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Unit 7: Genes and inheritance

Microorganisms — HIA International - Grade 8 Revision Notes & Topical Questions

5 min read 8 parts Lesson 2 of 9 2 quizzes

📚 HIA International - Grade 8 Hub / Topical Revision
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Lesson summary

Microorganisms — HIA INTERNATIONAL notes: Describe the main kinds of microorganism, how they are grown in the laboratory and how they are useful or harmful.Microorganism = a living organism so small that you can only see it clearly with a microscope.Cells — like all living organi…

  • Reproduction
  • Not always microscopic
  • Cell types
  • Bacteria colonies
  • Fungi colonies
  • Decomposers

Part 1 of 6What a microorganism is

What a microorganism is
Microorganism
Microorganism a living organism so small that you can only see it clearly with a microscope.
Cells
  • Cells like all living organisms they are made of cells, and many are single-celled.
Kinds
  • Kinds bacteria, microscopic fungi, protozoa and algae.
Viruses
  • Viruses even smaller and not made of cells, so they are not usually called microorganisms.

Part 2 of 6Bacteria

Bacteria
Singular
  • Singular one bacterium; they are everywhere.
Size
  • Size one cell, much smaller than an animal or plant cell; about 1000 fit across one millimetre.
Structure
  • Structure cell wall, cell membrane and cytoplasm, but no nucleus.
Harm
  • Harm most are harmless, a few make you ill; some live harmlessly in our digestive system.
Reproduction
  • Reproduction they split in two.

Part 3 of 6Fungi

Not always microscopic
  • Not always microscopic mushrooms and toadstools are only part of a fungus, which is mostly thin threads under the ground or in dead wood.
Yeast
  • Yeast a microscopic single-celled fungus, seen as a powder on grapes; it reproduces by budding.
Moulds
  • Moulds fungi made of thread-like hyphae that reproduce by spores.

Part 4 of 6Algae and protozoa

Algae and protozoa
Algae
  • Algae tiny plant-like organisms found in pond water.
Protozoa
  • Protozoa tiny animal-like organisms.
Cell types
  • Cell types protozoa have cells like animal cells and algae cells like plant cells.

Part 5 of 6Growing microorganisms

1
Use a sterile Petri dish containing sterile agar jelly.
2
Leave the dish open for 5–10 minutes so microorganisms from the air land on the jelly.
3
Put the lid back on and tape it down.
4
Turn the dish upside down so water droplets do not drown the microorganisms.
5
Label it and leave it for a few days.
6
Look for colonies without removing the lid.
Colony
Colony a collection of many cells from one dividing microorganism.
Bacteria colonies
  • Bacteria colonies have smooth edges.
Fungi colonies
  • Fungi colonies are furry or have rough edges.
Sterile
Sterile any living organisms on it have been killed.
Safety
  • Safety do not breathe or talk over the jelly and keep the lid on.

Part 6 of 6Useful and harmful microorganisms

TypeUsefulHarmful
BacteriaYoghurt and cheese, decomposition, sewage treatmentFood poisoning, tuberculosis
YeastBread (carbon dioxide) and brewing (ethanol)Thrush
MouldsPenicillin, some cheesesFood spoilage, athlete’s foot
Viruses—Flu, measles, COVID-19
Decomposers
  • Decomposers bacteria and fungi break down dead organisms and waste and return nutrients to the soil.
Antibiotics
  • Antibiotics kill bacteria but do not work on viruses.
Spread
  • Spread reduce by hand washing, covering coughs, cooking food, clean water, refrigeration and vaccination.

Key terms

TermMeaning
MicroorganismA living thing too small to see without a microscope.
ColonyA visible group of cells grown from one microorganism.
Agar jellyA jelly containing nutrients used to grow microorganisms.
SterileFree from living organisms.
YeastA microscopic single-celled fungus.
PathogenA microorganism that causes disease.
AntibioticA medicine that kills bacteria.

Avoid these mistakes

1
Viruses are microorganisms made of cells — viruses are not cells.
2
Bacteria have a nucleus — their DNA is loose in the cytoplasm.
3
All fungi are microscopic — mushrooms and toadstools are large.
4
Antibiotics kill viruses — they kill only bacteria.

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