Biological Diversity: Taxonomy and Oxygen Acquisition

Biological Diversity: Taxonomy & Classification

• Taxonomy: The classification of organisms into different categories (taxa).

• Taxonomic Rank: From most general to most specific.

  • Example: Humans are classified as Homo (genus) sapiens (species).

Oxygen Acquisition in Living Organisms

• Obligate Aerobes:

  • Require O2 to survive.

• Obligate Anaerobes:

  • Cannot survive in the presence of O2.

• Facultative Anaerobes:

  • Grow in the presence of O2 but can utilize anaerobic metabolism when O2 is absent.

Microbes

• Microbiome: Collection of microorganisms (bacteria, fungi) in/on our bodies.

  • Examples: Good and bad bacteria in the digestive tract.

  • Bad bacteria can lead to infections (gonorrhea, tuberculosis, leprosy, pneumonia).

  • Good bacteria help synthesize vitamins and enhance metabolism.

  • Extended use of antibiotics can deplete vitamin-metabolizing bacteria, leading to vitamin deficiency.

Bacteria

• Gram Positive:

  • Stain purple.

  • Thick peptidoglycan layer in the cell wall.

  • No outer membrane.

  • Do not produce endotoxins.

  • Teichoic acids increase cell wall flexibility.

• Gram Negative:

  • Stain pink.

  • Thin peptidoglycan layer in the cell wall.

  • Contains an outer membrane.

  • Produce endotoxins when broken down due to the presence of LPS (lipopolysaccharides) in the membrane.

    • LPS enhances integrity and protects the membrane from chemical attack.

• Endospores:

  • Durable structures produced by some bacteria that help them survive in extreme environmental conditions.

Early Forms of Life

• Anaerobic prokaryotes: The first types of living organisms to appear.

Prokaryotic vs. Eukaryotic: Cell Structure & Characteristics

Energy Acquisition for Growth and Metabolism

• Heterotrophs: Consumers of organic substances/food produced from autotrophs.

• Autotrophs: Producers of organic substances/food.

  • Earliest autotrophic cells were anaerobic but capable of photosynthesis (anaerobic photosynthesizers) – e.g., cyanobacteria.

• Chemoheterotrophs:

  • Use organic compounds as a source of energy.

  • Obtain carbon for metabolism through consuming organic materials.

• Chemoautotrophs:

  • Use inorganic chemicals (H2S, NH3) in reactions for energy.

  • Convert chemicals into biomass.

• Photoheterotrophs:

  • Use light for energy.

  • Obtain carbon for metabolism through consuming organic materials.

• Photoautotrophs:

  • Use light for energy.

  • Make organic substances/carbohydrates via photosynthesis.

  • Obtain carbon for metabolism through consuming inorganic carbon sources (CO2, HCO3^−).

  • Example: Bacteria found at the top of a pond.

• Decomposers:

  • Consume the remains of organisms & non – living organic material.