Protozoa, Algae, Monera, and Viruses: Characteristics & Types

Posted on Apr 4, 2025 in Biology

Protozoa: Characteristics and Types

  • Features:
    • Unicellular organisms capable of performing all vital functions.
    • Heterotrophic: They feed on bacteria, organic debris, and other organic matter.
    • Live in aquatic environments, both freshwater and saltwater; most are free-living.
  • Types:
    • Flagellates: Move by flagella. Some are free-living, and others are parasites. Trypanosoma causes sleeping sickness.
    • Ciliates: Move by cilia. Free-living and parasitic. The Paramecium has two nuclei and is slipper-shaped.
    • Rhizopods: Move through extensions of the cytoplasm called pseudopodia.
    • Sporozoa: Non-motile and entirely parasitic.

Algae: Characteristics and Types

  • Features:
    • Have chloroplasts and a cell wall.
    • Can be unicellular or multicellular, sometimes forming colonies. Each cell is capable of performing all vital functions.
    • Are autotrophs, possessing chlorophyll and other pigments.
    • Classified into three groups according to pigment: green, brown, and red.
    • Aquatic, marine, and freshwater.
  • Types:
    • Green Algae: The most abundant pigment is chlorophyll. Found in inland and marine waters.
    • Brown Algae: Have a yellowish pigment that dominates chlorophyll, giving them a brown color. They are marine.
    • Red Algae: In addition to chlorophyll, they possess a red pigment that can capture sunlight.

The Kingdom Monera: Characteristics and Types

  • Features:
    • Microscopic, unicellular prokaryotic cells.
    • Belong to the bacteria or cyanobacteria. Bacteria are found everywhere on the planet: in the ground, water, air, etc.
    • Live at or below zero, even at temperatures above 100°C, sometimes forming colonies.

Structure of Bacteria:

  • Cell Membrane: Regulates the entry and exit of substances.
  • Bacterial Cell Wall: Rigid sheath surrounding the cell membrane. Its function is to shape and protect the bacteria.
  • Bacterial Capsule: Surrounds the cell wall. Serves as protection and insulation for certain disease-causing bacteria.
  • Cytoplasm: Occupies the inside of the cell. Substances necessary for the bacteria to carry out its vital functions are manufactured here.
  • Genetic Material: Dispersed throughout the cytoplasm, it controls and regulates the functioning of the cell.
  • Flagella: Extensions present in certain bacteria that are used for movement.

Types of Bacteria:

  • Coccus: Rounded shape.
  • Bacillus: Long, comma-shaped.
  • Spirillum: Spiral shape.

Nutrition of Bacteria:

  • Parasites: Obtain food from other living beings, which they damage.
  • Saprophytes: Live on dead organic matter or decomposing material. They decompose and transform inorganic substances into organic substances used by plants.
  • Symbionts: Live in association with another individual, providing a mutual benefit.
  • Autotrophs: Capable of making their own organic substances from inorganic substances.

Reproduction and Response of Bacteria:

Reproduce by binary fission, producing two bacteria. The process is very fast; in a few hours, one bacterium can produce thousands of identical bacteria. They can capture and respond to environmental changes. When environmental conditions are not favorable, certain bacteria are surrounded by a thick, resistant layer and form spores.

Viruses: Characteristics and Structure

  • Characteristics:
    • Can only be seen with an electron microscope.
    • Cannot be considered living things because they do not perform any vital functions on their own.
    • Are capable of infecting living cells.
    • Produce copies of themselves.
    • Viruses are always obligate parasites.

Structure of Viruses:

  • Capsid: Protein wrapper that takes different forms.
  • Outer Sheath: Located outside the capsid. Only present in some viruses, such as influenza and HIV.
  • Nucleic Acid: Located inside the capsid.

Vaccines and Antibiotics

Vaccines: Preparations containing killed or weakened microorganisms of a particular disease, which lack the capacity to produce it. It is a preventive method. Generally, they protect throughout life, although the effect of some lasts for a certain time, so booster doses have to be re-administered.

Antibiotics: Substances produced by certain bacteria and fungi that can eliminate or prevent the growth of microorganisms that cause disease.