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Farmer Changes in weather have a strong influence in crop production. Farmers sometimes adapt by changing planting and harvesting dates, selecting a different crop, or changing water use. In your Science Journal, describe another profession affected by climate.

Science i

Topic: Weather Data

Visit booke.msscience.com for Web links to information about recent weather data for your area.

Activity In your Science Journal, describe how these weather conditions affect plants or animals that live in your area.

Figure 7 Winds are created when sunlight heats some portions of Earth's surface more than others. In areas that receive more heat, the air becomes warmer. Cold air sinks beneath the warm air, forcing the warm air upward.

SECTION 1 Abiotic Factors E ♦ 41

Cascade Rain Shadow
Figure 8 In Washington State, the western side of the Cascade Mountains receives an average of 101 cm of rain each year. The eastern side of the Cascades is in a rain shadow that receives only about 25 cm of rain per year.

The Rain Shadow Effect The presence of mountains can affect rainfall patterns. As Figure 8 shows, wind blowing toward one side of a mountain is forced upward by the mountain's shape. As the air nears the top of the mountain, it cools. When air cools, the moisture it contains falls as rain or snow. By the time the cool air crosses over the top of the mountain, it has lost most of its moisture. The other side of the mountain range receives much less precipitation. It is not uncommon to find lush forests on one side of a mountain range and desert on the other side.

Summary

Environmental Factors

• Organisms depend on one another as well as sunlight, air, water, and soil.

Air, Water, and Soil

• Some of the gases in air provide substances to support life.

• Water is a major component of the cells in all organisms.

• Soil supports plant growth.

Sunlight, Temperature, and Climate

• Light energy supports almost all life on Earth.

• Most organisms require temperature between 0°C and 50°C to survive.

• For most organisms, temperature and precipitation are the two most important components of climate.

Self Check

1. Compare and contrast biotic factors and abiotic factors in ecosystems.

2. Explain why soil is considered an abiotic factor and a biotic factor.

3. Think Critically On day 1, you hike in shade under tall trees. On day 2, the trees are shorter and farther apart. On day 3, you see small plants but no trees. On day 4, you see snow. What abiotic factors might contribute to these changes?

Applying Math

4. Use an Electronic Spreadsheet Obtain two months of temperature and precipitation data for two cities in your state. Enter the data in a spreadsheet and calculate average daily temperature and precipitation. Use your calculations to compare the two climates.

42 ♦ E CHAPTER 2 The Nonliving Environment SctanCe^ booke.msscience.com/self_check_quiz

Humu-s Farm

Besides abiotic factors, such as rock particles and minerals, soil also contains biotic factors, including bacteria, molds, fungi, worms, insects, and decayed organisms. Crumbly, dark brown soil contains a high percentage of humus that is formed primarily from the decayed remains of plants, animals, and animal droppings. In this lab, you will cultivate your own humus.

O Real-World Question

How does humus form? Goals

■ Observe the formation of humus.

■ Observe biotic factors in the soil.

■ Infer how humus forms naturally.

water marker metric ruler graduated cylinder

Materials widemouthed jar soil grass clippings or green leaves

Safety Precautions

Wash your hands thoroughly after handling soil, grass clippings, or leaves.

Humus Formation

Date

Observations Do not write in this book.

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