Introduction To Biology PDF

# Introduction and Terminology - **Biology:** Is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, and taxonomy. - **Why study of biology is important for medical college students?** - Studying biology...

# Introduction and Terminology - **Biology:** Is a natural science concerned with the study of life and living organisms, including their structure, function, growth, evolution, distribution, and taxonomy. - **Why study of biology is important for medical college students?** - Studying biology is crucial for medical college students because: - It forms the foundation for understanding the organism (including the human) body's structure, function, and processes. - It provides essential knowledge about cells, organs, systems, genetics, and diseases, which are fundamental for diagnosing and treating patients effectively. - Understanding biology is essential for grasping medical concepts, conducting research, and, making informed decisions in clinical practice. # Branches of Biology Biology includes several branches: - **Botany:** Focuses on the study of plants, including their structure, physiology, ecology, and evolution. - **Zoology:** Concentrates on the study of animals, covering their behavior, physiology, anatomy, classification, and evolution. - **Microbiology:** Deals with the study of microorganisms, such as bacteria, viruses, fungi, and protozoa, and their impact on health, agriculture, industry, and the environment. - **Genetics:** Investigates the principles of heredity and variation, including the study of genes, chromosomes, genetic traits, inheritance patterns, and genetic disorders. - **Ecology:** Explores the relationships between organisms and their environment, including the interactions between living organisms and their habitats, ecosystems, and the biosphere. - **Physiology:** Focuses on the study of the functions and processes of living organisms and their parts, including cells, tissues, organs, and organ systems. - **Anatomy:** Examines the structure of organisms, including the arrangement of tissues, organs, and organ systems, through dissection, imaging techniques, and comparative anatomy. - **Biochemistry:** Investigates the chemical processes and substances that occur within living organisms, including the structure and function of biomolecules such as proteins, carbohydrates, lipids, and nucleic acids. - **Biotechnology:** Applies biological principles and techniques to develop products and technologies for various purposes, including medicine, agriculture, industry, and environmental conservation. - **Cytology:** is a science, that deals with the study of cells in terms of structure, function, and chemistry. - **Histology:** is the study of the microscopic anatomy of cells and tissues of plants and animals. - **Immunology:** The study of the immune system and its response to pathogens and foreign substances. - **Embryology:** studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Additionally, embryology includes the study of congenital disorders that occur before birth, known as teratology. # Characters of living organisms Living organisms are characterized by many characteristics that distinguish them from non-living things such as: - **Organisms are composed of cells:** - All organisms are formed of basic structural and functional units called cells. - According to the number of cells that form the body of an organism, organisms may be; unicellular or multicellular. - **Unicellular organisms** consist of a single cell ex: Protozoa. - **Multicellular organisms** consist of many cells (billions) ex: man. - **Growth:** Means an increase in the size and number of cells. - **Development:** It is the process that includes all changes during the life of an organism from a fertilized egg to an individual. - **Reproduction:** It is the ability of an organism to reproduce its kind. - Reproduction may be **asexual** (without fusion between egg and sperm to form a fertilized egg), since It takes place by many different routes like **binary fission** (ex: Amoeba) or **Sexual** (carried out by the production of egg and sperm that fuse to form a fertilized egg that will develop to form the new individual). - **Movement:** Most organisms can crawl, walk, swim, and fly but micro-organisms move by special structures like (Cilia, Flagella, and Pseudopodia) - **Metabolism:** Is the sum of all chemical activities inside the cells and tissues of the organism. - **Homeostasis:** Is a balanced internal state of physical, chemical, and social conditions maintained by living systems (or self-regulating control systems). - This is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits (homeostatic range). - Other variables include the concentrations of sodium, potassium, and calcium ions, as well as the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity. Each of these variables is controlled by one or more regulators or homeostatic mechanisms, which together maintain life. - **Response to stimuli:** Responsiveness refers to the ability of an organism or a system within an organism to detect and respond to changes in its environment (temperature, light, sound, chemicals) or internal conditions, (hormones or neurotransmitters). - It involves the capacity to receive stimuli and generate appropriate responses to maintain homeostasis or adapt to new circumstances. - Examples include reflex actions, movement toward or away from stimuli (taxis), and physiological responses like changes in heart rate or hormone secretion. - **Adaptation:** Is the ability of organisms to survive in a particular environment. # Biological Organization There are three levels of biological organization: 1. **Chemical levels:** includes - **The Atom:** Is the basic and smallest building block of matter, consisting of a nucleus composed of protons and neutrons, surrounded by a cloud of electrons. Protons carry a positive charge, neutrons have no charge, and electrons carry a negative charge. - **The Molecule:** Is a neutral chemical structure consisting of two or more atoms held together by chemical bonds. 2. **Cellular levels:** - **Organelle:** Is a specialized subunit, usually within a cell, that has a specific function (ex. mitochondria, Golgi bodies, and lysosomes). - **Cell:** Is the basic structural and functional unit of all forms of life. Every cell consists of cytoplasm enclosed within a membrane; many cells contain organelles, each with a specific function (ex. Liver cells, muscle cells, and nerve cells). - **Tissue:** It is a group of similar or dissimilar cells having the same origin, that together carry out a specific function (ex. epithelial tissue and connective tissue). 3. **Ecological levels:** - **Population:** All individuals of the same species living within a specified area. - **Community:** Populations of different species inhabit a particular area. - **Ecosystem:** Community (Living components) that interact with the surrounding non-living environment. - **Biosphere:** Is a combination of all of the earth's ecosystems. (Planet Earth and all of its communities) # Diversity of life - The scientists classified the diversity of life into 6 kingdoms (others made it tens of kingdoms) and finer grouping according to structure, function, and other features. - **Debatable issue.** - Modern classifications are based on some other characteristics as **DNA sequencing.** - There are 3 **domains of life diversity:** - **Archea** - **Bacteria** - **Eukarya** - **Kingdom (Domain) Archea** - Prokaryotic - Single-celled - Microscopic - Divided by binary fission but no mitosis - Autotrophic - Live in salty lakes and hot springs - Its cell membrane has a branched hydrocarbon chain attached to glycerol by ether linkages - **Kingdom (Domain) Bacteria** - Prokaryotic - Single-celled - Microscopic - Divided by binary fission but no mitosis - Autotrophic - The most diverse and widespread prokaryotic - Its cell membrane has an unbranched hydrocarbon chain attached to glycerol by ester linkages - **Domain 3: Eukarya** - **Kingdom 3: Protists** - Are mostly unicellular eukaryotes and some multicellular. They have cell walls. They are autotrophic and heterotrophic. Includes protozoa, eukaryotic algae, and molds. - **Kingdom 4: Fungi** - Eukaryotic (multicellular) as mushrooms or (unicellular) as yeast. - They have cell walls like plants but have a substance called chitin rather than cellulose. - They are heterotrophic and saprotrophic meaning they decompose - so they break things down or are parasitic. The body of a fungus is composed of thin filaments called hyphae. They secrete enzymes, do external digestion and then absorb the resulting nutrients. - **Kingdom 5: Plantae** - Includes terrestrial multicellular eukaryotic plants, have cell walls with cellulose, also they are autotrophic i.e. use photosynthesis to make their energy from sunlight with CO2 and release O2. - Their growth is restricted to meristems - which are layers of dividing cells. - They are non-motile. - **Kingdom 6: Animalia** - Includes multicellular eukaryotic (no cell wall) organisms, - Developed from the blastocyst, - It has nervous and hormonal control systems, - Heterotrophic, ingest other organisms (feed on organic matter), - Undergoes cell division to enable growth. # Scientific Method (framework of scientific research) 1. **Observation** - Critical questions 2. **Develop Hypothesis** 3. **Make a Prediction that can be tested** 4. **Perform Experiments** 5. **RESULTS** - Further experiments - **Develop a theory and principle** - **Interpretation & Conclusions** - **New hypothesis** <start_of_image> え