In-Depth Notes on Viruses, Prokaryotes, and Plant Biology

Viruses

• Definition:
  • Extremely small infectious agents.
  • Not living, not cellular.
  • Lack metabolism; cannot reproduce independently (require a host).
  • Obligate parasites.
• Size Range:
  • Approximately 100 nanometers.
• Diversity:
  • Millions of species of viruses.

Virus Life Cycles

• Lytic Cycle:
  1. Phage attaches to a host cell and injects its DNA.
  2. New phage DNA and proteins are assembled into phages.
  3. The cell lyses (bursts), releasing new phages.
• Lysogenic Cycle:
  1. Phage DNA circularizes and integrates into the bacterial chromosome as a prophage.
  2. The bacterium reproduces normally, copying the prophage into daughter cells.
  3. Occasionally, the prophage exits the bacterial chromosome and initiates a lytic cycle.
• Factors Influencing Cycle Choice:
  • Certain environmental factors determine if the lytic or lysogenic cycle is induced.

Viral Diseases & Natural Remedies

• Historical Viruses:
  • Smallpox (notable for creating beauty marks).
  • H1N1 (similar to Spanish flu).
• Natural Treatments:
  • Sleep, rest, hydration, and isolation to aid recovery.
• Vaccinations:
  • Synthetic viruses introduced to stimulate immune response (e.g., Jonas Salk’s polio vaccine).

Prokaryotic Domains

• Domains:
  • Bacteria and Archaea are prokaryotic organisms (lack a nucleus).
• Characteristics:
  • Very small, simple structures.
  • Shapes:
  • Cocci (spherical)
  • Bacilli (rod-shaped)
  • Spirilla (spiral).
• Reproduction:
  • Binary fission
  • Conjugation (sharing genetic material).

Domain Archaea & Bacteria

• Archaea:
  • Extremophiles, live in extreme habitats (e.g., hot springs).
• Bacteria:
  • Examples: Cyanobacteria (photosynthesizers), mutualistic relationships with other organisms.
• Antibiotics:
  • Can control some bacterial strains.

Kingdom Eukarya

• Definition:
  • Eukaryotic cells contain a nucleus and organelles.
• Plant Evolution:
  • Transition from aquatic (algae) to terrestrial living.
  • Examples: Freshwater Charophyceans as ancestral algae.

Plant Classification

• Major Categories:
  • Non-vascular plants (Bryophytes - mosses, liverworts).
  • Vascular plants (Tracheophytes):
  • Seedless (ferns)
  • Seed plants (Gymnosperms - naked seeds, and Angiosperms - flowering plants).
• Plant Structures:
  • Cell Wall: Made of cellulose.
  • Xylem & Phloem:
  • Xylem transports water; Phloem transports sugars.

Plant Life Cycles

• Generational Alternation:
  • Haploid (n) and Diploid (2n) cycles.
  • Example: Fern life cycle showing alternation between sporophyte and gametophyte generations.

Spermatophytes - Seed Plants

• Seeds:
  • Contain embryo, surrounded by parent DNA in a seed coat.
  • Capable of dormancy until environmental conditions are suitable for growth.
• Pollen:
  • Transported by wind or animals (e.g., insects).

Angiosperms (Phylum Anthophyta)

• Flowers:
  • Reproductive structures that attract pollinators.
  • Key components: Carpel (female) and Stamen (male).
• Pollination:
  • Mechanisms include wind, insects, and animals to facilitate fertilization.
  • Double fertilization process (forming zygote and endosperm) during seed development.
  • Distinction between monocots (1 cotyledon) and dicots (2 cotyledons) based on leaf venation patterns.

Seed Dispersal

• Mechanism:
  • Fruits or seed pods serve as vehicles for dispersal (e.g., animals consuming fruit and processing seeds).
  • Misconception: Strawberries have their seeds on the outside,
  • Vectors (animals, wind) assist in the spread of seeds.