Kingdoms / Classification

There many different types of living organisms

We divide these organisms into groups or kingdoms:

• Animals
• Plants
• Viruses
• Bacteria
• Fungi
• Protoctists

We then break these groups down until we reach 'genus' and 'species'.

Take for example the scientific name of humans - homosapiens

Genus = homo

Species = sapiens

There are a wide variety of living organisms. Four out of these six fall under the category of pathogens

Pathogens

• Fungi
• Bacteria
• Protoctists
• Virus

Animals

• Vertebrates / invertebrates
• Animals are sorted into groups like birds, mammals, reptiles, insects, amphibians, fish
• Multicellular

Plants

• Multicellular
• Cells contain chloroplasts (normally, if plant is green)
• Makes own food - storage carbohydrate starch
  • Sugar sucrose

Virus

• Only reproduce inside the cell of another organism (viruses' host)
• Reproduces by taking over the host cell's genetic machinery to make more virus particles
  • see diagram ->
• Too small to be seen with a microscope - G ranging from 0.01 - 0.1 micrometre**

Virus particle:

• No nucleus or cytoplasm
• A core of genetic material (DNA or RNA)
• Genetic material surrounded by protein coat
• (sometimes) Envelope - 'stolen' from the surface membrane of host cell

Bacteria

• Single-celled organisms
• about 1 - 5 micrometre in length
• volume = 1000 times less than a cell

There are three basic shapes of bacteria - spheres, rods and spirals

Bacterium particle:

• Surrounded by a cell wall (made of chemicals made of polysaccharides and proteins)
• Some may have a capsule or slime layer outside the cell wall.
• Underneath cell wall, there is cell membrane
• Middle of cell is made of cytoplasm
• Has no nucleus - Genetic material (DNA) is in a chromosome, loose in cytoplasm, forms circular loop
• If can swim, then have flagella
• Plasmids can sometimes be found
  • Plasmids are circular rings of DNA, and carry some genes of bacterium

**(1 micrometer = 1 / 1 000 000 m or 1/1000 mm)

Fungi

• May be multicellular or unicellular (yeasts)
• Has a fruiting body (reproductive structure of the organism) is a mushroom or toadstool
• Mushroom has thread-like filaments - hyphae
• Whole network of fungi - mycelium
• Feed by absorbing nutrients from dead (or living) material

Reproduction of fungi (using mucor as an example)

• Spore lands on food
• Hypha grows and branches until mycelium covers surface (of food.. for example)
• Hyphae secrete digestive enzymes (and breaks down food into soluble substances)
• The substances are then absorbed by the mould.
• When food is used up, mould must infect another source of food

In this example, we can see that digestion takes place outside organism (saprotrophic nutrition)

Enzymes that are secreted out of cells because of this are extracellular enzymes