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Unlock This CourseCells are the basic building blocks of all living things. From the tiniest bacteria to massive blue whales, every organism is made up of one or more cells. Understanding cell structure is crucial for marine science because it helps us understand how marine organisms function, adapt and survive in their underwater environments.
Key Definitions:
Light microscopes use visible light and lenses to magnify specimens. They can magnify objects up to 1000 times their actual size and are perfect for observing living cells. Most school laboratories use compound light microscopes with multiple objective lenses.
There are two main types of cells: prokaryotic (without a nucleus) and eukaryotic (with a nucleus). Marine environments contain both types, from simple bacteria to complex algae and fish cells.
Prokaryotic cells are simpler and smaller than eukaryotic cells. They don't have a membrane-bound nucleus and their genetic material floats freely in the cytoplasm. Many marine bacteria are prokaryotes and play vital roles in ocean ecosystems.
Provides structure and protection. Made of peptidoglycan in bacteria.
Gel-like substance where chemical reactions occur and organelles float.
DNA that controls cell activities, not enclosed in a nucleus.
Eukaryotic cells are more complex and contain membrane-bound organelles. All marine plants, animals and many microorganisms have eukaryotic cells. These cells can be highly specialised for different functions.
Marine animal cells, like those found in fish, dolphins and sea anemones, share common features:
Controls cell activities and contains DNA. Often called the "control centre" of the cell.
Powerhouses that produce energy (ATP) through cellular respiration.
Tiny structures that make proteins essential for cell function and growth.
Diatoms are microscopic marine algae with beautiful glass-like cell walls called frustules. These single-celled organisms are responsible for producing about 20% of the world's oxygen. Under a microscope, their intricate patterns and shapes are stunning examples of natural engineering. Their cell walls are made of silica and come in thousands of different designs, each species having its own unique pattern.
Marine plants like seaweeds and sea grasses have additional structures that animal cells don't have. These adaptations help them survive in saltwater environments.
Plant cells have several structures that make them different from animal cells, allowing them to photosynthesise and maintain their shape in marine environments.
Contain chlorophyll and carry out photosynthesis, converting sunlight into chemical energy.
Rigid structure made of cellulose that provides support and protection.
Large storage compartment that maintains cell shape and stores water and nutrients.
Proper microscopy technique is essential for observing cell structures clearly. Understanding how to prepare specimens and use microscopes effectively will help you explore the microscopic world of marine life.
Follow these steps to observe cells effectively:
Total magnification = Eyepiece magnification × Objective lens magnification. For example: 10x eyepiece × 40x objective = 400x total magnification. This means the image appears 400 times larger than the actual specimen.
Proper specimen preparation is crucial for clear observation. Different techniques are used depending on what you want to observe:
Living specimens in water. Great for observing movement and natural cell behaviour.
Adding dyes like iodine or methylene blue to highlight specific cell structures.
Very thin slices of specimens that allow light to pass through for clear viewing.
Marine organisms have evolved amazing cell adaptations to survive in saltwater environments. These specialisations help them deal with salt concentration, pressure and unique feeding requirements.
Shark skin contains specialised cells that produce tiny tooth-like scales called denticles. Under a microscope, these cells show incredible organisation. The denticles reduce drag as sharks swim and prevent bacterial growth. Scientists study these cells to develop better swimsuits and ship hull coatings. Each denticle is made by multiple cells working together, showing how cell cooperation creates complex structures.
Marine cells have special features that help organisms survive in saltwater:
When studying marine biology, you'll often observe living cells from seawater samples, algae, or small marine organisms. These observations provide insights into how marine life functions at the cellular level.
Pond weed (Elodea), sea lettuce, marine diatoms and small crustacean cells are excellent for microscopy. They're easy to observe and show clear cellular structures that demonstrate key biological principles.
When observing marine cells under a microscope, focus on identifying these key features:
Understanding the limitations of light microscopy helps you interpret observations correctly and know when other techniques might be needed.
Light microscopes can't resolve details smaller than about 0.2 micrometers. This means some cellular structures, like individual ribosomes or detailed membrane structures, can't be seen clearly. For these, electron microscopes are needed, though they can't observe living cells.
The human eye can only distinguish objects about 0.1mm apart. A light microscope improves this to about 0.0002mm (0.2 micrometers). That's like being able to see a tennis ball from 100 kilometres away! This incredible magnification opens up the hidden world of cells that would otherwise be invisible to us.