Prokaryotic Organisms and Pathogens
This section focuses on prokaryotic organisms, particularly bacteria, and introduces the concept of pathogens, including viruses. This knowledge is crucial for understanding Common features shown by prokaryotic organisms in the Edexcel IGCSE Biology curriculum.
Prokaryotic Organisms:
Prokaryotes are characterized by their lack of a nucleus and membrane-bound organelles. Bacteria, the most common prokaryotes, have the following features:
- Microscopic, single-celled organisms
- Possess a cell wall, cell membrane, cytoplasm, and plasmids
- Contain circular chromosomes of DNA instead of a nucleus
- Some species can photosynthesize, while others rely on other organisms for nutrition
Example: Lactobacillus bulgaricus usedinyogurtproduction and Pneumococcus causespneumonia are examples of bacteria with different shapes and functions.
Pathogens:
Pathogens are disease-causing organisms that can include fungi, protoctists, bacteria, and viruses.
Definition: A pathogen is any organism capable of causing disease in another organism.
Viruses:
Viruses are unique entities that challenge our definition of living organisms:
- Not considered living organisms due to their inability to carry out life processes independently
- Smaller than bacteria and lack cellular structure
- Parasitic in nature, only able to reproduce within living host cells
- Composed of a protein coat and one type of nucleic acid DNAorRNA
- Capable of infecting all types of organisms
Highlight: Understanding the nature of viruses is crucial for comprehending Why are viruses not considered living organisms as compared to the other 5 kingdoms.
Example: The tobacco mosaic virus, which causes discoloration in tobacco plant leaves, and influenza are examples of viruses affecting different types of organisms.
This section provides essential information for students studying Understanding pathogens in living organisms edexcel igcse biology questions and prepares them for more advanced topics in microbiology and pathology.
