Unit 2

Essential Knowledge:

• Biodiversity in an ecosystem includes genetic, species, and habitat diversity.

• The more genetically diverse a population is, the better it can respond to environmental stressors. Additionally, a population bottleneck can lead to a loss of genetic diversity.

• Ecosystems that have a larger number of species are more likely to recover from disruptions.

• Loss of habitat leads to a loss of specialist species, followed by a loss of generalist species. It also leads to reduced numbers of species that have large territorial requirements.

• Species richness refers to the number of different species found in an ecosystem.

Essential Knowledge:

• There are four categories of ecosystem services: provisioning, regulating, cultural, and supporting.

Describe the results of human disruptions to ecosystem services.

Essential Knowledge:

• Anthropogenic activities can disrupt ecosystem services, potentially resulting in economic and ecological consequences.

Essential Knowledge:

• Island biogeography is the study of the ecological relationships and distribution of organisms on islands, and of these organisms’ community structures.

• Islands have been colonized in the past by new species arriving from elsewhere.

Describe the role of island biogeography in evolution.

Essential Knowledge:

• Many island species have evolved to be specialists versus generalists because of the limited resources, such as food and territory, on most islands. The long-term survival of specialists may be jeopardized if and when invasive species, typically generalists, are introduced and outcompete the specialists.

Essential Knowledge:

• Ecological tolerance refers to the range of conditions, such as temperature, salinity, flow rate, and sunlight that an organism can endure before injury or death results.

• Ecological tolerance can apply to individuals and to species.

Essential Knowledge:

• Natural disruptions to ecosystems have environmental consequences that may, for a given occurrence, be as great as, or greater than, many human-made disruptions.

• Earth system processes operate on a range of scales in terms of time. Processes can be periodic, episodic, or random.

• Earth’s climate has changed over geological time for many reasons.

• Sea level has varied significantly as a result of changes in the amount of glacial ice on Earth over geological time.

• Major environmental change or upheaval commonly results in large swathes of habitat changes.

• Wildlife engages in both short- and long-term migration for a variety of reasons, including natural disruptions.

Essential Knowledge:

• Organisms adapt to their environment over time, both in short- and long-term scales, via incremental changes at the genetic level.

• Environmental changes, either sudden or gradual, may threaten a species’ survival, requiring individuals to alter behaviors, move, or perish.

Essential Knowledge:

• There are two main types of ecological succession: primary and secondary succession.

• A keystone species in an ecosystem is a species whose activities have a particularly significant role in determining community structure.

• An indicator species is a plant or animal that, by its presence, abundance, scarcity, or chemical composition, demonstrates that some distinctive aspect of the character or quality of an ecosystem is present.

Describe the effect of ecological succession on ecosystems.

Essential Knowledge:

• Pioneer members of an early successional species commonly move into unoccupied habitat and over time adapt to its particular conditions, which may result in the origin of new species.

• Succession in a disturbed ecosystem will affect the total biomass, species richness, and net productivity over time.