as the stage when reproductive organs mature.

  • Changes in Boys:

    • Growth of facial hair, voice changes.

  • Changes in Girls:

    • Breast development, menstruation begins.

Male Reproductive System

  • Consists of testes (produces sperm), vas deferens, and glands (provide fluid nourishment).

Testes

  • Produce testosterone and sperm; located in scrotum for temperature regulation.

Female Reproductive System

  • Comprises ovaries (produces ova), fallopian tubes (fertilization), uterus (embryo development).

Gamete Formation in Humans

  • Males produce sperm continuously post-puberty.

  • Females release ova monthly until menopause.

Fertilization in Humans

  • Sperm fertilizes an ovum in the fallopian tube.

  • Zygote implants in the uterus for growth.

Menstrual Cycle

  • Involves hormonal control and monthly physiological changes:

    1. Preparation of the endometrium for potential implantation.

    2. If no fertilization occurs, menstruation follows (endometrium sheds).

Reproduction and Modern Technology

  • Issues preventing conception can arise in males and females.

    • Male Issues: Sperm production, motility problems.

    • Female Issues: Irregular cycles, ovulation difficulties.

Advanced Techniques

  1. In Vitro Fertilization (IVF): Fertilization occurs outside the body and the embryo is implanted in the uterus.

  2. Surrogacy: Embryo implanted in a surrogate mother's uterus.

  3. Sperm Bank: Collection and storage of sperm for use in IVF.

Twins

  • Monozygotic Twins: Originating from a single zygote; identical siblings.

  • Dizygotic Twins: Develop from two separate zygotes; genetically different.

Reproductive Health

  • Importance of physical, mental, and social wellbeing in reproduction.

  • Common sexually transmitted diseases: Syphilis and Gonorrhea.

    • Symptoms: Vary between diseases, affecting various body systems.