Classification of Living Things and Taxonomy

Classification of Living Things

• All living things share eight characteristics:
  • Composed of cells and DNA
  • Capable of reproduction
  • Exhibit ordered organization
  • Can grow and develop
  • Obtain and use energy
  • Respond to stimuli
  • Maintain homeostasis
  • Evolve over time

Taxonomy

• Taxonomy is the science of classifying organisms.
• Kingdoms are hierarchical levels used in taxonomy.
• Discovering new kingdoms depends on exploring new environments (sea, space, microscopes).

Current Kingdoms

• Animalia (animals)
• Plantae (plants)
• Fungi (mushrooms, molds, yeasts)
• Protista (single-celled organisms like algae)
• Eubacteria (true bacteria)
• Archaebacteria (ancient bacteria in extreme environments)

Taxonomic Levels

• The seven taxonomic levels (KPCOFGS):
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species

Importance of Taxonomy

• Organizes and classifies organisms.
• Creates a universal language for scientists.
• Helps understand evolutionary relationships.

Binomial Nomenclature

• Assigns unique scientific names to each species.
• Prevents confusion between common names in different languages.
  • Examples:
    • Grey wolf: Canis lupus
    • Potato: Solanum tuberosum
    • Water buffalo: Bubalus bubalis
    • Brain-eating amoeba: Naegleria fowleri
    • Goliath bird-eating spider: Theraphosa blondi

Dichotomous Keys

• Used to identify organisms.
• Consist of a series of choices (yes/no or true/false).
  • Example of a dichotomous key (using fictitious organisms):
    • 1. Has pointed ears...go to 3; Has rounded ears...go to 2
    • 2. Has no tail...Kentuckyus; Has tail...Dakotus
    • 3. Ears point upward...go to 5; Ears point downward...go to 4

Cladograms

• Diagrams showing evolutionary relationships based on shared traits.
• Branches represent lineages.
• Nodes represent common ancestors.
• Root represents the most recent common ancestor.
• Clade includes an ancestor and all its descendants, sharing derived traits.
• Outgroup is used to identify evolutionary paths.
• Derived characteristics are traits unique to a clade.
• Ancestral characteristics are found in the common ancestor.

Prokaryotes vs. Eukaryotes

• Prokaryotes lack a nucleus and membrane-bound organelles (bacteria and archaea).
• Eukaryotes have a nucleus and membrane-bound organelles.

Bacterial Cell Structure and Function

• Pill (pili): Cell surface structures for attachment and genetic exchange.
• Plasmid: Small circular DNA carrying extra genetic material.
• Ribosomes: Protein synthesis.
• Cytoplasm: Liquid holding organelles; regulates metabolism.
• Plasma membrane: Semipermeable membrane controlling substance passage.
• Peptidoglycan layer: Provides cell wall rigidity.
• Outer membrane: (Gram-negative) Protects cell, transports nutrients.
• Condensed DNA: Stores genetic instructions.
• Flagellum: Tail-like structure for movement to favorable environments.

Bacterial Shapes

• Cocci: Circular/spherical bacteria
• Bacilli: Rod-shaped bacteria
• Spirilla: Spiral-shaped bacteria
• Mono: One bacteria
• Diplo: Two bacteria
• Strepto: Chain bacteria
• Staphylo: Cluster bacteria
• Flagellates: Bacteria with flagella
• Vibrios: Comma-shaped or curved bacteria

Bacterial Metabolism

• Bacteria can obtain energy from chemical compounds (sugars, fats) or sunlight.
• Oxygen requirements:
  • Obligate aerobes need oxygen
  • Facultative aerobes can thrive with or without oxygen

Bacterial Reproduction

• Binary fission: Asexual reproduction where one cell divides into two identical cells. Steps involve cell growth, DNA replication, DNA migration, and pinching off.

Bacterial Genetic Exchange

• Bacterial conjugation: Direct transfer of DNA between cells via pili.
• Bacterial transformation: Uptake of free DNA from the environment.
  • Similarities: Both result in genetic variation and horizontal (non-parental) gene transfer.
  • Differences: Conjugation requires direct cell contact; transformation does not.

Endospores

• Dormant, resistant structures bacteria form for survival under harsh conditions.

Bacterial Resistance

• Natural selection can lead to antibiotic resistance in bacteria.
  • Killing weaker bacteria leaves stronger bacteria to reproduce.
  • Continued use of antibiotics is crucial even if feeling better.

Archaebacteria Characteristics

• Live in extreme environments.
• Cell walls contain pseudopeptidoglycan, polysaccharides, or proteins.
• Have ether-linked lipids.
• Have unique enzymes for transcription and translation.

Archaea Subgroups

• Methanogens: Produce methane
• Halophiles: Thrive in salty environments
• Extreme thermophiles: Prefer hot conditions
• Psychrophiles: Prefer cold conditions

Fungi

• Essential decomposers, breaking down organic matter and recycling nutrients.
• Characteristics: Eukaryotic, cell walls of chitin, heterotrophic.
• Structure: Hyphae (thread-like), mycelium (network of hyphae), fruiting bodies (reproductive structures).
• Reproduction: Asexual (fragmentation) and sexual (fusion of hyphae).
• Ecological roles: Decomposers, symbiotic relationships (mycorrhizae, lichens).
• Importance to humans: Food production (yeast), medicine (antibiotics), and pathogens (some cause disease).

Plants

• Provide oxygen, food (stored carbohydrates), and shelter.

Explore the fascinating world of taxonomy and the classification of living organisms. This quiz covers the characteristics shared by all living things, the current kingdoms of life, taxonomic levels, and the significance of taxonomy in organizing biological diversity. Test your knowledge on how living organisms are categorized!