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Zoology Laboratory Exercise 5-7, Study notes of Zoology

Xavier University (XU)Zoology

This document contains notes for experiments 5,6,7 which cover the following topics; Cellular Respiration; Cell Division (Mitosis and Meiosis); Genetics and Variations. It highlights key points from the laboratory manual that may be useful for written quizzes/exams.

Typology: Study notes

2023/2024

Available from 01/05/2024

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ZOOLOGY- LAB (Prelim notes)
Microscope
Organisms and other objects are studied with the use of magnifying instruments that
provide enlarged images of the object.
COMPOUND MICROSCOPE
A compound microscope consists of certain precise mechanical parts (chiefly of metal) to
support and facilitate the use of the optical parts (of glass) that provide the magnified
image.
Mechanical Parts
1. Base โ€“ heavy U- or V-shaped foot on which the microscope stands.
2. Pillar โ€“ a firm support arising from the base.
3. Stage - platform with central aperture and clips to hold the slide being studied.
4. Arm โ€“ a stout curved handle used in carrying the instrument.
5. Body tube โ€“ box-like structure attached to the arm and bears the lenses and prism.
6. Rotating (revolving) nosepiece โ€“ bears the four objective lenses.
7. Dust shield โ€“ metallic structure above the nosepiece that protects the objectives.
8. Coarse adjustment knob โ€“ outer rotary knob that quickly moves objectives to focus or
obtain an image of the object.
9. Fine adjustment knob โ€“ inner rotary knob attached within the arm. It is for more
delicate focusing especially at high magnification.
10. Draw tube โ€“ found on top of the body tube into which ocular (eyepiece) is inserted; can
be rotated 360โฐ for ease of viewing.
Optical Parts
1. Mirror โ€“ found below the stage; serves to gather and direct the light to illuminate the object.
The concave mirror will gather more light than the flat (plain) mirror, but the latter provides
more satisfactory lighting at high magnifications.
2. Iris diaphragm โ€“ a metal plate with circular openings with different diameters that control the
amount of light reaching the object.
3. Condenser (lens system) โ€“ found between the mirror and the stage and serves to further
concentrate light rays on the specimen.
4. Objectives of object lens โ€“ consist of two or more lenses fixed in a rigid mount that serve to
form a real image of the object within the body tube.
a) Scanner โ€“ smallest and shortest, with lowest magnification but allows viewer to see a greater
area.
1: MICROSCOPES AND MAGNIFICATION
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ZOOLOGY- LAB (Prelim notes)

Microscope Organisms and other objects are studied with the use of magnifying instruments that provide enlarged images of the object. COMPOUND MICROSCOPE A compound microscope consists of certain precise mechanical parts (chiefly of metal) to support and facilitate the use of the optical parts (of glass) that provide the magnified image. Mechanical Parts

  1. Base โ€“ heavy U- or V-shaped foot on which the microscope stands.
  2. Pillar โ€“ a firm support arising from the base.
  3. Stage - platform with central aperture and clips to hold the slide being studied.
  4. Arm โ€“ a stout curved handle used in carrying the instrument.
  5. Body tube โ€“ box-like structure attached to the arm and bears the lenses and prism.
  6. Rotating (revolving) nosepiece โ€“ bears the four objective lenses.
  7. Dust shield โ€“ metallic structure above the nosepiece that protects the objectives.
  8. Coarse adjustment knob โ€“ outer rotary knob that quickly moves objectives to focus or obtain an image of the object.
  9. Fine adjustment knob โ€“ inner rotary knob attached within the arm. It is for more delicate focusing especially at high magnification.
  10. Draw tube โ€“ found on top of the body tube into which ocular (eyepiece) is inserted; can be rotated 360โฐ for ease of viewing. Optical Parts
  11. Mirror โ€“ found below the stage; serves to gather and direct the light to illuminate the object. The concave mirror will gather more light than the flat (plain) mirror, but the latter provides more satisfactory lighting at high magnifications.
  12. I ris diaphragm โ€“ a metal plate with circular openings with different diameters that control the amount of light reaching the object.
  13. Condenser (lens system) โ€“ found between the mirror and the stage and serves to further concentrate light rays on the specimen.
  14. Objectives of object lens โ€“ consist of two or more lenses fixed in a rigid mount that serve to form a real image of the object within the body tube. a) Scanner โ€“ smallest and shortest, with lowest magnification but allows viewer to see a greater area.

1: MICROSCOPES AND MAGNIFICATION

b) Low power objective (LPO) โ€“ shorter lens with a magnifying power of 10x. c) High power objective (HPO) โ€“ the longer lens that magnifies 40x and forms a bigger image of the object. d) Oil immersion objective (OIO) โ€“ the longest objective, with a magnifying power of 100x, used only with immersion oil.

  1. Ocular or eyepiece โ€“ two larger lenses at the top of the draw tube that serve to further magnify the image. The lens of the ocular refracts (bends) the light rays passing from the real image to the retina of the eye in such a way as to produce the effect of a still virtual image (ghost image). THE BINOCULAR DISSECTING MICROSCOPE Certain exercises in this manual call for the use of a dissecting microscope. This microscope combines lower magnifications with binocular viewing and is of considerable value in making delicate dissections of small specimen. The techniques involved in the use of this instrument are basically similar to those used with the compound microscope. Magnification means the number of items an object is enlarged or reduced by a lens system of the microscope or by a drawing.

MAGNIFICATION

  1. Erythrocyte or red blood cells โ€“ more numerous, elliptical, stained blue and with central oval nucleus.
  2. Leukocytes or white blood cells โ€“ varied in shapes, about 1/3 the size of the erythrocytes; the cytoplasm is clear or granular and scanty. The cells that make up the body of multicellular organisms are of various sizes, forms, arrangements and perform different functions. Cells are organized into groups or layers known as tissues. we shall classify animal tissues into five major groups: 1. Epithelial or surface 2. Connective or supportive 3. Vascular 4. Muscular or contractile 5. Nervous These consist of cells that form a compact, continuous layer or sheet covering the body surface or lining the cavities within the body or in an organ. The cells are held together by a l imited amount of intercellular substance and supported underneath by a basement membrane.
  3. Squamous Epithelium. A single layer of thin, flat polygonal cells, scale-like in appearance fitted together like a mosaic or pavement. Nuclei are large and centrally located.

TISSUES

Epithelial Tissues

FROG SKIN

This is the single layer of cells that are long and cylindrical, sometimes forming tall, irregular prisms. This tissue may be simple (one layer thick) or stratified; and on the other surface, it may be bare, with a cuticle (a secreted non-cellular material), specialized to receive stimuli (sensory), or to secrete materials (glandular). Among some of the modifications of columnar epithelium are goblet cells and microvilli. CROSS SECTION OF SMALL INTESTINE

Columnar Epithelium

Also called supporting tissues , connective tissues perform variety of functions, all of which are related to support, protection, and binding various organs together. These are the most abundant and widely distributed of all animal tissues. Their cells secrete a large amount of non-living intercellular substances in the form of matrix of fibers that determines their nature and function. Fibrous Connective Tissue This consists mainly of c__ ollagenous (white) fibers __ that are very tough and strong yet flexible and resistant to pulling each other. Relatively few cells are distributed through the matrix of thick interlacing network of fibers. Section of tendon

  1. matrix โ€“ a visible gelatinous mass containing the cells and fivers.
  2. connective tissue cells โ€“ round or elongated with dark-staining nucleus.
  3. white (collagenous) fibers โ€“ bundles of interlaced, wavy, parallel and unbranched fibrils. Also called โ€œgristleโ€, it has a shapeless intercellular matrix. All types of cartilage are covered by a thin fibrous layer, the perichondrium. The types of cartilage are: Connective Tissues

Cartilage

i. hyaline โ€“ the most common type; has extensive bluish matrix without fibers, typically found at the ends of long bones. ii. elastic โ€“ contains many yellow (elastic) fibers and is the most flexible type of cartilage; found in external ear. iii. fibrocartilage โ€“ less firm than hyaline but of great strength; contains more collagenous fibers, less matrix and few cells; found in the pads of vertebrae. Hyaline Cartilage

  1. matrix โ€“ stained pinkish, rather translucent materials containing the cells.
  2. chondrocytes โ€“ are cartilage cells that occur singly or in twoโ€™s within the lacuna. Is also called osseous tissue, the hardest connective tissue. Living bone consists of an organic matrix (collagen) and deposits of mineral materials (calcium and phosphorus salts) secreted by special bone-forming cells (a.k.a. osteoblasts).
  3. concentric lamellae โ€“ group of concentric layers around a canal.
  4. Haversian canal โ€“ opening at the center of each group of concentric lamellae. Each Haversian canal contains the blood vessels and nerves that supply the bone.

Bone

Erythrocytes / Red Blood Cells (RBC) โ€“ are numerous, small disc-shaped cells, biconcave in profile and without nuclei. Leucocytes / White Blood Cells (WBC) โ€“ less numerous, nucleated, and bigger than human RBCs. They differ in the shape and size of the nucleus and in the presence and absence of granules in the cytoplasm. The following kinds may be distinguished: lymphocytes โ€“ with large rounded nucleus and colored blue by Wrightโ€™s stain. m onocytes โ€“ with a large centrally placed nucleus shaped like a kidney or horseshoe. granulocytes โ€“ with nuclei divided into two to five lobes connected by nuclear threads, and conspicuous cytoplasmic granules. Three types may be differentiated: neutrophils โ€“ neclei have 3 to 5 lobes, cytoplasm bluish. eosinophils โ€“ nuclei of two lobes, cytoplasm pinkish. basophils โ€“ S-shaped nuclei. Platelets โ€“ irregular bits of cytoplasm. Microscopically, muscles consist of elongated spindle-shaped or cylindrical cells containing many contractile fibers or myofibrils. The muscles of vertebrates are of three types: striated, smooth and cardiac. Striated Muscles are also known as skeletal muscles because they are attached to bones. Since their movement is under conscious control (you can use your โ€œwillโ€ to contract them), they are called voluntary muscles. Longitudinal section of skeletal muscles

  1. sarcolemma โ€“ the delicate cell membrane surrounding the muscle cells.
  2. nucleus โ€“ several nuclei may be found beneath the sarcolemma.
  3. sarcoplasm โ€“ the cytoplasm enclosed by sarcolemma.

Muscular Tissues

  1. cross-striation โ€“ alternating heavily shaded thin bands (dark) and light bands. These are designated as non-striated because they do not exhibit cross striations. Isolated smooth muscle fibers are elongated spindle-shaped cells with elongated oval nucleus occupying the central portion of the fiber. Not controlled consciously, smooth muscles are also termed involuntary muscles. cross-section of the stomach It is highly specialized tissue found only in the walls of the heart. Each cardiac muscle fiver is striated (but the striations are less pronounced than those of skeletal muscles). The fivers of the cardiac muscle branch freely with other fibers, forming a continuous network of cells called syncytium. Characteristic of this tissue is the presence of dense bands that occur at variable intervals across the fiber. These transverse lines are called intercalated discs. As in striated muscle tissue, there are several nuclei to a cell, but unlike the striated, the cardiac muscle is involuntary. longitudinal section of cardiac muscle The cells and fibers of nervous tissue form an interconnecting network that links every part of the organism. T The basic function of nervous tissue is to integrate the myriad of activities of the organism and to coordinate them with the external (physical) environment. Nervous tissue is composed of two kinds of cells: (1) neuroglia or supporting cells and (2) neurons or nerve cells. neurons may be classified as sensory (or afferent) neurons, motor (or efferent) neurons and interneurons (intermediate, connecting neurons together). Structurally, neurons are classified as multipolar, bipolar and unipolar depending upon the number of processes projecting from the cell body. a. cell body or perikaryon โ€“ contains a well0defined nucleus and nucleolus, surrounded by granular cytoplasm.

Smooth Muscles

Cardiac Muscle

Nervous Tissues