Chapter 1: Introduction to Biology

Science

Scientific Method

Science: Study of the fundamental laws underlying a system’s behavior

Scientific method: Method of practicing science based on observation and experiment:

• Observe a phenomena
• Pose a query about the phenomena
• Suggest a hypothesis which answers the question and explains the phenomena
  • The hypothesis must be testable and falsifiable; otherwise, it cannot be verified through the scientific method by surviving experimental testing.
• Make a prediction based on the hypothesis
• Perform an experiment to test the prediction
• If the prediction fails, reject the hypothesis
• If the prediction succeeds, do not reject the hyposthesis
• Theory: A hypothesis that survives multiple varied experiments
• Principle / Scientific Law: Theory that is accepted by the scientific community

Experiment Design

• Independent variable: Variable that is directly controlled by the experiment administrator and is not dependent on other factors within the experiment
• Dependent variable: Variable that is not directly controlled by the experiment administrator and is dependent on other factors within the experiment
• The prediction claims that a certain change in the independent variable will cause a certain result in the dependent variable
• Treatment group: Group that is treated with the changed independent variable
• Control group: Group that is left neutral and not treated with the changed independent variable
  • Used as a reference for the treatment group
• If the dependent variable varies between the treatment group and control group as predicted by the prediction, the hypothesis survives the test

Reasoning

Classes of reasoning:

• Inductive Reasoning: Formalizing a general principle from a specific instance
• Deductive Reasoning: Deducing a specific instance from a general principle

Biology

Biology and Life

Biology: Science of living things

Life: While ‘life’ is difficult to precisely define, living things exhibit these characteristics:

• Order
• Energy consumption
• Growth
• Reproduction
• Homeostasis
• Response to stimuli
• Adaptation and evolution

Taxonomy

Taxonomy: Science of categorizing by class

• In biology, classes are organized in a hierarchical system
• Each level has specific taxons; each level’s taxons contain those of the level below
• In descending order, the levels are:
  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• For example, the common leafcutter ant belongs to the following taxons in descending hierarchical order:
  • Eukarya > Animalia > Arthropoda > Insecta > Hymenoptera > Formicidae > Atta > cephalotes.
  • This means the leafcutter ant belongs to the domain: ‘Eukarya’, kingdom: ‘Animalia’, phylum: ‘Arthropoda’, class: ‘Insecta’, order: ‘Hymenoptera’, family: ‘Formicidae’, genus: ‘Atta’, and species: ‘cephalotes’.

Binomial Nomenclature:

• Naming system that uses two names for each entity
• Biology uses a binomial nomenclature
• Organisms are named by the genus and species, as follows: “Genus species”
  • Genus proceeds species
  • Both are italicized
  • Genus is capitalized; species is not.
• For example, the common leafcutter ant, belonging to genus Atta and species cephalotes, is named “Atta cephalotes”

Phylogenetic Tree:

• Shows the evolutionary relationships between distinct organisms

Hierarchical Organization of Life

The composition of living things exhibits a hierarchical organization:

• Higher levels arise from specific arrangements of lower ones
• Emergent properties: Properties that arise at higher levels of organization and are not identifiable in the simpler components at lower levels.

Levels:

• Atom: Most basic type of matter
• Molecule: Atoms chemically bond to form molecules
• Macromolecules: Large molecule, often composed of many smaller molecules
• Organelle: Group of molecules that collectively perform a function
• Cell: Most basic unit of life; composed of molecules, macromolecules, and organelle
• Tissue: Group of cells that collectively perform a function
• Organ: Group of tissues that collectively perform a function
• Organ System: System of organs that collectively perform a function
• Organism: Individual living entity
• Population: The set of organisms of a specific species within a specific area
• Community: The set of all populations within a specific area
• Ecosystem: The system of biotic communities and the abiotic system with which they interact within a specific area
• Biosphere: The system of all ecosystems on a planet