6.1 Plant Reproduction
Asexual Reproduction
Produces genetically identical offspring from one parent (no genetic recombination).
Plants reproduce asexually through vegetative parts: stems, roots, leaves.
Occurs naturally or artificially.
Natural Vegetative Reproduction
Vegetative organs modified for reproduction: runners, tubers, corms, rhizomes, bulbs,
leaves.
Examples:
Runners (stolons): horizontal above-ground stems (e.g., strawberry).
Rhizomes: horizontal underground stems (e.g., ginger, turmeric).
Tubers: swollen underground stems for storage and reproduction (e.g., potato).
Bulbs: short vertical underground stems with modified leaves (e.g., garlic, lily).
Modified leaves: e.g., Kalanchoe produces plantlets on leaf edges.
Vegetative reproduction is common in unstable environments; faster than sexual
reproduction.
Artificial Propagation
Human-assisted asexual methods.
Cutting: plant parts rooted to produce clones (e.g., sugarcane, pineapple).
Grafting: stem piece (scion) attached to root-bearing plant (stock).
Tissue culture: growth of plant cells in sterile media; methods include somatic
embryogenesis, meristematic culture, anther culture.
Sexual Reproduction in Flowering Plants (Angiosperms)
Involves fusion of male gametophyte (pollen grains) and female gametophyte (embryo sac).
Flowers contain:
Sepals (calyx): protect bud.
Petals (corolla): attract pollinators.
, Stamens (male): filament + anther (produces pollen).
Carpels (female): stigma, style, ovary (contains ovules).
Stages of Sexual Reproduction
Pollen and Egg Formation:
Microspore mother cells → meiosis → pollen grains (generative and tube cells).
Megaspore mother cell → meiosis → embryo sac with 8 nuclei.
Pollination: Transfer of pollen to stigma.
Self-pollination: pollen same plant.
Cross-pollination: pollen different plant; promotes genetic diversity.
Agents: wind, water, animals (bees, bats, birds).
Fertilization:
Pollen tube delivers two sperm cells; one fertilizes egg, another fuses with polar nuclei
(double fertilization).
Forms zygote and triploid endosperm.
Fruit Formation: Ovary ripens to fruit protecting seeds and aiding dispersal.
Seed Dispersal Methods
Wind (e.g., dandelion).
Water (e.g., coconut).
Animals (e.g., fleshy fruits eaten and seeds excreted).
Explosion or mechanical (e.g., pea pods).
Seed Structure and Germination
Seed contains embryo, food supply, seed coat (testa).
Germination needs water, oxygen, warmth.
Embryo grows into new plant; cotyledons start photosynthesis after emergence.
Lesson 6.2 Animal Reproduction
Asexual Reproduction in Animals
Single parent produces offspring without gamete fusion.
Asexual Reproduction
Produces genetically identical offspring from one parent (no genetic recombination).
Plants reproduce asexually through vegetative parts: stems, roots, leaves.
Occurs naturally or artificially.
Natural Vegetative Reproduction
Vegetative organs modified for reproduction: runners, tubers, corms, rhizomes, bulbs,
leaves.
Examples:
Runners (stolons): horizontal above-ground stems (e.g., strawberry).
Rhizomes: horizontal underground stems (e.g., ginger, turmeric).
Tubers: swollen underground stems for storage and reproduction (e.g., potato).
Bulbs: short vertical underground stems with modified leaves (e.g., garlic, lily).
Modified leaves: e.g., Kalanchoe produces plantlets on leaf edges.
Vegetative reproduction is common in unstable environments; faster than sexual
reproduction.
Artificial Propagation
Human-assisted asexual methods.
Cutting: plant parts rooted to produce clones (e.g., sugarcane, pineapple).
Grafting: stem piece (scion) attached to root-bearing plant (stock).
Tissue culture: growth of plant cells in sterile media; methods include somatic
embryogenesis, meristematic culture, anther culture.
Sexual Reproduction in Flowering Plants (Angiosperms)
Involves fusion of male gametophyte (pollen grains) and female gametophyte (embryo sac).
Flowers contain:
Sepals (calyx): protect bud.
Petals (corolla): attract pollinators.
, Stamens (male): filament + anther (produces pollen).
Carpels (female): stigma, style, ovary (contains ovules).
Stages of Sexual Reproduction
Pollen and Egg Formation:
Microspore mother cells → meiosis → pollen grains (generative and tube cells).
Megaspore mother cell → meiosis → embryo sac with 8 nuclei.
Pollination: Transfer of pollen to stigma.
Self-pollination: pollen same plant.
Cross-pollination: pollen different plant; promotes genetic diversity.
Agents: wind, water, animals (bees, bats, birds).
Fertilization:
Pollen tube delivers two sperm cells; one fertilizes egg, another fuses with polar nuclei
(double fertilization).
Forms zygote and triploid endosperm.
Fruit Formation: Ovary ripens to fruit protecting seeds and aiding dispersal.
Seed Dispersal Methods
Wind (e.g., dandelion).
Water (e.g., coconut).
Animals (e.g., fleshy fruits eaten and seeds excreted).
Explosion or mechanical (e.g., pea pods).
Seed Structure and Germination
Seed contains embryo, food supply, seed coat (testa).
Germination needs water, oxygen, warmth.
Embryo grows into new plant; cotyledons start photosynthesis after emergence.
Lesson 6.2 Animal Reproduction
Asexual Reproduction in Animals
Single parent produces offspring without gamete fusion.
