Marine Biology Notes

Marine organisms are profoundly influenced by various changes occurring in ocean environments. Evolution compels many organisms to adapt, often beginning at the cellular level, demonstrating the interconnectedness of life forms and their surroundings.

Light Microscopes:

• A light microscope allows for the examination of specimens placed on a microscope slide, which is critical in biological studies.

• Magnification Calculation: Magnification is determined by multiplying the magnification power of the objective lens by that of the eyepiece lens.

• Dye/Stains Used: Specimens often require staining to enhance contrast, with common dyes being methylene blue for animal cells and iodine for plant cells to highlight organelles and structures.

• Resolution: Represents the smallest distance between two distinct points that can be identified clearly. The resolving power of a light microscope is limited by the wavelength of light used, achieving a best resolution of approximately 200nm, which limits the details visible in small cellular structures.

Electron Microscopes:

• Unlike light microscopes, electron microscopes utilize a focused beam of electrons to achieve significantly greater detail, offering resolving power below 1nm, which allows visualization of much smaller cellular components (up to 200,000x magnification).

• Electron microscopes consist of electromagnet lenses that form high-resolution images displayed on a computer screen.

• To prevent interference from air molecules, specimens are prepared in a vacuum, and common staining materials are substituted with heavy metals such as lead or osmium to enhance electron contrast.

Comparison of Light and Electron Microscopes:

• Light Microscope:

  • Generally lower resolution, allowing for ease of use and accessibility.

  • More affordable for educational and field applications.

  • Portable and can easily be moved for on-site studies.

  • Less harsh staining techniques enable the observation of living specimens.

  • Provides the advantage of viewing specimens in color. Less technical skill is required for operation and maintenance.

• Electron Microscope:

  • Delivers superior resolution, revealing structures down to the molecular level.

  • Higher costs associated with purchase and maintenance due to complex technology.

  • Typically requires a fixed location due to size and operational needs.

  • More aggressive sample preparation can damage living cells, thus these microscopes cannot observe live samples directly.

  • Limited access to color representation as images produced are monochromatic. Requires skilled technicians to operate effectively and interpret results appropriately.

Plant and Animal Cells:

• Animal Cells:

  • Comprise a cell membrane that surrounds the cytoplasm, providing structural support.

  • Contain organelles such as mitochondria (powerhouses of energy), centrioles (involved in cell division), ribosomes (protein synthesis), and more.

  • Possess specific structures like the nuclear membrane, nucleus (which houses genetic material), nucleolus, chromosomes, vacuoles (smaller than in plants), and the Golgi apparatus (involved in protein processing).

  • Often contain flagella, which provide mobility in certain types of cells such as sperm.

• Plant Cells:

  • Enclosed by a rigid cell wall that grants stability and protection.

  • Carry out photosynthesis due to the presence of chloroplasts, which contain chlorophyll.

  • Include all organelles found in animal cells, but generally have larger vacuoles for storage and support. Vacuoles are critical for maintaining turgor pressure within the cell.

Organelles of a Cell:

• Includes key components such as the Cell Surface Membrane, Nucleus, Rough and Smooth Endoplasmic Reticulum, Ribosomes, Golgi Apparatus, Mitochondria, Chloroplasts, the Cell Wall, and Large Vacuoles. Each of these organelles has vital functions that contribute to the life and health of the cell, ultimately influencing the overall function of the organism.

Cell Surface Membrane:

• Acting as a protective barrier, the cell surface membrane is semi-permeable, allowing selective passage of substances in and out.

• It is composed primarily of phospholipids, proteins, and cholesterol -

  • Phospholipids: Comprised of a hydrophilic (water-attracting)