IGCSE Biology Organization of Organisms PDF

BY CELL :00201110983031 00201110983031 [email protected] CELL :00201110983031 00201110983031 [email protected]  1. Each living Organism consists of many cells. 2. The cell is and functional units of living Organism. 3. Th...

BY CELL :00201110983031 00201110983031 [email protected] CELL :00201110983031 00201110983031 [email protected]  1. Each living Organism consists of many cells. 2. The cell is and functional units of living Organism. 3. The plant cell is characterized by the presence of chloroplast cell wall and large vacuoles. 4. The animal cell is characterized by the presence of small vacuoles or vesicles. 5. There are some cells which are called modified cells It such as root hairs, Muscle fibers and Xylem tissue. 6. Magnification role is very important as magnification equals to images size divided by actual size. CELL :00201110983031 00201110983031 [email protected]  CELL STRUCTURE AND ORGANIZATION Structures found in plant cells only Structure Properties Functions Cell Wall 1. Found in plant cells only 1. Supports, protects and 2. Made of cellulose (non- gives the cells its living). shape 3. Fully permeable 2. Allows the freely movement of the different molecules Chloroplasts or Contain chlorophyll traps light energy and Chloroplastids convert it to chemical energy in photosynthesis to form starch. vacuole Consists of fluid surrounded Contain salt and minerals by a membrane support cell and keep it firm CELL :00201110983031 00201110983031 [email protected] Structures found in both plant cells and animal cells Structure Properties Functions Cytoplasm jelly like substance with Contains the cell particles and organelles Organism such as mitochondria Golgi apparatus Site of chemical reaction Cell membrane Partially permeable Pregnant scaping of cell membrane content Control the substances that enter or leave the cell. Mitochondria oval shape organum Responsible for aerobic respiration Nucleus Circular shape contains DNA Control cell division that forms chromosomes Control cell activity Control the cell development Ribosome Circular structure attached Responsible for protein to the cell membrane or synthesis found freely. ANIMAL CELL CELL :00201110983031 00201110983031 [email protected]  Similarities in both plant and animal cells 1. Cell membrane 2. Cytoplasm 3. Nucleus 4. Mitochondria Difference between plant and animal cells PLANT Cell ANIMAL Cell 1. Has a cell wall made of cellulose. 1. Has no cell wall 2. Has a large permanent sap vacuole 2. Has no or temporary small vacuole 3. Usually contain chloroplasts 3. No chloroplasts 4. Usually contains stored starch 4. Usually contains stored glycogen CELL :00201110983031 00201110983031 [email protected]  Levels of Organizations CELL The structural and functional unit of all living organisms. EX: PALLISADE CELL – KIDNEY CELLS TISSUE Group of similar cells which together perform particular function EX: XYLEM – PHLOEM ORGAN Group of several tissues which perform a particular function EX : LEAF -ROOT LIVER -SYSTEM ORGAN HEART ORGAN SYSTEM group of organs with closely related functions. EX : animals (Circulatory system respiratory system ) In plants shoot system - root system CELL :00201110983031 00201110983031 [email protected]  Modification a change in shape or structure or both, to be adapted to carry out a particular function. Modified cell Changing in cell shape or structure or both than the typical form to be adapted to perform a particular function Examples of Modified Cells 1. ROOT HAIR A cell modified for absorption of water and minerals Adaptation of the root hair cell to its function 1. Large in number and has a finger-like projection to increase the surface area of absorption 2. Contains a lot of mitochondria for production of energy 3. Contains a large concentrated sap vacuole for absorption of water by osmosis 4. Secretes viscous substance to: a. To imbibe water. b. To grow without being ruptured by the soil particles. CELL :00201110983031 00201110983031 [email protected]  2. Xylem Vessels Modified cells for: 1. Conduction of water and minerals 2. Support Adaptation of Xylem to its function 1. Are fine tubes to help in the ascent of water by capillary action 2. Have lignified walls for support and to be impermeable to water 3. Have pits at certain points for distribution of water and minerals 4. Have no cross walls, no cytoplasm or nuclei in order not to resist the movement of water and minerals CELL :00201110983031 00201110983031 [email protected]  3. Muscle Cells Are modified to carry out contraction for movement. Adaptation of muscles to their function 1. Have a lot of mitochondria to produce enough energy for their action 2. Can respire anaerobically in addition to aerobic respiration for production of enough energy for their action. 3. Store carbohydrates in the form of glycogen to be used as a source of energy. 4. Part of its cytoplasm is modified into contractile filaments. Other Modified Cells 1. Ciliated Epithelium. 2. Sperm cells. 3. Red blood cells. Magnification Means how many times the image is seen larger compared with the object To calculate magnification or actual length use the following triangle, cover the value you need to find out IMAGE SIZS ACTUAL MAGNIFICATI SIZE ON CELL :00201110983031 00201110983031 [email protected] Practical work Safety Eye protection must be worn. Take care when using a scalpel, follow your teacher’s guidance. Take care using the iodine and methylene blue stains – they will stain skin and clothing. 1 Plant cells – preparing a slide of onion epidermis cells Using forceps, peel a piece of epidermal tissue from the incurve of an onion bulb leaf. Place the epidermal tissue on a glass microscope slide. Using a scalpel, cut out a 1 cm square of tissue (throw away the rest) and arrange it in the centre of the slide. Add two to three drops of iodine solution. (This stains any starch in the cells and makes different parts of the cells distinct.) Using forceps, a mounted needle or a wooden splint, support a cover-slip with one edge resting near to the onion tissue, at an angle of about 45° (Figure 2.12(b)). Gently lower the cover-slip over the onion tissue. Try to avoid trapping any air bubbles.(Air bubbles reflect light when viewing under the light microscope, hiding the features you are trying to see.) Leave the slide for about 5 minutes. This allows the iodine stain to react with the specimen. The iodine stains the cell nuclei pale yellow and the starch grains blue. Place the slide on to the microscope stage, choose the lowest power objective lens and focus on the specimen. Increase the magnification using the other objective lenses. Under high power, the cells should look like those shown in Figure 2.13. CELL :00201110983031 00201110983031 [email protected] CELL :00201110983031 00201110983031 [email protected] 2.Animal cells – preparing human cheek cells Rinse your mouth with water. This will remove any fragments of food. Take a cotton bud from a freshly opened pack. Rub the cotton bud lightly on the inside of your cheek and gums to collect some cheek cells in saliva. Rub the cotton bud on to the centre of a clean microscope slide, leaving a sample of saliva. Repeat if the sample is too small. Then drop the cotton bud into a container of absolute alcohol or disinfectant. Add two to three drops of methylene blue dye. (This stains parts of the cheek cells to make nuclei more visible.) Using forceps, a mounted needle or wooden splint, support a coverslip with one edge resting near to the cheek cell sample, at an angle of about 45°. Gently lower the cover-slip over the tissue. Try to avoid trapping any air bubbles. (Air bubbles reflect light when viewing under the light microscope, hiding the features you are trying to see.) Leave the slide for a few minutes. This allows the methylene blue stain to react with the specimen Place the slide on to the microscope stage, choose the lowest power objective lens and focus on the specimen. Increase the magnification using the other objective lenses. Under high power, the cells should look like those shown in Figure 2.15, but less magnified. CELL :00201110983031 00201110983031 [email protected]