Biology Review

Biology Review

Middle School

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Learning Objectives

• Define the six characteristics of all living things.

• Explain the four unifying principles of biology.

• Describe the levels of ecological organization from population to biosphere.

• Differentiate between symbiotic and competitive relationships among organisms.

Key Vocabulary

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Evolution

Change in characteristics of living things over a very long period of time.

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Natural Selection

Organisms with favorable traits produce more offspring and pass on these helpful traits.

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Adaptation

A specific characteristic that helps an organism survive and reproduce in its environment.

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Homeostasis

The important process of keeping internal body conditions stable despite external environmental changes.

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Symbiosis

A close relationship where at least one organism benefits from another different organism.

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Ecosystem

All the living things and the nonliving factors that are in a given area.

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Characteristics of Life

• All living things, called organisms, share features that separate them from nonliving things.

• They respond to their environment, and they also grow and develop over time.

• Organisms reproduce and maintain stable internal conditions, a process which is called homeostasis.

• All life is made of cells and has a complex chemistry to stay alive.

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Multiple Choice

Which characteristic of life involves maintaining a stable internal environment, such as body temperature?

• Homeostasis

• Reproduction

• Response to the environment

• Complex chemistry

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Unifying Principles of Biology

• Cell Theory states all living things are made of one or more cells.

• Gene Theory explains how genes determine the traits of living things.

• Homeostasis is the ability to maintain a stable internal environment.

• Evolution shows how species change over time through natural selection.

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Multiple Choice

Which unifying principle of biology states that all living things are made of cells?

• Cell Theory

• Gene Theory

• Homeostasis

• Evolution

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Levels of Ecological Organization

• A population is a group of the same species living in a single area.

• A community is all the different populations that live together in one area.

• An ecosystem is the community plus nonliving factors like water, soil, and sunlight.

• A biome is a group of similar ecosystems. The biosphere is where all life exists.

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Multiple Choice

Which of the following represents all the living organisms and the nonliving factors in a given area?

• Ecosystem

• Population

• Community

• Biosphere

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Interactions Between Organisms

Symbiosis

• This is a close, long-term relationship between different species.

• In this interaction, at least one of the organisms benefits.

• These relationships are essential for the health of many ecosystems.

Competition

• This occurs when multiple organisms need the same limited resources.

• These limited resources can include things like food, water, or territory.

• It happens when organisms need resources at the same time and place.

Multiple Choice

What is it called when organisms need the same limited resources, such as food and water, in the same place?

• Competition

• Symbiosis

• Homeostasis

• Adaptation

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Common Misconceptions

Misconception	Correction
Evolution is just a 'theory'.	A scientific theory is a well-supported explanation backed by extensive evidence.
An organism can choose to adapt to its environment.	Adaptations are genetic traits that develop in a population over many generations.
In symbiosis, both organisms must benefit.	Symbiosis is any close interaction; the other organism may be unaffected or harmed.

Multiple Choice

How does the principle of homeostasis relate to an organism's ability to respond to its environment?

• It demonstrates that an organism must react to external changes to keep its internal conditions stable.

• It explains how genes are passed to offspring.

• It shows how organisms use energy to grow.

• It describes how all living things are made of cells.

Multiple Choice

A species of moth has coloring that perfectly matches the tree bark it rests on. Which biological concept best explains this coloring?

• Evolution by natural selection

• Homeostasis

• Cell Theory

• Competition

Multiple Choice

If a severe drought reduces the amount of water in an ecosystem, what is the most likely immediate effect on the community?

• Competition for water among organisms will increase.

• The number of symbiotic relationships will increase.

• The population of all organisms will increase.

• The biome will immediately change to a different type.

Multiple Choice

A biologist is studying all the different species of fish, insects, and plants in a river, along with the river's water chemistry and temperature. What level of ecological organization is being studied?

• An ecosystem, because it includes living organisms and nonliving factors.

• A community, because it involves multiple species.

• A population, because it is all contained within one river.

• A biosphere, because it includes water and life.

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Summary

• All living things share six key characteristics and are made of cells.

• Biology is guided by four main principles, including Cell Theory and Evolution.

• Evolution through natural selection allows organisms with favorable adaptations to survive.

• Life is organized into levels, and organisms interact through competition and symbiosis.

Poll

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

• 1

• 2

• 3

• 4