M1-Bio2-_CLASSIFICATION_OF_ORGANISMS (1)

Classification of Organisms

Taxonomy and Classification

• Definition: Classification of living organisms based on shared characteristics.

• Methods of classification include:

  • Comparison of appearance, anatomy, and structure.

  • Data from development, physical anatomy, biochemistry, DNA, behavior, ecological preferences, reproduction, mobility, and functionality.

• Organisms are grouped hierarchically into smaller categories based on detailed similarities to aid scientific study.

Historical Perspectives in Classification

• Early classifications:

  • Humans categorized into groups: Humans, Animals (e.g., cats & fishes), Plants (e.g., trees & grass), Non-living beings (e.g., rocks).

Evolution and Classification

• Diversity of life on Earth is a result of evolution over billions of years (3.5 - 4.5 billion).

• Evolution refers to changes in species over time, with fossils serving as evidence of past life and evolutionary processes.

Timeline of Evolution

• Key events include:

  • Big Bang: approx. 14 billion years ago.

  • Formation of Earth: approx. 4.5 billion years ago.

  • First prokaryotic organisms and the development of eukaryotes: 1.5 billion years ago.

  • Cambrian explosion (~541 million years ago): emergence of diverse life forms (sponges, annelids, arthropods, etc.).

  • Evolution of key organisms: Fish, reptiles, birds, and mammals emerging over time.

Theories of Evolution

• Several theories address how organisms evolved:

  • Special creation, spontaneous generation (abiogenesis), biogenesis, and chemical evolution.

• Evidence for evolution includes:

  • Morphology and anatomy (homologous, analogous, and vestigial organs).

  • Lamarckism (use and disuse theory) and Darwinism (natural selection).

  • Paleontology (fossils).

The Six Kingdom Classification Scheme

• Major kingdoms include:

  • Animalia (multicellular, eukaryotic).

  • Plantae (multicellular, eukaryotic).

  • Fungi (multicellular, eukaryotic).

  • Protista (unicellular and multicellular, eukaryotic).

  • Eubacteria (unicellular, prokaryotic).

  • Archaebacteria (unicellular, prokaryotic).

Characteristics of Major Kingdoms

• Key characteristics include:

  • Mobility: Eukaryotic, some mobile, others sessile.

  • Nutrition: Heterotrophic vs. autotrophic (photosynthesis and/or chemosynthesis).

  • Cellular structure: Cell walls (cellulose in plants, chitin in fungi, peptidoglycan in bacteria).

Systematics and Taxonomy

• Systematics: The science of organizing the diversity of life and studying evolutionary relationships.

  • Taxonomy: A branch focusing on identification, classification, and naming organisms.

  • Aristotle's early system classifying organisms by appearance, Linnaeus’s binomial nomenclature system proposed a two-name category for species.

Cladistics

• Cladistics focuses on monophyletic groups (common ancestors and descendants).

• Cladograms visually represent the phylogeny of organisms based on derived characteristics.

Linnaean Classification System

• Hierarchical classification:

  • Domain, Kingdom, Phylum/Division, Class, Order, Family, Genus, Species.

  • Mnemonic for taxonomy: "Did King Philip Call Out For a Good Soup?"

• Example taxonomy for humans:

  • Domain: Eukarya

  • Kingdom: Animalia

  • Phylum: Chordata

  • Class: Mammalia

  • Order: Primates

  • Family: Hominidae

  • Genus: Homo

  • Species: sapiens.

Classification Comparison

• Summary of classifications across various systems (Linnaeus, Haeckel, Whittaker, Woese).

• Cladistics compared with traditional classifications highlighting evolutionary relationships among organisms.

Types of Evidence for Classification

• Fossil records (relative and radioactive dating) validate evolutionary lineage.

• Comparative anatomy distinguishes homologous (similar structure) and analogous traits (similar function).

• Comparative embryology examines developmental stages across species revealing common ancestry.

• Biochemical information utilizes DNA and protein analysis for evolutionary relationships.

• Heredity studies inheritance patterns helping classify organisms.

• Cellular structure, behavior, and geographical range are critical in taxonomy.

Dichotomous Key

• A tool for identifying organisms through binary choices based on characteristics.

• Steps include dividing organisms into two groups based on a trait, leading to eventual identification of each specimen's name.

Constructing a Dichotomous Key

• Process involves separating organisms/features logically until each has distinct characteristics.

• Methods can include physical traits and observable behaviors.

Summary and Conclusion

• Classification helps systematize and understand the relationships and traits of the diverse life forms.

• Acknowledges the complexities and continuous adaptation of organisms over time.