Microorganisms

Microorganisms

Middle School

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Learning Objectives

• Describe what microorganisms are and list the different types.

• Identify the various environments where microorganisms can be found.

• Differentiate between harmful and helpful microorganisms.

• Explain the roles of helpful microorganisms in our bodies and the environment.

Key Vocabulary

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Microorganism

A living thing that is too small to be seen without a microscope, found everywhere on Earth.

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Bacteria

The single-celled organisms making up the largest group of microorganisms; they can be helpful or harmful.

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Virus

A non-living microorganism that causes diseases by invading living cells in order to reproduce.

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Fungi

A group of microorganisms that can cause plant diseases and human infections, or spoil food.

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Algae

The microrganisms that are the main producers of food and oxygen, especially in various water environments.

Microorganisms like bacteria and fungi that break down dead plants and animals into simpler matter.

Decomposer

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Key Vocabulary

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They are the medicines designed to cure diseases by killing harmful bacteria in the body.

Few helpful microorganisms that are a food source for water animals and aid in sewage treatment.

Protozoa

Antibiotics

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What Are Microorganisms?

• A microorganism is a living thing too small to be seen without a microscope.

• They are found everywhere on Earth, including in the soil, air, and water.

• Major groups include bacteria, fungi, algae, and protozoa.

• Viruses are also microorganisms, but they are not considered living things.

Multiple Choice

Which of the following best defines a microorganism?

• A type of cell that makes up larger living things

• Any small animal found in water

• A living thing that is too small to be seen without a microscope

• A non-living particle like dust or sand

Multiple Choice

Based on the information provided, where would you most likely find major groups of microorganisms like bacteria and protozoa?

• Only in places where there is no air

• Only in extremely hot or cold places

• Only inside the bodies of plants and animals

• In a wide variety of environments like soil and air

Multiple Choice

Which statement provides the best conclusion that can be drawn from all the information provided?

• Since viruses are not living, they cannot be microorganisms.

• All microorganisms are living things.

• An organism can be a microorganism without being classified as a living thing.

• An organism must be living to be found in the air, soil, or water.

Harmful Microorganisms

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Bacteria

• Some types of bacteria are harmful and can make you very sick.

• Salmonella and E. coli are found in raw or undercooked foods.

• These harmful bacteria are a common cause of food poisoning.

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Viruses

• Viruses are non-living and cause diseases like colds, flu, and chicken pox.

• They are smaller than bacteria and change constantly as they reproduce.

• This is why medicine for one virus may not kill another.

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Fungi

• Certain fungi can cause infections in people, such as athlete's foot.

• They are a common cause of food spoilage, like mold on bread.

• Some fungi can cause diseases in plants and are able to rot wood.

Multiple Choice

What is the main problem caused by the harmful microorganisms described?

• They only cause diseases in plants and rot wood.

• They are all non-living and difficult to see.

• They can cause illness, disease, or spoilage.

• They are only found in raw or undercooked foods.

Multiple Choice

What is a key difference between viruses and the other harmful microorganisms mentioned?

• Viruses are the only type that causes food spoilage.

• Viruses are much larger than bacteria and fungi.

• Viruses are the only type that causes infections in people.

• Viruses are non-living and change constantly as they reproduce.

Multiple Choice

A scientist creates a new medicine that cures the flu. However, the next year, the medicine does not work on people who get the flu. What is the most likely reason for this?

• The medicine was only designed to work on bacteria.

• People were getting sick from mold on bread instead.

• The flu was caused by eating undercooked food.

• The flu virus changed, making the medicine ineffective.

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Helpful Microorganisms: Part 1

Aiding Digestion

• Beneficial bacteria, such as E. coli, live inside your body and help to digest food.

• Without these microorganisms, we would not be able to break down the food that we eat.

• Bacteria also help cows digest grass and termites digest the wood they chew for energy.

Food Production

• Humans have learned to use helpful microorganisms to create many different types of foods.

• Specific kinds of bacteria are used in the process of turning milk into cheese and yogurt.

• Yeast, a type of fungus, is a crucial ingredient that makes dough rise for bread.

Multiple Choice

What is a major role of helpful microorganisms like bacteria and yeast?

• To cause diseases in humans and animals.

• To break down plastic and other waste materials.

• To convert sunlight into energy for plants.

• To help with processes like digestion and food production.

Multiple Choice

How do microorganisms like bacteria and yeast contribute to making foods like cheese and bread?

• They add color and flavor but are not essential.

• They are a byproduct of the food production process.

• They are used to transform ingredients like milk or dough.

• They remove harmful substances from the ingredients.

Multiple Choice

Based on the information, what would most likely happen if a cow could no longer host the specific bacteria that live in its digestive system?

• The cow would start eating wood instead of grass.

• The cow would produce bread dough instead of milk.

• The cow would have difficulty digesting the grass it eats.

• The milk from the cow would automatically turn into yogurt.

Helpful Microorganisms: Part 2

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Decomposers

• ​Bacteria and fungi are the main decomposers in most ecosystems.

• ​​They consume dead plants and animals, breaking them into simpler matter.

• ​Without them, dead material would cover the surface of the Earth.

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Producers

• ​Algae are major producers, especially in water environments.

• ​​They are a critical source of food and energy for other living things.

• ​Algae release the oxygen into the atmosphere that animals need to breathe.

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Water Treatment

• ​Protozoa are a food source for many animals that live in water.

• ​​They play a key role in our infrastructure at water treatment plants.

• ​These microorganisms help to remove harmful wastes from sewage.

Multiple Choice

What is the main function of decomposers, such as bacteria and fungi, in an ecosystem?

• To produce oxygen for other living things to breathe

• To serve as a critical source of food and energy for animals

• To help remove harmful wastes from water systems

• To break down dead plants and animals into simpler matter

Multiple Choice

What is the relationship between algae and other animals in a water environment?

• Algae compete with animals for the same food sources.

• Algae provide a source of food and release the oxygen that animals need.

• Algae help to break down harmful wastes produced by animals.

• Algae use up the oxygen that animals need to survive.

Multiple Choice

Imagine an ecosystem where dead material is piling up and harmful wastes are not being removed from the water. The absence of which two microorganisms would best explain these observations?

• Fungi and protozoa

• Algae and protozoa

• Bacteria and algae

• Algae and fungi

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Common Misconceptions

Misconception	Correction
All microorganisms are harmful germs.	Most microorganisms are harmless, and many are essential for life.
A virus is just a smaller type of bacteria.	Viruses are not living and need a host cell to reproduce.
Antibiotics can cure the common cold or flu.	Antibiotics only kill bacteria, not the viruses that cause colds and flu.

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Summary

• Microorganisms like bacteria, fungi, and algae are found almost everywhere.

• Some microorganisms are harmful and can cause diseases or spoil food.

• Many are helpful, acting as decomposers or producing oxygen.

• We use helpful microbes to make foods like cheese, yogurt, and bread.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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