BIO 101 General Biology 1 Lecture Notes 2024 PDF

Mrs. E.N ONWE [email protected] BIO 101 GENERAL BIOLOGY 1 Course outline  Cell structure and organization  Functions of cellula...

Mrs. E.N ONWE [email protected] BIO 101 GENERAL BIOLOGY 1 Course outline  Cell structure and organization  Functions of cellular organelles  Diversity of cells  Characteristics and classification of living things  General reproduction  Interrelationship of organisms  Heredity and evolution  Elements of ecology and types of habitats CELL STRUCTURE AND ORGANISATION The cell is best defined as the integrated unit of structure and vital function. It was first observed and described by Robert Hooke in 1665, while he was examining the thin slice of the cork bark of an oak tree. Several other workers made significant contributions to the understanding of the structure and function of the cell. The findings of these workers were later gathered together in the formulation of the cell theory by two Germans- Mathias Schleiden (Botanist) and Theodore Schwann (Zoologist) in 1839. The basic principles of the cell theory is outlined as follows: 1. The cell is the unit of structure in all living things 2. The cell is the unit of function in all living things 3. All cells come from previously existing cells 4. The activity of an organism is the sum of the activities and interactions of all its cells. Cells vary in size and complexity from the tiny and relatively simple cells of bacteria to the giant complex yolk of chicken or ostrich eggs. When examined under the simple light microscope, a typical plant cell will be seen to consist of an outer covering made of a rigid cell wall and cell membrane, a protoplasm made up of the cytoplasm with its cell organelles, a nucleus and vacuole. A typical animal cell will possess all these structures except the cell wall and a large vacuole. (Fig. 1&2)  FIGURES. 1. A TYPICAL PLANT CELL FIGURES. 2. A TYPICAL ANIMAL CELL FUNCTIONS OF CELLULAR ORGANELLES The organization in an individual cell as revealed by an electron microscope is known as its fine structures or ultra-structures. The specific entities making up these organization are called organelles which includes: CELL WALL The cell wall is secreted by the protoplasm and the original cell wall material formed during cell division later becomes the middle lamella composed mainly of calcium pectate. Later, deposition of pectose, hemicellulose, cellulose, lignin, suberin etc. fortifies the cell wall into primary and secondary cell wall. The cell wall gives strength, rigidity and shape to the cell. CELL MEMBRANE The cell membrane also known as plasma membrane or plasmalemma covers the protoplasm of all cells. It is lipo-protein or phospholipid bilayer and usually semi-permeable, differential or selective (the police man of the cell). Such membranes allow the passage of some substances through them while disallowing others. The cell membrane is therefore regarded as a biological membrane with characteristics such as low surface tension and high electrical resistance due to the lipid content. PROTOPLASM This is the living part of the cell where most physiological processes such as food synthesis, growth, respiration, reproduction etc. takes place. The protoplasm is made up of the cytoplasm and the nucleus. CYTOPLASM The cytoplasm is the non-living component of the cell. It is made up of protein substances, water, fats, inorganic salts, carbohydrates, enzymes etc. known as “cell inclusions” or cytosol. The cytoplasm also contains some small compartments called cell organelles each bounded by semi- permeable membrane. The organelles include mitochondria, ribosomes, endoplasmic reticulum, Golgi body apparatus, lysosomes, plastids, vacuoles etc. MITOCHONDRIA Occurs in all cells as rods or filaments but absent in bacteria and blue green algae. It consists of double membrane with many convolutions called cristae and granular matrix composed of proteins, lipids, nucleic acids and several DNA rings. The mitochondrion is regarded as the “power house” of the cell and contains the enzymes associated with respiration, Krebs cycle, cytochrome oxidase system and photosynthesis. RIBOSOMES These are minute organelles found scattered freely in the cytoplasm or associated with the membrane of the rough endoplasmic reticulum. The ribosome is made up of RNA (ribonucleic acid) and proteins and are the main site of protein synthesis. ENDOPLASMIC RETICULUM (ER) This consists of a network of tubules in the cytoplasm, it connects the nuclear membrane, cytoplasm and then opens outside the cell membrane. They are two major types of ER: the rough ER (with attached ribosome) and smooth ER (without ribosome) (FIG 1&2). The ER increases the surface area of the cytoplasm for metabolic activities, enhances enzyme formation, storage and transport of metabolites. GOLGI BODY APPARATUS Discovered by an Italian physician named Camillo Golgi in 1849. It consists of flattened network of sacs with two membrane known as dictyosomes. The main function of the Golgi apparatus includes secretion of enzymes, hormones and storage of proteins. LYSOSOMES The lysosome is called “suicide bags”. They are tiny spherical structures found in the cytoplasm of cells. Their main function includes housing enzymes for destruction of foreign and dead structures and causing intercellular digestion. CENTROSOMES These are minute bodies occurring near the nucleus in animal cells and those of lower plants. They help in formation of cilia or flagella in motile cells and in the formation of spindle fibers during cell division. VACUOLES The vacuoles occur in both plants and animal cells but are very large and central in plant cells. The cavity is filled with fluid called cell-sap in which many compounds are dissolved. The vacuole has a membrane called Tonoplast. Its functions are storage of water, salts, food materials, anthocyanins etc. maintaining cellular turgidity and provides means of cellular transport. PLASTIDS Mainly found in plant cells, discoidal or spherical in shape and have a double membrane with a protein matrix called stroma. Three types of plastids are known: Leucoplast, chloroplast and chromoplast. These types of plastids are interchangeable; for instance, chloroplast usually green changes to leucoplast (colourless) in the dark and back to green when exposed to light again. Chloroplast in green young tomato fruit also changes to red chromoplast in the ripe fruit. Leucoplast are colourless plastids associated with the storage of carbohydrates usually as starch and are called amyloplasts. When they help with forming and storing fats, they are called elaioplast and proteinoplast when they store proteins. Chloroplast are green plastids containing chlorophyll which absorbs light energy used in photosynthesis. Chromoplast are coloured plastids such as xanthophylls (yellow), carotenes (orange-red) which are associated with pigmentation of flowers and fruits. CELL INCLUSIONS These includes raw materials or by-products of cellular metabolism. They include food substances, sugar, fats, oils, vitamins, carbohydrates, starch, glycogen, proteins and essential minerals such as calcium, potassium, phosphorus, iron, Sulphur etc. other substances includes tannins, resins, gums, latex, alkaloids etc. NUCLEUS This is usually oval or elongated in shape. Some plants and animal have true well-developed nuclei and are eukaryotes as opposed to prokaryotes with undeveloped nuclei as in blue green algae and bacteria. In higher plants each cell contains one nucleus while in some algae and fungi some cells have many nuclei. The nucleus consists of a nuclear membrane, nuclear sap or nucleoplasm, chromatin network or chromosome and the nucleolus. The red blood cell (erythrocytes) and the mature sieve tubes of plant phloem tissue lack nuclei at maturity. The nucleus carries out the following functions: 1. With the protoplasm it controls the cell life 2. Takes part in both sexual and asexual reproduction 3. Initiates cell division and growth  4. Its chromosome carries the genetic material 5. It controls DNA, RNA and protein synthesis. Table 1. DIFFERENCE BETWEEN PLANT AND ANIMAL CELL PLANT CELL ANIMAL CELL Cellulose cell wall present Cellulose cell wall absent Plastids (chloroplasts) present Plastids (chloroplast) absent Centrioles and centrosomes absent Centrioles and Centrosomes present Vacuoles are large and few Vacuoles are small and many Have definite shape No definite shape Protoplasm less dense Protoplasm denser Stores carbohydrate as starch granules Stores carbohydrate as glycogen Stores lipid as oil Stores lipid as fat Lysosomes are absent Lysosomes are present SIMILARITIES Plants and animal cells are similar in the presence of the following organelles: Both cells possess cell membrane, Cytoplasm, Nucleus, Golgi bodies, Endoplasmic reticulum, Ribosomes, Nuclear membrane, Mitochondria etc. THE DIVERSITY OF CELLS FIG. 3. Cell Diversity A All cells are not identical, they are striking diversity of cells among organisms. This diversity is seen between different species where shape, form and content of individual cells show much variation (Fig. 3). Thus, the cells of Hydra differ considerably from those of humans despite the fact that they share the same basic features and to some extent perform the same function. Within the body of hydra, there are seven different types of cells specialized to perform a particular task. In the human body they are numerous different types of cells highly specialized to perform a particular function. Epithelial cells possess a shape and form that makes them suitable for lining the surface of the body and the organs and cavities within it. Glandular cells are responsible for producing secretions such as mucus, saliva, sweat etc. such cells have a particular prominent Golgi body, an indirect piece of evidence implicating the Golgi apparatus in secretion. Chondroblasts and osteoblasts produce cartilages and bones. Blood contains several kinds of specialized cells. Erythrocytes (red blood cells), biconcave, disc-shaped and loaded with the red pigment haemoglobin are responsible for conveying oxygen round the body, they are one of the few cells to lack nucleus. Leucocytes (white blood cells), generally amoeboid, play important part in defending the body against disease. Nerve cells or neurons having a slender arm-like shape, transmit electrical impulses through the nervous system. Sensory cells also, are capable of electrical activity which is generated by specific kind of stimulation such as touch, sound, light, heat or chemical substances. Muscle fibres with elongated cells make movements and electrical activities accompanied by contraction. Spermatozoon, a single cell with an elongated tail are capable of powerful undulations, the tail propels the spermatozoon forward in its watery medium. Muscle cell and spermatozoa, with their high energy requirements contain large number of densely packed mitochondria which are site of energy-producing chemical reactions. Other specialized cell in organisms below the level of mammals include Chromatophores stellate cells which are contained in the skin of amphibians and reptiles. It is a pigment which if concentrated or expanded, changes the colour of their body. Flame cells are found in flatworms where they play important role in osmoregulation. Nematoblast or Stinging cells of sea anemone, jelly fish and Hydra contains a toxic fluid capable of piercing and poisoning prey. In plants, photosynthetic cells of various shapes and forms, packed with chloroplast perform the task of building up complex molecules. Parenchyma cells with its thin wall and alive at maturity is one among the three ground tissues of plants which play important role in healing and repair of wounds. Epidermal cells whose outer walls possess waxy cuticle, protect the plant from excessive water loss. Guard cells control the opening and closing of air pores (stomata). Cells of the root hairs absorb water and mineral salts from the soil. Collenchyma cells are elongated and are involved in strengthening the plant particularly the young stem. Sieve tubes are involved in transporting food materials from one part of the plant to the other. Lignified vessels such as Tracheids and Fibers play important parts in transporting water and mineral salts from the root to the leaves. The cells of Amoeba, Euglena, Paramecium and the filamentous green algae Spirogyra which are single-celled organisms differ from photosynthetic cells of higher plant but they all perform those functions which are necessary for the maintenance of life metabolic processes. FIG. 4. Cell Diversity B TYPES OF CELLS Cells are majorly categorized into two major types 1. Prokaryotic cells  Lack true nucleus  Small size (1.5µm)  Simple structure  No membrane-bound organelles  Single-celled organisms  Metabolic processes: Methanogenesis, thermophily  Cell wall: Pseudopeptidoglycan, peptidoglycan or glycoprotein  Example: bacteria, archaea 2. Eukaryotic cells  True nucleus  Large size (10-100 µm)  Complex structure  Single celled or multicellular organisms  Membrane-bound organelles  Metabolic processes: cellular respiration, photosynthesis  Cell walls: cellulose, chitin, collagen  Example: plants, animals, fungi protists  Prokaryotic cells are cells which lack nucleus. They are the simpler types of cells which lacks organelles but has a single chromosome consisting of a single strand of DNA in the form of a ring. The chromosome is coiled up in the centre of the cell to form what is called a nucleoid. In bacteria which is a typical prokaryotic cell there is smaller ring of DNA called Plasmid which serve as accessory chromosome. Examples includes bacteria, blue-green algae, mycoplasma, PPLO (Pleuro Pneumonia Like Organisms) etc. Eukaryotic cells are defined as cells containing organized nucleus which are enveloped by membrane-bound organelles such as mitochondria, chloroplast, endoplasmic reticulum golgi body apparatus, lysosomes etc. They are found in all domains of life. Examples are plants, animals, protists, fungi etc. Their genetic materials are organized in chromosomes and they are characterized by cell division (mitosis and meiosis for reproduction and genetic diversity), cell signaling involving complex networks and regulation of cellular processes and cytoskeleton (microtubules, microfilament and intermediate filaments providing structural support. IMPORTANT NOTES:  In animal cells which lack cell wall, the cell membrane provides the boundary.  The cells of the bacteria (Prokaryotes) have different shapes and they are classified based on the shape as Bacilli (rod shaped), Cocci (spherical shaped) Vibrio (comma shaped), Spirilla (spiral/helical shaped)  In Eukaryotes (plant, animal, fungal cells), the shape of the cell depends on its function;  Humans have cells of various shapes; circular and biconcave (RBC), amoeboid (WBC), long stretched and branched cells (nerve cells), long and narrow cells (columnar epithelium) etc.  Plant cells usually have square or rectangle shape. Even in plants some specialized cells have different shapes e.g. Guard cells of stomata (kidney/Dumbell shaped)  Fungal cells have a variety of shapes. Single cellular fungi are usually spherical and some fungi are tubular and some form long chains of cells. Characteristics and Classification of Living Things. Everything in the world is classified as either living or non-living. There are six qualities that make up a living thing. They are: made up of cells, produce movement, get and use energy from a source, reproduce, grow and develop, respond and adapt to their environment. Something is alive if it exhibits all of the characteristics of a living thing. If it doesn’t then it is non-living. Living things are distinguished from non-living things by having life in them with a number of characteristics which includes, Movement: The ability of organisms to change position is known as movement. Living things move in order to search for food, reproduce or escape from danger. Animals move its whole body from one place to another while plants move parts of their body in response to external Stimuli. The process of movement is also known as locomotion. Nutrition: This is the ability of organisms to feed. Living things take in materials from their surroundings that they use for growth or to provide energy. Nutrition is the process by which organisms obtain energy and raw materials from nutrients such as proteins, carbohydrates and fat. It also refers to the biochemical and physiological process by which an organism uses food to support its life. Failure to obtain sufficient nutrient causes malnutrition. Living things feed in order to carry out life processes such as growth, respiration, reproduction etc. They are two types of nutrition;  Autotrophic or holophytic nutrition where green plants manufacture their own food through the process of photosynthesis.  Heterotrophic or holozoic nutrition which is a type of feeding exhibited by animals and other organisms which cannot manufacture their own food but depend on plants directly or indirectly Excretion: is defined as the removal of waste and toxic products from the body. It also entails the removal of metabolic waste products such as water, sweat, carbon dioxide, urine etc. from the body. Excretion is done to prevent accumulation of harmful substances in the biological system. Unlike animals, plants do not have special organs for excretion. They excrete through their vegetative parts only. Reproduction: The ability of organisms to give birth to young-ones or offspring is known as reproduction. It is the passing on of genetic information to a new generation. Thus, the purpose of reproduction is to ensure continuity of life from one generation to another. They are two types of reproduction viz;  Asexual Reproduction: Some living things reproduce asexually, meaning they make an identical copy of their DNA, which carries genetic instructions that help create a new living form. Asexual reproduction involves only one organism to produce another offspring. Forms of asexual reproduction includes binary fission, budding, fragmentation, spore formation, apomixis, micropropagation etc.  Sexual Reproduction: Involves two individuals coming together and sharing their gametes to produce a new organism. Sexual reproduction entails fertilization and the combination of genetic information of two individuals of different sexes. Respiration: This is a chemical reaction that happens within cells to release energy from food. Respiration is more than just an act of breathing (moving in and out of oxygen and carbon dioxide respectively). It represents the ability of living organisms to obtain oxygen it needs to release energy and break down sugars, carbon dioxide and so on. Respiration can be of three types – external, internal and cellular.  C6H12O6 + 6O2 → 6H2O + 6CO2 + Energy (ATP) Glucose Oxygen Water Carbon dioxide Irritability: Irritability is defined as response to stimuli. It is the ability of living organisms to detect changes in the surrounding environment. Living things are sensitive to heat, light, pain, water, sound, chemical substances, cold etc. which are known as Stimuli. Many experiments have been done with plants to show how they respond and grow towards light which is known as phototropism. Some responses are easy to observe such as the pupil of an eye that constricts when a light is shone into it. Growth: Growth and development is a characteristic of a living thing and is defined as increase in size and mass of an organism with time. An increase in mass and number of individuals are twin characteristics of growth in a living organism. Organisms grow and develop following specific instructions coded by their genes. These genes provide instructions that will direct cellular growth and development, ensuring that a species young will grow up to exhibit many of the same characteristics as its parents. The purpose of growth is to enable organisms get larger and also repair or replace damaged or worn out tissues in their body. The food eaten provides the basis for growth of organisms. A multicellular organism grows by cell division. Death. All living things must die because they have a defined period of existence. Living things must pass through these five stages of life; Birth → Growth → Maturity → Decline (old age) → Death These characteristics can be summarized into eight (8): 1. Organization  Cellular structure (cells, tissues, organs and systems)  Complexity and hierarchy 2. Metabolism  Energy conversion (photosynthesis, respiration)  Nutrient uptake and utilization  Waste elimination 3. Homeostasis  Maintenance of internal environment  Regulation of temperature, pH, and other factors 4. Growth and Development  Increase in size and complexity  Differentiation and specialization 5. Reproduction  Production of offspring (asexual or sexual)  Continuation of species 6. Response to Stimuli  Sensitivity to environment (light, temperature, touch)  Adaptation and reaction  7. Adaptation and Evolution  Change over time (mutation, natural selection)  Diversity and speciation 8. Movement and Locomotion  Voluntary or involuntary movement  Migration, dispersal, and colonization Classification of Living Things. Classification involves placing into groups, organisms that have certain features in common which distinguish them from other groups. Classification is the process of grouping living things into categories based on their shared characteristics. This helps us understand the relationships between different organisms and their place in the natural world. Why Classify Living Things? 1. Understand relationships between organisms 2. Identify and name organisms 3. Study evolutionary history 4. Organize and communicate knowledge The process of identifying, classifying and naming organisms is called Taxonomy. The system of classification living things used today is based on that introduced by a swiss scientist called Carolus Linneaus where he categorized living things into two major kingdoms (plants and animals). Carolus Linneaus is therefore known as the Father of Taxonomy. But Robert Whittaker proposed the five Kingdom classification which includes; Monera, Protists, Fungi, Plantae and Animalia. The Kingdoms are sub divided into Phyla (singular phylum) for animals and division for plants. All the members of a phylum or division have certain features in common and each phylum is broken down to Classes, each class into Order, Family, Genera, and Species as represented below Domain ↓ Kingdom ↓ Phylum ↓ Class ↓ Order ↓ Family ↓ Genus ↓ Species The basic unit of classification is the Species. which can only interbreed with each other. Members of a species cannot interbreed with members of another species. So, both human beings and monkeys cannot interbreed. The table (table 2) below classifies humans and lions. Humans Lions Kingdom Animalia Animalia Phylum Chordata Chordata Class Mammalia Mammalia Order Primate Carnivore Family Hominidae Felidae Genus Homo Panthera species Sapien Leo Domains: 1. Archaea (ancient bacteria) 2. Bacteria (true bacteria) 3. Eukarya (complex cells) Kingdoms: 1. Monera (bacteria) 2. Protista (single-celled eukaryotes) 3. Fungi 4. Plantae (plants) 5. Animalia (animals) Classification Systems: 1. Linnaean System (binomial nomenclature) 2. Phylogenetic System (based on evolutionary relationships) Characteristics Used for Classification: 1. Cell structure 2. Metabolic processes 3. Reproduction 4. Development 5. Morphology Types of Classification: 1. Artificial Classification (based on visible characteristics) 2. Natural Classification (based on evolutionary relationships) 3. Phylogenetic Classification (based on evolutionary history) Recommended Textbooks for Further Reading (Bio 101 & 102)  Biological Science 1 & 2 Authors: D.J Taylor, N.P.O. Green, G.W Stout and R. Soper 3rd Revised edition. Cambridge University Press.  Essential Biology Author: M.C. Michael  Modern Biology Author: Sarojini T. Ramalingam 2018 Revised Edition