MS-LS1-1: Cells and Organisms

MS-LS1-1
Cells and Organisms

Middle School

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Learning Objectives

• Provide evidence that living things are made of cells, but non-living things are not.

• Explain the three main ideas of the Cell Theory and the microscope's role.

• Compare unicellular and multicellular organisms and describe cells as the basic unit of life.

• Distinguish between prokaryotic and eukaryotic cells and identify their main structures.

Key Vocabulary

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Cell

The cell is the smallest unit of a living thing that can be said to be alive.

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Organism

An organism is a single living thing that is made of one or many different cells.

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Unicellular

A unicellular organism is a living thing that is made up of only one single cell.

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Multicellular

A multicellular organism is a living thing that is made of many different types of cells.

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Cell Theory

The cell theory states that all life is made of cells, which are life's basic units.

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Microscope

A microscope is an important tool for magnifying objects that are too small to be seen.

Key Vocabulary

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Prokaryote

A prokaryote is a simple type of cell that does not have a nucleus, like bacteria.

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Eukaryote

A eukaryote is a complex cell that contains a nucleus and other specialized parts called organelles.

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Organelle

An organelle is a tiny, specialized structure found inside a eukaryotic cell that performs specific jobs.

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Cilia

Cilia are small, hair-like structures on a paramecium that help it move around and eat.

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Scale

Scale refers to the size of an object, helping us understand things that are microscopic.

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What Are All Living Things Made Of?

• All living things are made of one or more tiny units called cells.

• This is the main feature separating living from non-living things.

• For example, plants have cells, but non-living things like rocks do not.

• A cell is the smallest unit of life that performs all basic functions.

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Multiple Choice

What are cells?

• The basic units of all living things

• The parts that make up rocks

• The smallest particles of water

• The gases that make up air

Multiple Choice

What is the key difference between living and non-living things?

• Living things are made of cells, while non-living things are not.

• Living things are always larger than non-living things.

• Non-living things can be found underground, while living things cannot.

• Non-living things are harder and stronger than living things.

Multiple Choice

If a scientist examines a sample under a microscope and discovers it is made of tiny units that perform basic life functions, what can be concluded?

• The sample is from a living thing because it is made of cells.

• The sample is a non-living thing because it is a tiny unit.

• The sample is a type of special rock that has small parts.

• The sample is from a plant because all tiny units come from plants.

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Unicellular vs. Multicellular Organisms

Unicellular Organisms

• ​Unicellular organisms are living things made up of only one single cell.

• ​​This single cell is responsible for all of the organism's life functions.

• ​Common examples of these organisms include bacteria, amoeba, and paramecia.

Multicellular Organisms

• ​Multicellular organisms are living things made up of many different cells.

• ​​The cells in these organisms are specialized to perform specific functions.

• ​For instance, muscle cells help in movement, and nerve cells transmit signals.

Multiple Choice

What is the fundamental difference between a unicellular and a multicellular organism?

• The number of cells they are made of.

• The environment where they primarily live.

• The kingdom that they belong to.

• The way that they reproduce.

Multiple Choice

Based on the characteristics of different life forms, why is an amoeba classified as a unicellular organism?

• It is a single cell that is responsible for all of its life functions.

• It is made of many cells that are specialized for different tasks.

• It contains both muscle cells for movement and nerve cells for signals.

• It works together with other amoebas in a larger organism.

Multiple Choice

If a complex multicellular organism's nerve cells were damaged, what would be the most likely impact on the organism, even if its muscle cells remained healthy?

• The organism would not be able to coordinate movement because signals could not be transmitted.

• The muscle cells would also stop working immediately.

• The muscle cells would learn to transmit their own signals.

• The organism would be unaffected because each cell type works independently.

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Seeing the Unseen: Technology and Cells

• The world of cells is invisible to the unaided human eye.

• What can be observed at one scale may not be seen at another.

• The microscope was an engineering advance that let scientists finally see cells.

• New engineered tools often lead to important scientific discoveries.

Multiple Choice

What technological advancement was necessary for scientists to discover the world of cells?

• The microscope

• The telescope

• The computer

• The human eye

Multiple Choice

What does the discovery of cells reveal about the relationship between science and technology?

• They are completely separate fields of study.

• They rely on each other for new discoveries and advancements.

• Science is more important than technology.

• Technology creates problems that science has to solve.

Multiple Choice

Based on the information, what is the most logical conclusion you can draw about what would have happened if the microscope had never been invented?

• Our understanding of biology would be very limited because we wouldn't know about cells.

• Scientists would have eventually seen cells without any special tools.

• The size and scale of objects would no longer be an important concept in science.

• Technology would have stopped advancing, but science would have continued to progress.

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The Foundation of Biology: Cell Theory

Early Discoveries

• The invention of the microscope was essential for the discovery of cells.

• In 1665, Robert Hooke first saw box-like shapes in cork which he called cells.

• Antoni van Leeuwenhoek observed tiny single-celled organisms that he named animalcules.

The Cell Theory

• All living things are made up of one or more cells.

• Cells are the basic units of structure and function in living things.

• All new cells are produced from other cells that have already existed.

Multiple Choice

What is the most important idea of the Cell Theory?

• They are the basic units of structure and function in living things.

• They were first seen in cork by Robert Hooke.

• They can only be observed with a microscope.

• They were once called animalcules by scientists.

Multiple Choice

What was the role of the microscope in the development of the Cell Theory?

• It allowed scientists to observe cells for the first time.

• It proved that all cells come from other cells.

• It helped create the first single-celled organisms.

• It was used to name the parts of the cell.

Multiple Choice

A scientist observes a single-celled 'animalcule' through a microscope and watches it divide into two separate organisms. Which principle of the Cell Theory does this observation provide evidence for?

• A new cell is forming from a pre-existing cell.

• All living things are made of at least one cell.

• Cells are the basic building blocks of all organisms.

• Living things can be observed using a microscope.

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Prokaryotes vs. Eukaryotes

Prokaryotic Cells

• ​These are very simple cells that do not have a nucleus.

• ​​Their genetic material, or DNA, floats freely inside the cell.

• ​Bacteria are the most common examples of prokaryotic cells.

Eukaryotic Cells

• ​These complex cells have a nucleus that holds the cell's DNA.

• ​​They also have many other specialized parts called organelles.

• ​Plants, animals, fungi, and protists are made of eukaryotic cells.

Multiple Choice

What is the main structural difference between prokaryotic and eukaryotic cells?

• The presence or absence of a nucleus

• Whether they contain genetic material

• Whether they are part of a plant or an animal

• The overall color of the cell

Multiple Choice

How is the genetic material organized differently in prokaryotic cells compared to eukaryotic cells?

• In prokaryotes DNA floats freely, while in eukaryotes it is inside a nucleus.

• In eukaryotes DNA floats freely, while in prokaryotes it is inside a nucleus.

• Prokaryotic cells have organelles, while eukaryotic cells do not.

• Eukaryotic cells are simple, while prokaryotic cells are complex.

Multiple Choice

A scientist discovers an organism made of complex cells that each have a nucleus and other specialized organelles. Which of the following could this organism be?

• A fungus

• A bacterium

• A prokaryote

• A simple cell

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The Importance of a Cell's Size

• Most cells are microscopic, measured in units called micrometers (μm).

• A cell's small size provides a large surface area compared to its volume.

• This high ratio helps nutrients enter and waste exit the cell efficiently.

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Multiple Choice

What is the main advantage of most cells being very small?

• It allows the cell to store more water.

• It helps the cell hide from predators.

• It provides a large surface area for its volume.

• It makes the cell stronger and harder to damage.

Multiple Choice

How does having a large surface area compared to its volume help a cell survive?

• It helps the cell move around more quickly.

• It allows for the efficient exchange of nutrients and waste.

• It makes it easier for the cell to divide.

• It generates more energy for the cell.

Multiple Choice

What would most likely happen if a cell grew to a very large size?

• The cell would divide into two smaller cells immediately.

• The cell would become more efficient at its job.

• The cell would not be able to get enough nutrients in or waste out.

• The cell would need less energy to survive.

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Common Misconceptions

Misconception	Correction
Something is living if it moves or grows, like a crystal.	Living things must be made of one or more cells.
Single cells are not 'alive' in the same way animals are.	Single cells are complete living organisms performing all life functions.
All microbes are bacteria.	Microbes also include protists and fungi, which are different from bacteria.
Bigger cells are better or more evolved than smaller cells.	Small cells are more efficient at transporting nutrients and waste for survival.

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Summary

• All living things are made of cells, which are the basic units of life.

• Living things can be unicellular or multicellular, with prokaryotic or eukaryotic cells.

• Technology like the microscope was essential to discovering and studying cells.

• A cell's small size is critical for its ability to function efficiently.

Poll

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

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• 2

• 3

• 4