Ecology and Classification

• Parasitism is a type of ecological interaction where one organism (parasite) benefits at the expense of another organism (host).
• Living organisms come in great numbers and diversity
• Attempts have been made to organize living organisms into groups based on common characteristics for communication and meaningful study
• Biological classification is the sorting out of living things into groups based on their common characteristics
• Taxonomy is the branch of biology concerned with the principles of classification based on the structure of living organisms
• Importance of classification of living things:
• For easy identification of living things
• For easy study/research
• To show the relationship between different categories of living organisms
• To show evolutionary trend in different groups
• Historical background of taxonomy:
• Aristotle was the first biologist to classify living things based on movement, habitat, and body parts
• John Ray identified plants and animals based on natural relationships and developed the modern concept of a species
• Carolus Linnaeus is known as the father of the modern system of classification, classified organisms based on body plan into groups using the binomial system of nomenclature
• Taxonomic hierarchy and units:
• Living organisms are classified into seven ranks (taxa): Kingdom, phylum, class, order, family, genus, species
• There are five kingdoms: Prokaryotae (Monera), Protoctista (protista), Fungi, Plantae, and Animalia
• Viruses are not included in the five kingdoms because they are non-cellular infectious particles and considered non-living outside a host cell
• Kingdom Prokaryotae (Monera):
• Organisms in this kingdom are bacteria and cyanobacteria (blue-green algae)
• Characteristics:

  • Unicellular and microscopic
  • No membrane-bound nucleus; nuclear material lies freely in the cytoplasm
  • Lack membrane-bound organelles
  • Possess cell wall made of polysaccharide and amino acid
  • Some possess flagella for locomotion
  • Reproduce asexually by binary fission and sexually by conjugation
  • Have varied modes of nutrition, some are autotrophic while others are heterotrophic
• Economic importance of bacteria:

  • Improve soil fertility by decomposing dead organic matter
  • Employed in industry for processes like fermentation to produce food
  • Symbiotic bacteria in intestines of herbivores digest cellulose to release nutrients
  • Cause diseases to humans and livestock
• Kingdom Protoctista:
• Characteristics:

  • Have varied body forms: unicellular, microscopic, or multicellular thalloids
  • Have cellular membranes, hence eukaryotic
  • Some are heterotrophic and autotrophic
  • Reproduce asexually through fission, fragmentation, or sporulation
• There are nine Phyla under this kingdom:

  • Protoctists with animal-like features (protozoans)
  • Protoctists with both animal-like and plant-like features
  • Protoctists with fungi features (slimy molds)
  • Protoctists with plant-like features (algae)
• Phylum Rhizopoda (Rhizopoda):
• Characteristics:

  • Reproduction is asexual by binary fission
  • Possess pseudopodia for locomotion
  • Unicellular and microscopic
  • Some are infectious
  • Examples: Amoeba, Entamoeba, Marcella
• Phylum Zoomastigina (flagellates):
• Characteristics:

  • Unicellular and heterotrophic
  • Possess flagella for locomotion
  • Undergo both sexual and asexual reproduction
  • Some are infectious
  • Examples: Trypanosoma, Trichomonas
• Phylum Apicomplexa (sporozoans):
• Characteristics:

  • Unicellular
  • Undergo both sexual and asexual reproduction
  • Lack locomotory structures
  • Have apical complex for penetration
  • Example: Plasmodium
• Phylum Ciliophora (ciliates):
• Characteristics:

  • Have cilia for locomotion
  • Possess two nuclei: meganucleus and micronucleus
  • Are heterotrophic
  • Example: Paramecium, Vorticella
• Phylum Euglenophyta (euglenoid flagellates):
• Characteristics:

  • Aquatic organisms
  • Possess flagella for locomotion
  • Are photosynthetic
  • Some species do not photosynthesize and are heterotrophic
  • Reproduce asexually by binary fission
  • Example: Euglena
• Phylum Oomycota:
• Characteristics:

  • Form spores
  • Are biflagellates
  • Reproduce both sexually and asexually
  • Examples: Phytophthora, water mold
• Phylum Chlorophyta (green algae):
• Characteristics:

  • Aquatic
  • Photosynthetic
  • Reproduce both sexually and asexually
  • Dominant pigment is chlorophyll, appearing green in color
  • Examples: Chlamydomonas, Volvox, Ulva, Spirogyra
• Phylum Rhodophyta (red algae):