Students will identify environmental variables and their effects on plants and animals.
Environmental variables, microclimates
Pa. Standards Addressed Doing the Activity
- Teaching Methods Assessment and Evaluation
- Background Extensions
- Getting Ready Resources
Pennsylvania Environment and Ecology Standards Addressed
- 4.6.4. Ecosystems and their Interactions
A. Understand that living things are dependent on nonliving things in the environment for survival.
- 4.7.4. Threatened, Endangered and Extinct Species
B. Know that adaptations are important for survival.
Other Pennsylvania Standards Addressed
- Science and Technology
- Teaching Methods
- Observation, comparison, data collection, small group, hands-on
Rulers, Plants and Animals worksheets.
Planning & Planting Tips
Plant the same types of flowers in different conditions – sun/shade, wet/dry, etc. to insure variation in plant growth.
Plants and animals are influenced by environmental variables such as moisture, light, temperature, wind, and other plants and animals. These variables can change from season to season, day to day, and hour to hour. The variables create microclimates which are special climate conditions that occur in small specific areas, such as under a bush. These microclimates cause organisms to make changes, such as moving to another location, turning their leaves, or using more water.
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. Soil temperature changes more slowly than air temperature. 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.
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.
Before the activity determine whether you want students to compare conditions within one large garden area or between two or more gardens. For each group, select two plants of the same type that are found in different parts of the garden or in different gardens. For example, two petunia plants with one found in a sunny area and one found in partial shade. If possible, assign at least two groups the same type of plant for comparison purposes.
- Take students to the garden area(s) they will study. Break the students into groups and assign the pre-selected plant pairs to each group (see Getting Ready). Give each student a copy of the Plants and Animals Worksheet, a ruler, and a pencil. Explain that the students will be gathering information on each plant for comparison.
- Send students to their first plant and have them complete the Plant #1 column of the worksheet. Have students identify the type of plant they are observing. Student should use the ruler to measure the height of the plant and size of the leaves.
- Have students record animal life or signs of life near Plant #1. Look for animals on or under leaves, on flowers, or on the ground beneath the plant. Look for other signs such as chewed leaves, egg masses, webs, or tracks.
- Repeat steps 2 and 3 for the second plant. Have students record results on the worksheet in the Plant #2 column.
- Group students together. Discuss their results. Did they notice any differences between the two plants they examined? Were there any differences in the type of animals? Where were the animals located at each plant? What do you think might be causing the differences?
- Ask the students which areas of the garden(s) they think would be warm, cool, wet, dry, windy, light, dark, or have the most animals. Introduce the term environmental variables to describe the physical features of an environment that can change.
- Ask students the following: How do the variables relate to each other? Are the warmest areas also the lightest? Driest? Are the wettest areas also the coolest? Darkest?
- Have students look at the areas where each of their plants is located. Are the variables different where each of the plants is growing? How do the variables affect the way the plants grow? Use the information in the background section to discuss how environmental variables might cause variation in the plants. Are the plants in shaded areas taller than those in sunny areas? Are the leaves bigger on plants in shaded or sunny areas? Are plants in dry, sunny areas wilted?
- How do you think the variables affect the type of animals you found? How would the variables affect where you found the animals? How would they affect the animal’s activities?
- How might the variables change throughout the day? As the variables change throughout the day, how do you think they will affect the plants and animals? What will happen to the plants and animals throughout the season or the year? How do they adapt to the changes in environmental variables?
- Student participation in activities 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 or animal.
- Conduct the activity at different times of the day or in a different season.
- Conduct the activity at various times throughout the same day.
- Collect information on environmental variables in a garden and another area such as a yard, schoolyard, or natural area. Compare the plants and animals of the garden to the other location.
- University of California, Lawrence Hall of Science, Outdoor Biology Instructional Strategies, 1979.
- American Forest Foundation, Project Learning Tree, 1993.
- The American Horticultural Society, A-Z Encyclopedia of Garden Plants, 1997.
- Penn State College of Agricultural Sciences, The Penn State Master Gardener Manual