arrow_backBack to Study Resources

Chapter 8: Biodiversity

Form 5 Biology Bab 8: Biodiversity

8.1 Classification System and Naming of Organisms

Taxonomic Hierarchy

Taxonomy is the field of biology involving the classification, identification, and naming of organisms in an organized system. Organisms are classified into seven main hierarchical taxonomic levels:

  1. Domain (Highest level)
  2. Kingdom
  3. Phylum
  4. Class
  5. Order
  6. Family
  7. Genus
  8. Species (Basic unit of classification)

The Six Kingdoms

  • Archaebacteria: Prokaryotic, unicellular, lacks peptidoglycan in cell walls, lives in extreme environments (e.g., methanogens, halophiles, thermophiles).
  • Eubacteria: Prokaryotic, unicellular, cell walls made of peptidoglycan, true bacteria (e.g., Escherichia coli, Lactobacillus sp.).
  • Protista: Eukaryotic, mostly unicellular or simple multicellular, simple organization without specialized tissues (e.g., Amoeba sp., Paramecium sp., Spirogyra sp., Euglena sp.).
  • Fungi: Eukaryotic, non-photosynthetic (heterotrophic/saprophytic), cell walls made of chitin (e.g., Yeast, Mucor sp., mushrooms).
  • Plantae: Eukaryotic, multicellular, photosynthetic autotrophs containing chlorophyll, cell walls made of cellulose (e.g., ferns, flowering plants).
  • Animalia: Eukaryotic, multicellular heterotrophs, lack cell walls, mostly motile (e.g., invertebrates, vertebrates).

Binomial Nomenclature System

Introduced by Carl Linnaeus. Every organism is assigned a unique two-part scientific name:

  • First word: Represents the Genus (capitalized first letter).
  • Second word: Represents the Species (all lowercase letters).
  • Formatting Rules: Italicized when printed (e.g., Panthera tigris) or individually underlined when handwritten (e.g., Panthera tigris).

Dichotomous Key

A tool used by biologists to identify unknown organisms based on pairs of contrasting structural features (couplets) leading step-by-step to the correct identification.

8.2 Biodiversity

Three Major Levels of Biodiversity

  • Genetic Diversity: Variations in genes within a single species (e.g., different varieties of rice plants, human skin tones).
  • Species Diversity: The variety and abundance of different species present within a specific ecosystem.
  • Ecosystem Diversity: The variety of biological habitats, ecosystems, and ecological processes across the biosphere (e.g., tropical rainforests, mangrove swamps, coral reefs, deserts).

Phylogenetic Tree

A evolutionary diagram that illustrates the evolutionary relationships and common ancestry among various biological species based on genetic and morphological evidence.

8.3 Microorganisms and Viruses

Main Groups of Microorganisms

  • Bacteria: Single-celled prokaryotes classified by shape (coccus, bacillus, spirillum, vibrio).
  • Protozoa: Unicellular eukaryotic animal-like microorganisms (e.g., Plasmodium sp., Amoeba sp.).
  • Algae: Photosynthetic unicellular or simple multicellular eukaryotic organisms (e.g., Chlamydomonas sp., Diatoms).
  • Fungi: Microscopic saprophytes or parasites (e.g., Saccharomyces cerevisiae).
  • Viruses: Non-living obligate intracellular parasites consisting of nucleic acid (DNA or RNA) enclosed within a protein coat (capsid). They reproduce only inside living host cells.

Roles of Microorganisms in the Nitrogen Cycle

  • Nitrogen-Fixing Bacteria: Convert atmospheric nitrogen gas ($N_2$) into ammonium ions ($NH_4^+$) (e.g., Rhizobium sp. in root nodules of legumes, free-living Azotobacter sp.).
  • Nitrifying Bacteria:
    • Nitrosomonas sp. converts ammonium ions ($NH_4^+$) into nitrite ions ($NO_2^-$).
    • Nitrobacter sp. converts nitrite ions ($NO_2^-$) into nitrate ions ($NO_3^-$).
  • Decomposers / Saprophytic Bacteria & Fungi: Break down dead organic matter (proteins, urea) into ammonium ions ($NH_4^+$) via ammonification.
  • Denitrifying Bacteria: Convert nitrate ions ($NO_3^-$) back into atmospheric nitrogen gas ($N_2$) under anaerobic conditions (e.g., Pseudomonas denitrificans).

Applications of Microorganisms in Biotechnology and Industry

  • Food Production: Lactobacillus sp. in yogurt/cheese manufacturing; Saccharomyces cerevisiae in bread baking and alcohol fermentation.
  • Medicine: Production of antibiotics (e.g., Penicillium chrysogenum producing penicillin), vaccines, and recombinant human insulin via Escherichia coli.
  • Agriculture & Environment: Nitrogen fixation, composting, and bioremediation (using bacteria to break down oil spills and toxic chemical pollutants).
Sponsored