Science · 7th Grade · Inheritance and Variation · Weeks 19-27

Ecosystems and Biomes

Students investigate the components of ecosystems and how different biomes are characterized by their climate and dominant life forms.

• Common Core State Standards
• MS-LS2-1

About This Topic

An ecosystem is a community of living organisms interacting with each other and with their physical environment. A biome is a larger geographic region characterized by a specific climate and the organisms adapted to it. North America contains several major biomes: temperate deciduous forests in the East, grasslands across the Great Plains, deserts in the Southwest, coniferous forests in the northern Rockies and Alaska, and tropical zones in Hawaii. Each biome supports organisms whose traits reflect the dominant abiotic conditions.

Within any ecosystem, biotic factors (producers, consumers, decomposers) and abiotic factors (temperature, precipitation, sunlight, soil chemistry) are tightly interdependent. The MS-LS2-1 standard asks students to analyze data on how resource availability shapes organisms and populations. A shift in one abiotic variable -- a prolonged drought, a hard freeze -- can restructure the entire community.

Active learning is especially effective here because students can compare real climograph data, match organisms to biomes based on evidence, and construct food webs that reveal how the physical environment controls the biological community.

Key Questions

1. Differentiate between various biomes based on their climate and characteristic organisms.
2. Analyze the interactions between biotic and abiotic factors within an ecosystem.
3. Construct a food web to illustrate energy flow in a specific biome.

Learning Objectives

• Compare the characteristic climate data (temperature, precipitation) and dominant life forms of at least three major world biomes.
• Analyze the interdependence of biotic and abiotic factors within a given ecosystem by identifying at least two specific interactions.
• Construct a food web for a chosen biome that accurately illustrates the flow of energy from producers to consumers and decomposers.
• Explain how changes in a specific abiotic factor, such as water availability, can impact the populations of organisms within an ecosystem.

Before You Start

Introduction to Living Organisms

Why: Students need a basic understanding of what living things are and how they are classified to identify biotic factors in an ecosystem.

Basic Weather and Climate Concepts

Why: Prior knowledge of temperature, precipitation, and climate is necessary to differentiate between various biomes.

Key Vocabulary

Biome	A large geographic area characterized by specific climate conditions and distinct plant and animal communities adapted to those conditions.
Ecosystem	A community of living organisms (biotic factors) interacting with each other and their non-living physical environment (abiotic factors).
Abiotic Factors	The non-living components of an ecosystem, such as temperature, sunlight, water, soil type, and atmospheric gases.
Biotic Factors	The living or once-living components of an ecosystem, including producers, consumers, and decomposers.
Food Web	A diagram that shows the feeding relationships between different organisms in an ecosystem, illustrating the flow of energy.

Watch Out for These Misconceptions

Common Misconception

All rainforests are tropical.

What to Teach Instead

Temperate rainforests also exist, such as those in the Pacific Northwest. Comparing climographs and species lists for both types shows that 'rainforest' is defined by precipitation amount and seasonal distribution, not by temperature alone.

Common Misconception

Abiotic factors are background scenery -- organisms only depend on each other.

What to Teach Instead

Abiotic factors like sunlight, water availability, and soil chemistry fundamentally control which organisms can survive in an area. Case studies showing how a single abiotic change (a drought, a temperature shift) restructures entire communities make this cause-and-effect relationship concrete.

Active Learning Ideas

Gallery Walk: Biome Comparison Posters

Assign each group a different biome (tundra, desert, tropical rainforest, temperate forest, grassland, taiga). Groups create a poster with a climograph, dominant organisms, and key adaptations. During the gallery walk, pairs complete a comparison chart noting how differences in abiotic factors correspond to differences in the organisms present.

50 min·Small Groups

Inquiry Circle: Biotic and Abiotic Scavenger Hunt

Students observe the school grounds (or a set of photographs) and categorize everything as biotic or abiotic, recording each item's role in the local ecosystem. Back inside, groups build a simple interaction diagram showing how three biotic and three abiotic factors they identified connect to each other.

40 min·Small Groups

Think-Pair-Share: Ecosystem Disruption Chain Reaction

Present a scenario such as a multi-year drought hitting a temperate forest. Students individually predict which abiotic factors change first and which biotic factors respond in turn. Pairs compare their reasoning and present one complete cause-and-effect chain to the class.

20 min·Pairs

Real-World Connections

• Ecologists conduct field research in biomes like the Amazon rainforest or the Sonoran Desert to study species interactions and the impact of climate change on these delicate systems.
• Urban planners and landscape architects use principles of ecosystem design to create sustainable green spaces in cities, considering native plants, water management, and the needs of local wildlife.
• Conservation scientists work to protect endangered species by understanding their specific biome requirements and mitigating threats from habitat loss or altered abiotic conditions.

Assessment Ideas

Quick Check

Provide students with a list of 5-7 organisms and 3-4 climate data sets (e.g., average temperature, annual rainfall). Ask them to match each organism to the biome it is most likely to inhabit and justify their choices based on climate and known adaptations.

Exit Ticket

On an index card, have students write the definition of an ecosystem and list two biotic and two abiotic factors found in a temperate deciduous forest. They should also briefly describe one interaction between a biotic and an abiotic factor.

Discussion Prompt

Pose the question: 'Imagine a prolonged drought occurs in a grassland biome. How might this change affect the producers, consumers, and decomposers in that ecosystem?' Facilitate a class discussion where students share their predictions and reasoning.

Frequently Asked Questions

What is the difference between a biome and an ecosystem?

A biome is a large geographic region defined by climate and the dominant life forms adapted to it, such as a desert or tropical rainforest. An ecosystem is a smaller-scale unit that includes all living organisms in an area and the physical environment they interact with. Multiple ecosystems can exist within a single biome.

What are biotic and abiotic factors in an ecosystem?

Biotic factors are all living components: plants, animals, fungi, and bacteria. Abiotic factors are nonliving components: temperature, sunlight, water, soil type, and atmospheric gases. Both sets of factors interact to determine which organisms can survive and how many can be supported in a given ecosystem.

Which biomes are found in the United States?

The contiguous US contains temperate deciduous forests in the East, temperate grasslands across the Great Plains, desert and chaparral in the West and Southwest, and coniferous forest in the Rockies. Alaska includes tundra and taiga. Hawaii has tropical rainforest zones. This diversity makes the US an excellent case study for comparing biome characteristics.

How does active learning help students understand ecosystems and biomes?

Building food webs and comparing real climograph data requires students to reason about cause and effect rather than memorize definitions. When a student traces a specific organism's adaptations back to the abiotic conditions of its biome, the connection between climate and life becomes far more durable than reading about it in a textbook.