Introduction to Biological Science and Methodology

Defining Biology and Living Systems

  • Biology is the formal scientific study of living things and organisms.
  • Biology is ubiquitous and can be observed in the world all around us (e.g., nature, wildlife, human structures).
  • The field is defined not just by its subject matter, but by its rigorous methodology.

The Eight Characteristics of Life

Life is defined by a specific set of characteristics that distinguish living organisms from non-living matter.

  • 1. Order: Biological systems follow a systems approach to organization. According to the 2nd Law of Thermodynamics, energy is required to maintain this order and prevent systemic decay.
  • 2. Energy Conversion and Chemical Metabolism:
    • Metabolism involves the chemical conversion of energy to maintain biological functions and fight entropy.
    • This characteristic excludes viruses, as they do not carry out their own independent metabolism.
    • Key considerations in metabolism include identifying the source of energy, how energy is lost, and the flow of molecules (where they come from and where they go).
  • 3. Interaction with Environment: Life interacts with both biotic (living) and abiotic (non-living) components of the ecosystem.
    • Example: Plants capture energy from the sun (abiotic) and transform it into chemical energy. Consumers then harvest this energy by eating the plants.
  • 4. Regulation and Homeostasis:
    • Because environments are dynamic and not static, organisms must regulate their internal environment to maintain stability.
    • Management occurs through feedback loops:
      • Negative feedback: This occurs when an excess of a product stops its further production. For example, in a pathway from Enzyme 1 through Enzyme 3, an accumulation of product D blocks the initial step.
      • Positive feedback: This occurs when an excess of a starting or intermediate product triggers further processing or stimulates a step. For example, an excess of product Z stimulates the action of Enzyme 4.
  • 5. Composition of Cells: All life is composed of cells, the basic unit of structure. Examples of cell sizing include:
    • Neuron in brain: 300×400 μm300 \times 400\,\mu\text{m} wide.
    • Ovum (Egg cell): 100 μm100\,\mu\text{m}.
    • Fat cell: 50×150 μm50 \times 150\,\mu\text{m}.
    • Red blood cell: 7.5 μm7.5\,\mu\text{m}.
    • White blood cell: 15 μm15\,\mu\text{m}.
    • Smooth muscle cell: 15×200 μm15 \times 200\,\mu\text{m} long.
    • Sperm cell: 5 μm5\,\mu\text{m} long.
  • 6. Reproduction: Cells arise from pre-existing cells. The instructions for reproduction are stored in the genetic code of DNA.
    • Reproduction can be Asexual (e.g., budding in hydra) or Sexual.
  • 7. Growth and Development: Organisms undergo predictable changes and maturation over time. Comparative embryology shows similar developmental stages across different species, including Fish, Salamander, Tortoise, Chick, Hog, Calf, Rabbit, and Human.
  • 8. Evolutionary Adaptations: DNA is passed through successful reproduction, impacting the traits present in a population over time. This implies that all species are connected through shared ancestry, which is categorized via Taxonomy and Phylogeny.

Biological Organization and Taxonomy

  • Taxonomy Hierarchy: Biological classification follows a nested hierarchy starting from the broadest category to the most specific:
    • Domain (e.g., Eukarya)
    • Kingdom (e.g., Animalia)
    • Phylum (e.g., Chordata)
    • Class (e.g., Mammalia)
    • Order (e.g., Carnivora)
    • Family (e.g., Felidae)
    • Genus (e.g., Felis)
    • Species (e.g., Felis catus)
  • The Three Domains of Life:
    • Bacteria
    • Archaea
    • Eukarya: Comprised of Kingdom Fungi, Kingdom Animalia, Kingdom Plantae, and Protists (which represent multiple kingdoms).

Biological Themes

Modern biology is organized around several recurring themes:

  • The cell as the basic unit of life.
  • Heritable information (DNA).
  • Emergent properties of biological systems.
  • Regulation (Homeostasis).
  • Interaction with the environment.
  • Energy and life processes.
  • Unity and diversity of organisms.
  • Evolution and population change.
  • Relationship between structure and function.
  • Scientific inquiry.
  • The intersection of science, technology, and society.

The Scientific Method and Reasoning

Biology is a science defined by its methodology:

  • The Scientific Process: Question →\rightarrow Research →\rightarrow Hypothesis →\rightarrow Experiment →\rightarrow Data →\rightarrow Conclusion.
  • Types of Reasoning:
    • Inductive reasoning: Reasoning from the specific to the general. This involves making broad statements based on multiple specific observations.
    • Deductive reasoning: Reasoning from the general to the specific. This involves "If/then" logic.
  • Data Reliance: Science depends entirely upon data. The subject matter must be measurable for scientific analysis.

Scientific Theory and Principles

  • Scientific Theory: A hypothesis or synthesis of a group of hypotheses that has been tested and verified many times.
    • It must have no negative evidence produced against it.
    • It must possess predictive power.
    • Note: A theory can never be absolutely proven; science is a continuous process of adjusting theories to fit new data.
  • Scientific Principle: A theory that has been supported by data over an extensive period of time (e.g., the Theory of Evolution).

Historical Evolution of Taxonomy

The classification of life has shifted as scientific tools and data have improved, illustrating the scientific method in action:

  • 1735 (Linnaeus): 2 Kingdoms (Animalia, Vegetabilia).
  • 1866 (Haeckel): 3 Kingdoms (Animalia, Plantae, Protista).
  • 1925 (Chatton): 2 Groups (Eukaryote, Procaryote).
  • 1938 (Copeland): 4 Kingdoms (Animalia, Plantae, Monera, Protoctista).
  • 1969 (Whittaker): 5 Kingdoms (Animalia, Plantae, Fungi, Protista, Monera).
  • 1977, 1990 (Woese): 3 Domains (Bacteria, Archaea, Eukarya).

Instructional Guidance

  • Students are encouraged not to write down every word from every slide.
  • Focus on documenting personal questions and identifying specific slides that cause confusion.
  • The classroom is a judgment-free zone where students should feel comfortable asking for the instructor to slow down.