Lesson 2: Looking for Biodiversity

Students will complete plot studies or transects of two habitats: one near their school and one near their home. They will analyze the biodiversity in each habitat and draw conclusions about the importance of biodiversity to a habitat.

Length of Lesson:

2-3 class sessions, some of which is spent outside, time outside of school

Subject Area(s):

Science

Objectives

Students will:

Complete a plot study or transect of a habitat near their school and a habitat near their home.
Compare and contrast the plot studies.
Draw conclusions about the importance of biodiversity to habitats.

Materials

Field guides of regional plant life, reference materials, computer with Internet access, meter sticks or tape measures, stakes, flagging tape or string, permanent marker, data chart.

Background Information:

Procedure

Ask students to share what they know about habitats, a designated area where plants and animals live. Then discuss with students the various habitats that surround the school, such as woods, meadows or grassy fields. Ask students what kind of plant life is found in each of these habitats. Is there great variety, or diversity, or do only a few kinds of similar plants, such as grass in a field, live there?
Discuss with students the advantages of diverse plant life in a habitat. For example, a greater variety of plants provide nutrients to a greater variety of insects. It also ensures that if a disease strikes one plant, such as Dutch elm disease hitting elm trees, other plant species will survive. For these reasons, biodiversity—a measure of the variety of life in a specific habitat—is also an indicator of the environmental health of a habitat.
Explain to students that they are going to work in teams of three or four students to complete a biodiversity study of plants in one local habitat. Brainstorm with students about their study design. Two common methods that ecologists use are line transects and plot studies. A transect is a long, narrow sampling area, while a plot study is a square area (often 100 meters by 100 meters) that can be divided into subplots. Transects extend over a longer portion of a study area than a plot does, resulting in a larger sample of different plant species. However, plot studies are useful for small areas that have a great variety of plant life. The diagrams below show what a transect and a plot study look like.

Transect: 20 meters long divided into 10 subplots each measuring 2 meters

Plot Study: 100 meters by 100 meters divided into 25-meter subplots

Divide the students into teams. Have each team decide where to do their habitat diversity study. Possible sites include woods, a forest, a meadow, a lawn (of three-year-old grass cover not chemically treated), a marsh or an edge of a pond or lake. If students live in an urban area, they could focus on a local city park or areas where trees are planted along the school’s street. If they focus on smaller areas, you may need to decrease the size of their plots and transects.
Depending on the habitat chosen, students should decide the size and design of their study. Have students keep in mind the size of the plants they plan to count and study as they decide on the area to observe. Larger plant specimens, such as trees, need a larger plot or transect area than do short grasses. If sufficient space exists, have students choose plots or transects that do not touch or intersect. Also, if a range of habitats is available for study, have each team work in different habitats. This will provide the class with more data for comparison. Students should record their results in the Classroom Activity Sheet Data Chart.
If students are doing a plot study, they should follow the steps below:
- Measure a square area of sufficient size for a team study. Students should use a meter stick to measure each of the four sides of the plot, and they should put a stake at each of the four corners. This plot size is determined by the size of the plants that the students will be observing.
- Have students outline the plot study area with string or flagging tape. After the plot has been laid out, have the team spread out to cover the entire plot area.
- Students should survey the area and identify the species of pants that are present. Then students should count the number of plants, measure the height of each plant and map where the plants are found on the plot.
If students are conducting a transect study, they should follow the steps below:
- Have students measure 20 meters of string. Tie one end of the string to a stake so the string stays in place. Using a permanent marker, students should measure and mark the 5-meter, 10-meter and 15-meter locations on the string.
- Have students observe and identify all plants along the 20-meter transect. The width of the transect should be 2 meters, with all plants 1 meter from the string on both sides counted.
- Have students identify the species of plants along the transect, measure the height of each plant, count the number of plants, and map all plants along the transect.
Have students complete a study of their entire plot or transect area for at least a week. If time permits, students could work on this project throughout the school year.
Discuss the students’ data. What does the data tell them about their habitats of study? Was more plant diversity found in one particular area? Did the students observe this area as being healthier? Was a large population of a specific plant species found? Suggest that students write a paragraph describing their results.
After students have completed their school-based biodiversity study, assign the Take Home Activity Sheet: Local Biodiversity Study. Have students study a completely different area than the one completed for the first project, such as a habitat in their neighborhood or even in their own backyard. Have students count both plants and animals in this study.
Compare and contrast the habitats studied. Which area had the greatest diversity of life? Which had the highest population number? Why were some areas more diverse than others?
At the end of this activity, return to your definition of biodiversity—the variety of living organisms in a given area. Look back at the biodiversity studies students completed at home and at school. Point out that some areas have a greater number of species than others: they have more biodiversity. Explain that on a global scale, some areas are more diverse than others. Tropical rain forests have the greatest number of species than any other biome. Some experts believe that 50% of all known species on Earth are found in tropical rain forests—yet rain forests cover only about 6–7% of the world’s land surface. Ask students to consider why tropical rain forests have so much biodiversity. Why should we care about preserving the biodiversity in these rain forests?
Have students draw conclusions about why biodiversity is important to a habitat.

Extensions

Have students research the current state of the world’s rainforests as it relates to biodiversity.
Have the class create a field guide for the plants found in their plot or transect study. Each page should include a sketch of the plant and a description of its flower, leaves, size, bloom time and a general description of the habitat, as well as a map of the range where the plant can be found. Gather the field guide pages together to use as a reference for studying plants throughout the school year.

Evaluation

You can evaluate your students using the following three-point rubric:

Three points: Students worked well in their teams; counted a wide range of plants in their study area; identified most of the plants in their study area; created a complete and accurate data chart; completed an accurate sketch of their study area
Two points: Students worked somewhat well in their teams; counted many of the plants in their study area; identified some plants in their study area; created a chart that was mostly complete and accurate; completed a partial sketch of their study area
One point: Students counted some plants in their study area; identified a few plants; created a chart that incorporated some of the data; included some plants on a sketch of their study area

National Standards

This lesson plan may be used to address the National Science Education Standards listed below.

Grade Level: 5-8
Subject: Science as Inquiry
Standard: Understandings about Scientific Inquiry
Benchmark:

Different kinds of questions suggest different kinds of scientific investigations. Some investigations involve observing and describing objects, organisms or events; some involve collecting specimens; some involve experiments; some involve seeking more information; some involve discovery of new objects and phenomena; and some involve making models.

Grade Level: 5-8
Subject: Life Science
Standard: Regulation and Behavior
Benchmark:

An organism’s behavior evolves through adaptation to its environment. How a species moves, obtains food, reproduces and responds to danger are based in the species’ evolutionary history.

Grade Level: 5-8
Subject: Life Science
Standard: Population and Ecosystems

A population consists of all individuals of a species that occur together at a given place and time. All populations living together and the physical factors with which they interact compose an ecosystem.
Populations of organisms can be categorized by the function they serve in an ecosystem. Plants and some microorganisms are producers—they make their own food. All animals, including humans, are consumers, which obtain food by eating other organisms. Decomposers, primarily bacteria and fungi, are consumers that use waste materials and dead organisms for food. Food webs identify the relationships among producers, consumers, and decomposers in an ecosystem.
For ecosystems, the major source of energy is sunlight. Energy entering ecosystems as sunlight is transferred by producers into chemical energy through photosynthesis. That energy then passes from organism to organism in food webs.
The number of organisms an ecosystem can support depends on the resources available and abiotic factors, such as quantity of light and water, range of temperatures and soil composition. Given adequate biotic and abiotic resources and no disease or predators, populations (including humans) increase at rapid rates. Lack of resources and other factors, such as predation and climate, limit the growth of populations in specific niches in the ecosystem.

Grade Level: 5-8
Subject: Life Science
Standard: Diversity and Adaptation of Organisms

Millions of species of animals, plants and microorganisms are alive today. Although different species might look dissimilar, the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes and the evidence of common ancestry.
Biological evolution accounts for the diversity of species developed through gradual processes over many generations. Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations. Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment
Extinction of a species occurs when the environment changes and the adaptive characteristics of a species are insufficient to allow its survival. Fossils indicate that many organisms that lived long ago are extinct. Extinction of species is common; most of the species that have lived on Earth no longer exist.

Academic Standards

This lesson plan may be used to address the academic standards listed below. These standards are drawn from Content Knowledge: A Compendium of Standards and Benchmarks for K-12 Education: 2nd Edition and have been provided courtesy of the Mid-continent Research for Education and Learning in Aurora, Colorado.

Grade level: 6-8
Subject: Life Science
Standard: Knows About the Diversity and Unity That Characterize Life
Benchmarks:

Knows ways in which living things can be classified (e.g., taxonomic groups of plants, animals and fungi; groups based on the details of organisms’ internal and external features; groups based on the roles within an ecosystem, such as producers, consumers and decomposers).

Grade level: 6-8
Subject: Life Science
Standard: Understands How Species Depend on One Another and on the Environment for Survival
Benchmarks:

Knows how an organism’s ability to regulate its internal environment enables the organism to obtain and use resources, grow, reproduce and maintain stable internal conditions while living in a constantly changing external environment.