Students compare the differences between natural and managed ecosystems and describe ways in which farmers can protect agricultural ecosystems. Grades 3-5

abiotic: relating to nonliving things in an environment

apex predator: a predator at the top of the food chain that does not have any natural predators

biodiversity: diversity among and within plant and animal species in an environment

biotic: relating to living things in an environment

carnivore: an animal that feeds on animal matter

decomposer: an organism that feeds on and breaks down dead plant or animal matter

ecosystem: a biological community of living organisms interacting with the nonliving parts of their environment

food chain: a hierarchical series of organisms each dependent on the next as a source of food

herbivore: an animal that feeds on plants

living: organisms that display the key characteristics of life including movement, breathing or respiration, excretion, growth, sensitivity, and reproduction

nonliving: anything that was never alive

omnivore: an animal or person that eats food of both plant and animal origin

primary consumer: an animal that eats producers

producer: an organism that serves as a source of food for other organisms in a food chain; an organism that can make its own food

secondary consumer: an animal that eats primary consumers

sustainable agriculture: an approach to agriculture that focuses on producing food while improving the economic viability of farms, protecting natural resources, and enhancing quality of life for farmers and society as a whole

tertiary consumer: an animal that eats primary consumers and secondary consumers

An ecosystem is a biological community of living organisms interacting with the nonliving parts of their environment. There are two main components of an ecosystem. The biotic factor is made up of living organisms like plants, animals, fungi, and bacteria. The abiotic factor is made up of nonliving components like soil, weather, water, and rocks.

Ecosystems need energy. A food chain, a series of organisms that are each dependent on the next as a food source, shows how energy moves through an ecosystem. Typically, this energy originates from sunlight. Producers, organisms like green plants that can make their own food, use energy from sunlight and convert it into usable energy through the process of photosynthesis. Animals (consumers) consume the energy from plants and then are eaten by other animals or decompose back into the soil. Primary consumers are animals that eat producers. They are usually herbivores that feed on plants. Secondary consumers are animals that eat primary consumers. They can be either carnivores that feed on animals or omnivores that feed on both plants and animals. Tertiary consumers are animals that eat primary consumers and secondary consumers. They are typically carnivorous predators but can also be omnivores. Apex predators are the predators at the top of the food chain that have no natural predators. As part of an ecosystem, animals and plants depend on each other for survival. Beginning with plants and ending with animals, organisms eat other organisms to obtain energy.

An agricultural ecosystem is a managed ecosystem with the purpose of producing crops and/or animal products. Agricultural ecosystems comprise about 37% of the total land area of the Earth,¹ with approximately 11% being arable land used to cultivate crops and the rest used to raise livestock.² 

Natural ecosystems consist of many species of plants and animals while managed ecosystems have fewer species that are selected by humans and are limited in diversity. Natural ecosystems are self-sustaining as opposed to managed ecosystems that require the assistance of humans. Humans control many of the interactions in an agricultural ecosystem, including soil condition, soil erosion, water quality, and animal habitats. While sunlight is the energy source for both natural and managed ecosystems, managed systems may supply additional fertilizer and nutrients to the soil. Food chains in a natural system are more complex than in a managed system.

There are many techniques farmers can use to protect agricultural ecosystems, including managing water wisely; building and maintaining healthy soil; minimizing air, water, and climate pollution; and promoting biodiversity. Sustainable agriculture refers to farming practices and methods that are economically profitable, environmentally sound, and good for communities.³ Sustainable farming practices include rotating crops, planting cover crops, reducing or eliminating tillage, applying integrated pest management (IPM), integrating livestock and crops, adopting agroforestry practices, and managing whole systems and landscapes.⁴

1. Ask the students to make a list of living and nonliving things that can be found on a farm. Guide the students to include the following on their list:
   • sunlight
   • air
   • water
   • soil
   • plants
   • animals
   • insects
   • decomposers
   • farmers
2. Lead a discussion about how the living and nonliving things on a farm are interconnected. Include the following points in the discussion:
   • Plants need light, water, nutrients, and air to survive.
   • Animals and insects need water, food, air, and shelter to survive.
   • Plants produce their own food, and animals depend on plants, or animals that eat plants, for food.
   • Insects, like bees and butterflies, are necessary for the reproduction of most of the world's flowering plants.
   • Animal waste is an important nutrient source for plants.
   • Grazing animals are able to digest plants that humans cannot.
   • Decomposers break down wastes that collect on the earth into materials that are used by plants.
   • The farmer controls and monitors food/fiber production on the farm.
3. Explain to the students that, in this lesson, they will be investigating natural and managed ecosystems, communities of living things interacting with the nonliving parts of their environment.

Activity 1: What is an Ecosystem?

1. Have the students view the Understanding Ecosystems video.
2. Lead a discussion about ecosystems. Include the following points in the discussion:
   • Ecosystems are communities of living things interacting with the nonliving things in their environment.
   • The nonliving parts of an ecosystem include sunlight, temperature, air, weather, water, rocks, and soil.
   • The living parts of an ecosystem are the plants and animals living in it. There are three main types of living things in an ecosystem—producers, consumers, and decomposers.
   • Producers make their own food typically through the process of photosynthesis.
   • All animals are consumers that rely on producers and/or other consumers for food.
   • Decomposers consume dead plants and animals and break them down into nutrients that are released into the soil. The nutrients are used by plants to help them grow.
   • We can protect ecosystems by cleaning up trash, planting trees, conserving water and electricity, and creating habitats for wild animals.
3. Project the Ecological Regions of North America Map onto a large screen. As a class, identify the major ecosystem(s) in your region. Guide the students to research the ecosystem(s) and identify the following features:
   • Climate 
   • Plants
   • Animals
   • Natural Resources
4. As a class, use the information from the State Agricultural Facts for your state to identify the crops and livestock that are grown and raised in your region.

Activity 2: Comparing Natural and Managed Ecosystems

1. Prior to this activity, place one of the Four Corners Signs into each corner of the classroom.
2. Show the students the Definition Signs. Ask them to match the words with the definitions. Match the words and definitions together on the board:
   • natural: existing in or caused by nature; not made or caused by humankind
   • manage: to take charge or care of
3. Provide each student with an Ecosystem Card. Ask the students to determine the corner in which their card fits—Natural Ecosystems, Managed Ecosystems, Both Natural and Managed Ecosystems, or Neither Natural nor Managed Ecosystems—and move to stand in that corner.
4. Have each student share with the class why their card fits with the corner they chose.
5. Discuss the differences between natural and managed ecosystems. Include the following points in the discussion:
   • Natural ecosystems consist of many species of plants and animals. Species in managed ecosystems are selected by humans and limited in diversity.
   • Natural ecosystems are self-sustaining. Managed ecosystems require the assistance of humans.
   • Humans control many of the interactions in a managed ecosystem, including soil condition, soil erosion, water quality, and animal habitats.
   • While sunlight is the energy source for both natural and managed ecosystems, managed systems may supply additional fertilizer and nutrients to the soil.
   • Food chains in a natural system are more complex than in a managed system.

Activity 3: Farm Food Chains

1. Prior to this activity, prepare a food chain model by attaching the Food Chain Model Pictures to the plastic cups.
2. Use the food chain model to explain the following points:
   • A food chain is a series of organisms that are each dependent on the next as a food source. A food chain shows how energy moves through an ecosystem.
   • Show the students the sunlight cup. In an ecosystem, organisms are dependent on each other for energy in the form of food. Typically, this energy originates from sunlight.
   • Show the students the producer cup. Producers are organisms that can make their own food. Green plants are producers that use the energy from sunlight to make their own food through the process of photosynthesis. (Use the Desktop Greenhouses lesson to further explore the topic of photosynthesis.) Place the producer cup onto the sunlight cup.
   • Show the students the primary consumer cup. Primary consumers are animals that eat producers. They are usually herbivores that feed on plants. Place the primary consumer cup onto the producer cup.
   • Show the students the secondary consumer cup. Secondary consumers are organisms that eat primary consumers. They can be either carnivores that feed on animals or omnivores that feed on both plants and animals. Place the secondary consumer cup onto the primary consumer cup.
   • Show the students the tertiary consumer cup. Tertiary consumers are animals that eat primary consumers and secondary consumers. They are typically carnivorous predators but can also be omnivores. Place the tertiary consumer cup onto the secondary consumer cup.
   • Show the students the apex predator cup. Apex predators are the predators at the top of the food chain. They have no natural predators. Place the apex predator cup onto the tertiary consumer cup.
3. Organize the students into four groups—Ocean, Jungle, Grassland, and Farm.
4. Provide each group with plastic cups and their corresponding book and Food Chain Pictures.
   • Ocean: Dory Story by Jerry Pallotta
   • Jungle: Once Upon a Jungle by Laura Knowles
   • Pond: Pond Circle by Betsy Franco
   • Farm: Pigs & Pork in the Story of Agriculture by Susan Anderson and JoAnne Buggey
5. Have each group read their book and identify the producer, consumers, and apex predators in their food chain.
6. Instruct the students to attach the Food Chain Pictures for their ecosystem to the plastic cups and create a model of the food chain.
7. Provide time for each group to present their food chain model to the class.
8. Ask the students to compare the stacked cups of each food chain. Which stack is shortest? (The farm food chain.) Explain to the students that the food chains in natural ecosystems are longer and more complex than in managed ecosystems. While agricultural ecosystems are less diverse than natural ecosystems, sustainable agricultural practices allow farmers to efficiently produce reliable sources of food for a growing population while protecting the environment. Discuss ways in which farmers can protect agricultural ecosystems. Include the following points in the discussion:
   • There are many techniques farmers can use to protect agricultural ecosystems, including managing water wisely; building and maintaining healthy soil; minimizing air, water, and climate pollution; and promoting biodiversity (diversity among and within plant and animal species in an environment).
   • Sustainable agriculture refers to farming practices and methods that are economically profitable, environmentally sound, and good for communities.
   • Sustainable farming practices include rotating crops, planting cover crops, reducing or eliminating tillage, applying integrated pest management (IPM), integrating livestock and crops, adopting agroforestry practices, and managing whole systems and landscapes.

After conducting these activities, review and summarize the following key concepts:

• An ecosystem is a biological community of living organisms interacting with the nonliving parts of their environment.
• A food chain, a series of organisms that are each dependent on the next as a food source, shows how energy moves through an ecosystem. Typically, this energy originates from sunlight.
• Natural ecosystems consist of many species of plants and animals, while species in managed ecosystems are selected by humans.
• There are many techniques farmers can use to protect agricultural ecosystems, including managing water wisely; building and maintaining healthy soil; minimizing air, water, and climate pollution; and promoting biodiversity.

1. https://data.worldbank.org/indicator/ag.lnd.agri.zs
2. https://www.sciencedirect.com/science/article/pii/B978008045405400313X
3. https://www.westernsare.org/About-Us/What-is-Sustainable-Agriculture
4. https://www.ucsusa.org/food-agriculture/advance-sustainable-agriculture/what-is-sustainable-agriculture
5. https://www.nasa.gov/content/goddard/seeing-photosynthesis-from-space-nasa-scientists-use-satellites-to-measure-plant-health/
6. https://thesustainabilityalliance.us/5-facts-sustainability-in-agriculture/

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