Nature of Science: Classification – Study Notes for General Biology

Nature of Science

Scientific Inquiry and Investigation

Scientific inquiry is the process by which scientists ask questions, develop hypotheses, and conduct investigations to understand natural phenomena. This process is fundamental to the advancement of biological knowledge.

• Ask and Investigate Scientific Questions: Scientists begin by observing the world and asking testable questions.

• Develop and Test Hypotheses: A hypothesis is a proposed explanation that can be tested through experimentation.

• Understand Scientific Evidence and Measurement: Reliable data collection and measurement are essential for drawing valid conclusions.

• Plan and Conduct Ethical Investigations: Ethical considerations ensure that research is conducted responsibly and safely.

• Analyze Relationships and Construct Scientific Explanations: Scientists interpret data to explain relationships and mechanisms in biology.

Classification in Biology

Purpose and Importance of Classification

Classification is the systematic arrangement of organisms into groups based on shared characteristics. This organization helps scientists communicate, study, and understand the diversity of life.

• Definition: Classification is the process of grouping organisms by similarities and differences in their structure, function, and genetic makeup.

• Examples: Grocery stores organize food items for easy access; similarly, biological classification organizes living things for easier study.

• Applications: Classification allows scientists to predict characteristics, understand evolutionary relationships, and identify new species.

Historical Systems of Classification

Early classification systems were based on observable traits, but advances in technology and genetics have led to more accurate groupings.

• Aristotle: Classified organisms into groups based on appearance, but this system had many flaws due to overlapping traits.

• Carl Linnaeus: Developed a hierarchical system and introduced binomial nomenclature, giving each species a unique scientific name.

• Binomial Nomenclature: Each species is named using two parts: Genus (capitalized) and species (lowercase), e.g., Puma concolor.

• Scientific Names: Universal and consistent, unlike common names which vary by region.

Modern Classification: Domains and Kingdoms

Modern classification uses genetic and molecular evidence to group organisms into three domains and six kingdoms.

• Three Domains: Archaea, Bacteria, and Eukarya.

• Six Kingdoms: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, Animalia.

• DNA Analysis: DNA sequencing helps determine evolutionary relationships and classify organisms more accurately.

Domain	Kingdoms	Characteristics
Archaea	Archaebacteria	Prokaryotic, live in extreme environments, no peptidoglycan in cell walls
Bacteria	Eubacteria	Prokaryotic, cell walls with peptidoglycan, reproduce asexually by binary fission
Eukarya	Protista, Fungi, Plantae, Animalia	Eukaryotic, cells with nuclei, diverse forms and functions

Characteristics of the Six Kingdoms

Each kingdom has unique features that distinguish its members.

• Archaebacteria: Unicellular, prokaryotic, live in extreme environments.

• Eubacteria: Unicellular, prokaryotic, cell walls with peptidoglycan, some beneficial, some pathogenic.

• Protista: Mostly unicellular, eukaryotic, diverse (includes algae, protozoa).

• Fungi: Mostly multicellular, eukaryotic, cell walls with chitin, decomposers.

• Plantae: Multicellular, eukaryotic, cell walls with cellulose, photosynthetic.

• Animalia: Multicellular, eukaryotic, no cell walls, heterotrophic.

Kingdom	Cell Type	Cell Wall	Nutrition	Examples
Archaebacteria	Prokaryotic	No peptidoglycan	Varied	Methanogens, Halophiles
Eubacteria	Prokaryotic	Peptidoglycan	Varied	Streptococcus, E. coli
Protista	Eukaryotic	Varied	Autotrophic/Heterotrophic	Amoeba, Algae
Fungi	Eukaryotic	Chitin	Heterotrophic	Mushrooms, Yeast
Plantae	Eukaryotic	Cellulose	Autotrophic	Ferns, Mosses
Animalia	Eukaryotic	None	Heterotrophic	Humans, Insects

Viruses: Living or Nonliving?

Viruses are unique biological entities that challenge the definition of life. They share some characteristics with living organisms but lack others.

• Structure: Composed of nucleic acid (DNA or RNA) surrounded by a protein coat (capsid); some have an outer membrane.

• Size: Even smaller than prokaryotes.

• Not Living: Cannot reproduce independently; must infect host cells to replicate.

• No Metabolism: Do not carry out metabolic processes.

• No Growth or Development: Do not grow or develop like living organisms.

Characteristic	Living Organisms	Viruses
Cellular Structure	Yes	No
Metabolism	Yes	No
Growth/Development	Yes	No
Reproduction	Yes (independently)	Only within host cell

Cell Theory and Specialization

Parts of Cell Theory

Cell theory is a foundational concept in biology describing the properties of cells.

• All living things are composed of cells.

• Cells are the basic units of structure and function in living organisms.

• All cells arise from pre-existing cells.

Specialization and Multicellularity

Specialization allows cells to perform specific functions, leading to the development of complex multicellular organisms.

• Cell Specialization: Cells differentiate to perform unique roles (e.g., muscle cells, nerve cells).

• Multicellularity: Specialized cells work together, forming tissues, organs, and organ systems.

• Homeostasis: The maintenance of stable internal conditions is essential for life; multicellular organisms use specialized cells and systems to achieve homeostasis.

Summary Table: Domains and Kingdoms

Domain	Kingdoms	Cell Type	Cell Wall	Examples
Archaea	Archaebacteria	Prokaryotic	No peptidoglycan	Methanogens, Halophiles
Bacteria	Eubacteria	Prokaryotic	Peptidoglycan	Streptococcus, E. coli
Eukarya	Protista, Fungi, Plantae, Animalia	Eukaryotic	Varied	Amoeba, Mushrooms, Ferns, Humans

Key Equations and Concepts

• Binary Fission (Bacterial Reproduction):

$\text{Parent Cell} \rightarrow \text{DNA Replication} \rightarrow \text{Cell Division} \rightarrow 2 \text{Daughter Cells}$

• Homeostasis: The process by which organisms maintain a stable internal environment.

$\text{Homeostasis} = \text{Stable Internal Conditions}$

Additional info: DNA sequencing and cladistics are modern tools used to infer evolutionary relationships and refine classification systems. The study of viruses highlights the boundaries of what is considered 'alive' in biology.