Reproduction in Plants and Animals

1. Number of Parents: Asexual requires only one single parent; Sexual requires two parents (male and female).
   2. Gamete Involvement: Asexual involves no gametes or fertilization; Sexual involves formation and fusion of haploid gametes (sperm and egg).
   3. Genetic Variation: Asexual offspring are genetically identical clones of the parent; Sexual offspring exhibit genetic variation due to crossing over and independent assortment in meiosis.
   4. Type of Cell Division: Asexual involves only mitotic division; Sexual involves meiosis (for gametogenesis) and mitosis (for embryonic development).

• (a) Potato: Stem Tuber (using dormant axillary vegetative buds called "eyes").
• (b) Bryophyllum: Leaf (using adventitious foliar buds produced in the marginal notches).
• (c) Ginger: Underground Stem / Rhizome (bearing nodes, internodes, and scaly leaves).
• (d) Sweet Potato: Tuberous Root (adventitious storage root capable of sprouting new shoots).

• (a) Ovary: Enlarges, ripens, and develops into the Fruit (its wall becomes the fruit wall or Pericarp).
• (b) Ovule: Matures, dehydrates, and develops into the Seed (its integuments form the outer seed coats: Testa and Tegmen).
• (c) Zygote: Undergoes repeated mitotic divisions and cell differentiation to form the diploid Embryo inside the seed.
• (d) Sepals, Petals, Stamens & Style: Wither, dry up, and fall off (in some fruits like brinjal and tomato, sepals remain persistent).

• Self-Pollination: Transfer of pollen grains from the anther of a flower to the stigma of the same flower or another flower on the same individual plant.
• Cross-Pollination: Transfer of pollen grains from the anther of one flower to the stigma of a flower on a genetically different plant of the same species (via wind, insects, birds).
• Biological Advantage: Cross-Pollination is vastly superior for evolutionary survival.
Why? It mixes genetic material from two distinct parents, introducing beneficial genetic variations, enhancing disease resistance, increasing vigor (heterosis), and producing offspring better adapted to changing environmental climates.

• Internal Fertilization: Fusion of male and female gametes takes place inside the female reproductive tract (e.g., humans, birds, reptiles).
• External Fertilization: Fusion of gametes occurs outside the female body in water (e.g., frogs, fishes).
• Why Thousands of Eggs?
In aquatic external fertilization, gametes face severe hazards: they are easily washed away by water currents, desiccated, or eaten by aquatic predators. To compensate for these massive losses and ensure that at least a few survive to perpetuate the species, animals lay thousands of eggs.

• Metamorphosis: The biological process of profound, dramatic structural and physiological transformation from an immature larval stage into a sexually mature adult body form.
• Stages in Frog Life Cycle:
1. Egg (Spawn): Laid and fertilized externally in fresh water.
2. Early Tadpole: A fish-like aquatic larva possessing a long swimming tail, external branchial gills for breathing, and an herbivorous mouth.
3. Late Tadpole: Develops hind limbs, followed by forelimbs; internal lungs develop; gills and tail gradually regress and are reabsorbed.
4. Adult Frog: A carnivorous, tail-less, 4-limbed amphibian breathing through lungs, moist skin, and buccopharyngeal cavity.

• Grafting: An artificial vegetative method in which parts of two different plants are joined together so that they fuse their vascular cambium tissues and grow as a single unified plant.
• Stock: The rooted, basal lower plant selected for its strong root system, disease resistance, and soil adaptability.
• Scion: The upper detached stem cutting or bud containing superior floral or fruit characteristics (high yield, sweet taste).
• The cambium layers of stock and scion are tightly bound together with grafting wax until vascular connections fuse.

• Oviparous Animals:
1. Animals that lay eggs covered with protective shells or gelatinous coats.
2. Embryonic development occurs outside the mother's body using yolk for nourishment.
Examples: Birds (crow, hen), Reptiles (lizards, snakes), Amphibians.
• Viviparous Animals:
1. Animals that give birth to living young ones.
2. The embryo develops internally inside the mother's uterus, nourished via the placenta.
Examples: Humans, dogs, cows, whales.