🌟 Important Words & Concepts Explained

Here are the key terms and concepts that students need to understand before or during the lecture on Domain Bacteria and Domain Eukarya. Each concept is clearly explained in simple, student-friendly language to build strong foundational knowledge.

🔹 1. Domain

Definition: The highest level in biological classification, above kingdom.
Context: Life is divided into three domains — Archaea, Bacteria, and Eukarya.

🔹 2. Prokaryote

Definition: A simple cell that does not have a true nucleus or membrane-bound organelles.
Found in: Bacteria and Archaea.

🔹 3. Eukaryote

Definition: A complex cell with a nucleus and membrane-bound organelles.
Found in: Domain Eukarya — includes plants, animals, fungi, and protists.

🔹 4. Peptidoglycan

Definition: A strong, net-like molecule made of sugars and amino acids.
Function: Gives structure and protection to the bacterial cell wall.
Not found in: Archaea or Eukarya.

🔹 5. Plasmid

Definition: A small, circular piece of DNA in bacteria that is separate from the main chromosome.
Function: Helps in gene transfer, adaptation, and antibiotic resistance.

🔹 6. Binary Fission

Definition: A form of asexual reproduction in prokaryotes. One cell splits into two identical daughter cells.
Used by: Bacteria and Archaea.

🔹 7. Autotrophs and Heterotrophs

Autotrophs: Make their own food (e.g., photosynthetic bacteria).
Heterotrophs: Get food from other organisms (e.g., decomposers).

🔹 8. Bacterial Shapes

Types:

  • Cocci: Round/spherical
  • Bacilli: Rod-shaped
  • Spirilla: Spiral-shaped
  • Vibrios: Comma-shaped

🔹 9. Cell Arrangements

Examples:

  • Diplococci: Pairs
  • Streptococci: Chains
  • Staphylococci: Clusters
  • Arrangement helps identify species and function.

🔹 10. Flagella

Definition: Long, whip-like tails used for movement in many bacteria.

🔹 11. Pili and Fimbriae

Definition: Short, hair-like structures on bacteria.
Function: Help in attachment and exchange of genetic material between cells.

🔹 12. Respiration in Bacteria

Types:

  • Obligate aerobes – Need oxygen
  • Obligate anaerobes – Can’t tolerate oxygen
  • Facultative anaerobes – Can live with or without oxygen
  • Microaerophiles – Need a little oxygen
  • Aerotolerant anaerobes – Don’t use oxygen but can tolerate it
    Some perform fermentation to produce energy without oxygen.

🔹 13. Extremophiles

Definition: Organisms that live in extreme environments (heat, salt, acid).
Example: Thermophilic (heat-loving) or halophilic (salt-loving) bacteria.

🔹 14. Pathogenicity

Definition: The ability of an organism (like bacteria) to cause disease.

🔹 15. Symbiosis

Definition: A close relationship between two different organisms.
Types:

  • Mutualism: Both benefit
  • Commensalism: One benefits, other is unaffected

🔹 16. Eukaryotic Cell

Definition: A cell with:

  • A true nucleus
  • Organelles (mitochondria, chloroplasts, ER, Golgi apparatus)
  • Cytoskeleton for shape and movement

🔹 17. Linear Chromosomes

Definition: DNA in eukaryotes is arranged in multiple straight strands, not circular like in bacteria.

🔹 18. Histones

Definition: Special proteins that help package and organize DNA in eukaryotes.

🔹 19. Mitosis and Meiosis

  • Mitosis: Asexual reproduction in eukaryotes — creates identical cells.
  • Meiosis: Sexual reproduction — creates genetic variation.

🔹 20. Endosymbiosis

Definition: The theory that some organelles (like mitochondria and chloroplasts) were once free-living bacteria that were taken inside another cell and became part of it.
Importance: Explains the origin of eukaryotic cells.

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