BIO 101 General Biology 1 (Part 1) PDF Lecture Notes

LECTURE NOTES ON BIO 101 – GENERAL BIOLOGY 1 [PART 1] INTRODUCTION The term "Biology" originates from the Greek words "Bio," meaning "life," and the suffix "- λoуia," or "-logia," meaning "study of." Thus, biology literally translates to "the study...

LECTURE NOTES ON BIO 101 – GENERAL BIOLOGY 1 [PART 1] INTRODUCTION The term "Biology" originates from the Greek words "Bio," meaning "life," and the suffix "- λoуia," or "-logia," meaning "study of." Thus, biology literally translates to "the study of life." Biology is defined as the scientific study of life and living organisms. It explores a vast range of life forms, from microscopic bacteria to complex plants and animals, including humans. The study of life encompasses the fundamental principles and processes that define living things, such as growth, reproduction, adaptation, evolution, and metabolism. It is a broad exploration of what constitutes "life" and includes the conditions, mechanisms, and laws that sustain it, such as energy flow and genetic information transfer. In contrast, the study of living organisms focuses on specific entities that exhibit life—such as plants, animals, fungi, bacteria, and protists - and examines their anatomy, physiology, behavior, interactions, and evolutionary history Figure 1. While studying life addresses the overarching concepts, studying living organisms involves detailed examination of the actual beings that embody these concepts. Biology examines fundamental processes like cellular function, metabolism, and genetic inheritance, as well as how organisms adapt, reproduce, and evolve. As a natural science, biology investigates life and living organisms comprehensively, including their structure, function, growth, evolution, distribution, and taxonomy. It's a diverse and expansive field, comprising numerous branches and sub-disciplines, each contributing to our understanding of the complexities of life. Figure 1: Forms of living organisms LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 1 Despite its diversity, biology acknowledges certain fundamental principles. It recognizes the cell as the basic unit of life, genes as the fundamental units of heredity, and evolution as the driving force behind the emergence of new species. Moreover, modern biology elucidates that all organisms sustain themselves by acquiring and transforming energy, while also regulating their internal environment to maintain stability and vitality. In essence, biology provides a unified framework for comprehending life in all its forms, from the molecular mechanisms within cells to the ecological dynamics shaping our planet. The complexity of living systems is made possible by a constant source of energy – the sun. The conversion of this radiant energy into organic molecules by photosynthesis is one of the most beautiful and complex reactions known in chemistry and physics. Biological systems are the most complex chemical systems on earth and their many functions are both determined and constrained by the principles of chemistry and physics. By understanding biology, scientists can address challenges like disease, environmental conservation, and food security, enhancing our knowledge of life and improving health and sustainability. Theories that Contributed to Modern Biology Modern biology is based on several ideas, or theories: a. The cell theory b. The central dogma c. Homeostasis d. The theory of evolution by natural selection. a. Cell Theory: Robert Hooke (1635:1703), one of the first scientists to use a microscope to examine pond water, cork and other things, referred to the cavities he saw in cork as ―cells‖, Latin for chambers. Matthias Schleiden (in 1838) concluded that all plant tissues consisted of cells. In1839, Theodore Schwann came to a similar conclusion for animal tissues. Rudolf Virchow in 1858 combined the two ideas and added that all cells come from pre-existing cells, formulating the Cell Theory. Thus there is a chain of existence extending from your cells back to the earliest cells, over 3.5 billion years ago. The cell theory states that all organisms are composed of one or more cells, and that those cells have arisen from pre-existing cells. b. Central dogma: In 1953, American scientist James Watson and British scientist Francis Crick developed the model for deoxyribonucleic acid (DNA), a chemical that had (then) recently been deduced to be the physical career of inheritance. Crick hypothesized the mechanism for DNA replication and further linked DNA to proteins, an idea since referred to as the central dogma. Information from DNA “language” is converted into RNA (ribonucleic acid) “language” and then to the “language” of proteins (Figure 2). The central dogma explains the influence of heredity (DNA) on LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 2  the organism (proteins). The central dogma explained the influence of heredity (DNA) on the organism (Proteins). DNA is found in almost all living organisms and directs protein synthesis. Examples of proteins are: enzymes (lactase), hormone (insulin), antibodies (IgA, IgG, IgM, IgE, IgD), haemoglobin, membrane protein and receptor molecules. Figure 2: Central Dogma: DNA to RNA to Protein c. Homeostasis: Homeostasis is the process by which biological systems maintain a relatively stable internal environment despite changes in external conditions. It involves complex regulatory mechanisms that keep variables like temperature, pH, glucose levels, and electrolyte balance within a narrow range, essential for the proper functioning of cells and organs. This dynamic equilibrium is achieved through feedback mechanisms, primarily negative feedback, where a change in a particular condition triggers a response to counteract that change (Figure 3). For humans, the optimal temperature range for normal bodily function is approximately 36.5 – 37.5°C (97.7 – 99.5°F). Deviations from this range can impair enzyme function and metabolic processes, which is why the body tightly regulates temperature through mechanisms like sweating and shivering. The optimal pH range in human blood is around 7.35 – 7.45, which is slightly alkaline. Much of our own metabolic energy goes towards keeping within our own homeostatic limits. If you run a high fever for long enough, the increased temperature will damage certain organs and impair your proper functioning. Swallowing of common household chemicals, many of which are outside the pH (acid/base) levels we can tolerate, will likewise negatively impact the human body’s homeostatic regime. Muscular activity generates heat as a waste product. This heat is removed from our bodies by sweating. Some of this heat is used by warm-blooded animals, mammals and birds, to maintain their internal temperatures. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 3  Figure 3: Cells, body systems and homeostasis d. The theory of evolution by natural selection: Darwin’s theory of evolution, known as natural selection, proposes that species evolve over time through gradual changes. Individuals in a population show variations in traits, and those with advantageous traits are more likely to survive and reproduce. These traits are then passed down to future generations, gradually leading to the adaptation of species to their environments. Over long periods, natural selection can result in the formation of new species, with shared ancestry linking all organisms. This process is driven by environmental pressures, competition, and survival challenges, making natural selection a fundamental mechanism in the diversity of life. Evolution is the engine that propels the synthesis and creation of new species. This will be discussed in details on the section for evolution. MAIN BRANCHES ON OF BIOLOGY These are main branches of biology: i. Anatomy – the study of form and function, in plants, animals and other organisms or specifically in humans. ii. Histology – the study of cells and tissues, a microscopic branch of anatomy. iii. Biochemistry – the study of the chemical reactions required for life to exist and function, usually a focus on the cellular level. iv. Bioengineering – the study of biology through the means of engineering with an emphasis on applied knowledge and especially related to biotechnology. v. Biogeography – the study of the distribution of species spatially and temporally. vi. Bioinformatics – the use of information technology for the study, collection and storage of genomic and other biological data. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 4  vii. Biomedical research – the study of health and disease. viii. Pharmacology – the study and practical application of preparation, use, and efforts of drugs and synthetic medicines. ix. Biophysics – the study of biological processes through physics, by applying the theories and methods traditionally used in the physical sciences. x. Biotechnology – the study of the manipulation of living matter, including genetic modification and synthetic biology. xi. Botany – the study of plants. xii. Cell biology – the study of the cell as a complete unit, and the molecular and chemical interactions that occur within a living cell. xiii. Conservation biology – the study of the preservation, protection or restoration of the natural environment, natural ecosystems, vegetation and wildlife. xiv. Developmental biology – the study of the processes through which an organism forms, from zygote to full structure. xv. Ecology – the study of the interactions of living organisms with one another and with the non-living elements of their environment. xvi. Environmental biology – the study of the natural world, as a whole or in a particular area, especially as affected by human activity. xvii. Epidemiology – a major component of public health research, studying factors affecting the health of populations. xviii. Evolutionary biology – the study of the origin and descent of species over time. xix. Genetics – the study of genes and heredity. xx. Hematology (also known as Haematology) – the study of blood and blood forming organs. xxi. Integrative biology – the study of whole organisms. xxii. Limnology – the study of inland waters. xxiii. Marine biology (or Biological oceanography) – the study of ocean, ecosystems, plants, animals and other living beings. xxiv. Microbiology – the study of microscopic organisms (microorganisms) and their interactions with other living things. xxv. Molecular biology – the study of biology and biological functions at the molecular level, some cross over with biochemistry. xxvi. Mycology – the study of fungi xxvii. Neurobiology – the study of the nervous system, including anatomy, physiology and pathology. xxviii. Population biology – the study of groups of conspecific organisms, including: a. Population ecology – the study of how population dynamics and extinction. b. Population genetics – the study of changes in gene frequencies in populations of organisms. xxix. Paleontology – the study of fossils and sometimes geographic evidence of prehistoric life. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 5  xxx. Pathology – the study of diseases, and the causes, processes, nature and development of disease. xxxi. Physiology – the study of the functioning of living organisms and the organs and parts of living organisms. xxxii. Zoology – the study of animals, including classification, physiology, development and behaviour. Benefit and Opportunities in Studying Biology The study of biology offers numerous benefits and opportunities: a. Understanding Life: Biology provides insights into the nature of life itself, from its molecular foundations to its ecological complexities. b. Health and Medicine: A solid understanding of biology is crucial for advancements in healthcare, including the diagnosis, treatment, and prevention of diseases. c. Conservation and Environmental Stewardship: Biology informs efforts to protect and preserve biodiversity, ecosystems, and natural resources. d. Biotechnology and Innovation: Biological knowledge drives innovations in fields such as agriculture, biomedicine, and renewable energy. e. Critical Thinking and Problem-Solving: Studying biology hones your analytical skills and fosters a deeper appreciation for evidence-based reasoning. f. Career Opportunities: A background in biology opens doors to a wide range of career paths, including research, education, healthcare, environmental management, and biotechnology. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 6  CHARACTERISTICS OF LIVING THINGS The characteristics of living things are a set of criteria that help distinguish living organisms from non-living entities (Figure 4). Living organisms are characterized by the following: Figure 4: Characteristics of Living things i. Movement – Some living organisms, such as animals and some bacteria have the ability to move from place to place that is they show locomotion. Some movement of whole body structures can occur in plants, as when a leaf grows towards the sun or a flower closes at night. Movement allows organisms to seek out resources, avoid predators, find mates, and respond to environmental cues. Whether it's the movement of muscles in animals, the growth of roots in plants, or the swimming of microorganisms, mobility is a characteristic feature of life. ii. Respiration – this is the breakdown of food substances to release energy. All life processes require energy and much of the food obtained by nutrition is used as a source of this energy. The energy released is stored in molecules of adenosine triphosphate (ATP). ATP occurs in all living cells and is often referred to as the universal energy carrier. Respiration stands as a fundamental characteristic of living organisms, essential for their survival and functioning. It refers to the biochemical process through which cells obtain energy from organic molecules, typically glucose, and convert it into usable forms, such as adenosine triphosphate (ATP). This energy conversion occurs through a series of metabolic reactions, primarily in the presence of oxygen, in a process known as aerobic respiration. Aerobic respiration involves the breakdown of glucose molecules in the presence of oxygen to produce carbon dioxide, water, and ATP, which serves as the energy currency of the cell. This process occurs within specialized cellular structures called mitochondria, where enzymes catalyze the sequential reactions of glycolysis, the citric acid cycle, and oxidative phosphorylation. In addition to aerobic respiration, some organisms, such as certain bacteria and yeast, can carry out anaerobic respiration in the absence of oxygen. This process involves the incomplete breakdown of glucose, yielding ATP and metabolic byproducts such as lactic acid or ethanol. Respiration not only provides energy for cellular processes but also facilitates the exchange of gases, such as oxygen and carbon dioxide, between an organism and its environment. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 7 iii. Nutrition – Nutrition serves as a fundamental characteristic of living organisms, vital for their growth, development, and survival. It encompasses the processes by which organisms obtain and utilize nutrients from their environment to sustain cellular functions and maintain homeostasis. Living organisms require various nutrients, including carbohydrates, proteins, lipids, vitamins, minerals, and water, to support their metabolic activities and fulfill their physiological needs. These nutrients serve as building blocks for cellular structures, energy sources for metabolic processes, and cofactors for enzymatic reactions. Nutrient acquisition occurs through ingestion, digestion, absorption, and assimilation. Organisms employ diverse feeding strategies based on their ecological niche and nutritional requirements. For instance, autotrophs, such as plants and algae, produce their own food through photosynthesis, utilizing sunlight, water, and carbon dioxide to synthesize organic molecules like glucose. Heterotrophs, including animals, fungi, and many bacteria, obtain nutrients by consuming organic matter from other organisms. Once nutrients are acquired, they undergo digestion, where complex molecules are broken down into simpler forms that can be absorbed by cells. Absorption then facilitates the uptake of nutrients into cells, where they are utilized for energy production, growth, repair, and other metabolic processes. iv. Irritability (sensitivity) – Irritability, as a characteristic of living organisms, denotes their ability to respond to stimuli in their environment. This fundamental trait is observed across various taxa, from single-celled organisms to complex multicellular organisms, showcasing its evolutionary significance. At its core, irritability facilitates survival and adaptation by enabling organisms to react swiftly to changes in their surroundings. In unicellular organisms such as bacteria, irritability manifests as chemotaxis, where they move towards or away from specific chemicals in their environment. This sensitivity to chemical cues allows them to locate nutrients or avoid toxins, optimizing their chances of survival. Similarly, in multicellular organisms, irritability is evident in responses such as phototaxis (movement towards or away from light) and thigmotaxis (response to touch). In more complex organisms like animals, irritability is intricately linked with the nervous system. Nerve cells, or neurons, transmit electrical impulses in response to various stimuli, coordinating rapid and precise reactions. For instance, when a predator approaches, an animal's irritability prompts it to flee, thereby avoiding danger. Additionally, in plants, irritability is seen in responses like tropism, where they grow towards or away from stimuli such as light or gravity. v. Growth – Growth is a fundamental characteristic of living organisms, distinguishing them from inanimate objects. It represents the increase in size, mass, or complexity of an organism over time. This process is not limited to physical expansion but encompasses various aspects such as cellular differentiation, development of specialized tissues, and overall maturation. At the cellular level, growth involves the replication and division of cells through processes like mitosis and meiosis. As cells divide, they contribute to the overall expansion and renewal of tissues and organs. This continuous renewal is essential for the maintenance and repair of living organisms. Growth is not uniform across all organisms. While some exhibit rapid growth during specific life LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 8 stages, others grow at a steady pace throughout their lifespan. Factors such as genetics, environmental conditions, nutrition, and hormonal regulation influence the rate and pattern of growth in different species. Furthermore, growth is not solely restricted to physical dimensions but extends to intellectual, emotional, and behavioral aspects in more complex organisms like humans. Cognitive development, learning, and adaptation are integral components of growth in higher organisms, contributing to their survival and evolutionary success. vi. Excretion – Excretion is a fundamental characteristic of living organisms, essential for maintaining internal balance and eliminating metabolic waste products. It is the process by which organisms remove waste materials resulting from metabolic activities, ensuring the body's proper functioning. This process is vital across all levels of biological organization, from single-celled organisms to complex multicellular organisms. In single-celled organisms such as bacteria and protozoa, excretion involves the expulsion of waste products like ammonia or carbon dioxide directly into the surrounding environment. This helps prevent the accumulation of toxic substances that could interfere with cellular functions. Multicellular organisms have developed specialized excretory systems to manage waste disposal more efficiently. For example, in humans, the kidneys play a central role in filtering waste products from the blood, producing urine, and maintaining water and electrolyte balance. The respiratory system eliminates carbon (iv) oxide through breathing. Excretion not only removes waste products but also helps regulate various physiological processes, including pH balance, osmotic pressure, and electrolyte levels. Failure to excrete waste properly can lead to serious health problems and even death. Examples of waste products of metabolism in humans are: a. Carbon dioxide (CO₂) – Produced during cellular respiration and excreted by the lungs. b. Urea – Formed in the liver from ammonia and excreted by the kidneys in urine. c. Ammonia – A toxic byproduct of protein metabolism, converted to urea in the liver. d. Creatinine – A waste product from muscle metabolism, filtered out by the kidneys. e. Uric acid – Produced from the breakdown of purines and excreted by the kidneys. f. Bilirubin – Formed from the breakdown of red blood cells, excreted in bile. g. Water – A byproduct of cellular respiration and various metabolic reactions, excreted via urine, sweat, and breath. vii. Reproduction – The life span of organisms are limited, but they all have the ability to perpetuate ―life‖ thereby ensuring the survival of the species. The resulting offsprings have the same general characteristics as the parents, whether such individuals are produced by asexual or sexual reproduction. Reproduction stands as one of the defining characteristics of living organisms, serving as the means by which species perpetuate and evolve over time. This fundamental process ensures the continuation of life and the preservation of genetic diversity within populations. Living organisms employ various reproductive strategies, each tailored to their specific ecological niche and evolutionary history. Asexual reproduction, seen in simple LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 9 organisms like bacteria and some plants, involves the creation of genetically identical offspring from a single parent organism. This method offers efficiency but limits genetic variation. Sexual reproduction, prevalent among more complex organisms, involves the fusion of gametes from two different parents to produce genetically diverse offspring. This process introduces genetic variation through the shuffling of parental genes during meiosis and fertilization, facilitating adaptation to changing environmental conditions and driving evolutionary change. Reproduction is tightly regulated by hormonal and environmental cues, ensuring the timing and frequency of offspring production are conducive to survival and reproductive success. From the intricate courtship rituals of birds to the synchronized spawning events of corals, reproductive behaviors vary widely across the animal kingdom, reflecting adaptations to specific ecological challenges. 1.1 UNIFYING FRAMEWORK AND THEMES IN THE STUDY OF LIFE These are important frameworks within which biologists approach the diversity of organisms. All life forms share these themes in common. They include: i. Evolutionary oneness – all organisms are united at all level because of their common evolutionary origin and the shared forces that influenced their history. Evolutionary processes are remarkable for their relative simplicity, yet they are awesome because of the effects they have had on life forms. Evolutionary processes have resulted in an estimated 4-30 million species of organisms living today. Organisms living on earth today are the modified descendants of common ancestors. ii. Genetic unity – all life is based on the fundamental molecule, deoxyribonucleic acid (DNA). This molecule carries the genetic code and codes for all proteins that make up the structural and functional components of life. The continuity of life is based on heritable information in the form of DNA. Simply put all life forms are one big extended family. iii. Fundamental cellular structure: The cell is the fundamental unit of life. The cells are organism’s basic units of structure and function. In life’s structural and hierarchy, the cell has a special place as the lowest level of organization that can perform all activities for life. The activities of organisms are all based on the activities of a cell. For instance, the division of cells to form new cells is the basis for all reproduction and for the growth and repair of multicellular organisms. Even a global process such as the recycling of carbon is the cumulative produce of cellular activities, including the photosynthesis that occurs in the chloroplasts of leaf cells. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 10  iv. Common environment - organisms interact with their environment, exchanging matter and energy. In any ecosystem, each organism interacts continuously with its environment, which includes both living and nonliving factors. For example, a tree, absorbs water and mineral from soil, through its roots and its leaves take in carbon (iv) oxide from the air and use sunlight absorbed by chlorophyll to drive photosynthesis, converting water and carbon (iv) oxide to sugar and oxygen. The tree releases oxygen to the air and its root help form soil by breaking up rocks. Both organism and environment are affected by the interaction between them. The tree also interacts with other organisms such as soil microorganisms associated with its roots and animals that eat its leaves and fruits. v. Feedback mechanisms regulate biological systems – Feedback mechanisms are essential regulatory systems in biology, maintaining balance (homeostasis) in organisms by adjusting processes in response to changes. They operate primarily through negative and positive feedback loops. In negative feedback, a change in a system triggers a response that counteracts that change, bringing the system back to its original state. For example, body temperature regulation in humans relies on negative feedback. When body temperature rises above normal, sweat glands release sweat, which evaporates to cool the body. Conversely, if body temperature drops, shivering generates heat to restore warmth (Figure 5). Similarly, blood glucose levels are controlled by insulin and glucagon. High blood glucose stimulates insulin release, which helps cells absorb glucose, reducing blood levels. When glucose levels are low, glucagon promotes glucose release into the blood (Figure 6). LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 11 Figure 5 – Negative feedback loop as seen during temperature regulation Figure 6 – Negative feedback loop as seen during blood glucose regulation LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 12 In positive feedback, the response amplifies the initial stimulus, driving a process to completion. A well-known example is childbirth. During labor, the hormone oxytocin intensifies contractions, which further stimulates oxytocin release until delivery is complete (Figure 7). Figure 7 – Positive feedback loop as seen during temperature regulation These feedback mechanisms are critical to maintaining stability and functionality in biological systems, responding dynamically to internal and external changes. By regulating body conditions, they enable organisms to adapt and function optimally across various environments. Feedback is a regulatory mechanism common to life at all levels, from the molecular level to ecosystem and the biosphere. 1.2 Hierarchy of Biological Organization The hierarchy of biological organization is a structured system that organizes life from simplest to most complex levels. It begins with atoms and molecules that form the building blocks of cells, the basic units of life. Cells combine to form tissues, which in turn create organs, each with specialized functions. Organs work together in organ systems to sustain organisms, individual living beings. Organisms of the same species form populations, which interact to create communities. Communities and their environments constitute ecosystems, and all ecosystems collectively make up the biosphere. This hierarchy illustrates how life’s complexity builds upon simpler components, forming interconnected levels. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 13 Figure 8 – Hierarchy of Biological Organization The Hierarchy of Biological Organization includes: i. The biosphere – this includes all environments on earth that are inhabited by life. The biosphere includes most regions of land, most bodies of water and atmosphere to an altitude of several kilometers. ii.Ecosystems – an ecosystem consists of all the living things in a particular area, along with all nonliving components of the environment with which life interacts, such as soil, water, atmospheric gases and light. All of earth’s ecosystems combined make up the biosphere. iii.Communities – the entire array of organisms inhabiting a particular ecosystem is called a biological community. iv.Population – a population consists of all the individuals of a species living within the bounds of a specified area. v.Organisms – individual living things are called organisms. vi.Organs and organ system – an organ is a body part consisting of two or more tissues that carries out a particular function in the body. Examples are leaf, stem, roots of plants and brain, heart and kidney in humans. vii. Tissue – a tissue is a group of similar cells that perform a particular function. Example includes honey combed tissue in the interior of the leaf and muscular, nervous, adipose tissue in animals. viii. Cell – the cell is life’s fundamental unit of structure and function. Some organisms such as amoebas and bacteria are single cells. Plants and animals are multicellular. A human body consists of trillions of microscopic cells of many different kinds such as muscle cells and nerve cells which are organized into the various specialized tissues. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 14 ix.Organelles – organelle are various functional components of two or more small chemical units called atoms. Chlorophyll is the pigment molecule that makes a leaf green. It absorbs sunlight during the first step of photosynthesis. Within each chloroplast, millions of chlorophyll and other molecules are organized into the equipment that converts light energy to the chemical energy of food. LECTURE NOTES ON BIO 101, PART 1 – Prof. J. C. Ozougwu Page 15