4th Quarter>
LS2.C ETS1.B The Dynamic Ecosystem
Ecosystems are dynamic, open systems
1. The nested relationship between population (one species, usually in a geographically connected region), community (the biotic component of an ecosystem), and ecosystem (the community and its abiotic environment) needs to be understood so that these terms are used appropriately. The specific characteristics of particular ecosystems therefore arise as a result of the interactions between biotic and abiotic components, although abiotic factors ultimately determine productivity, which in turn determines carrying capacity and many community characteristics. (HS-LS2-2)
2. An ecosystem's 'steady' state (actually a dynamic equilibrium) refers to the maintenance of relatively constant conditions by negative feedback systems operating within the ecosystem. Stable ecosystems usually use sunlight as their energy source of energy, recycle all elements, maintain sustainable consumer levels, and maintain biodiversity. (HS-LS2-6)
3. Keystone species are seen as important because they occupy key functional positions in ecosystems. These roles may be different in each case but include species with roles in nutrient recycling (termites), as predators (sea otters, mountain lions, sea stars), in shaping the characteristics of the environment (elephants, prairie dogs), and even as pollinators (hummingbirds in the Sonoran desert). (HS-LS2-2, HS-LS2-6)
4. Ecosystem resilience refers to the ability of an ecosystem to regain its normal structure and function after a disturbance (as opposed to its resistance to disturbance). Species diversity is often the key to both ecosystem resistance and resilience, as diverse systems have many biotic interactions, which buffer them against small internal fluctuations (such as a decline in the population of a single component species). (HS-LS2-2, HS-LS2-6)
5. Students could cite examples of where population 'explosions' result in extreme changes in ecosystem structure and function. Any of the keystone species examples provided (activity #158 and also crosscutting to LS4.D) would be appropriate. Extreme fluctuations can destroy normal negative feedback (self-limiting) regulation and lead to destructive positive feedback loops and irreversible change. One example of this is the ice-albedo feedback loop, where melting snow exposes more dark ground or ocean surface, which in turn, absorbs heat and causes more snow to melt and so on. A good discussion point (ETS1.B) is the positive feedback loop between growth in the human population and rapidly advancing agricultural developments. What will be the outcome? (HS-LS2-2, HS-LS2-6)
6. Ecosystems with a high biodiversity are regarded as having higher ecosystem stability because there are more biological interactions (and more functional redundancy) to buffer against species loss. Having many different species may stabilize ecosystem processes, such as nutrient cycling, because different species will respond to environmental changes in different ways. (HS-LS2-2)
Anthropogenic changes can threaten species survival
7. Students should appreciate that biodiversity and ecosystem resilience are not academic notions; humans depend on the resilience of terrestrial and aquatic ecosystems to provide essential ecosystem services (such as nutrient cycling and provision of clean water). Human-induced loss of biodiversity can reduce the resilience of natural ecosystems and make them more vulnerable to long-term irreversible change. (HS-LS2-7)
8. Students should recognize and describe human activities that threaten biodiversity. Human activities can reduce biodiversity directly or indirectly through species loss (e.g. deforestation or overfishing) or by creating environments that are less favorable to species survival or cause shifts in species distribution, timing of breeding, or migration (e.g. climate change). (HS-LS2-7)
9. Students can appreciate through (individual or group) activities #161, 165, and 167 that there are almost always conflicts involved in making any conservation decision. The best decision will be one that achieves its aims with the east cost and most favorable outcomes for all concerned parties (HS-ETS1-3, HS-ETS1-4)
Crosscutting concepts
1. SPQ: The concept of orders of magnitude can be used to understand how a model of the factors affecting ecosystems can operate at different scales. (HS-LS2-2)
2. SC: Many aspects of science, including ecology, involve explaining how things (e.g. ecosystems) change and how they remain stable. (Not aligned to a performance expectation)
Science and engineering practices
1. Analyze examples of ecosystem resilience using second-hand data.
SEP: Using mathematics and computational thinking (Not aligned to a performance expectation)
2. Use mathematical representations to support explanations about the factors affecting biodiversity and populations in ecosystems.
SEP: Using mathematics and computational thinking (HS-LS2-2)
3. Evaluate the evidence for the role of complex interactions in the stability of ecosystems and the role of changing conditions in ecosystem change.
SEP: Engaging in argument from evidence (HS-LS2-6)
4. Develop and evaluate solutions for sustaining biodiversity while allowing essential human use of resources.
SEP: Constructing explanations and designing solutions (HS-LS2-7)
Nature of Science
Scientific argument is a mode of logical discourse used to clarify the strength of relationships between ides and evidence that may result in revision of an explanation. (HS-LS2-6)
LS2.B PS2.D Energy Flow and Nutrient Cycles
Energy flows through ecosystems
1. Students should recall that photosynthesis and respiration are, to use an analogy like opposite sides of the same coin and the waste products from one process are the raw materials for the other. 6CO2 + 12H2O + light energy → C6H12O6 + 6O2 + 6H2O C6H12O6 + 6O2 → 6CO2 + 6H2O + usable energy Together, these two pathways provide almost all the energy for life's processes (crosscutting to HS-PS3.D). (HS-LS2-3)
2. Aerobic respiration requires oxygen in order to generate ATP. Oxygen is the terminal electron acceptor in the electron transport chain and is reduced to water. (HS-LS2-3)
3. Students should distinguish anaerobic respiration from fermentation. Respiration always involves H+ passing down a chain of carriers to a terminal acceptor. In anaerobic respiration, the terminal H+ acceptor is a molecule other than O2 e.g. Fe2+ or nitrate. Energy yield is higher than in glycolysis but not as high as aerobic respiration. Fermentation is anaerobic but no chain of electron carriers is involved and the energy (ATP) yield is low. Anaerobic respiration plays a major role in the global nitrogen, sulfur, and carbon cycles. (HS-LS2-3)
4. The terminology associated with acquiring energy and carbon can be confusing for many students. Strictly speaking, the organisms students regard as heterotrophs are more correctly chemoheterotrophs, given that they rely on organic compounds for both their energy and their carbon. Photoheterotrophic organisms use light for energy, but cannot use CO2 as their sole carbon source and use organic compounds from the environment to satisfy their carbon requirements. Examples are purple non-sulfur bacteria and green non-sulfur bacteria. Students should appreciate that, when describing nutritional groups, sources of energy can be light and organic or inorganic compounds and the sources of carbon can be of organic or inorganic origin. All combinations occur in nature. (HS-LS2-4)
5. A food chain describes a sequence of feeding relationships, where each organism in the chain is the source of food for the next. Food webs are constructed from the many food chains within a community. Any community for which there is sufficient information on feeding relationships can be used to construct a food web, as described in activity #141. Marine and estuarine communities also provide good examples. (HS-LS2-4)
6. Energy is dissipated as it is transferred through trophic levels and, as a general rule, only around 10% of the energy at one trophic level is available to the next. This limits the length of food chains. Students should appreciate that although energy is often referred to as being 'lost', this refers to its loss from the system to the wider environment and it accounts for the fact that ecosystems require a constant input of energy. If students construct energy flow diagrams to explain this 10% law, they should include trophic levels, arrows to indicate the direction of energy flow, processes involved in energy transfer (e.g. feeding, decomposition), energy sources, and energy sinks. Matter moves through ecosystems and cycles within the ecosystem itself and through exchanges with other parts of the biosphere and with the atmosphere, hydrosphere, and geosphere. (HS-LS2-4)
7. Students should explain why pyramids of biomass or energy are usually preferable to pyramids of numbers, and account for the shape of ecological pyramids in different situations. Ecological pyramids provide a good visual representation of the 10% law. (HS-LS2-4)
Energy flows through ecosystems but matter is recycled
8. Students should understand that nutrients and water move within and between ecosystems in biogeochemical cycles involving exchanges between the air (atmosphere), the Earth’s crust (geosphere), bodies of water (hydrosphere), and organisms (biosphere). The should recognize the basic processes involved in the transformations of different elements (e.g. photosynthesis, decomposition, combustion, biological fixation, and atmospheric deposition) and understand the role of environmental reservoirs in nutrient cycles. The functional position of detritivores and decomposers in cycling nutrients in ecosystems should be emphasized (crosscutting to PS3.D) (HS-LS2-5)
9. Discussion of the carbon cycle can focus on processes involved in the cycle (e.g. respiration, decomposition, combustion, photosynthesis/fixation) and begin to examine the role of human intervention in the cycle, e.g. by fossil fuel consumption and deforestation (crosscutting to LS4.D and ETS1.B) (HS-LS2-5)
Crosscutting concepts
1. EM: Energy cannot be created or destroyed; it only moves between one place and another, between objects or fields, or between systems. (HS-LS2-4)
2. EM: Energy drives the cycling of matter within and between systems. (HS-LS2-3)
3. SSM: Models can be used to simulate flow of energy and cycling of matter. (HS-LS2-5)
Science and engineering practices
1. Construct an explanation based on evidence for how matter cycles and energy flows in aerobic and anaerobic conditions.
SEP: Constructing explanations and designing solutions (HS-LS2-3)
2. Use mathematical representations to describe energy transfers in ecosystems.
SEP: Using mathematics and computational thinking (HS-LS2-4)
3. Use mathematical representations to show that matter and energy are conserved as matter cycles and energy flows through ecosystems.
SEP: Using mathematics and computational thinking (HS-LS2-4)
4. Develop an evidence-based model to show how photosynthesis and cellular respiration are involved in carbon cycling.
SEP: Developing and using models (HS-LS2-5)
Nature of Science
Scientific knowledge is subject to change based on new evidence or reinterpretation of existing evidence. (HS-LS2-3)
LS2.D Social Behavior
Social interactions and group behavior increase the chances of survival
1. Students should recognize that behavior, like morphology and physiology, is subject to selection pressure and will be maintained and reinforced if it is adaptive. Appropriate responses to communicated information are "rewarded" by higher fitness. (HS-LS2-8)
2. Students should understand that there are both benefits and costs to sociality; sociality shouldn't be assumed to be the superior option. Most of the benefits of sociality relate to predation pressure and resource distribution. (HS-LS2-8)
3. Students should understand that group behavior is a wider term than social behavior. Schools and flocks are not social groupings although they have survival benefits. Group behavior involving cooperation are most often shown by social groupings. (HS-LS2-8)
4. Schooling, herding, and flocking behaviors involve the group moving together but without any planned direction or purpose. The group appears to move together as a unit, but this pattern emerges from the behavior of individuals acting to benefit themselves. The survival benefits accrue primarily through increased predator surveillance (which increases foraging efficiency) and reduced energy expenditure for locomotion (especially in flight). (HS-LS2-8)
5. Examples of social behaviors include kin selection and altruism, cooperative hunting and defense, and dominance behavior and hierarchies. These categories are not mutually exclusive. Learning plays a large role in the behaviors of animals with complex social structures. (HS-LS2-8)
6. Sociality invariably involves cooperation (although does not preclude agonistic behavior). Cooperative behavior must extend beyond sexual and parental behavior and includes examples of cooperative breeding (such as helpers at the nest and social systems where only the dominant individuals breed), cooperative defense and alarm calls, and cooperative feeding behaviors. Such behaviors offer group and individual benefits; cooperation directly or indirectly increases fitness in those who behave appropriately. Kin selection refers to selection that favors altruism towards relatives. Examples of apparently altruistic behavior include:
Helpers at the nest: This behavior occurs most frequently in birds and describes a social structure in which juveniles and sexually mature adolescents stay with their parents and assist in raising subsequent broods, instead of breeding themselves. The behavior can be explained in an evolutionary sense by the fact that the helpers are related. Helpers may also be advantaged through protection at the parental nest or by acquiring skills for their own subsequent parenting.
Alarm calls: Many species living in social groups will give alarm calls when a predator is identified, even though this may increase their chance of being attacked. Females with female relatives in the area are often more likely to give these alarm calls. (HS-LS2-8)
7. Students should appreciate that group defense and attack behaviors are characteristic of, but not exclusive to, social species (e.g. cooperative mobbing behavior by birds). Students should understand that in order for group defense or attack to evolve, it must benefit the fitness of individuals, and they should explain the ways in which it could do this. Defense and attack behaviors are often part of the same suite of behaviors aimed at defending the group against threats to procuring the resources necessary for survival (HS-LS2-8)
8. Cooperative behavior in food gathering is nicely illustrated by group hunting tactics of large social predators (lions, hyena, orca). In other cases, group foraging simply provides more workers to locate and take advantage of concentrated food supplies (e.g. in foraging eusocial species such as ants and bees). This may be supported by division of labor amongst foragers (e.g. leafcutter ants and army ants). Communication between individuals in the group contributes to foraging success. (HS-LS2-8)
Crosscutting concepts
1. CE: Empirical evidence enables us to distinguish between cause and correlation and support claims about the benefits of group behavior to survival and reproduction. (HS-LS2-8)
Science and engineering practices
1. Evaluate the evidence for how group behavior benefits survival during migration.
SEP: Engaging in argument from evidence (HS-LS2-8)
2. Evaluate the evidence for how the degree of cooperation (help given) can depend on relatedness of the individuals involved.
SEP: Engaging in argument from evidence (HS-LS2-8)
3. Evaluate the evidence for the benefits of group behaviors such as flocking.
SEP: Engaging in argument from evidence (HS-LS2-8)
4. Evaluate the evidence for the benefits to survival and reproduction of cooperative behaviors in hunting, foraging, or group defense.
SEP: Engaging in argument from evidence (HS-LS2-8)
Nature of Science
Scientific argument is a mode of logical discourse used to clarify the strength of relationships between ides and evidence that may result in revision of an explanation. (HS-LS2-8)
LS4.D ETS1.B Biodiversity
Humans depend on biodiversity
1. Students should recall ("The Dynamic Ecosystem") that human exploitation of the natural environment has consequences to the stability and diversity of natural systems. In this chapter, they should gain a further appreciation of the fact that these impacts ultimately affect the viability of ecosystems and their populations. Examples, including those described in the student book, provide empirical evidence of these impacts. The latest casualty and the first extinction directly attributable to human-induced climate change is the recent extinction of the Bramble Cay melomys (a small rodent) which has disappeared from its tiny island in the Great Barrier Reef following cycles of inundation and habitat loss. (HS-LS4-6)
2. Students should have an appreciation of the different aspects of biodiversity (ecosystem diversity, genetic diversity, species diversity) and their interrelatedness. Distinguishing between species richness and evenness also allows evaluation of diversity at the ecosystem level. Protecting habitats is integral to maintaining species diversity and species cannot remain viable if there is substantial loss of genetic diversity. The biodiversity hotspots provide students with an appreciation of where the Earth's biodiversity is located and why these regions are at particular risk. (HS-LS4-6)
3. Students should recall ("The Dynamic Ecosystem") that humans exploit natural systems for their own gain. In this chapter, they should gain a greater appreciation for why the conservation of biodiversity is crucial to human well being. They should understand the range of services provided by ecosystems and explain why biodiverse, healthy ecosystems are able to provide these services more efficiently. (HS-LS4-6)
4. Two points are important here: (1) the reliance of humans on biodiversity for essential ecosystem services and (2) the impact that humans are having on the biodiversity on which they depend (crosscutting to HS-LS4.D). Students can argue from evidence for the benefits of maintaining biodiversity and consider the wider role of humans as custodians of the planet. (HS-LS4-6, HS-ETS1-3, HS-ETS1-4)
5. Students should be able to list the positive benefits to humans of healthy, well functioning and biodiverse ecosystems. These include the obvious provision of resources, but also regulating services such as filtering of water and air, recycling of nutrients, storage of carbon, and moderation of climate. They should also recognize the cultural, aesthetic, and recreational benefits provided by natural systems (HS-LS4-6).
Developing possible solutions
6. Students will recall (crosscutting to HS-LS4.D) that solutions to problems are a compromise between the most desirable solution and the economic, social, and environmental costs of implementing that solution. (HS-LS4-6, HS-ETS1-3, HS-ETS1-4)
7. Population projections and population recovery models for endangered or threatened species provide suitable ways for students to explore the possible outcomes of conservation solutions. These conservation solutions can easily incorporate aspects of engineering design. We have provided information and suggested links for bison, Florida panther, and the Indiana bat (summative assessment). The Maasai Mara case study exposes students to an example illustrating how conflict over land use might be successfully resolved. (HS-LS4-6, HS-ETS1-3, HS-ETS1-4)
Crosscutting concepts
1. CE: Empirical evidence enables us to support claims about the ways in which humans are affecting the Earth's biodiversity. (HS-LS4-6)
2. CE: Empirical evidence enables us to support claims about the best ways to reduce the adverse effects of human activity on biodiversity. (HS-LS4-6)
Science and engineering practices
1. Create or revise a simulation to test a solution to reduce the adverse effects of human activity on biodiversity.
SEP: Using mathematics and computational thinking. (HS-LS4-6)
2. Explain based on evidence how a range of conservation methods can be used to restore the species and genetic diversity of endangered populations.
SEP: Constructing explanations and designing solutions (Not aligned to a performance expectation)
3. Devise a solution based on current evidence for the recovery of an endangered species.
SEP: Constructing explanations and designing solutions (HS-LS4-6)
Yea! We are done. It must be summer. Lets go home.
