Environmental Science: Interdependent Relationships and Dynamics of Ecosystems

EN.LS2.1 Use mathematical and/or computational representations to support explanations of factors that affect carrying capacity of ecosystems at different scales.

EN.LS2.2 Use mathematical representations to support and revise explanations based on evidence about factors affecting biodiversity and populations in ecosystems of different scales.

EN.LS2.4 Use mathematical representations to support claims for the cycling of matter and flow of energy among organisms in an ecosystem.

EN.LS2.6 Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem.

Populations are influenced by the availability of both living and nonliving resources.   A variety of factors may influence the amount of individuals that can be sustained in one area such as climate, natural disasters, predation, competition and disease. Students can use mathematical representations such as graphs, charts, and histograms to support explanations of factors that affect carrying capacities of ecosystems. Populations and the number of organisms in ecosystems vary. Students support and revise evidence based explanations (trends, averages and graphs) of factors that may affect biodiversity and population levels.  Students also use mathematical representations to model the movement of matter and energy through an ecosystem with an emphasis on the transfer of biomass to higher trophic levels and the conservation of atoms and molecules crucial to biological processes. Changes to ecosystems may disrupt these and other complex interactions that maintain ecosystem stability. Students can evaluate trends from graphical representations to identify drivers of ecosystem stability and change.

Student Actions

Teacher Actions 

• Utilize a mathematical model to explain how an ecosystem's carrying capacity represents the limit of organisms and populations that an ecosystem can support at specified scales.

• Use mathematical representations such as trends, averages, histograms, graphs and spreadsheets to support explanations of factors (including boundaries, resources, climate, and competition) that can affect carrying capacity of an ecosystem at a variety of scales. 

• Use mathematical representations to support explanations that factors affecting carrying capacity are interrelated; some factors have larger effects than other factors; the significance of a factor is dependent on the scale (e.g., a pond vs. an ocean) at which it occurs. 

• Use mathematical and/or computational representations as evidence to support and identify which factors will have the largest effect on the carrying capacity of a given population.

• Utilize mathematical representations (including trends, averages, and graphs) of factors affecting biodiversity and ecosystems to identify changes over time in the numbers and types of organisms in ecosystems of different scales.

• Use mathematical representations from investigations to support claims about the effects modest to extreme disturbances have on an ecosystem’s ability to return to original status or become a different ecosystem.

• Use mathematical or computational models to describe how factors at one scale can cause observable changes in ecosystems at a different scale. 

• Use mathematical representations of factors affecting ecosystems to identify the most important factors that determine biodiversity and population numbers of an ecosystem at different scales. 

• Use mathematical representations to explain the transfer of matter (as atoms and molecules)and flow of energy upward between organisms (trophic levels) and their environment.

• Use mathematical representations to explain how relative quantities related to organisms, matter, energy, and the food web in an ecosystem support the claims for the cycling of matter and energy flow among organisms in an ecosystem.

• Use mathematical representations to support the claim that the relative proportion of organisms at the lowest trophic level (producers) have the greatest biomass and energy and that biomass and energy decrease at higher trophic levels (consumers).

• Develop mathematical models to support and explain the claim that some matter and energy are not transferred to higher trophic levels and are instead used for growth, maintenance, or repair, and/or transferred to the environment.

• Evaluate claims, evidence, and reasoning about the relationship between the severity of ecosystem disturbances and the ability of the ecosystem to return to its original state. 

• Evaluate graphical representations and other evidence to describe possible drivers (modest and extreme) of ecosystem stability and change. 

• Facilitate meaningful discourse as students use mathematical models to show how an ecosystem's carrying capacity represents the limit of organisms and populations that an ecosystem can support at specified scales.

• Assist students in using and connecting mathematical representations to explain the degree in which limiting factors (including boundaries, resources, climate, and competition) can affect the carrying capacity of an ecosystem. 

• Support students in using mathematical representation to develop models that explain how factors affecting carrying capacity are interrelated with impacts of varying significance and scales 

• Support students in using mathematical representation to compare and contrast population data to use as evidence in the support of claims about an event’s effect and significance on carrying capacity.

• Elicit and use evidence from students’ mathematical representations to explain how factors affecting biodiversity and ecosystems can cause changes over time in the numbers and types of organisms in ecosystems of different scales.

• Guide students through creation of mathematical representations and communication of how changes to a particular environment at various scales can impact biodiversity and population number changes.

• Elicit meaningful conversations around mathematical and/or computational models that describe how modest or extreme factors at one scale can cause observable changes in ecosystems at a different scale. 

• Support students in revising their explanations, based on data illustrating the effect of a disturbance, on biodiversity and populations at various scales.

• Support students in using mathematical models from investigations to track the movement of matter (as atoms and molecules) and flow of energy through an environment.

• Facilitate meaningful scientific discourse to support students in developing claims about the transfer of matter and flow of energy, between organisms, using mathematical models of trophic levels.

• Promote the analysis of mathematical models as evidence to explain the loss of energy and matter to the environment due to growth, maintenance, or repair, and/or transfer to the environment.

• Provide students opportunities to explore various examples of changes to ecosystem conditions and to evaluate the claim that changing conditions may result in new ecosystems. 

• Facilitate student discussions as they investigate, identify and evaluate evidence in support of the claim that the number and type of organisms in an ecosystem should remain constant in the absence of changing conditions. 

Key Concepts 

Misconceptions 

Interdependent Relationships in Ecosystems

• Ecosystems have carrying capacities, which are limits to the number of organisms and populations they can support. 

• These limits result from such factors as the availability of living and nonliving resources and from such challenges as predation, competition, and disease.

• Organisms would have the capacity to produce populations of great size were it not for the fact that environments and resources are finite. 

• This fundamental tension affects the abundance (number of individuals) of species in any given ecosystem. 

Ecosystem Dynamics, Functioning, and Resilience

• A complex set of interactions within an ecosystem can keep its number and types of organisms relatively constant over long periods of time under stable conditions.

• If a modest biological or physical disturbance to an ecosystem occurs, it may return to its more or less original status (i.e., the ecosystem is resilient) as opposed to becoming a very different ecosystem.

• Extreme fluctuations in conditions or the size of any populations, however, can challenge the functions of ecosystems in terms of resources and habitat availability. 

Cycles of Matter and Energy Transfer in Ecosystems

• Plants or algae form the lowest level of the food chain.

• At each link upward in a food web, only a small fraction of the matter consumed at the lower level is transferred upward to produce growth and release energy in cellular respiration at the higher level.

• Given this inefficiency, there are generally fewer organisms at higher levels of a food web.

• Some matter reacts to release energy for life functions, some matter is stored in newly made structures, and much is discarded.

• The chemical elements that make up the molecules of organisms pass through food webs and into and out of the atmosphere and soil, and they are combined and recombined in different ways.

• At each link in an ecosystem, matter and energy are conserved. 

• Carrying capacity is a fixed number.

• Ecosystems do not change.

• All organisms have a similar carrying capacity.

• Change in an ecosystem will always decrease the number of individuals who can survive in a population.

• Food webs only have linear relationships.

• Water is an energy source for producers.

• Energy can be recycled.

• Disturbances are always detrimental to an ecosystem.

• New species are beneficial to an ecosystem because they increase biodiversity.

Instructional Resources 

Unit 2: Interdependent Relationships and Dynamics of Ecosystems