2. Learning Objectives
Describe the study of ecology.
Explain how biotic and abiotic factors influence an
ecosystem.
Describe the methods used to study ecology.
3. Ecology
The scientific investigation and
analysis of interactions among
organisms and their responses
to external factors in their
environment
Click to reveal each of the learning objectives.
Have students identify living and nonliving things in the classroom and record their responses in two bulleted lists on the board. Explain that the classroom is similar to an ecosystem in that it has interacting living and nonliving parts.
Hand out the worksheet. Explain to students that this lesson introduces many new vocabulary words and that the worksheet can help keep these words organized.
Explain that the root of the word ecology is the Greek word oikos, which means “house.” Explain that organisms are linked with one another and their environments in ways that are always changing. Organisms respond to external factors in their environments and also change their environments.
Explain that the Greek word oikos is also the root of the word economics. Economics is the study of human “houses” and interactions based on money or trade. Interactions among nature’s “houses” are based on energy and nutrients. Economics and ecology are linked because humans are part of the biosphere. We depend on ecological processes to provide such essentials as food and drinkable water that can be bought and sold or traded. Also, our actions, like those of other animals, can change our environment.
Ask students to discuss specific example of how ecological processes affect the economy.
Sample answers: A drought can decrease the amount of a crop available, which would increase the cost of food; a natural disaster, such as a hurricane, can destroy businesses; diseases or predators can kill crops and livestock, thereby decreasing the profit to the farmer.
Tell students: A species is a group of similar organisms that can breed and produce fertile offspring.
Ask students to give examples of organisms that are and are not the same species.
Sample answer: Horses are a species, but are a different species from donkeys because the offspring of a horse and a donkey is not fertile.
Tell students: A population is a group of individuals that belong to the same species and live in the same area.
Ask students to list examples of populations.
Sample answer: all of the people in my state, all of the dogs in my county
Ask: What is the possible meaning of “community,” based on the image?
Answer: A community is an assemblage of different populations that live together in a defined area.
Ask students to give examples of populations in their community.
Students should list examples of living things in the area.
Ask: What is the possible meaning of “ecosystem,” based on the image?
Answer: An ecosystem is all the organisms that live in a place and their physical environment.
Ask students to list components of their ecosystem.
Students should list examples of living and nonliving things in their location.
Tell students: A biome is a group of ecosystems that share similar climates and typical organisms.
Ask students to identify ecosystems other than their own that are in their biome.
Students should other locations that have a similar climate and organisms.
Ask: What is the possible meaning of “biosphere,” based on the image?
Answer: A biosphere is the entire planet with all its organisms and physical environments.
Explain that the biosphere consists of all life on Earth and all parts of the Earth in which life exists, including land, water, and the atmosphere. The biosphere contains all organisms, from bacteria living underground to giant trees in rain forests, whales in polar seas, mold spores drifting through the air—and, of course, humans. The biosphere extends from about 8 kilometers above Earth’s surface to as far as 11 kilometers below the surface of the ocean.
Tell students: An environment is all external factors that determine conditions surrounding an organism.
Click to reveal and discuss the term biotic.
Point out the word part bio- in the term biotic. Explain that bio- means “life.” Explain that the biotic factors in an environment include all of its living parts, such as plants, animals, and bacteria. Biotic factors important to a bullfrog, for example, might include algae it eats as a tadpole, insects it eats as an adult, herons that eat bullfrogs, and other species that compete with bullfrogs for food or space.
Ask students to identify biotic factors that are important to them.
Sample answers: things they eat, other people, pets
Click to reveal and define the term abiotic.
Tell students that the prefix a- means “not.” Explain that the abiotic factors are the nonliving parts of the environment, such as water, air, and rocks. For example, a bullfrog could be affected by abiotic factors such as water quality, temperature, and humidity.
Ask students to list abiotic factors that are important to them.
Sample answers: water quality, temperature, humidity.
Notice that this is the same list that affects other organisms.
Explain that differences between biotic and abiotic factors may seem clear and simple. But interactions in the biosphere are complex and often cannot be easily described by simple terms. These terms are perfect examples.
Tell students: Many so-called abiotic factors can be strongly influenced by organisms. Bullfrogs, for example, hang out in soft muck along the shores of ponds. You might think that this muck is a strictly physical external factor, because it contains nonliving particles of sand and mud. But typical pond muck contains leaf mold and other decomposing plant material from trees and other plants around the pond. Microorganisms, such as bacteria and fungi, also live in the muck, and use that once-living material as food.
Tell students: And that’s just the beginning. Abiotic conditions around that mucky shore are shaped by organisms. A canopy of trees and shrubs can shade the edge of the pond from hot sun and protect it from strong, dry winds. So organisms around the pond affect the amount of sunlight the muck receives and the range of temperatures it experiences. Trees around a pond also affect the humidity of air close to the ground. The roots of trees and other plants determine how much soil is held in place and how much washes into the pond. Even chemical conditions in the soil can be affected by living organisms. If most nearby trees are pines, their decomposing needles make the soil acidic. If the nearby trees are oaks, the soil will be more alkaline. This mix of biotic and abiotic external factors shapes every environment.
Explain that modern ecologists use three methods in their work. Each of these approaches relies on scientific methodology to guide inquiry.
Click to reveal and discuss the bullet point Observation.
Explain that observation is often the first step in asking ecological questions. Some observations are simple: Which species live here? How many individuals of each species are there? Other observations are more complex: How does an animal protect its young from predators? These types of questions may form the first step in designing experiments and models.
Click to reveal and discuss the bullet point Experimentation.
Explain that experiments can be used to test hypotheses. An ecologist may, for example, set up an artificial environment in a laboratory or greenhouse to see how growing plants react to different conditions of temperature, lighting, or carbon dioxide concentration. Other experiments carefully alter conditions in selected parts of natural ecosystems.
Click to reveal and discuss the bullet point Modeling.
Explain that any ecological events, such as effects of global warming on ecosystems, occur over such long periods of time or over such large distances that they are difficult to study directly. Ecologists make models to help them understand these phenomena. Many ecological models consist of mathematical formulas based on data collected through observation and experimentation. Further observations by ecologists can be used to test predictions based on those models.
Ask students to list the levels of ecological organization.
Click to reveal the list.
Ask students to match the terms with the images onscreen in order, from the lowest level of organization to the highest level of organization (organism to biosphere).
Click to reveal the match after each guess until all six pairs are revealed.
Ask: Which levels of organization include both biotic and abiotic components?
Answer: ecosystem, biome, biosphere
Have students work in groups of four. Ask one group member to name an individual organism. Then, have a second group member identify a population in which that organism belongs. The third group member should then describe a community in which the population belongs. Finally, the fourth group member should describe an ecosystem in which the community is found.
Next, group students into new groups and have each group discuss one of the levels of organization. Ask each group to develop a question an ecologist may ask at that level of organization. Have student groups report their findings.
Sample answer: What is the relationship between rainfall and amphibian diversity in an ecosystem?
Remind students that they should have been using the worksheet to keep track of new vocabulary terms.
List each vocabulary term and ask a volunteer to provide the meaning. Ask another volunteer to provide a hint on how to remember the term. Correct any misconceptions.
Worksheet Answers:
Ecology: the scientific investigation and analysis of interactions among organisms and their responses to external factors in their environment – it is the study of our “house,” Earth
Species: a group of similar organisms that can breed and produce fertile offspring – species are similar
Population: a group of individuals that belong to the same species and live in the same area – I am part of a population of people in my state
Community: an assemblage of different populations that live together in a defined area – a community includes diverse populations
Ecosystem: all the organisms that live in a place, together with their physical environment – a system that includes living and nonliving things
Biome: a group of ecosystems that share similar climates and typical organisms – our ecosystem is part of a bigger biome
Biosphere: our entire planet, with all its organisms and physical environments – Earth is a bio “sphere”
Environment: all external factors that determine conditions surrounding an organism – our environment envelops us
Biotic: biological influences on organisms – “bio” means “living”
Abiotic: physical components of an ecosystem – “a” “biotic” means “non” “living”
