✓Lab 3

stereoscopic microscope (anatomy)

-Used for viewing and manipulating relatively large objects. Similar to compound mostly, but differs in a few ways: 1. Depth of field much greater, so objects are seen in three dimensions. 2. Light source can be directe down onto as well as up through an object, which permits the viewing of objects too thick to transmit light. Light directed down on the object is called reflected or incident light. Light passing through the object is called transmitted light. -Anatomy of stereoscopic microscope: Oculars are attached to a binocular head (may be movable). There are magnification control knobs on either side of the arm. The objective lense is below that, with the focus knob located on the arm attached to the base. The incident light that projects downward is internal. The transmitted light is located on the stage, and the light adjustment is plus/minus buttons on the stage. Calculate total magnification (lens x eyepiece). Eyepiece for compound is 10x, multiply that by the objective lens in use.

Volvox

An aquatic green alga that is common in aquaria, ponds, and lakes. Used to be described as colonial/unicellular, but now, they are considered to be multicellular. To prepare the slide, prepare a wet mount but place several glass chips on the slide to prevent the volvox from being crushed. The cells should lie in a transparent matrix forming a large hollow sphere. The approximately 500 to 50,000 (depending on species) nonreproductive somatic cells are permanently united by cytoplasmic connections. The cells have chloroplasts and flagella that beat in a coordinated motion to move the colony like a ball. During asexual reproduction, certain cells in the sphere (reproductive) enlarge and migrate inward to become daughter colonies.

How to use compound

Clean the lenses--ocular, objective, condenser (use lense paper moistened with di water, dry with lense paper). Plug in microscope, turn on light to mid-range. Rotate to 4X. Wipe slide if pre-prepared. Move the oculars to your interpupillary distance (should not see a double image). Raise condenser to highest position, fully close iris diaphragm. Slowly lower condense until gain is gone. Slowly open diaphragm until entire field of view is illuminated. Rotate to 10X. Slowly focus upward with coarse adjustment until in rough focus, the switch to fine adjustment. Don't turn the fine adjustment more than twice. If the image does not come into focus, return to 10X and refocus using coarse adjust. For binocular microscopes, cover left eye, use fine adjust knob to focus the fixed (right) ocular until in max focus. Then cover right eye and using the diopter ring on the left ocular, bring the image into focus. Can increase or decrease contrast by adjusting iris diaphragm opening. Max amount of light provides little contrast. Adjust the aperture until the image is sharp. Never focus with the coarse adjustment knob when you are using the high-power objective.

Scenedesmus

Multicellular and usually exists in colonies. It is an aquatic alga that usually occurs in simple colonies of four cells connected by the cell wall. Each cell has its own nucleus (center), vacuoles are the transparent spheres that tend to occur at either end of the cells. There is chloroplast scattered throughout, and a spine attached to each corner of the outside of the cells. The cells always occur in groups of 4-8 cells, and are permanently united.

Protococcus

Multicellular. It is a terrestrial green alga that forms loose aggregates on the bark of trees (north sides, aka moss). Supposed to use a dissecting needle to brush off of the bark into a drop of water on a clean microscope slide. The cells are aggregates: the size of the cell groupings is random, and there are no permanent connections between cells. Each cell is surrounded by a cell membrane and an outer cell wall.

Trichonympha

Unicellular organisms, but form colonies. They are termite gut flagellates: they inhabit the intestine of termites and digest wood. Termites cannot digest food without trichonympha, and trichonympha cannot survive outside of the termite. Trichonympha are pear-shaped, and the flagella at the tip makes it look like it's wearing a wig. The nucleus is located towards the tip. Wood particles may be visible at the base.

Amoebas

Unicellular. They have a cell membrane that separates the organism from its surroundings. Ectoplasm is the thin, transparent layer of cytoplasm directly beneath the cell membrane. Endoplasm is the granular cytoplasm containing the cell organelles. The nucleus is grayish and football-shaped, somewhat granular in appearance. Contractile vacuoles are clear, spherical vesicles of varying sizes that gradually enlarge as they fill with excess water. They serve an excretory function. Food vacuoles are small, dark, irregularly shaped vesicles within the endoplasm, which contain undigested food particles. Pseudopodia "false feet" are projections of the cytoplasm. Used for locomotion as well as for trapping food (phagocytosis).

Compound Binocular Light Microscope (anatomy)

look through oculars (10x magnification). Oculars attached to head, which is attached to the base of the microscope by the arm. The revolving nosepiece has 4 objective lenses attached to it: (scanning 4X/40, intermediate 10X/100, high power 40X/400 are what we use. There is a 4th that has 100X/1000 magnification but this one is used with oil). The image being viewed can be focused with the coarse & fine adjustment knobs. The slides are placed on the mechanical stage, and are held in place by stage clips. The stage can be moved with stage adjustment knobs. Just below the stage is the condenser, which is responsible for collecting and focusing light. The height of the condenser can be adjusted by the condenser adjustment knob. The iris diaphragm controls the width of the circle of light (and therefore the amount of light passing through the specimen). The microscope may have phase-contrast optics--the condenser may be housed in a revolving turret. When the turret is set to 0, the normal optical arrangement is in place. This condition is called bright-field microscopy. To use phase-contrast, the turret setting must correspond to the magnifying power of the objective being used. The lamp is at the base of the microscope and can be adjusted with the light intensity lever. Generally, ore light is needed when using high magnification than when using low magnification.