JK-TK/Newdata huggingface dataset:
External Features of Organisms
In plants we should look for:-
Spore capsule and rhizoids in moss plants. Sori and fronds in ferns. Stem, leaves, roots, flowers, fruits and seeds in plants. In animals, some important features to look for are:
Segmentation, presence of limbs and, number of body parts, presence and number of antennae. These are found in phylum arthropoda:
Visceral clefts, notochord, nerve tube, fur or hair, scales, fins, mammary glands, feathers and wings. These are found in chordata. Binomial Nomenclature
Organisms are known by their local names. Scientists use scientific names to be able to communicate easily among themselves. This method of naming uses two names, and is called Binomial nomenclature. The first name is the name of the genus: (generic name) which starts with a capital letter. The second name is the name of the species (specific name) which starts with a small letter. The two names are underlined or written in italics. Man belongs to the genus Homo, and the species, sapiens. The scientific name of man is therefore Homo sapiens. Maize belongs to the genus Zea, and the species mays. The scientific name of maize is Zea mays. Practical Activities
Use of Collecting Nets, Cutting Instruments and Hand Lens. Forceps are used to collect crawling and slow moving animals. Sweep nets are used to catch flying insects. Cutting instrument like scapel is used to cut specimen e.g. making sections. Hand lens is used to magnify small plants and animals. Drawing of the magnified organism are made and the linear magnification of each calculated. Collection and Detailed Observation of Small Plants and Animals
e.g. moss, ferns, bean. Look for the following:
Moss plants: Rhizoids and spore capsules. Fern plants: Rhizomes with adventitious roots; large leaves (fronds) with Sori (clusters of sporangia). Seed plants: Tree/shrub (woody) or non-woody (herbs) e.g. bean. Root system - fibrous, adventitious and tap root. Stem - position and length of interrnodes. Type of leaves - simple or compound; arranged as alternate, opposite or whorled.
Root system - fibrous, adventitious and tap root. Stem - position and length of interrnodes. Type of leaves - simple or compound; arranged as alternate, opposite or whorled. Flower - colour, number of parts, size and relative position of each:
Fruits - freshy or dry; edible or not edible. Seeds - monocotyledonous or dicotyledonous. Small animals e.g. earthworms, tick, grasshopper, butterfly, beetles. Observe these animals to see:
Number of legs. Presence or absence of wings. Number of antennae. Body covering. Body parts. THE CELL
Introduction
The cell is the basic unit of an organism. All living organisms are made up of cells. Some organisms are made up of one cell and others are said to be multicellular. Other organisms are made of many cells and are said to be multicellular. Cells are too little to see with the naked eye. They can only be seen with the aid of a microscope. The microscope
The microscope is used to magnify objects. Magnification
The magnifying power is usually inscribed on the lens. To find out how many times a specimen is magnified, the magnifying power of the objective lens is multiplied by that of the eye piece lens. If the eye piece magnification lens is x10 and the objective lens is x4, the total magnification is x40. Magnification has no units. It should always have the multiplication sign.e.g.x40
Microscope parts and their functions
To View the Object
Turn the low power objective lens until it clicks into position. Looking through the eye piece, ensure that enough light is passing through by adjusting the mirror. This is indicated by a bright circular area known as the field of view. Place the slide containing the specimen on stage and clip it into position. Make sure that the specimen is in the centre of the field of view. Using the coarse adjustment knob, bring the low power objective lens to the lowest point. Turn the knob gently until the specimen comes into focus. If finer details are required, use the fine adjustment knob. When using high power objective always move the fine adjustment knob upwards. Care of a Microscope
Great care should be taken when handling it. Keep it away from the edge of the bench when using it. Always hold it with both hands when moving it in the laboratory. Clean the lenses with special lens cleaning paper.
Keep it away from the edge of the bench when using it. Always hold it with both hands when moving it in the laboratory. Clean the lenses with special lens cleaning paper. Make sure that the low power objective clicks in position in line with eye piece lens before and after use. Store the microscope in a dust-proof place free of moisture. Cell Structure as Seen Through the Light Microscope
The cell as seen above has the following:
Cell membrane (Plasma membrane):
This is a thin membrane enclosing cell contents. It controls the movement of substances into and out of the cell. Cytoplasm:
This is a jelly-like substance in which chemical processes are carried out. Scattered all over the cytoplasm are small structures called organelles. Like an animal cell, the plant cell has a cell membrane, cytoplasm and a nucleus. vacuole. Plant cells have permanent, central vacuole. It contains cell sap where sugars and salts are stored. Cell wall:
This is the outermost boundary of a plant cell. It is made of cellulose. Between the cells is a middle lamella made of calcium pectate. Chloroplasts;
With special staining techniques it is possible to observe chloroplasts. These are structures which contain chlorophyll, the green pigment responsible for trapping light for photosynthesis. The Electron Microscope (EM)
Capable of magnifying up to 500,000 times. The specimen is mounted in vacuum chamber through which an electron beam is directed. The image is projected on to a photographic plate. The major disadvantage of the electron microscope is that it cannot be used to observe living objects. However, it provides a higher magnification and resolution (ability to see close points as separate) than the light microscope so that specimen can be observed in more detail. Cell Structure as Seen Through Electron Microscope
The Plasma Membrane
Under the electron microscope, the plasma membrane is seen as a double layer. This consists of a lipid layer sandwiched between two protein layers. This arrangement is known as the unit membrane and the shows two lipid layers with proteins within. Substances are transported across the membrane by active transport and diffusion. The Endoplasmic Reticulum (ER)
This is a network of tubular structures extending throughout the cytoplasm of the cell. It serves as a network of pathways through which materials are transported from one part of the cell to the other. An ER encrusted with ribosomes it is referred to as rough endoplasmic reticulum.
The Endoplasmic Reticulum (ER)
This is a network of tubular structures extending throughout the cytoplasm of the cell. It serves as a network of pathways through which materials are transported from one part of the cell to the other. An ER encrusted with ribosomes it is referred to as rough endoplasmic reticulum. An ER that lacks ribosomes is referred to as smooth endoplasmic reticulum. The rough endoplasmic reticulum transports proteins while the smooth endoplasmic reticulum transports lipids. The Ribosomes
These are small spherical structures attached to the ER. They consist of protein and ribonucleic acid (RNA). They act as sites for the synthesis of proteins. Goigi Bodies
Golgi bodies are thin, plate-like sacs arranged in stacks and distributed randomly in the cytoplasm. Their function is packaging and transportation of glycol-proteins. They also produce lysosomes. Mitochondria
Each mitochondrion is a rod-shaped organelle. Made up of a smooth outer membrane and a folded inner membrane. The foldings of the inner membrane are called cristae. They increase the surface area for respiration. The inner compartments called the matrix. Mitochondria are the sites of cellular respiration, where energy is produced. Lysosomes
These are vesicles containing hydrolytic enzymes. They are involved in the breakdown of micro-organisms, foreign macromolecules and damaged or worn-out cells and organelles .. The Nucleus
The nucle s is surrounded by a nuclear membrane which is a unit membrane. The nuclear membrane has pores through which materials can move to the surrounding cytoplasm. The nucleus contains proteins and nucleic acid deoxyribonucleic acid (DNA) and RNA. The chromosomes are found in the nucleus. They are the carriers of the genetic information of the cell. The nucleolus is also located in the nucleus but it is only visible during the non-dividing phase of the cell. The Chloroplasts
These are found only in photosynthetic cells. Each chloroplast consists of an outer unit. membrane enclosing a series of interconnected membranes called lamellae. At various points along their length the lamellae form stacks of disc like structures called grana. The lamellae are embedded in a granular material called the stroma. The chloroplasts are sites of photosynthesis.
At various points along their length the lamellae form stacks of disc like structures called grana. The lamellae are embedded in a granular material called the stroma. The chloroplasts are sites of photosynthesis. The light reaction takes place in the lamellae while the dark reactions take place in the stroma. Comparison between animal cell and plant cell
Cell Specialisation
Cells are specialised to perform different functions in both plants and animals. Example;
Palisade cells have many chloroplasts for photosynthesis. Root hair cells are long and thin to absorb water from the soil. Red blood cells have haemoglobin which transports oxygen. Sperm cells have a tail to swim to the egg. Multicellular organisms cells that perform the same function are grouped together to form a tissue. Each tissue is therefore made up of cells that are specialised to carry out a particular function. Animal Tissues- Examples of animal tissues
Plant Tissues
Example of plant tissues
Organs
An organ is made up of different tissues
e.g. the heart, lungs, kidneys and the brain in animals and roots, stems and leaves in plants. Organ systems
Organs which work together form an organ system. Digestive, excretory, nervous and circulatory in animals and transport and support system in plants. organism
Different organ systems form an organism. Practical Activities
Observation and Identification of parts of a light microscope and their functions
A light microscope is provided. Various parts are identified and observed. Drawing and labelling of the microscope is done. Functions of the parts of the mircroscope are stated. Calculations of total magnification done using the formula. Eye piece lens maginification x objective lens rnaginification. Preparation and Observation of Temporary Slides of Plant Cells
A piece of epidermis is made from the fleshy leaf of an onion bulb. It is placed on a microscope slide and a drop of water added. A drop of iodine is added and a cover slip placed on top. Observations are made, under low and medium power objective. The cell wall and nucleus stain darker than other parts. A labelled drawing is made. The following are noted: Nucleus, cell wall, cytoplasm and cell membrane. Observation of permanent slides of animal cells
Permanent slides of animal cells are obtained e.g, of cheek cells, nerve cells and muscle cells. The slide is mounted on the microscope and observations made under low power and medium power objectives.
The following are noted: Nucleus, cell wall, cytoplasm and cell membrane. Observation of permanent slides of animal cells
Permanent slides of animal cells are obtained e.g, of cheek cells, nerve cells and muscle cells. The slide is mounted on the microscope and observations made under low power and medium power objectives. Labelled drawings of the cells are made. A comparison between plant and animal cell is made. Observation and Estimation of Cell Size and Calculation of Magnification of Plant Cells. Using the low power objective, a transparent ruler is placed on the stage of the microscope. An estimation of the diameter of the field of view is made in millimeters. This is converted into micrometres (1mm=1000u)
A prepared slide of onion epidermal cells is mounted. The cells across the centre of the field of view are counted from left and right and top to bottom. The diameter of field of view is divided by the number of cells lying lengthwise to give an estimate of the length and width of each cell. Cell Physiology
Meaning of cell physiology
The term physiology refers to the functions that occur in living organisms. Cell physiology refers to the process through which substances move across the cell membrane. Several physiological processes take place inside the cell.e.g. respiration. Oxygen and glucose required enter the cell while carbon (IV) oxide and water produced leave the cell through the cell membrane. Structure and properties of cell membrane
The cell membrane is the protective barrier that shelter cellular contents. Movement of all substances into and out of the cells takes place across the cell membrane. It is made up of protein and lipid molecules. Lipid molecules have phosphate group attached to it on one end. They are then referred to phospholipids. The phospholipids are arranged to form a double layer. The ends with phosphate group face outwards. the proteins are scattered throughout the lipid double layer. Some of these proteins act as carrier molecules that channel some material in and outside the cells. The cell membrane allows certain molecules to pass through freely while others move through with difficulty and still others do not pass through at all. This is selective permeability and the cell membrane is described as semi-permeable. Properties of cell membrane
Permeability
The cell membrane is semi-permeable. it allows small molecules that are soluble in lipid to pass through with more ease than water soluble molecules. this is due to the presence of the phospholipids double layer.
Properties of cell membrane
Permeability
The cell membrane is semi-permeable. it allows small molecules that are soluble in lipid to pass through with more ease than water soluble molecules. this is due to the presence of the phospholipids double layer. Polarlity
The cell membrane has electrical charges across its surface.it has positive charged ions on the outside and negatively charged ions on the inside.this property contributes to electrical impulses sent along nerve cells. Sensitivity to changes in temperature and pH
Very high temperatures destroy the semi-permeability nature of the cell membrane because the proteins are denatured by extreme pH values have the same effect on the membrane permeability. Physiological processes
Some of the physiological processes include diffusion, osmosis and active transport. Diffusion
Diffusion is the movement of molecules or ions from a region of high concentration to a region of low concentration aided by a concentration gradient.. diffusion continues to occur as long as there is a difference in concentration between two regions (concentration gradient). Stops when an equilibrium is reached i.e., when the concentration of molecules is the same in both regions. Diffusion is a process that occurs inside living organisms as well as the external environment.. Does not require energy. Factors Affecting Diffusion
.~ -
Concentration Gradient
An increase in the concentration of molecules at one region results in a steeper concentration gradient which in turn increases the rate of diffusion. Temperature
High temperature increases kinetic energy of molecules. They move faster hence resulting in an increase in rate of diffusion, and vice versa. Size of Molecules or Ions
The smaller the size of molecules or ions, the faster their movement hence higher rate of diffusion. Density
The denser the molecules or ions diffusing, the slower the rate of diffusion, and vice versa. Medium
The medium through which diffusion occurs also affects diffusion of molecules or ions. For example, diffusion of molecules through gas and liquid media is faster than through a solid medium. Distance
This refers to the thickness or thinness of surface across which diffusion occurs. Rate of diffusion is faster when the distance is small i.e., thin surface. Surface Area to Volume Ratio
The larger the surface area to volume ratio, the faster the rate of diffusion. For example, in small organisms such as Amoeba the surface area to volume ratio, is greater hence faster diffusion than in larger organisms.
Rate of diffusion is faster when the distance is small i.e., thin surface. Surface Area to Volume Ratio
The larger the surface area to volume ratio, the faster the rate of diffusion. For example, in small organisms such as Amoeba the surface area to volume ratio, is greater hence faster diffusion than in larger organisms. Role of Diffusion in Living Organisms
Some processes that depend on diffusion include the following:
Gaseous exchange: Movement of gases through respiratory surfaces is by diffusion. Absorption of materials into cells Cells obtain raw materials and nutrients from the surrounding tissue fluid and blood through diffusion, e.g., glucose needed for respiration diffuses from blood and tissue fluid into cells. Excretion: Removal of metabolic waste products like carbon (IV) oxide, and ammonia out of cells is by diffusion. Absorption of the end-products of digestion from the intestines is by diffusion. Osmosis
Osmosis is the movement of water molecules from a region of high water concentration to a region of low water concentration through a semi-permeable membrane. Osmosis is a special type of diffusion that involves the movement of water molecules only and not solute molecules. Osmosis takes place in cells across the cell membrane as well as across non-living membranes
e.g. cellophane or visking tubing which are also semi-permeable,
It is purely a physical process. Factors Affecting Osmosis
Size of solute molecules-
Osmosis' occurs only when solute molecules are too large to pass through a semi-permeable membrane. Concentration Gradient . Osmosis occurs when two solutions of unequal solute concentration are separated by a semi-permeable membrane. Temperature ,. High temperatures increase movement of water molecules hence influence osmosis. However, too high temperatures denature proteins in cell membrane and osmosis stops. Pressure
Increase in pressure affects movement of water molecules. As pressure increases inside a plant cell, osmosis decreases. Roles of Osmosis in Living Organisms
The following processes depend on osmosis in living organisms:
Movement of water into cells from the surrounding tissue fluid and also from cell to cell. Absorption of water from the soil and into the roots of plants. Support in plants especially herbaceous ones, is provided by turgor pressure, which results from intake of water by osmosis. Absorption of water from the alimentary canal in mammals. Re-absorption of water in the kidney tubules.
Support in plants especially herbaceous ones, is provided by turgor pressure, which results from intake of water by osmosis. Absorption of water from the alimentary canal in mammals. Re-absorption of water in the kidney tubules. Opening and closing stomata. Water Relations in Plant and Animal Cells
The medium (solution) surrounding cells or organisms is described by the terms hypotonic, hypertonic and isotonic. A solution whose solute concentration is more than that of the cell sap is said to be hypertonic. A cell placed in such a solution loses water to the surroundings by osmosis. A solution whose solute concentration is less than that of the cell sap is said to be hypotonic. A cell placed in such a solution gains water from the surroundings by osmosis. A solution which has the same solute concentration as the cell sap is said to be isotonic. When a cell is placed in such a solution there will be no net movement of water either into or out of the cell. Osmotic Pressure
The term osmotic pressure describes the tendency of the solution with a high solute concentration to draw water into itself when it is separated from distilled water or dilute solution by a semi-permeable membrane. Osmotic pressure is measured by an osmometer. When plant cells are placed in distilled water or in a hypotonic solution, the osmotic pressure in the cells is higher than the osmotic pressure of the medium. This causes the water to enter the cells by osmosis. The water collects in the vacuole which increases in size. As a result the cytoplasm is pushed outwards and it in turn presses the cell membrane next to the cell wall. This builds up water pressure (hydrostatic pressure) inside the cell. When the cell is stretched to the maximum, the cell wall prevents further entry of water into the cell. Then the cell is said to be fully turgid. The hydrostatic pressure developed is known as turgor pressure. Plasmolysis
When a plant cell is placed in a hypertonic medium, it loses water by osmosis. The osmotic pressure of the cell is lower than that of the medium. The vacuole decreases in size and the cytoplasm shrinks as a result of which the cell membrane loses contact with the cell wall. The cell becomes flaccid. The whole process is described as plasmolysis.
The vacuole decreases in size and the cytoplasm shrinks as a result of which the cell membrane loses contact with the cell wall. The cell becomes flaccid. The whole process is described as plasmolysis. Incipient plasmolysis is when a cell membrane just begins to lose contact with the cell wall. Plasmolysis can be reversed by placing the cell in distilled water or hypotonic solution. However, full plasmolysis may not be reversed if cell stays in that state for long. Wilting
The term wilting describes the drooping of leaves and stems of herbaceous plants after considerable amounts of water have been lost through transpiration. It is observed in hot dry afternoons or in dry weather. This is when the amount of water lost through transpiration exceeds the amount absorbed through the roots. Individual cells lose turgor and become plasmolysed and the leaves and stems droop. The condition is corrected at night when absorption of water by the roots continue while transpiration is absent. Eventually, wilting plants may die if the soil water is not increased through rainfall or watering. Water Relations in Plants and Animals
Haemolysis
Haemolysis is the bursting of cell membrane of red blood cells releasing their haemoglobin. It occurs when red blood cells are placed in distilled water or hypotonic solution. This is because the cell membrane does not resist further entry of water by osmosis after maximum water intake. Crenation
Takes place when red blood cells are placed in hypertonic solution. They lose water by osmosis, shrink and their shape gets distorted. Animal cells have mechanisms that regulate their salt water balance (osmoregulation) to prevent above processes that lead to death of cells. An Amoeba placed in distilled water, i.e. hypotonic solution, removes excess water using a contractile vacuole. The rate of formation of contractile vacuoles increases. Active Transport
Active transport is the movement of solutes such as .glucose, amino acids and mineral ions;
From an area of their low concentration to an area of high concentration. It is movement against a concentration gradient and therefore energy is required. As such it only takes place in living organisms. The energy needed comes from respiration. Certain proteins in the cell surface membrane responsible for this movement are referred to as carrier proteins or channel proteins. The shape of each type of carrier protein is specific to the type of substances conveyed through it.