The document provides an overview of cell structure and function at multiple levels of organization. It discusses that cells are the basic unit of structure and function in living things. It then describes several organelles and structures within plant and animal cells and their specific functions, including the nucleus, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, chloroplasts, cytoskeleton, and cell wall in plant cells. Advanced microscopy techniques are also summarized that allow visualization of cellular structures at different magnifications.

5. Differential-interference-contrast (Nomarski). Like phase-contrast microscopy, it uses optical modifications to exaggerate differences in density, making the image appear almost 3D. Fluorescence. Shows the locations of specific molecules in the cell by tagging the molecules with fluorescent dyes or antibodies. These fluorescent substances absorb ultraviolet radiation and emit visible light, as shown here in a cell from an artery. Confocal. Uses lasers and special optics for “ optical sectioning” of fluorescently-stained specimens. Only a single plane of focus is illuminated; out-of-focus fluorescence above and below the plane is subtracted by a computer. A sharp image results, as seen in stained nervous tissue (top), where nerve cells are green, support cells are red, and regions of overlap are yellow. A standard fluorescence micrograph (bottom) of this relatively thick tissue is blurry. 50 µm 50 µm (d) (e) (f)

12. Figure 6.6 A, B (b) A thin section through the bacterium Bacillus coagulans (TEM) Pili: attachment structures on the surface of some prokaryotes Nucleoid: region where the cell’s DNA is located (not enclosed by a membrane) Ribosomes: organelles that synthesize proteins Plasma membrane: membrane enclosing the cytoplasm Cell wall: rigid structure outside the plasma membrane Capsule: jelly-like outer coating of many prokaryotes Flagella: locomotion organelles of some bacteria (a) A typical rod-shaped bacterium 0.5 µm Bacterial chromosome

61. Irreducible Complexity or WPP of organ systems and body tissues Irreducible complexity (Popularized by Michael Behe) is the argument that certain biological systems are absolutely too complex to have evolved naturally from simpler, or "less complete" predecessors. An “irreducibly complex system" is defined as "one that could not function if it were any simpler", and therefore, could not possibly have been formed by successive additions to a precursor system with the same functionality. WPP – Whole Package Phenomenon