Biol 101 Ch 1 part 2

Introduction to Biology

  • Biology is defined as the study of life.

  • Key characteristics of living organisms:

    • Cellular: Life is composed of cells.

    • Genetic Material: Contains DNA, the genetic blueprint, which is transcribed to RNA, and ultimately translated into proteins.

    • Ordered Structure: Life is organized on a size scale starting from atoms, which combine to form molecules.

    • Macromolecules of Life: Four main types of macromolecules are critical: carbohydrates, proteins, lipids, and nucleic acids.

    • Cell Structure: Eukaryotic cells have membrane-bound organelles.

    • Smallest Unit of Life: The cell is the fundamental unit, which can form tissues, organs, and organ systems.

    • Homeostasis: Organisms maintain internal balance and respond to environmental changes.

    • Reproduction: Ability to reproduce either sexually or asexually.

    • Growth and Differentiation: Organisms grow and develop into more complex forms.

    • Adaptation and Evolution: Organisms can adapt over time through evolutionary processes.

Taxonomy and Classification of Life

  • Taxonomy: The scientific discipline of naming and classifying organisms based on shared characteristics.

  • Organism Grouping: Organisms categorized based on characteristics such as if they are plants, animals, fungi, or bacteria.

    • Three Domains of Life:

    1. Bacteria

    2. Archaea

    3. Eukarya

  • Characteristics of Domains:

    • Domains Bacteria and Archaea include prokaryotic cells (cells without a nucleus).

      • Prokaryotic Cells: Small cells with DNA free-floating in the cytoplasm (e.g., bacteria and archaea).

    • Eukarya Domain: Contains eukaryotic cells (cells with a nucleus).

      • Nucleus: A membrane-bound structure containing DNA.

  • Taxonomic Hierarchy:

    • Levels of classification from broad to specific:

    • Domain

    • Kingdom

    • Phylum

    • Class

    • Order

    • Family

    • Genus

    • Species

    • Example Using Humans:

    • Domain: Eukarya

    • Kingdom: Animalia

    • Phylum: Chordata

    • Class: Mammalia

    • Order: Primates

    • Family: Hominidae

    • Genus: Homo

    • Species: sapiens

    • Binomial Nomenclature:

    • Scientific naming system consisting of genus and species names (e.g., Homo sapiens).

    • Rules: Genus is capitalized, species is lowercased, italicized or underlined when handwritten.

  • Examples of Binomial Nomenclature:

    • Escherichia coli (E. coli) - First time full genus name is used before abbreviation.

    • Corn scientifically named Zea mays.

Characteristics of the Three Domains

Domain Bacteria

  • Composed of prokaryotic, unicellular organisms

  • Examples include:

    • Escherichia coli

    • Staphylococcus aureus

    • Shigella flexneri

    • Salmonella typhimurium

  • Size approximately 1 micrometer (10^−6 meters), visible only under a microscope.

  • Most bacteria possess a cell wall made of peptidoglycan, crucial for structural integrity.

Domain Archaea

  • Also consists of prokaryotic, unicellular organisms, similar in size to bacteria.

  • Distinct from bacteria as they do not have peptidoglycan in cell walls, which can be composed of various substances.

  • Known as extremophiles, organisms thriving in extreme environments (high temperature, acidity, salinity).

Domain Eukarya

  • Composed of organisms with eukaryotic cells.

    • Characteristics include:

    • Presence of a nucleus to contain DNA.

  • Four Kingdoms of Eukarya:

    • Animalia:

    • Multicellular organisms, heterotrophs requiring food consumption, internal digestion.

      • Examples: Humans, fish, frogs.

    • Fungi:

    • Mostly multicellular, some unicellular (e.g., yeast).

    • Heterotrophs with external digestion via enzyme secretion.

      • Examples: Yeasts, molds, mushrooms.

    • Plantae:

    • Always multicellular autotrophs, capable of photosynthesis.

    • Protista:

    • Diverse kingdom for organisms that do not fit other kingdoms, eukaryotic, can be unicellular or multicellular.

      • Examples: Algae (autotrophs), protozoans (heterotrophs), Plasmodium (causes malaria).

  • Cell Wall Characteristics:

    • Animal cells: Lack a cell wall, flexible plasma membrane.

    • Plant cells: Have a rigid cell wall made of cellulose.

    • Fungal cells: May have a cell wall made of chitin or other materials.

    • Protists:

    • Algal forms have cell walls of cellulose; protozoans lack cell walls.

Scientific Method

  • Definition: A systematic method for investigating questions and experimental verification.

  • Steps in the Scientific Method:

    1. Observation: Notice phenomena that pique interest.

    2. Question: Pose a question regarding the observation.

    3. Hypothesis: Formulate a testable statement providing a possible answer to the question.

    4. Prediction: Create an if-then statement based on the hypothesis, predicting potential outcomes.

    5. Experiment: Conduct an experiment to test the hypothesis, collecting and analyzing data.

    6. Conclusion: Determine whether the data supports or refutes your hypothesis, and report findings.

  • Experimental Design:

    • Control Group: Group not receiving the experimental treatment (may receive placebo).

    • Experimental Group: Group receiving the treatment being tested.

    • Sample Size: Larger groups yield more reliable results by minimizing variability and outliers.

    • Double-Blind Study: Neither participants nor researchers know group assignments to reduce bias.

    • Variables:

    • Independent Variable: The factor that is manipulated (e.g., treatment given).

    • Dependent Variable: The outcome measured (e.g., growth rate).

    • Standardized Variables: Factors kept constant to ensure a fair test.

  • Goal of Scientific Method: To ensure reliable data collection and reproducibility for valid conclusions.