INTERACTIONS IN AN ENVIRONMENT

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1 reflect Earth is full of living things. Our planet has many kinds of organisms including bacteria, fungi (like mushrooms), plants, and animals. In some ways, living things are alike. Almost all living things need water and oxygen to survive. But Earth s organisms are also different from each other. For example, bacteria are simple, one-celled organisms, while plants and animals are complex organisms made of many cells. Plants can make their own food, but animals eat other organisms for energy. The characteristics of an organism determines how it interacts with the living and nonliving things in its ecosystem. But what are some of the living and nonliving parts of an ecosystem? What are the ways that organisms interact with these parts of the ecosystem? Interactions with the Living Things in an Ecosystem A squirrel runs onto the forest fl oor to fi nd an acorn. It carefully watches for predators such as hawks and foxes. Soon, it fi nds an acorn and hides it in a dead tree trunk. When a chipmunk tries to steal the acorn, the squirrel chases the chipmunk away. The living things that the squirrel interacts with are called biotic factors. A biotic factor is anything made up of cells. This includes organisms with just one cell, such as bacteria and some kinds of fungi. It also includes organisms with many cells, such as plants and animals. Biotic factors may be a nonmoving part of the ecosystem, such as a tree. Other biotic factors may move through an ecosystem, such as migrating birds. Anything that is alive or used to be alive is biotic. A squirrel is a biotic factor. It is made up of cells and is alive. The dead tree trunk is also a biotic factor. The tree is made up of cells and used to be alive. ecosystem: the living and nonliving things that interact within a given area predator: an animal that hunts and eats other animals Organisms interact with the biotic factors in their ecosystem to get food, energy, and other resources that help them survive. In the example above, the squirrel collected an acorn for food. It used a tree trunk to hide its food. It looked out for predators and chased off other animals that were competing for its food source. 1

2 Interactions with the Nonliving Things in an Ecosystem The squirrel s ecosystem is also made up of nonliving parts. Organisms interact with the nonliving parts of their ecosystem to get food, energy, and other resources that help them survive. The nonliving parts of the ecosystem are called abiotic factors. Sunlight: Sunlight provides energy that plants and certain bacteria absorb to make their own food. This process is called photosynthesis. In photosynthesis, sunlight and carbon dioxide (CO 2 ) combine to make glucose (C 6 H 12 O 6 ) and oxygen (O 2 ). Sunlight also provides heat. Some animals use the Sun s heat to warm their bodies. Soil: Soil provides plants with a place to grow. It gives plants nutrients and room for their roots to grow. Soil is also a home to other living things. Earthworms, prairie dogs, fungi, and some snakes live in soil. There are many types of soil. Some soil is sandy and dry. Some soil is moist and full of nutrients. The type of soil determines which organisms can live there. A cactus can grow in sandy, dry soil because it is able to conserve water. It holds a lot of water in its stem. Plants that grow in moist soil like marsh grasses have shallow roots because the soil holds plenty of water that the plant roots can easily take in. Temperature: The temperature of an ecosystem affects what kinds of organisms can live there. Some living things are able to live in cold ecosystems. These organisms usually have characteristics that keep their bodies warm. For example, some rabbits grow longer, thicker fur in winter. Organisms that live in hot ecosystems have characteristics that help them stay cool. Many animals that live in hot deserts have very short fur year-round. glucose: a simple form of sugar that is used as a source of energy in living things nutrient: a vitamin that helps a living thing grow 2

3 Water: All living things need water to survive. Plants, animals, and other organisms need to absorb water to stay healthy. Some organisms use water as a habitat. For example, fi sh, whales, seaweed, and other aquatic organisms live in water. Some animals, such as frogs, lay their eggs in water. Seasons: A change in seasons brings a change in temperature and the amount of daily sunlight. This abiotic factor is an important signal for many processes. The change from winter to spring signals some organisms to wake up from hibernation. Spring and summer is when most organisms start to breed, or produce young. Fall weather lets some organisms know it is time to migrate to warmer areas. what do you think? migrate: to move from one area to another, often in response to seasonal changes Look at the photograph below. What biotic and abiotic factors can you identify? Describe as many as you can. How are the biotic and abiotic factors interacting? 3

4 look out! You might think that if two ecosystems share the same abiotic factors, they will also have the same biotic factors. For example, deserts are dry and have very little rainfall. But a desert in Africa has organisms native to that continent, such as lions. Deserts in the United States have different organisms, such as mountain lions. Even though both deserts share many abiotic factors, they have different species living in them. Roles of Organisms in a Habitat A habitat is the place in which an organism usually lives and grows. For example, a squirrel may live in a forest habitat. A fi sh may live in a pond habitat. An organism has a special role in its habitat. The role of an organism is called its niche and is determined by how the organism interacts with biotic and abiotic factors. For example, a strawberry plant makes its own food in a process called photosynthesis. This process also produces oxygen. The strawberry plant provides food energy and oxygen to the other biotic factors in its ecosystem. Animals can eat the strawberry plants and breathe the oxygen. The strawberry plant also interacts with the abiotic factors in its ecosystem. It uses the energy in sunlight and the nutrients and water in the soil to survive. The strawberry plant is not the only plant in its ecosystem. There are other plants around it that also need soil, water, and sunlight. The amount of soil and sunlight is limited. This leads to competition. The strawberry plant competes with other plants for the soil and sunlight in its ecosystem. The amount of available sunlight determines how many plants can grow in one area. Since animals rely on plants for food, the amount of sunlight also determines how many animals can live there. The natural world is organized into several levels. To understand how the natural world is organized, think fi rst about how your world is organized. Your home is part of a neighborhood. Several neighborhoods make up a city or town. Many cities and towns make up a state. States are part of a country. Hundreds of countries make up the world. The human world is organized from small to large. The natural world is organized in a similar way. A single organism is the first and smallest level of organization. A population is the second level of organization. A population is a group of the same species of organisms. species: a group of organisms that look like each other and are able to breed among themselves 4

5 The third level of organization is a community. A community is made up of several populations of different species. An ecosystem is the fourth level of organization. As you learned earlier in the lesson, an ecosystem is made up of all the living and non-living things in an area. Finally, the biosphere is made up of all the ecosystems on Earth. Getting Technical: Counting Penguins from Space How do you count a population that lives in one of the coldest, windiest places on Earth? Emperor penguins make their home in Antarctica. Scientists are worried that these penguins might be threatened by climate change. They want to keep a close eye on the Emperor penguins, but it is hard for scientists to count individual penguins in such harsh conditions. Luckily, some researchers noticed they could see the Emperor penguins in satellite images of Antarctica. It is difficult to see the penguins from the satellite, but scientists can easily see what the penguins leave behind. So instead of looking for the penguins themselves, the scientists look for the guano. Guano is penguin waste. Its brown color stains the ice and shows up in satellite photos. Once the scientists see the guano, they can zoom in on the penguin colony and count individual penguins. This clever trick helped scientists identify about 300,000 Emperor penguins. 5

6 What do you know? An ecosystem has biotic and abiotic factors. A biotic factor is a living or once living part of an ecosystem and includes anything that is made of cells. An abiotic factor is a non-living part of the ecosystem. Look at the list below. Decide whether each example is a biotic factor or an abiotic factor. Some items may include both biotic and abiotic factors. Then write each item in the correct section of the Venn diagram. Sunshine heating the air A wolf hunting a deer Plants growing in sunshine Water falling as rain Frogs laying eggs in water A mushroom growing on a dead tree Birds fl ying north at the end of summer Soil forming from rocks Abiotic Abiotic and Biotic Biotic 6

7 connecting with your child Levels of Organization To help your child learn more about the levels of organization in the biosphere, work together to create a diagram that illustrates the different levels of organization and shows the biotic and abiotic factors present at each level. 1. First, review the levels of organization with your child: organism, population, community, ecosystem, and biosphere. Have your child define each level in his or her own words. 2. Choose a structure for your diagram. Since the natural world is organized into levels of increasing size and complexity, you might make a diagram of concentric circles. Each circle could represent a level of organization. Or, you could draw several circles side by side, increasing in size. 3. Find examples of the first level of organization an organism. You could choose an organism from a local, familiar ecosystem, or you could choose an organism from an unfamiliar, exotic ecosystem, such as a hyena or a bamboo tree. Represent the organism in a visual way using drawings or photographs. Label this level of the diagram as organism, and include information about the organism you and your child have chosen, such as its natural habitat, what it eats, and where it lives (state, country, etc.). 4. Do the same for the following levels of organization: population, community, ecosystem, and biosphere. The population level should show a group of the organism you selected at the organism level. Describe how these organisms interact with each other. The community level should show this population interacting with populations of other species. Describe the ways t hese populations are interacting with each other. The ecosystem level should show the community of organisms interacting with the abiotic factors in their habitats. Describe at least three of these interactions between biotic and abiotic factors on the diagram. 5. The biosphere level should include an image of planet Earth. Your child can list any additional biotic or abiotic factors he or she can think of. Here are some questions to discuss with your child: What is the smallest level of organization in the biosphere? What is the largest? How would you classify yourself into the levels of organization? How would you classify a group of you and your classmates? How do the biotic and abiotic factors interact in the ecosystem you described? 7