Students will identify environmental variables and their effects on plants and animals.
Environmental variables, microclimates, living and nonliving components
Pa. Standards Addressed Doing the Activity
- Teaching Methods Assessment and Evaluation
- Background Extensions
- Getting Ready Resources
Pennsylvania Environment and Ecology Standards Addressed
- 4.6.7. Ecosystems and their Interactions
A. Explain the flows of energy and matter from organisms to organism within an ecosystem.
- 4.7.7. Threatened, Endangered and Extinct Species
B. Explain how species of living organisms adapt to their environment.
Other Pennsylvania Standards Addressed
- Science and Technology
- Teaching Methods
- Observation, comparison, data collection, small group, hands-on
One set per group: Air thermometer, soil thermometer, light meter, wind meter, trowel, ruler, Environmental Variables worksheet, pencil.
Ecosystems have both living and nonliving components. Living components are called biotic factors and include plants, animals, fungi, and microorganisms. The abiotic or nonliving factors include air, water, wind, soil nutrients, temperature, and energy. Biotic and abiotic factors interact and affect each other. A raccoon drinks water from a stream. A plant is stunted by excessive wind. Microorganisms release nutrients into the soil. Shade from a tree cools the temperature.
Each species of organism does best within a certain range of environmental conditions. Even on a small scale, changes in these conditions can affect their behavior, growth, or survival. Environmental variables such as moisture, light, temperature, wind, soil, and other plants and animals can interact to create microclimates. Microclimates are special climate conditions that occur in small specific areas, such as under a bush, and can affect the plants and animals that live there.
Microclimates can change from season to season, day to day, and hour to hour. Many factors can affect microclimates, including buildings, fences, slope, or other plants. A garden in an open field has very different microclimate conditions than one surrounded by trees. These microclimates cause organisms to adapt to conditions by making changes, such as moving to another location, turning their leaves, or using more water. The changes the organisms make can affect their growth or survival.
All plants need light. It is the source of energy for photosynthesis, which fuels their growth. Heat from sunlight also warms the air and soil, and increases humidity through the evaporation of water. Plants need light to photosynthesize, which supplies the food for growth. The rate of plant growth is largely dependent on the amount of light received, and therefore on day length and the extent of the growing season. Individual plants may vary in their need for and response to sunlight. Those that need full sun grow pale and elongated in poor light. Those that are adapted to shaded conditions will often scorch in strong sunlight.
Rainfall is the main source of water for plants grown outdoors and is vital for plant growth. Rain drains through the soil where it is absorbed by plant roots, along with essential nutrients. Most plants require an aerated soil that is moist but well-drained. Waterlogged soil lacks oxygen and is fatal to many plants, since the roots will rot if deprived of oxygen.
The movement of air over leaf surfaces increases a plant’s rate of water transpiration or water loss. If water loss is greater than uptake, the plant suffers leaf scorch and desiccation. These effects are more severe in winter, especially with evergreens, since water lost from leaves cannot be replaced when the soil is frozen. Strong persistent winds may stunt the top-growth of plants. Marginally hardy plants can benefit from a sunny location near a fence or wall that provides shelter from wind.
Temperature affects a plant’s productivity and growth in various ways depending on the plant’s needs. Cool season plants, such as cabbage or spinach, grow best when day time air temperatures are between 60°F and 65°F. Warm season plants like corn or beans grow best when day time air temperatures are between 70°F and 80°F. Generally, plants produce maximum growth when the daytime temperature is about 10 to 15 degrees higher than the nighttime temperature. This allows the plant to produce enough energy from photosynthesis for growth. If temperatures are too warm, plants may lose excess water through transpiration. Temperatures that are too low can result in poor growth, because photosynthesis is slowed down.
Soil temperature changes more slowly than air temperature. Soil temperature is important because the microorganisms that benefit plant growth become active in temperatures over 40°F.
Plants also have critical temperatures below which they won’t germinate or grow. On the other hand, extremely high temperatures over 85°F will also slow or stop plant growth. Soil temperatures between 60°F and 85°F support the best plant growth. Cool season plants prefer the cooler end of this range and warm season plants prefer the warmer end.
|Soil Temperature||Plant growth|
|Less than 40°F||No growth, bacteria & fungi not very active|
|40°- 65°F||Some growth|
|65°- 70°F||Fastest growth|
|70°- 85°F||Some growth|
|Above 85°F||Little or no growth|
An animal’s answer to microclimate changes is to move. If temperatures become too hot, they may move to a shady area under a leaf, shrub or tree. They may also require more water as their metabolism increases in the heat and they may need to move to find it. If temperatures are too cold they may move to sunny areas to bask or burrow into the ground where temperatures are more stable. Since the body temperature of cold-blooded animals is directly affected by the surrounding air temperature, movement is necessary for their very survival. In cold, windy or stormy conditions, many animals seek shelter. Shelter protects the animals from injury and heat loss. Without shelter fragile insects, like butterflies, can sustain serious damage in very windy conditions. Depending on the animal shelter can be anything from a well-dug burrow to the underside of a leaf.
- Divide the garden into grids. Select fairly small areas so that temperature, wind, light, or moisture conditions are not likely to vary much within the grid. However, the overall sample area should be large enough to show some variation between grids. If your garden is small, consider comparing two or more different areas. For example, one in shade versus one in sun or one near a building and one in the open.
- Prepare a master data sheet. This sheet should show the garden with the grids. It should be large enough that students can write their results in their grid area. Use this as a visual when students look for variation in their results.
- Review equipment and how to take samples. The worksheet lists directions for the tests. Directions on how to use a device will vary with the equipment used. Follow the directions that come with the equipment.
In the classroom
- Explain that living (biotic) and nonliving (abiotic) components of an ecosystem interact and affect each other. Discuss examples of each.
- Introduce the term environmental variables to describe the physical features of an environment that can change. Discuss the concept of microclimates and how it might affect garden plants and animals.
- Tell students they will be taking measurements to see how much variation in temperature, moisture, wind speed, and light there is within the garden. Review the worksheet and demonstrate how to use thermometers, wind meters, light meters, and trowels to take various measurements.
In the garden
- Ask the students which areas of the garden they think would be warm, cool, wet, dry, windy, bright, dark, or have the most animals.
- Divide the class into small groups. Each group should receive an air thermometer, a soil thermometer, a trowel, a wind meter, a light meter, and an Environmental Variables worksheet. Option: Students can take more than one reading for each parameter and average their results. If you wish to use averages, give each group 2 air thermometers and 2 soil thermometers to save time.
- Explain that the garden has been divided into grids and that each group will work within a grid. Send each group to a garden grid area to take their measurements and complete the worksheet.
- Have students record their findings on the master sheet. Review each parameter. Was there much variation in the measurements? Which areas were warmest, coolest, wettest, driest, lightest, darkest, or windiest?
- How do the variables relate to each other? Are the warmest areas also the brightest? Are the wettest areas also the darkest? How do air and soil temperatures compare?
- What might be making these spots the warmest/coolest, wettest/driest, etc.? Discuss the effect of buildings, trees, fences, pavement, soil variation, slope, etc. on the results.
- Do the plants in the garden have any effect on the variables? (They may produce shade that cools soil temperature; they may reduce the effect of wind on other parts of garden; etc.)
- How might these variables change throughout the day? How would they change throughout the season or year?
- As the variables change throughout the day, how do you think they will affect the plants and animals that live here? What will happen to the plants and animals throughout the season or the year? How do they adapt to the changes in environmental variables?
- How can we use this information to keep our garden healthy? (Select plants that fit the microclimate conditions, use mulch to adjust moisture and temperature levels, use barriers to reduce wind, determine when to plant, etc.) When planning a new garden how can we use environmental variables to assist us? (Determine whether it is a good site for a garden, what improvements it might need, or which plants it would support.)
- Student participation in activities, use of equipment, and discussion may be used to evaluate this activity.
- Have students write a paper or present a report on how changes in environmental variables throughout one day might affect a particular plant.
- Conduct the activity at different times of the day, in a different season, or various times throughout the same day.
- Take students to an existing garden or an unprepared spot for a new garden and conduct the activity. Give each student several flower seed packets. Have students review the information on the back of the seed packet that describes the sun, water, and temperature requirements of the plant. Using the data collected at the site, have students determine whether the plant is appropriate for the garden site. If so, have them select a location within the garden that will best meet the plant’s needs.
- Collect information on environmental variables other areas such as a yard, schoolyard, or natural area. Draw comparisons between the areas and how plant an animal life would be affected by conditions in each area.
- Ball, Jeff, Rodale’s Garden Problem Solver, 1988
- Pearson Learning Group, Environment and Ecology for Pennsylvania, 2003
- Pennsylvania Bureau of State Parks, Activities for Environmental Learning, 1989
- University of California, Lawrence Hall of Science, Outdoor Biology Instructional Strategies, 1979.