Introduction to Biology: Core Principles

• Biology is the scientific study of life, examining the structure, function, growth, origin, evolution, and distribution of living organisms.

Core Principles

• Cell theory: All living organisms are composed of cells, which are the basic units of life.
• Gene theory: Traits are inherited through genes, located on chromosomes.
• Evolution: Life evolves over time through processes like natural selection.
• Homeostasis: Living organisms maintain a stable internal environment.
• Thermodynamics: Life depends on the flow and transformation of energy.

Levels of Biological Organization

• Molecules: Atoms combine to form molecules, such as DNA, proteins, and carbohydrates.
• Cells: The basic unit of life, containing organelles and carrying out life functions.
• Tissues: Groups of similar cells performing a specific function.
• Organs: Structures composed of different tissues working together.
• Organ systems: Groups of organs that cooperate to perform major bodily functions.
• Organisms: Individual living entities.
• Populations: Groups of individuals of the same species living in the same area.
• Communities: Populations of different species interacting with each other.
• Ecosystems: Communities and their non-living environment (e.g., water, soil, air).
• Biosphere: All ecosystems on Earth.

Branches of Biology

• Biochemistry: Study of chemical processes within and relating to living organisms.
• Botany: Study of plants, including their physiology, structure, genetics, and ecology.
• Cell Biology: Study of cell structure and function.
• Ecology: Study of the interactions between organisms and their environment.
• Evolutionary Biology: Study of the evolutionary processes that have produced the diversity of life.
• Genetics: Study of genes, heredity, and variation in living organisms.
• Microbiology: Study of microorganisms, such as bacteria, viruses, and fungi.
• Molecular Biology: Study of the molecular basis of biological activity.
• Physiology: Study of the functions and mechanisms of living organisms and their parts.
• Zoology: Study of animals, including their behavior, physiology, and evolution.

Cell Structure and Function

• Prokaryotic Cells: Simple cells lacking a nucleus and other complex organelles; include bacteria and archaea.
• Eukaryotic Cells: Complex cells with a nucleus and membrane-bound organelles; found in plants, animals, fungi, and protists.

Key Organelles

• Nucleus: Contains the cell's genetic material (DNA) and controls cell activities.
• Mitochondria: Powerhouse of the cell, responsible for ATP (energy) production through cellular respiration.
• Ribosomes: Sites of protein synthesis.
• Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis; can be rough (with ribosomes) or smooth.
• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.
• Lysosomes: Contain enzymes for breaking down cellular waste and debris.
• Chloroplasts (in plant cells): Site of photosynthesis, converting light energy into chemical energy.
• Cell Membrane: Outer boundary of the cell, controlling what enters and exits.
• Cell Wall (in plant cells): Rigid outer layer providing support and protection.

Genetics

• DNA (Deoxyribonucleic Acid): The molecule carrying genetic information.
• Genes: Segments of DNA that code for specific traits.
• Chromosomes: Structures containing DNA; humans have 46 chromosomes arranged in 23 pairs.
• DNA Replication: Process by which DNA copies itself.
• Transcription: Process by which RNA is synthesized from DNA.
• Translation: Process by which proteins are synthesized from RNA.
• Mutations: Changes in the DNA sequence that can lead to variations in traits.
• Mendelian Genetics: Principles of inheritance based on the work of Gregor Mendel, including the laws of segregation and independent assortment.

Evolution

• Natural Selection: Process by which organisms with traits better suited to their environment survive and reproduce more successfully.
• Adaptation: Inherited traits that enhance survival and reproduction in a specific environment.
• Genetic Variation: Differences in genes among individuals within a population.
• Speciation: Process by which new species arise from existing species.
• Evidence for Evolution: Includes fossil records, comparative anatomy, embryology, and molecular biology.

Ecology

• Populations: Groups of individuals of the same species living in the same area.
• Communities: Groups of populations of different species interacting with each other.
• Ecosystems: Communities and their physical environment, including interactions like energy flow and nutrient cycling.
• Biomes: Large-scale ecosystems characterized by specific climate conditions and plant communities (e.g., rainforests, deserts, tundra).
• Food Chains and Food Webs: Diagrams showing the flow of energy and nutrients through an ecosystem.
• Trophic Levels: Position an organism occupies in a food chain (e.g., producers, consumers, decomposers).
• Symbiosis: Interactions between different species, including mutualism (both benefit), commensalism (one benefits, the other is unaffected), and parasitism (one benefits, the other is harmed).
• Biodiversity: the variety of life in the world or in a particular habitat or ecosystem.

Plant Biology

• Photosynthesis: Process by which plants convert light energy into chemical energy in the form of glucose.
• Plant Structures: Roots (absorb water and nutrients), stems (provide support), leaves (site of photosynthesis), flowers (reproduction).
• Plant Transport: Xylem (transports water), phloem (transports sugars).
• Plant Hormones: Regulate plant growth and development (e.g., auxins, gibberellins, cytokinins).
• Plant Reproduction: Sexual (involving pollination and fertilization) and asexual (vegetative propagation).

Animal Biology

• Animal Tissues: Epithelial (covering surfaces), connective (support and structure), muscle (movement), nervous (communication).
• Organ Systems: Digestive, circulatory, respiratory, excretory, nervous, endocrine, reproductive, skeletal, muscular, and immune.
• Animal Behavior: Responses to stimuli (e.g., innate behaviors and learned behaviors).
• Animal Classification: Based on evolutionary relationships (e.g., vertebrates and invertebrates).

Microbiology

• Bacteria: Unicellular prokaryotic organisms; can be beneficial or harmful.
• Viruses: Non-cellular entities consisting of genetic material (DNA or RNA) enclosed in a protein coat; require a host cell to replicate.
• Fungi: Eukaryotic organisms including yeasts, molds, and mushrooms; can be decomposers or pathogens.
• Microbial Ecology: Study of the interactions between microbes and their environment.
• Importance of Microbes: Nutrient cycling, decomposition, disease, and biotechnology.

Human Biology

• Anatomy: Study of the structure of the human body.
• Physiology: Study of the function of the human body.
• Human Genetics: Study of genes, heredity, and genetic variation in humans.
• Human Evolution: Study of the evolutionary history of humans.
• Human Health: Study of diseases and disorders affecting the human body.

Scientific Method

• Observation: Observing a phenomenon and asking a question.
• Hypothesis: Formulating a testable explanation for the observation.
• Experiment: Designing and conducting a controlled experiment to test the hypothesis.
• Data Analysis: Analyzing the data collected during the experiment.
• Conclusion: Drawing a conclusion based on the data analysis; either supporting or rejecting the hypothesis.
• Communication: Sharing the results with the scientific community.