Characteristics of Life

Characteristics of Life

Middle School

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Learning Objectives

• Tell the difference between living and nonliving things.

• List and describe the eight characteristics that all living things share.

• Define key terms like cell, homeostasis, metabolism, and reproduction.

• Explain the levels of organization in organisms with many cells.

Key Vocabulary

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Cell

The basic and smallest unit of structure and function in all living things.

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Homeostasis

The process of maintaining a stable internal environment regardless of the external conditions.

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Metabolism

The total of all the biochemical reactions that happen in a cell or organism.

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Reproduction

The process by which living things give rise to offspring for the next generation.

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Organization

The hierarchical arrangement of living things from simplest to the most complex levels.

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Made of Cells and Organization

Made of Cells

• All life is made of at least one cell, which is the smallest and most basic unit of life.

• Organisms like bacteria are unicellular because they are made of only one single cell.

• Organisms like plants and animals are multicellular and are made of many different cells.

Shows Organization

• Living things arrange their parts in an orderly way, from the very simple to the complex.

• In complex organisms, similar cells group together to form tissues, which then create different organs.

• Organs work together in organ systems, which then make up the entire living organism.

Multiple Choice

What is the correct hierarchical organization of multicellular organisms, from simplest to most complex?

• Cells → Tissue → Organs → Organ systems → Organism

• Cells → Organs → Tissue → Organism → Organ systems

• Tissue → Cells → Organs → Organ systems → Organism

• Organism → Organ systems → Organs → Tissue → Cells

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Growth and Response in Living Things

• All living things grow, develop, and change throughout their lives.

• For example, a seed grows into a plant as it gets older.

• Living things respond to changes in their environment called stimuli.

• A turtle moving when touched is a response to a stimulus.

Multiple Choice

A plant turning its leaves toward the sun is an example of which characteristic of life?

• Responding to stimuli

• Reproduction

• Homeostasis

• Growth and development

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Reproduction and Adaptation

Can Reproduce

• ​Reproduction is the process by which living things give rise to new individuals or offspring.

• ​​Sexual reproduction involves two parents and creates offspring that are genetically different from them.

• ​Asexual reproduction needs only one parent and results in genetically identical offspring.

Adapted to Environment

• ​Living things adapt over time to better suit their specific home or environment.

• ​​Adaptations include an organism's appearance, its behavior, and its unique way of life.

• ​These traits help them to survive and reproduce successfully in their particular habitats.

Multiple Choice

What is the key difference between sexual and asexual reproduction?

• Only bacteria can perform sexual reproduction.

• Asexual reproduction involves two parents, while sexual involves one.

• Asexual reproduction involves a single parent and produces identical offspring.

• Sexual reproduction creates genetically identical offspring.

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Homeostasis and Metabolism

Maintains Homeostasis

• Homeostasis is the process of maintaining a stable internal environment.

• This balance is kept steady, no matter the external conditions.

• For example, your body shivers to warm you up when it's cold.

Has a Metabolism

• Metabolism is the total of all chemical reactions in an organism.

• Living things need continuous energy to grow, develop, and reproduce.

• The energy currency used for these life processes is called ATP.

Multiple Choice

The process of maintaining a stable internal body temperature, regardless of the outside weather, is an example of what?

• Organization

• Adaptation

• Metabolism

• Homeostasis

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Common Misconceptions About Life

Misconception	Correction
If something moves, it must be alive.	A car moves, but it is not alive.
Anything that grows is alive.	Non-living things, like crystals, can grow but are not alive.
Viruses are simple living things.	Viruses are non-living because they are not made of cells.

Multiple Choice

Why is a wooden decoy duck considered non-living, even though it looks like a real duck?

• It does not live in water.

• It does not possess all the characteristics of life.

• It is made of wood.

• It cannot fly.

Multiple Choice

A bacterium reproduces by splitting into two identical cells. This is an example of which two characteristics of life?

• Metabolism and Organization

• Growth and Response

• Homeostasis and Adaptation

• Being made of cells and Reproduction

Multiple Choice

You find an unknown object. To determine if it is a living organism, what is the most crucial question you would need to answer?

• Can it move on its own?

• Is it made of at least one cell?

• Does it use energy?

• Does it look like other organisms?

Multiple Choice

If an organism could not perform metabolism, what would be the direct consequence for its other life functions like growth and reproduction?

• It would adapt more quickly.

• It would have no energy to carry out these processes.

• Its cells would become more organized.

• It would maintain homeostasis more effectively.

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Summary

• Living things are made of cells and show organization.

• All living things grow, develop, and reproduce.

• Organisms respond to stimuli and maintain a stable internal environment.

• Living things use energy and adapt to their environment.

Poll

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

• 1

• 2

• 3

• 4