Microorganisms On and In the Human Body

Microorganisms On and In the Human Body

Middle School

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Learning Objectives

• Define what a microorganism is and provide some common examples.

• Explain the concept of scale for observing tiny cells and molecules.

• Describe the basic structure and function of cells in living organisms.

• Compare unicellular and multicellular organisms, and how cells form tissues.

Key Vocabulary

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Microorganism

An organism that is too small to be seen with the naked eye, like bacteria or fungi.

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Scale

This refers to the relative size of things, helping us understand how small microorganisms really are.

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Cell

The cell is the basic and smallest unit of life that makes up all living organisms.

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Unicellular

An organism that is made of only one single cell, such as a bacterium or an amoeba.

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Multicellular

An organism made of many cells that work together, such as plants and animals we see daily.

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Tissue

A group of similar cells that work together to perform a specific job within an organism.

Key Vocabulary

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Organ

A structure made of different types of tissues that work together to perform a complex function.

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Cell Membrane

The protective outer layer of an animal cell that controls what enters and leaves the cell.

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Cell Wall

The rigid outer layer of a plant cell that provides structural support and protection.

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Nucleus

The control center of the cell that contains the cell's genetic information and directs its activities.

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What is the Human Microbiome?

• Our bodies have trillions of tiny microorganisms living on and inside us.

• This community of microorganisms is called the human microbiome.

• Cells are measured in micrometers (μm), one millionth of a meter.

• Molecules are measured in nanometers (nm), 1,000 times smaller than a micrometer.

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Multiple Choice

What is the human microbiome?

• A community of microorganisms living on and in the human body.

• The different types of cells found in the human body.

• A measurement used for tiny molecules and cells.

• The smallest part of a human, measured in nanometers.

Multiple Choice

How does the size of a nanometer compare to a micrometer?

• A nanometer is 1,000 times smaller than a micrometer.

• A nanometer is 1,000 times larger than a micrometer.

• A nanometer is one millionth the size of a micrometer.

• A nanometer and a micrometer are the same size.

Multiple Choice

A scientist is studying a single microorganism from the human microbiome, which is a type of cell. Which unit of measurement would be most appropriate for describing its size?

• Micrometers (μm)

• Nanometers (nm)

• Meters (m)

• Trillions

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The Cell: The Basic Unit of Life

• All living things are made up of tiny building blocks called cells.

• The cell is the smallest unit of life that can function on its own.

• Unicellular organisms, like bacteria, are made of just a single cell.

• Multicellular organisms like plants and animals have many specialized cells which performs complex specific functions

Multiple Choice

What is the basic unit of life from which all living things are made?

• A cell

• A bacterium

• A muscle

• An organism

Multiple Choice

How are unicellular and multicellular organisms different?

• Unicellular organisms have one cell, while multicellular organisms have many specialized cells.

• Unicellular organisms have a nucleus, while multicellular organisms do not.

• Unicellular organisms include plants and animals, while multicellular organisms are bacteria.

• Unicellular organisms use muscle cells for movement, while multicellular organisms do not.

Multiple Choice

Based on the roles of specialized cells, what would likely happen if a complex animal's cells all had to perform every function, instead of having specific jobs?

• The organism would not be able to perform complex functions like movement and sending signals efficiently.

• The organism would become a unicellular organism like a bacterium.

• The organism's cells would learn to perform all functions better than specialized cells.

• The organism would grow larger because its cells are doing more work.

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Inside a Cell: Structures and Functions

• A cell's organelles are like tiny departments, each with a specific job.

• The cell membrane controls what substances can enter and leave the cell.

• The nucleus holds the DNA and directs all of the cell’s activities.

• Plant cells have a cell wall that provides extra structure and support.

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Multiple Choice

Which statement best describes the role of organelles within a cell?

• Each organelle has a specific job to carry out.

• All organelles are involved in creating energy.

• Organelles are responsible for cell movement.

• Only plant cells have organelles.

Multiple Choice

How do the functions of the nucleus and the cell membrane differ?

• The nucleus provides a rigid structure, while the cell membrane holds the DNA.

• The nucleus directs the activities of the cell, while the cell membrane controls what enters and leaves.

• The nucleus controls what enters and leaves the cell, while the cell membrane directs the cell's activities.

• The nucleus and the cell membrane both provide structure and support for the cell.

Multiple Choice

If a plant cell's cell wall was damaged, what would be the most likely consequence for the cell?

• The cell would lose its rigid structure.

• The cell would no longer have a nucleus.

• The cell could no longer control what substances enter or leave.

• The cell's activities would no longer be directed.

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Plant vs. Animal Cells

Animal Cells

• These cells have a flexible cell membrane as their outer boundary, which allows the cell to move.

• They do not have a cell wall for structure or chloroplasts for making food, unlike plant cells.

• Animal cells get the energy they need to function by consuming food from other living things.

Plant Cells

• These cells possess a rigid cell wall outside the cell membrane, which provides support and fixed shape.

• They contain special organelles known as chloroplasts, where the process of photosynthesis occurs in the cell.

• Plant cells can make their own food by converting light energy from the sun into chemical energy.

Multiple Choice

What key structure is found in plant cells that provides support and a fixed shape, but is absent in animal cells?

• A rigid cell wall

• A flexible nucleus

• A large vacuole

• A smooth mitochondrion

Multiple Choice

How does the method of obtaining energy differ between plant and animal cells?

• Plant cells create their own food using chloroplasts, while animal cells must consume other living things for energy.

• Plant cells use a cell membrane to get energy, while animal cells use a cell wall.

• Animal cells convert sunlight into energy, while plant cells get energy from movement.

• Animal cells store energy in chloroplasts, while plant cells store energy in the nucleus.

Multiple Choice

If a plant cell's cell wall were to disappear, what would be the most likely outcome for the cell?

• The cell would lose its fixed shape and become more flexible.

• The cell would start making its own food.

• The cell would develop a cell membrane on the outside.

• The cell would be unable to consume other living things.

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• Specialized cells group together to form tissues for specific jobs.

• Different tissues work together to create organs, like the heart.

• Organs and tissues combine to form organ systems for complex functions.

Cells to Organ System

Multiple Choice

What is formed when a group of specialized cells works together to perform a specific job?

• A single cell

• A tissue

• An organ

• An organ system

Multiple Choice

What is the relationship between tissues and organs?

• An organ is made of only one type of tissue.

• Tissues are more complex than the organs they form.

• They combine and work together to perform a more complex task.

• Tissues and organs function independently of each other.

Multiple Choice

If a specific type of tissue within an organ were damaged, what is the most likely conclusion?

• Only the individual cells of that tissue would be affected.

• The organ's function within its system would be impaired.

• The organ would be able to create a new type of tissue.

• The entire organ system would stop working immediately.

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Common Misconceptions

Misconception	Correction
All germs and bacteria are bad for you.	Many bacteria are harmless or even helpful to our bodies.
All cells are the same size and shape.	Cells have different sizes and shapes based on their jobs.
Bigger animals have bigger cells than smaller animals.	Larger animals just have more cells, not bigger ones.
You can see a cell without a microscope.	Most cells require a microscope to be seen.

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Summary

• All living things are made of one or many cells.

• We use scale to understand microscopic things like the microbiome.

• Cells have specialized parts like the nucleus and cell membrane.

• In multicellular organisms, cells form tissues, organs, and complex systems.

Poll

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

• 1

• 2

• 3

• 4