Human Development and Plant Reproduction

Implantation

• The blastocyst attaches to the uterine lining, a critical step in early pregnancy.
• Allows the embryo to receive nutrients and oxygen from the mother's blood.

Gastrulation

• The inner cell mass of the blastocyst undergoes complex changes.
• Establishes the three primary germ layers: ectoderm, mesoderm, and endoderm.
• These germ layers will give rise to all tissues and organs of the body.

Embryonic Stage

• Lasts from the third through the eighth week of pregnancy.
• Development of major organs and organ systems.
• Formation of the neural tube, which will eventually become the brain and spinal cord.
• Development of the limbs and eyes

Fetal Stage

• Lasts from the ninth week of pregnancy until birth.
• Continued growth and development of all organs and organ systems.
• Development of the senses.
• Maturation of the lungs and other organs in preparation for birth.

Plant Reproduction

• Angiosperm: Flowering plants, having seeds enclosed within their fruit.
• Gymnosperm: No flowers or fruits, have naked seeds on the surface of their leaves. Example: conifers, ginkgo, gnetophytes.

Flower Structure

• Stamen: Male portion, made up of anther and filament.
• The anther produces haploid pollen grains by meiosis.
• Carpel/Pistil: Female portion, consisting of stigma, style, and ovary.
• Stigma: Sticky, traps pollen.
• Style: Hollow tube connecting stigma and ovary.
• Ovary: Produces female gametes.

Monoecious Plants

• Stamens and pistils occur on separate flowers, but the same plant.
• Examples: Cucurbita maxima (Pumpkin), Carica papaya (Papaya)

Dioecious Plants

• Staminate and pistillate flowers occur on separate plants.

Gametogenesis

• Formation of Male Gametophyte:
  • Inside the anthers' microsporangia, male gametophytes divide by meiosis to generate haploid microspores.
  • Microspores undergo mitosis and give rise to pollen grains.
  • Pollen grain contains two cells: generative and tube cell.
• Formation of Female Gametophyte:
  • The ovule inside the ovary contains the megasporangium.
  • Within each megasporangium, a megasporocyte undergoes meiosis, generating four megaspores.

Pollination

• Transfer of pollen from an anther to a receptive stigma.
• Agents: animals, wind, water, humans.
• Self-pollination: Pollen from the same flower.
• Cross-pollination: Pollen from a different flower.

Fertilization

• One sperm and egg combine, forming a diploid zygote, the future embryo.
• Double Fertilization: The other sperm fuses with the 2n polar nuclei, forming a triploid cell, which becomes the endosperm (food reserve).

Embryonic Development

• Embryogenesis occurs as a result of single or double fertilization.
• Gives rise to the plant embryo and the endosperm.

Seed Development

• Ovules become seeds.
• Ovary matures into a fruit.

Seed Germination and Growth

• Resumption of growth and development after a period of seed dormancy.
• Epigeal germination: Germination above the ground.
• Hypogeal germination: Germination under the ground.

Modes of Nutrition

• Autotrophic: Producers, can produce their own food.
• Heterotrophic: Consumers, cannot produce their own food.

Plant Nutrition: Photosynthesis

• Process of converting light energy to chemical energy for food production.
• Two stages:
  • Light-dependent reaction.
  • Light-independent reaction (Calvin cycle).
• Equation: 6CO2 + 6H2O + sunlight  C6H12O6 + 6O2

Plant Parts Involved in Photosynthesis

• Leaves: Site of photosynthesis.
• Stomata: Exchange of oxygen and carbon dioxide.
• Chloroplast: Contains chlorophyll, which traps sunlight.
  • Thylakoid membrane: Light-dependent reactions.
  • Stroma: Light-independent reactions (Calvin cycle).

Feeding Mechanism of Carnivorous Plants

• Insect-eating plants capture and digest prey through pitfalls and traps.

Pitcher Plant

• Gives a sweet odor to attract prey.
• Trapping Mechanisms:
  • Slip-and-fall mechanism: Insects land on the rim or lid, fall into the pitcher.
  • Slippery waxy coating, downward-facing hairs guide insects inward.
  • Constricted entrance prevents exit.
• Attracting Mechanisms:
  • Visual: Bright color, shiny surfaces, nectar on the lid and rim.
  • Chemical: Sweet nectar like scent.
  • Structural: Slippery waxy coating.