The Five Kingdoms of Life and Mechanisms of Speciation

Biological Classification: Kingdoms and Taxonomy

Kingdom Monera (Prokaryotes)

Characteristics: Prokaryotes that are unicellular and lack organelles. They possess a cell wall composed of murein (peptidoglycan).

Archaebacteria (Archaea)

• Halophiles (salt-loving)
• Methanogens (methane-producing)
• Thermoacidophiles (heat and acid-loving)

Eubacteria (True Bacteria)

Heterotrophic Bacteria

• Forms: Cocci (spherical), Spirilla (spiral), Bacilli (rod-shaped)
• Nutrition: Saprophytic, Symbionts, Commensals, Parasites
• Staining: Gram-positive, Gram-negative

Autotrophic Bacteria

• Chemosynthetic
• Photosynthetic

Kingdom Protoctista (Protists)

Characteristics: Eukaryotes, uni- or pluricellular. Includes autotrophs (algae) and heterotrophs (protozoa).

Autotrophic Protoctists (Algae)

• Microalgae: Euglenoids, Dinoflagellates, Diatoms, Golden Algae.
• Macroalgae: Chlorophyta (Green Algae), Rhodophyta (Red Algae), Phaeophyta (Brown Algae).

Heterotrophic Protoctists

• Molds: Slime molds and Oomycetes.
• Protozoa: Amoeba, Flagellates, Ciliates, Sporozoans.

Kingdom Fungi

Organization: Formed by a thallus composed of hyphae (tubular filaments forming a mycelium). Cell walls contain chitin. They store glycogen, are heterotrophic, and often reproduce via asexual spores.

Fungal Classification

• Zygomycetes: Mycelium composed of non-septate hyphae.
• Ascomycetes: Possess septate hyphae.
• Basidiomycota: The most evolved group.

Kingdom Plantae (Plants)

Organization: Cormophytic organization. Cell wall composed of cellulose. They store starch and are autotrophic via photosynthesis.

Plant Divisions

• Non-Vascular Plants (Bryophyta): Mosses. Lack conducting tissues.
• Vascular Plants (Tracheophytes): Possess conducting tissues.
• Seedless Vascular Plants (Pteridophyta): Ferns.
• Seed Plants (Spermatophyta): Form seeds.
  • Gymnosperms: Naked seeds.
  • Angiosperms: Protected seeds (Monocotyledons or Dicotyledons).

Kingdom Animalia (Animals)

Characteristics: Pluricellular eukaryotes lacking cell walls. They possess tissues and exhibit bilateral or radial symmetry. They store glycogen or fat, are heterotrophic, reproduce sexually, and typically have the capacity for displacement.

Animal Phyla Classification

Invertebrates (Without Skeleton)

• Diploblastic: Porifera (Sponges), Cnidarians.
• Triploblastic: Platyhelminthes, Nematodes, Annelids, Mollusks.

Invertebrates (External Skeleton)

• Arthropods: Crustaceans, Insects, Arachnids, Myriapods.

Vertebrates (Internal Skeleton)

• Echinoderms and Chordates.
• Chordate Subgroups: Lampreys and Hagfishes, Chondrichthyes (Cartilaginous Fish), Bony Fish, Amphibians, Reptiles, Birds, Mammals.

Chordate Organization

• Urochordates
• Cephalochordates (Lancelets)
• Vertebrates

Taxonomy and Species Formation

The Species Concept

Species: A taxonomic category representing the fundamental unit of biological classification.

Biological Species: A group of organisms that possess a large number of characters in common, can interbreed, and produce fertile offspring. This group is maintained by reproductive isolation.

Speciation Mechanisms

Speciation is the mechanism by which new species arise from previous ones.

• Allopatric Speciation: Occurs when a given population becomes physically isolated due to geographical barriers.
• Sympatric Speciation: Occurs when a species occupying a territory diversifies into two populations due to mechanisms preventing reproduction (e.g., behavioral or genetic isolation).

Taxonomic Hierarchy

The standard classification levels, from broadest to most specific:

Kingdom, Phylum, Class, Order, Family, Genus, Species.