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, Topic 1: Biodiversity of Microorganisms
● Biodiversity refers to the variety of different organisms in an
ecosystem. Organisms which are too small to be seen with a
naked eye are called microorganisms
● These microorganisms can be unicellular or multicellular
● There are several groups of microorganisms, including:
○ Viruses
○ Bacteria
○ Protists
○ Fungi
● Microorganisms are the most abundant organisms & thrive in
optimum temperature, moisture and sufficient food
Viruses
● Are classified separately & not put in any kingdom because they display some
non-living as well as living characteristics
● They do not show the 7 characteristics of life (excluding reproduction)
● Viruses are acellular (do not consist of cells) & therefore cannot be classified as
pro/eukaryotes
The structure & characteristics of a virus
● Viruses are around 20-450 nm in diameter and
consist of a central nucleic acid surrounded by
a capsid (protein coat)
● They do not have a cytoplasm or any
membrane bound organelles such as a
mitochondria
● Some viruses such as the flu are enclosed by an
envelope of lipid & protein molecules
● Viruses do not contain chlorophyll & therefore cannot produce their own food
● Viruses are obligate internal parasites (obligate: forced; a parasite organism
can’t complete his life cycle without exploiting a suitable host) & multiply by
infecting other living organisms/ host (an organism that harbours a parasite)
● Viruses can infect bacteria, protists, plants and animals. Viruses that infect
bacteria are called bacteriophages.
● Viruses are pathogens (an organism that causes disease) & cause diseases
such as herpes, the common flu, Aids/ HIV
● Viruses reproduce by converting the genetic material of host cells into viral
nucleic acids so that new viruses can be produced & if they cannot find a
host, they become dormant
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, Bacteria
● Belong to the Kingdom Monera
● Smallest & simplest living organisms & are found EVERYWHERE on earth
● Can be pathogenic & cause diseases e.g tuberculosis, while most are useful
● Some bacterias live in the presence of oxygen & are known as aerobic, while
others live in the absence & are known as anaerobic
The structure & characteristics of Bacteria
● Unicellular & Larger than viruses
● The bacteria is covered by a cell wall consisting of
polysaccharides, proteins & lipids & that is covered by a
slime layer (capsule) which protects the cell from desiccation
& enemies (immune cells)
● Below the cell wall is a cell/ plasma membrane which
encloses the cytoplasm
● The cytoplasm has no membrane-bound organelles
(vacuoles, ER, mitochondria, etc) but do consist of ribosomes
● The DNA forms in a loop called a nucleoid
● Use flagellum to propel itself forward in liquid
● Bacteria reproduce through binary fission
These bacterias can occur in many shapes :
Nutrition of bacteria
● Autotroph defines organisms which can synthesize their own food e.g. green
plants, algae and some bacteria. Autotrophic bacteria can produce their own
food.
○ Photosynthetic bacteria use sunlight energy
○ Chemosynthetic bacteria get energy from chemical processes
● Heterotroph defines any organism that sources food from its environment
because it cannot make its own food, e.g. animals, fungi, most bacteria
○ Parasitic bacteria: obtain food from other organisms
○ Saprotrophic bacteria: decomposers & get food from dead organisms
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, Topic 1: Biodiversity of Microorganisms
● Biodiversity refers to the variety of different organisms in an
ecosystem. Organisms which are too small to be seen with a
naked eye are called microorganisms
● These microorganisms can be unicellular or multicellular
● There are several groups of microorganisms, including:
○ Viruses
○ Bacteria
○ Protists
○ Fungi
● Microorganisms are the most abundant organisms & thrive in
optimum temperature, moisture and sufficient food
Viruses
● Are classified separately & not put in any kingdom because they display some
non-living as well as living characteristics
● They do not show the 7 characteristics of life (excluding reproduction)
● Viruses are acellular (do not consist of cells) & therefore cannot be classified as
pro/eukaryotes
The structure & characteristics of a virus
● Viruses are around 20-450 nm in diameter and
consist of a central nucleic acid surrounded by
a capsid (protein coat)
● They do not have a cytoplasm or any
membrane bound organelles such as a
mitochondria
● Some viruses such as the flu are enclosed by an
envelope of lipid & protein molecules
● Viruses do not contain chlorophyll & therefore cannot produce their own food
● Viruses are obligate internal parasites (obligate: forced; a parasite organism
can’t complete his life cycle without exploiting a suitable host) & multiply by
infecting other living organisms/ host (an organism that harbours a parasite)
● Viruses can infect bacteria, protists, plants and animals. Viruses that infect
bacteria are called bacteriophages.
● Viruses are pathogens (an organism that causes disease) & cause diseases
such as herpes, the common flu, Aids/ HIV
● Viruses reproduce by converting the genetic material of host cells into viral
nucleic acids so that new viruses can be produced & if they cannot find a
host, they become dormant
1
, Bacteria
● Belong to the Kingdom Monera
● Smallest & simplest living organisms & are found EVERYWHERE on earth
● Can be pathogenic & cause diseases e.g tuberculosis, while most are useful
● Some bacterias live in the presence of oxygen & are known as aerobic, while
others live in the absence & are known as anaerobic
The structure & characteristics of Bacteria
● Unicellular & Larger than viruses
● The bacteria is covered by a cell wall consisting of
polysaccharides, proteins & lipids & that is covered by a
slime layer (capsule) which protects the cell from desiccation
& enemies (immune cells)
● Below the cell wall is a cell/ plasma membrane which
encloses the cytoplasm
● The cytoplasm has no membrane-bound organelles
(vacuoles, ER, mitochondria, etc) but do consist of ribosomes
● The DNA forms in a loop called a nucleoid
● Use flagellum to propel itself forward in liquid
● Bacteria reproduce through binary fission
These bacterias can occur in many shapes :
Nutrition of bacteria
● Autotroph defines organisms which can synthesize their own food e.g. green
plants, algae and some bacteria. Autotrophic bacteria can produce their own
food.
○ Photosynthetic bacteria use sunlight energy
○ Chemosynthetic bacteria get energy from chemical processes
● Heterotroph defines any organism that sources food from its environment
because it cannot make its own food, e.g. animals, fungi, most bacteria
○ Parasitic bacteria: obtain food from other organisms
○ Saprotrophic bacteria: decomposers & get food from dead organisms
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