| Lesson | Topic | Essential Idea and Objective(s) | IB Curriculum Connections | Activities |
| 1 | Populations | A population is a group of organisms of the same species, living in the same place at the same time and interacting with one another. Cooperative intraspecific relationships have advantages as well as some disadvantages. In a group, any given individual may be more protected from predation, herbivory and/or extreme environments as well as having greater availability of others to breed with or assist with caring for young. Within a group, the close proximity of many individuals may decrease the availability of limited resources, increase the risk of infection by pathogenic transfer or attract more consumers overall (herbivores or predators). The growth of a new population in a suitable environment usually has a lag phase before passing into a log phase (or exponential growth stage). As a result of limited resources, the carrying capacity of an ecosystem for a population is reached after any exponential growth has occurred. Carrying capacity is defined as the average maximum number of individuals of a species that an ecosystem can support. Populations in ecosystems that have reached their carrying capacity are in their stationary phase. Numbers of individuals in a population may fluctuate around the carrying capacity due to a number of density dependent and density independent factors. Effects of density dependent factors vary with the population size and include factors such as disease, migration and availability of resources. Density independent factors include environmental factors such as light intensity, and temperature, which often vary on a seasonal basis. In some cases, a population may enter a phase of decline. |
Not currently taught |
Bears limiting factors role play |
| 2 | Community | A community of organisms is a group of organisms comprising the populations of all the different species that coexist and interact with each other in the same ecosystem due to having overlapping habitats and niches. |
4.1.U7: A community is formed by populations of different species living together and interacting with each other
|
Scitable: Characterizing communities A&B: LIfe that Springs from Leaves A&B: Meet the Mice Who Make the Forest |
| 3 | Community Interactions | Ecological interactions include mutualistic (++), competition (--), predation (+-), herbivory (+-), parasitic and pathogenic interactions (+-), commensalism (+0), amensalism (-0) and no overall effect (00). Ecological relationships can affect the distributions and population sizes of species. Competition occurs when different organisms require the same limited resource from their Ecosystem. Intraspecific competition is inevitable between members of the same species as the resources required by its members will be the same. Interspecific competition can be identified when one species is more successful in the absence of the other. Predation is the process of predators catching, killing and eating other animals, known as prey. The numbers of predators and prey in a predator-prey relationship can be modeled mathematically to provide evidence for both experimental data and for the real-life fluctuations seen in their population sizes over time. Prey animals have defense mechanisms against predators which include physical characteristics such as shells, spines, quills and camouflage as well as chemicals such as toxins, foul-tasting and foul-smelling substances that may only be released when threatened. Herbivory is the process of organisms feeding on plants. Plants can have defense mechanisms against herbivores such as spines, thorns or heavily lignified tissue as well as produce toxins that have a bad taste or contain toxins. Allelopathy is the chemical inhibition of one species by another and is an effective competitive strategy shown by a number of organisms including plants, fungi and bacteria. Plants are known to release chemicals which are detrimental to the growth of other plants or to the germination of their seeds. Fungi and bacteria release antibiotic substances to kill or restrict the growth of other microorganisms. A cooperative interspecific interaction is referred to as a mutualism or mutualistic symbiosis. Examples of mutualisms should include the mutualistic relationships between plants and fungi (forming mycorrhiza) and those between many flowering plants and their pollinators. |
9.4.U3: Most flowering plants use mutualistic relationships with pollinators in sexual reproduction
|
Community interaction video clips Example of association between species A&B: Top 10 Natural History Moments |
| 4 | Sampling | The population size of a species can be estimated using random sampling The numbers of a population of a sessile species can be estimated using randomly placed quadrats. The numbers of a population of a motile species can be estimated using the mark-release-recapture method. |
SAPS Virtual sampling lab Data Nuggets finding a foothold Tongue point virtual sampling lab Submission form for virtual sampling lab |
|
| 5 | X2 Test | Testing for the association between two species using the chi-squared test with data obtained from random sampling in two locations can be used to investigate possible evidence for interspecific Competition. Assessing risks and benefits associated with scientific research—scientists inevitably cause some damage to ecosystems when carrying out field work, but without the field work they may not make important discoveries that are vital to any understanding of the ecosystems concerned or to their conservation. |
4.1.S3: Testing for association between two species using the chi-squared test with data obtained from quadrat sampling (students should obtain data themselves; in each quadrat, the presence or absence of the chosen species should be recorded)
|
Submission form for practice problems SHS Plant Community Association lab Data submission form for SHS plants |
| 6 | Ecosystems | 4.1.U8: A community forms an ecosystem by its interactions with the abiotic environment
|
Ecosystems Biotic and Abiotic notes A&B: Rewilding Ecosystems |
|
| 7 | Sustainability | A sustainable ecosystem is one that is able to support itself and provide requirements without external Influences. A sustainable ecosystem has high biodiversity. Biodiversity is the variation of different species in an ecosystem and is vital to the stability of the ecosystem. Non-renewable resources are finite, and their use contributes to the release of pollutants, including greenhouse gasses. Renewable resources are abundant, cannot be exhausted and are renewed by the environment within a relatively short period of time. Mesocosms can be used to study the effect of variables on ecosystem sustainability. |
4.1.U11: Ecosystems have the potential to be sustainable over long periods of time
Outline three requirements of a sustainable ecosystem. 4.1.S4: Setting up sealed mesocosms to try to establish sustainability (Practical 5)
|
A&B: Biosphere reading A&B: Biosphere 2 youtube questions A&B: The sealed bottle garden still thriving after 40 years without fresh air or water Mesocosm in water bottles protocol |
| 8 | Conservation |
|
9.4.NOS: Paradigm shift-more than 85% of the world’s 250,000 species of flowering plants depend on pollinators for reproduction. This knowledge has led to protecting entire ecosystems rather than individual species
|
Google Earth Timelapse |
| 9 | Succession | Ecological succession is the reasonably predictable change in species structure in a community over time. The succession may be primary or secondary. A climax community is a state of equilibrium and is the final stage in primary or secondary succession. It results when the community is stable and full functioning. A climax community is tolerant of the environmental conditions and has a wide diversity of species. Primary succession occurs in an area not previously occupied by an ecological community and usually lacking in soil or other organic matter. Humans can influence an ecosystem and prevent the community from developing or reaching a climax community, which results in a plagioclimax. Pioneer species are opportunists (r-selected) and are replaced by more competitive species (k-selected) as succession proceeds. Mass extinction results in earth system succession. Biotic change pushes both the biosphere and geosphere out of equilibrium. |
Not currently taught | |
| 10 | Biomes | Not currently taught | Biomes notes | |
| 11 | Wrap Up and Review |