Biology: Classification of Living Organisms

Study Notes

Classification is the process of grouping living organisms based on their shared characteristics and evolutionary relationships.
The most widely used system of classification is the five-kingdom system, which divides living organisms into:
1. Monera (bacteria and cyanobacteria)
2. Protista (protozoa, algae, and fungi-like organisms)
3. Fungi
4. Plantae (plants)
5. Animalia (animals)

Microorganisms are living organisms that are too small to be seen with the naked eye.
They can be found almost everywhere, including in soil, water, air, and the human body.
Characteristics of microorganisms include:
- Small size
- Simple structure
- Ability to reproduce rapidly
- Ability to adapt to different environments
- Can be beneficial or harmful to humans and the environment

Microorganisms can be classified based on their cell structure, metabolism, and other characteristics.
The three main domains of microorganisms are:
1. Archaea: ancient microorganisms that thrive in extreme environments (e.g. hot springs, salt lakes)
2. Bacteria: microorganisms that lack a true nucleus and are typically found in soil, water, and the human body
3. Eukarya: microorganisms with a true nucleus, including protists, fungi, and some algae
Microorganisms can also be classified as:
- Prokaryotes: microorganisms without a true nucleus (bacteria and archaea)
- Eukaryotes: microorganisms with a true nucleus (protists, fungi, and some algae)

Bacteria:
- Examples: E. coli, Staphylococcus aureus, Bacillus subtilis
- Can be beneficial (e.g. gut flora) or harmful (e.g. pathogens)
Viruses:
- Not considered living cells, but can replicate inside host cells
- Examples: influenza, HIV, COVID-19
Fungi:
- Examples: yeast, mold, mushrooms
- Can be beneficial (e.g. fermentation) or harmful (e.g. fungal infections)
Protists:
- Examples: protozoa, algae, slime molds
- Can be beneficial (e.g. photosynthesis) or harmful (e.g. parasitic infections)

Classification is the process of grouping living organisms based on shared characteristics and evolutionary relationships
The five-kingdom system divides living organisms into Monera, Protista, Fungi, Plantae, and Animalia

Microorganisms are living organisms too small to be seen with the naked eye
Found almost everywhere, including soil, water, air, and the human body
Characteristics include small size, simple structure, rapid reproduction, adaptability, and being beneficial or harmful to humans and the environment

Microorganisms can be classified based on cell structure, metabolism, and other characteristics
Three main domains: Archaea, Bacteria, and Eukarya
Archaea: ancient microorganisms thriving in extreme environments
Bacteria: microorganisms lacking a true nucleus, typically found in soil, water, and the human body
Eukarya: microorganisms with a true nucleus, including protists, fungi, and some algae
Microorganisms can also be classified as Prokaryotes (bacteria and archaea) or Eukaryotes (protists, fungi, and some algae)