Sustainability of Ecosystems 2

SE2 Examine biodiversity within local ecosystems

Suggested time: 7-9 hours

Scientists often use measures of biodiversity as an indicator of an ecosystem's health. Students should visit an aquatic or terrestrial ecosystem (e.g., schoolyard, field, forest, garden, creek, river, pond) in order to gain experience in documenting biodiversity within an ecosystem using appropriate ecological methods and technologies to understand the range of biodiversity that does exist within an ecosystem. The importance of the field trip cannot be understated as it provides students the opportunity to observe all of the interrelationships between biotic and abiotic factors of an ecosystem in a natural setting.

Students should already understand general concepts related to food webs and food chains, including terms used to indicate organisms' roles (e.g., producer, consumer, herbivore, carnivore, omnivore, and decomposer). At this grade, students should be able to create representations of food webs, food chains, and pyramids of energy or biomass to represent energy flow through a specific local ecosystem.

Freshwater - Environment Canada {656:10317}

As part of their study of biodiversity, students should research species that are at risk in Saskatchewan , the Prairies, and across Canada . Students should be able to develop case studies of at-risk species and document ongoing efforts to address these concerns.

Learning Objectives

Observe and document a range of organisms to illustrate the biodiversity within a local ecosystem.
Select and use apparatus and materials safely when documenting biodiversity.
Identify biotic and abiotic components of an ecosystem.
Explain how the biodiversity of an ecosystem contributes to its sustainability .
Identify energy flow in ecosystems using the concept of the pyramid of energy, numbers, or biomass. (NUM)
Describe the mechanisms of bioaccumulation and biomagnification.
Explain the process of biomagnification on the viability and diversity of consumers at all trophic levels.
Describe and apply classification systems and identify key ecological terms used in the environmental sciences. (COM)
Demonstrate a sense of personal and shared responsibility for maintaining a sustainable environment. (PSD)
Examine the impact of invasive species on an ecosystem.
Identify the factors that result in species becoming at-risk in Saskatchewan , the Prairies, and Canada .
Explore ecology-related work settings and work roles in the community. (CD 5.2)

Key Questions

What is biodiversity and how is it measured?
How does biodiversity serve as an indicator of an ecosystem's health?
How does energy flow through an ecosystem?
How does an interruption in energy flow affect components of an ecosystem?
How does matter such as a toxin become more concentrated in an ecosystem?
How and why are plant and animal species introduced to new areas?
How do Canadian scientists classify at-risk species?
What are some examples of at-risk species in Saskatchewan ? Canada ?
How does protecting at-risk species help to improve an ecosystem's health?

Key Concepts

A set of interrelated components forms a system .
The living and non-living components of a biological community and their interrelationships form an ecosystem .
Non-living components (sunlight, temperature, wind, water, and rock) of an ecosystem are abiotic .
Living components (animals and plants) of an ecosystem are biotic .
Biodiversity is a measure of the number and variety of species in an ecosystem.
An organism is a living thing or something that was once alive.
Organisms may be classified as producers or consumers depending on their relation to energy flow through an ecosystem.
The trophic level of an organism identifies its position in the energy flow pyramid of an ecosystem.
A food chain shows the movement of energy through a system by indicating the path of food from a producer to a final consumer.
A food web is a pictorial representation of the feeding relationships between organisms in an ecosystem and consists of interlocking food chains.
Biomass is a measure of the mass of the dry matter contained in a group of living things.
A pyramid of energy is a graphical model that shows the amount of energy available at each trophic level of an ecosystem.
A pyramid of numbers is a graphical model that shows the numbers of organisms that exist at trophic levels in an ecosystem.
A pyramid of biomass is a graphical model that shows the dry mass of organisms at each trophic level of an ecosystem.
Biological accumulation (also called bioaccumulation ) is the increase in concentration of a pollutant from the environment to the first organism in a food chain.
Biological magnification (also called biomagnification or bioamplification ) is the tendency of pollutants to become concentrated in successive trophic levels.
An introduced species is an organism that is not native to the place or area where it is considered introduced and instead has been accidentally or deliberately transported to the new location by human activity.
An invasive species means an alien species whose introduction does, or is likely to, cause economic or environmental harm or harm to human health.
A species that is no longer found anywhere on Earth is extinct .
A species that is close to extinction in all parts of Canada or in a significantly large location is endangered .
A vulnerable species is at risk due to low or declining numbers in some restricted area of its range.
A threatened species is likely to become endangered if factors that make it vulnerable are not reversed.
An extirpated species no longer exists in one particular area, but still exists in other locations.
Classifying is a systematic procedure developed by humans to impose order on collections of objects or events.
Classification systems are not fixed. They change over time as new information is discovered and new techniques are developed.
Interpreting data means to find patterns in data collections that can lead to generalizations about the data.
Scientists use models to represent objects, events, or processes.
Ecologists use systematic and random (but not arbitrary) sampling techniques to examine representative portions of an ecosystem.

Pre-Instructional Questions

Are students able to suggest organisms that they might see when visiting a local aquatic or terrestrial ecosystem?
Do students understand how to collect ecological data safely and respectfully?
What is students' understanding of biodiversity?
Do students understand the differences between producers and consumers?
Do students understand the differences between food webs and food chains?
Are students aware of common food webs or food chains in local ecosystems?
Do students understand the processes of bioaccumulation or biomagnification?
What is students' understanding of an introduced species?
Are students able to identify examples of species that have been introduced into an ecosystem?
Are students aware of Canadian classification systems for at-risk species?
Can students provide examples of at-risk species in Saskatchewan ? Canada ?

Suggested Teaching Strategies and Activities

Students should conduct a field trip to a local aquatic or terrestrial ecosystem to collect data about the organisms that inhabit that region. Possible locations could include a pond, riparian area, lake, schoolyard, or field. Student groups could collect data from different locations within the ecosystem to document differences in biodiversity within a relatively small region. For example, there could be significant differences between a playing field in the middle of a schoolyard, and a heavily shaded and treed corner of a schoolyard. Students need to determine what equipment is appropriate to use for data collection and how to collect data without harming organisms or habitats. For example, students may use tools such as a quadrat, data loggers, or a GPS receiver. Students should develop a data table to organize the information they collect about biotic and abiotic factors within the ecosystem. Students must receive permission to enter private land. If a field trip is not feasible, students could view videos or pictures of particular ecosystems and identify examples of biotic and abiotic factors in those ecosystems. This activity could be integrated with data collection in the Weather Dynamics unit.
Students could create their own closed terrestrial or aquatic ecosystem using a large jar, aquarium, or terrarium. They could add appropriate organisms and provide food sources for those organisms. The students could keep a daily journal documenting changes in the ecosystem over a given period. They could also create a visual or written representation of a food chain for their ecosystem.
Students should create a visual representation (e.g., food chain or food web) to illustrate their understanding of energy flow through a local ecosystem. For example, a typical prairie food chain might be grass => grasshopper => mouse =>snake => hawk. Students should share and compare their representations and identify similarities and differences. Students should be able to explain that any food chain or food web is typically more complicated than is identified on their representations. Students should also explain the value of categorizing organisms by trophic level.
Organisms in an ecosystem may be identified by their trophic level (1^st , 2^nd , 3^rd , 4^th ), their consumer level (producer; primary, secondary, or tertiary consumer), or by how they obtain food for life processes (producer, herbivore, carnivore, omnivore, scavenger, decomposer). Students should classify organisms in a specific ecosystem using each of these classification systems and then discuss the advantages and disadvantages of each classification system.
Students could create a visual representation or model of a pyramid of energy, a pyramid of numbers, or a pyramid of biomass to represent energy flow in an ecosystem. These representations help show the relationships between numbers of organisms at each tropic level. Students should use these representations to explore cause-effect relationships such as how large quantities of producers are required to sustain a single tertiary consumer and the ways in which human activities can influence the energy flow in an ecosystem. Students could also explore why scientists use biomass to determine changes in ecosystems rather than relying solely on changes in numbers of organisms. From these representations, students should be able to explain why there is a practical limit of four or five steps in a food chain.
Students could participate in a role play or simulation to demonstrate the biomagnification of a toxin within a specific food chain.
Students could prepare a case study and visual representation of the bioaccumulation of a toxin within an ecosystem. The case should name the toxin; describe how it progresses through the food chain and identify the consequences for other consumers in the ecosystem. Examples of toxins to research include: DDT to control insects, 2,4-D to control weeds, heavy metals such as mercury being discharged into rivers, polychlorinated biphenyls (PCBs) as insulators in electrical transformers, and cyanide for the leaching of gold in gold mines. Students should discuss how scientists are able to measure the amount of toxins present in consumers at each trophic level. (COM)
Students could interview or invite to class an elder, trapper, hunter, local conservation officer, or other person who has an ecology-related career or who can offer cultural perspectives on ecology, ecosystems, and sustainability. These guest speakers could become valuable information resources, role models, or mentors for the students. (CD 5.3)
Students should research species that humans introduced into an ecosystem to determine why and how these species were introduced and to determine the positive and negative effects of this new species on the local ecosystem. Students should consider what factors enable many introduced species to become firmly established in their new homes. Students should determine potential consequences (positive and negative) on the entire ecosystem of removing, or attempting to remove, these invasive species at a later date. Examples of primary invasive species in the Prairies include: purple loosestrife, reed canary grass, leafy spurge (wolf's milk), smooth brome grass, and Canada thistle. Note that not all introduced species are considered invasive.
Students could research methods of removing invasive or introduced species (e.g., herbicide control, physical control, prescribed burning, biological control, and integrated pest management methods) and describe the effectiveness of various methods. They should also consider what future problems these methods might cause. (IL, CCT)
Students should research one or more Canadian at-risk species and identify natural and human factors (e.g., habitat loss, genetic and reproductive isolation, environmental contamination, climate change, disease, invasive species, and suppression of natural events) that contribute to the at-risk classification of the species. Students could prepare a presentation on their species that includes range maps, distribution and population maps, habitat, threats, legislative protection, and any recovery initiatives. Students could use GIS software to produce and analyze maps demonstrating population and distribution data for that species. Students should also identify specific methods that might help restore the natural balance of that species in the region(s) where it is at-risk. As an extension, students might predict the effect on one or more ecosystems if that species became extinct.