Biology Reproduction Overview

Reproduction Overview

• Reproduction is a biological process creating new individuals to ensure species survival and prevent extinction.
• Two main types exist: sexual and asexual.

Sexual Reproduction

• Involves two parents.
• Genetic material combines.
• Gametes (sex cells) are produced by meiosis.
• Gametes fuse during fertilization to form a zygote.

Asexual Reproduction

• Involves one parent.
• Offspring have the same genetic makeup as the parent.
• No gametes are involved.
• Process occurs via mitosis.

Differences Between Asexual and Sexual Reproduction

• Asexual:
  • No gametes needed.
  • One parent needed.
  • No variation in offspring (identical).
  • Happens quickly.
  • Many offspring produced.
  • Less energy required.
• Sexual:
  • Gametes needed.
  • Two parents needed.
  • Variation in offspring.
  • Happens slowly.
  • Few offspring produced.
  • More energy required.

Advantages of Asexual Reproduction

• Fast population growth in favorable conditions.
• Requires less energy.
• No need to find a mate.
• Offspring can easily adapt to the environment since they are identical to their parent.
• Few mutations occur.

Disadvantages of Asexual Reproduction

• No genetic diversity.
• Inability to adapt to changing environments.
• May lead to extinction.

Advantages of Sexual Reproduction

• Variation in offspring allows for better adaptation to changing environments.

Disadvantages of Sexual Reproduction

• Longer process due to gamete production.
• Fewer offspring produced, reducing survival chances.
• More energy is required.

Importance of Asexual Reproduction in Agriculture

• Cloning plants with desired characteristics creates identical offspring.
• Saves time and money by avoiding seed germination wait.
• Allows for faster crop production.
• Leads to the continuous production of better quality crops by allowing farmers to select desirable qualities.

Asexual Reproduction in Plants

• Also known as vegetative propagation.
• Part of the parent plant separates and grows independently.
• Common artificial methods include stem cuttings, grafting, and tissue culture.

Stem Cuttings

• Plant stems are cut into pieces.
• Placed in furrows and covered with soil.
• Pieces must include nodes and an internode.
• Roots and shoots grow from nodes.

Grafting

• Used for plants such as fruit trees to produce identical offspring from a single parent plant.
• Piece of a plant with desirable features is grafted onto a strong, resistant plant.
• A cut stem (scion) of one plant is attached to the rootstock of another plant (stock).

Tissue Culture

• Isolating cells with desired traits from a parent plant.
• Placing them in a sterile nutrient medium (often agar).
• Cells divide by mitosis to form plantlets.
• Plantlets are planted in soil.

Flowers as Reproductive Organs in Plants

• Flowers are the reproductive organs in flowering plants (angiosperms).
• Hermaphrodite flowers have both male and female parts on the same flower.
• Unisexual flowers have separate male and female flowers.

Floral Whorls

• Flowers have four floral whorls: sepals, petals, stamens, and pistils.

Structure of a Flower: Pistil

• Female reproductive structure.
• Stigma: sticky tip that traps pollen.
• Style: slender tube transporting pollen to the ovary.
• Ovary: contains ovules.
• Ovule: contains the egg cell, developing into a seed after fertilization.

Structure of a Flower: Stamen

• Male reproductive structure.
• Filament: thin stalk supporting the anther.
• Anther: knob-like structure producing pollen.
• Pollen: contains microscopic cells that become sperm cells.

Structure of a Flower: Sepals

• Encloses and protects the flower before it blooms.

Structure of a Flower: Petals

• Usually colorful and scented to attract pollinators.

Pollination and Fertilization

• Pollination: Pollen transfer from the anther to the stigma.
• Necessary for fertilization.
• Cross-pollination: Pollen from one flower to another on a different plant.
• Self-pollination: Pollen from one flower to the stigma of the same flower, or other flowers on the same plant.

Cross Pollination Steps

• Pollen from the anther is caught by the stigma.
• Travels through the style to ovules in the ovary.
• Via pollen tube.
• Result: fertilization.

Fertilization

• Pollen grain lands on the sticky stigma and develops a pollen tube.
• Pollen tube grows down the style to the ovary; fertilization occurs.
• Zygote produced.
• Ovary becomes fruit, ovules become seeds.

Seeds as Food Source

• Seeds store lots of food and are a vital food source.
• Categorized as grains, legumes, and nuts.
• Crucial as staple diets globally due to their affordability and nutritional value.

Seed Banks

• Used to preserve seeds and maintain biodiversity.
• Conserve endangered or extinct plant species.
• Rehabilitate damaged or destroyed habitats.
• Cultivate plants overused or develop new hybrids.
• Preserve endemic species.