Describe prokaryotic and eukaryotic cells with diagrams and differentiate them in tabular form.

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2. a. Describe prokaryotic and eukaryotic cells with diagrams.

• Prokaryotic Cells: These are the simplest and most ancient forms of life. They lack a true nucleus and other membrane-bound organelles. Their genetic material (DNA) is located in a region called the nucleoid within the cytoplasm. Prokaryotic cells typically have a cell wall, a plasma membrane, and ribosomes. Examples include bacteria and archaea. (A typical diagram would show a cell wall, cell membrane, cytoplasm, ribosomes, and a nucleoid region containing DNA, possibly with a flagellum or pili).
• Eukaryotic Cells: These are more complex cells characterized by the presence of a true nucleus, which encloses their genetic material, and various membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, chloroplasts in plants). These organelles perform specialized functions within the cell. Examples include plant cells, animal cells, fungi, and protists. (A typical diagram would show a nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, cytoplasm, and a cell membrane, with a cell wall and chloroplasts if it's a plant cell).

2. b. In a tabular form, differentiate between prokaryotes and eukaryotes.

Feature	Prokaryotic Cell	Eukaryotic Cell
Nucleus	Absent; DNA in nucleoid region	Present; DNA enclosed within a nuclear membrane
Membrane-bound organelles	Absent	Present (e.g., mitochondria, ER, Golgi)
DNA	Circular, usually single chromosome	Linear, multiple chromosomes
Size	Generally smaller ($0.1-5 \mu\text{m}$)	Generally larger ($10-100 \mu\text{m}$)
Cell Wall	Present (peptidoglycan in bacteria)	Present in plants (cellulose) and fungi (chitin); absent in animals
Ribosomes	Smaller ($70S$)	Larger ($80S$)
Reproduction	Asexual (binary fission)	Asexual (mitosis) and sexual (meiosis)
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

3. Write short note on the following

• a. Calcium oxalate crystals: These are metabolic byproducts found in many plant cells, often in the vacuoles. They occur in various shapes, including raphides (needle-shaped), druses (spherical aggregates), prisms (single crystals), and styloids (elongated prisms). They play roles in plant defense against herbivores and calcium regulation.
• b. Calcium carbonate crystals: These crystals are typically found as cystoliths, which are outgrowths of the cell wall into the lumen of epidermal cells, particularly in plants like those in the Urticaceae (nettle) and Moraceae (fig) families. They are usually grape-like or club-shaped and are thought to be involved in light scattering and defense.
• c. Silica: Silica (silicon dioxide, $\text{SiO}_2$) is deposited in various forms within plant tissues, especially in the epidermal cells and cell walls of grasses (Poaceae) and horsetails (Equisetaceae). It provides structural rigidity, enhances resistance to pests and diseases, and contributes to the abrasive nature of some plant surfaces.

4. Describe the various types of trichomes found in plants with example(s) of each

Trichomes are epidermal outgrowths of plants, varying widely in structure and function.

• Unicellular Trichomes: Single-celled hairs, often elongated.
  • Example: Cotton fibers (from Gossypium species).
• Multicellular Trichomes: Composed of multiple cells, which can be uniseriate (single row of cells) or multiseriate (multiple rows).
  • Example: Stinging hairs of nettle (Urtica dioica).
• Glandular Trichomes: Possess a secretory head, often on a stalk, that produces and releases various substances (e.g., essential oils, resins, mucilage).
  • Example: Mentha species (peppermint, spearmint) which produce menthol.
• Non-glandular Trichomes: Do not secrete substances; primarily serve protective functions, reducing water loss or deterring herbivores.
  • Example: Stellate (star-shaped) hairs on Verbascum species (mullein).
• Branched Trichomes: Hairs that divide into multiple arms or branches.
  • Example: Found in Artemisia species.
• Scales (Peltate Trichomes): Flattened, shield-like structures that lie parallel to the epidermal surface.
  • Example: Found on the leaves of Olea europaea (olive).

5. Explain with an example how to calibrate an eyepiece micrometer

Calibrating an eyepiece micrometer (EM) is essential to determine the actual length represented by each of its divisions at different magnifications.