Ecology Education Consulting, Inc.

Nor is this article a guide to what specific lessons to conduct using a garden in order to convey these ecological concepts. What this article will do is provide a general conceptual framework that can help to guide your thinking if you want to use a garden for teaching fundamental ecology concepts.

First let’s clarify how adaptations relate to ecology. Adaptations are the “tools” (structures, physiological processes and behavior patterns) that organisms use to meet their survival needs. The interactions that occur among living things and between living things and nonliving things as they use their adaptations to meet their survival needs represents the basis for the field of ecology. The take home message is that by just studying plant adaptations you have not completed a course of study with your students in ecology.

Ecological Principle #1 - Ecosystems require energy, which is most often obtained from the sun through photosynthesis. This energy is constantly being lost as it moves along a linear series of feeding relationships.

All organisms that can convert solar energy into chemical energy (by a process called photosynthesis) are called producers. If you have a garden at your school or in your back yard, then it is loaded with energy production factories. Depending on the type of garden ecosystem there may or may not be easily discernible grazing food chains and food webs. (See
Nature Notes - Food Chains and Food Webs in an Ecosystem). The herbivore populations may consist of such organisms as different species of songbirds, hummingbirds, rabbits, chipmunks, butterflies, bees and grubs. Different species will focus on eating different parts of the plants. In turn, the carnivore populations such as cats, preying mantis’, toads, robins, hawks, feed on these herbivores and in some cases on other carnivores. There may also be a very significant detritus food chain to study with primary and secondary detritus feeders such as bacteria, fungi, moles, ants and earthworms.


Living - Nonliving Community Interactions

While living organisms interact with one another, they must also successfully interact with a host of nonliving factors in order to survive. These will include such environmental variables as water, sunlight, wind, and soil conditions (e.g., pH, nutrient availability, moisture). For every environmental factor, each species has a range of tolerances. As the variable becomes more abundant or more reduced (e.g., pH that is too high or too low) the species will become more stressed and subject to death.

Ecological Principle #4 - Ecosystems undergo change due to natural events or human interference.

Ecosystems can change due to natural disturbances (e.g., fire, storm). They then reestablish themselves by undergoing progressive changes over time (succession). For example, a plowed field if left untouched may be invaded by weeds, shrubs and then trees, whereupon it eventually turns into a forest. In most cases, the cultivating that occurs with a garden will limit such an invasion by opportunistic plants (e.g., weeds); however, part of an outdoor garden can be left uncultivated to study successional modifications. The changes that occur with the seasons are also an opportunity to study this ecological principle. Ecosystems can also change in response to human-caused disturbances (e.g., setting fires, lumbering, pollution). Excellent lessons using garden plants (seeds, seedlings, adult plants of different species) can be used to study the impact of human activities on an ecosystem.

In summary, your garden ecosystem can be an excellent vehicle to teach your students a good overview of major ecological principles. In so doing, they will be better able to understand how the natural world works no matter what the ecosystem - field, forest, river, stream, pond or lake.

K-12 Garden Ecology

Indoor and outdoor gardens are used by many schools to teach students a variety of lessons in science and other curricular areas, as well as actively engage them in a relevant and easy to understand environmental stewardship activites. However, what may elude many teachers is the extent to which a garden can teach major ecological concepts. These may include:

          1. energy flow (food chains and food webs)
          2. nutrient cycling
          3. community interrelationships
          4. ecosystem change

When each concept is grasped and their linkages to each other understood, your students will gain an excellent understanding of how nature works.

In this article, we are going to take these ecological principles and apply them to gardens. This is NOT an article about how to set up and grow plants in a garden. An excellent on-line reference source for such activities is School Garden Wizard, which is a partnership between the U.S. Botanic Garden and the Chicago Botanic Garden.


Young girl potting soil
               http://www.schoolgardenwizard.org/

Another very good on-line resource is the Brooklyn Botanic Garden’s website:

               http://www.bbg.org/gar2/index.html
Garden in Backyard
Garden flowers
An ecology study project can utilize a variety of garden types ranging from a small flower bed to a large, highly diversified system.
Ecological Principle #2 - Unlike energy, nutrients must continually be recycled in an ecosystem, since they are present on earth in a fixed amount.

The living organisms and the nonliving constituents (e.g., water, soil and air) in our garden recycle vital nutrients (such as carbon, nitrogen, phosphorus). The decomposition process is an integral part of nutrient recycling.

Earthworms and many other organisms associated with gardens serve as detritivores and are responsible for shredding the waste matter and bodies of dead plants and animals. In addition, bacteria and fungi in the garden represent the decomposers that release powerful enzymes that break down the decomposing organic matter into simple nutrients that are then recycled back into the root systems of the plants growing in the garden. A variety of nice lesson plans could be set up to demonstrate nutrient cycling, as well as air and water cycling.

Ecological Principle #3 - An ecosystem is composed of a community of organisms that are interacting with one another and with their nonliving environment.

Each species in our garden belongs to one of 5 major groups:
  • Producers - convert solar energy to chemical energy
  • Herbivores - eat producers
  • Carnivores - eat herbivores and other carnivores
  • Detritivores - eat dead organic matter but are not able to release enzymes to decompose the organic matter
  • Decomposers - release enzymes to break down dead organic matter, thereby releasing nutrients

Furthermore, every species has many individuals, and collectively they are referred to as a population (e.g., daisy population, earthworm population, chipmunk population). All the garden’s populations comprise the garden’s community. Depending on how large or small your garden, the community may have low or high biodiversity (the variety of species and their abundance). You may, in fact, want to manipulate your garden in order to create greater biodiversity. This could be done by doing such things as selecting plant species favored by wildlife for food, setting up feeders and houses (bird, butterfly), and having a water supply available.

Your lessons may focus on cataloging the community diversity over time. Moreover, you may want to teach about some of the different types of interrelations that occur between the different living members and/or the living members and the garden’s nonliving (abiotic) environment. The area (garden) where all of these interactions (living - living and living - nonliving) are occurring is called an ecosystem. The ecosystem is the garden community (all of its populations) and the nonliving factors that interrelate with them.

Living - Living Interactions

Your garden may have species from 5 major kingdoms of life - plants, animals, protists, fungi and bacteria. Ecology lesson plans may center on one or more of the following types of interrelationships occurring in the garden. Predator-prey interactions move energy and nutrients through the community creating food chains and food webs within the garden. Mutualistic interactions are those in which both species benefit. For example, bees and hummingbirds acquire food from some of the plants while they carry pollen from one plant to another, thereby assisting with plant propagation. Another example would be the fungi relying on the dead flowers to acquire their nutrients and energy and in turn cycling nutrients back to the living plants. If resources become limited (e.g., space, food, water), the populations in the garden may compete with members of their own species (e.g., all the eastern cottontail rabbits) or members of other species (e.g., eastern cottontail rabbits versus chipmunks) that utilize the same resource.
Credits: Girl with Soil (Nick Daly) / Two Gardens (Dorling Kindersley)
Gardens are an excellent resource for teaching basic ecology concepts.