The Biology of Monera, Protista, Fungi, and Plants

Posted on Nov 2, 2024 in Biology

Kingdom Monera

Bacteria: These organisms are prokaryotic, unicellular, and the first on Earth. They include:

  • Eubacteria: Green bacteria are photoautotrophs that don’t produce O2 and have bacteriochlorophyll.
  • Proteobacteria: A broad group of gram-negative bacteria, including photosynthetic and heterotrophic types like Legionella.
  • Spirochetes: Gram-negative bacteria without chlorophyll (e.g., Spirochaeta sicilis).
  • Cyanobacteria (Blue-Green Algae): Photosynthetic bacteria with chlorophyll, ancestors of chloroplasts. Many fix atmospheric nitrogen.
  • Chlamydia: Intracellular parasites.
  • Gram-Positive Bacteria: Common heterotrophic bacteria, some important for food industry, others cause diseases like tuberculosis.

Archaebacteria: Live in extreme conditions:

  • Halophiles: Live in extremely saline environments (e.g., Dead Sea).
  • Methanogens: Produce methane from CO2 and H2, found in digestive tracts and wetlands.
  • Thermoacidophiles: Live in acidic and very hot environments (above 60°C).

Kingdom Protista

Eukaryotic organisms living in moist environments. This diverse group includes:

Algae

Mostly aquatic, photosynthetic organisms forming the base of food chains:

  • Dinoflagellates: Unicellular with two flagella, abundant in oceans. Can produce toxins and cause red tides.
  • Diatoms: Unicellular in fresh and saltwater, surrounded by a protective shell.
  • Euglenoids: Unicellular, freshwater organisms with flagella, chloroplasts, and can live without light by consuming organic compounds.
  • Red Algae (Rhodophyta): Multicellular, color due to chlorophyll and other pigments. Some form calcium carbonate reefs.
  • Brown Algae: Multicellular, live in rocky coastal areas, some form large underwater “forests”.
  • Green Algae: Unicellular and multicellular, similar chlorophyll to land plants, live mainly in freshwater.

Protozoa

Unicellular heterotrophs:

  • Zooflagellates: Move using flagella, live in soil or water, some cause diseases (e.g., sleeping sickness).
  • Sarcodines: Move using pseudopods, mostly free-living, some are parasites.
  • Sporozoans: Parasitic, lack locomotion in adult form.
  • Ciliates: Live in fresh and saltwater, covered in cilia.

Water Molds and Slime Molds

Similar to fungi, with filamentous bodies:

  • Oomycetes (Water Molds): Filamentous, some cause diseases.
  • Myxomycetes (Acellular Slime Molds): Form plasmodia (mass of cytoplasm with many nuclei).
  • Acrasiomycetes (Cellular Slime Molds): Independent cells that engulf bacteria and aggregate under unfavorable conditions.

Kingdom Fungi

Heterotrophic, mostly multicellular eukaryotes. Their bodies are made of hyphae forming mycelia. Cell walls contain chitin:

  • Zygomycetes: Decomposers, live on plant or animal matter.
  • Ascomycetes: Produce spores in asci (sac-like structures). Many are colorful and fruiting.
  • Basidiomycetes: Form spores in fruiting bodies (mushrooms).

Kingdom Plantae

Multicellular, autotrophic eukaryotes with cuticle, stomata, and roots:

Bryophytes

Non-vascular plants without lignin, seeds, or flowers:

  • Liverworts: Small, primitive plants without stomata.
  • Mosses: Sensitive to pollution, have phyllodes (leaf-like structures) and rhizoids.

Pteridophytes

Vascular plants with lignin:

  • Horsetails: Live in humid places, stems resemble bamboo, contain silica.
  • Ferns: Largest group of seedless vascular plants, produce spores in sporangia and sori.

Gymnosperms (Seed Plants)

  • Cycads: Resemble palm trees, ancient seed plants.
  • Ginkgos: Some abundant in cultivation, maintained through gardening.
  • Conifers: Largest group of gymnosperms, form extensive forests, characteristic reproductive structure is the cone.

Angiosperms (Flowering Plants)

Dominate the plant kingdom, characterized by flowers:

  • Monocots: Examples: irises, tulips, wheat, palms. Seeds contain one cotyledon, parallel leaf veins, fibrous root system, flower parts in multiples of three.
  • Dicots: Examples: roses, oaks, almonds. Seeds contain two cotyledons, net-like leaf veins, taproot system, flower parts in multiples of four or five.

Taxonomy

The science of classifying organisms based on similarities. Taxonomic ranks: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.

Nomenclature: The system of naming organisms using binomial nomenclature (two names derived from Latin).

History of Classification

  • 18th Century: Carl Linnaeus – Binomial nomenclature, two kingdoms (animals and plants).
  • 19th Century: Charles Darwin – Theory of evolution, three kingdoms (animal, vegetable, protist).
  • 20th Century: R.H. Whittaker – Five kingdoms (animal, plant, protist, fungi, monera).
  • L. Margulis and K. Schwartz – Modified five kingdoms, three domains (bacteria, archaea, eukarya).

Phylogenetic Tree: A diagram representing evolutionary relationships among species.

Plant Nutrition

The process of obtaining materials and energy for growth and vital functions.

Essential Nutrients

  • Carbon (CO2)
  • Oxygen (O2)
  • Hydrogen (H2O)
  • Nitrogen (NO3)
  • Potassium (K)
  • Calcium (Ca2+)
  • Phosphorus (PO42-)
  • Magnesium (Mg2+)
  • Sulfur (SO42-)

Phases of Plant Nutrition

  1. Absorption of Water and Minerals: Through root hairs, via symplastic (through cells) or apoplastic (between cells) pathways.
  2. Transport of Water and Minerals through Xylem: Cohesion-tension theory (transpiration and cohesion) and root pressure theory.
  3. Gas Exchange: Through stomata.