Enduring Understandings

Enduring Understandings are the College Board's AP Biology course objectives that you need to know for the AP exam. Below, you'll find those Enduring Understandings relevant to this unit. Numbering and lettering matches the course objective document linked from the main page of this website.
Every Enduring Understanding will NOT necessarily be covered during class time; you will be independently responsible for some of them.

A. Growth, reproduction and maintenance of the organization of living systems require free energy and matter.
1. All living systems require a constant input of free energy.
  • l. Reproduction and rearing of offspring require free energy beyond that used for maintenance and growth. Different organisms use various reproductive strategies in response to energy availability.
  • o. Changes in free energy availability can result in changes in population size.
  • p. Changes in free energy availability can result in disruptions to an ecosystem.
2. Organisms capture and store free energy for use in biological processes.
  • a. Autotrophs capture free energy from physical sources in the environment.
  • b. Photosynthetic organisms capture free energy present in sunlight.
  • c. Chemosynthetic organisms capture free energy from small inorganic molecules present in their environment, and this process can occur in the absence of oxygen.
  • d. Heterotrophs capture free energy present in carbon compounds produced by other organisms.
3. Organisms must exchange matter with the environment to grow, reproduce and maintain organization.
  • a. Molecules and atoms from the environment are necessary to build new molecules.
  • b. Carbon moves from the environment to organisms where it is used to build carbohydrates, proteins, lipids or nucleic acids. Carbon is used in storage compounds and cell formation in all organisms.
  • c. Nitrogen moves from the environment to organisms where it is used in building proteins and nucleic acids. Phosphorus moves from the environment to organisms where it is used in nucleic acids and certain lipids.

D. Growth and dynamic homeostasis of a biological system are influenced by changes in the system’s environment.
1. All biological systems from cells and organisms to populations, communities and ecosystems are affected by complex biotic and abiotic interactions involving exchange of matter and free energy.
  • b. Organism activities are affected by interactions with biotic and abiotic factors.
  • c. The stability of populations, communities and ecosystems is affected by interactions with biotic and abiotic factors.
3. Biological systems are affected by disruptions to their dynamic homeostasis.
  • b. Disruptions to ecosystems impact the dynamic homeostasis or balance of the ecosystem.

A. Interactions within biological systems lead to complex properties.
5. Communities are composed of populations of organisms that interact in complex ways.
  • a. The structure of a community is measured and described in terms of species composition and species diversity.
  • b. Mathematical or computer models are used to illustrate and investigate population interactions within and environmental impacts on a community.
  • c. Mathematical models and graphical representations are used to illustrate population growth patterns and interactions.
  • d. Reproduction without constraints results in the exponential growth of a population.
  • e. A population can produce a density of individuals that exceeds the system's resource availability.
  • f. As limits to growth due to density-dependent and density-independent factors are imposed, a logistic growth model generally ensues.
  • g. Demographics data with respect to age distributions and fecundity can be used to study human populations.
6. Interactions among living systems and with their environment result in the movement of matter and energy.
  • a. Energy flows, but matter is recycled.
  • b. Changes in regional and global climates and in atmospheric composition influence patterns of primary productivity.
  • c. Organisms within food webs and food chains interact.
  • d. Food webs and food chains are dependent on primary productivity.
  • e. Models allow the prediction of the impact of change in biotic and abiotic factors.
  • f. Competition for resources and other factors limits growth and can be described by the logistic model.
  • g. Competition for resources, territoriality, health, predation, accumulation of wastes and other factors contribute to density-dependent population regulation.
  • h. Human activities impact ecosystems on local, regional and global scales.
  • i. As human populations have increased in numbers, their impact on habitats for other species have been magnified.
  • j. In turn, this has often reduced the population size of the affected species and resulted in habitat destruction and, in some cases, the extinction of species.
  • k. Many adaptations of organisms are related to obtaining and using energy and matter in a particular environment.

B. Competition and cooperation are important aspects of biological systems.
2. Cooperative interactions within organisms promote efficiency in the use of energy and matter.
  • d. Interactions among cells of a population of unicellular organisms can be similar to those of multicellular organisms, and these interactions lead to increased efficiency and utilization of energy and matter.
3. Interactions between and within populations influence patterns of species distribution and abundance.
  • a. Interactions between populations affect the distributions and abundance of populations.
  • b. Competition, parasitism, predation, mutualism and commensalism can affect population dynamics.
  • c. Relationships among interacting populations can be characterized by positive and negative effects, and can be modeled mathematically (predator/prey, epidemiological models, invasive species).
  • d. Many complex symbiotic relationships exist in an ecosystem, and feedback control systems play a role in the functioning of these ecosystems.
  • e. A population of organisms has properties that are different from those of the individuals that make up the population. The cooperation and competition between individuals contributes to these different properties.
  • f. Species-specific and environmental catastrophes, geological events, the sudden influx/ depletion of abiotic resources or increased human activities affect species distribution and abundance.
4. Distribution of local and global ecosystems changes over time.
  • a. Human impact accelerates change at local and global levels.
  • b. Geological and meteorological events impact ecosystem distribution.
  • c. Biogeographical studies illustrate these changes.

C. Naturally occurring diversity among and between components within biological systems affects interactions with the environment.
4. The diversity of species within an ecosystem may influence the stability of the ecosystem.
  • a. Natural and artificial ecosystems with fewer component parts and with little diversity among the parts are often less resilient to changes in the environment.
  • b. Keystone species, producers, and essential abiotic and biotic factors contribute to maintaining the diversity of an ecosystem. The effects of keystone species on the ecosystem are disproportionate relative to their abundance in the ecosystem, and when they are removed from the ecosystem, the ecosystem often collapses.

Textbook Reference

This is the part of your textbook that covers the material for this unit.
Ch 40-43 (Over the summer, also read Chapter 1 as an introduction to Biological Science in general)

Relevant Files

Here, you'll find files for this unit.

Go to http://www.masteringbiology.com to complete part 3 of the summer assignment.


These connect to materials on other teachers' websites that you may find helpful. Generally speaking, I put links to helpful review materials - like video lectures summarizing the material - towards the top, and links to interesting extensions towards the bottom.
Scitable from Nature: Population Ecology
Scitable from Nature: Ecosystem Ecology & Community Ecology & Conservation/Restoration
The Vlogbrothers' Crash Course in Ecology series of youtube videos
Saving Life on Earth E O Wilson (TED Talk)
When The Water Ends: Africa's Climate Conflicts (short online documentary film on the intersection between ecology and society - in this case, desertification and war)
Yale e360 Documentaries (If you liked the one above, there are several more here, also on ecology and society topics. Students have especially liked the "Warriors of Qiugang" in the past.)
Water Hyacinth Podcast
Beetles & Moths Podcast
Red Paper Lantern Jelly Podcast
Perfecting Compost
Population Systems and Mutualism
First Comes Global Warming and Then an Evolutionary Explosion
Effect of Environmental Toxins on Wildlife- Wildlife Forensics
Algae making Biofuel
Algae and Animals living together: Going Green (endosymbiosis and mutualism)
Online Food Web Simulator: http://www.learner.org/courses/envsci/interactives/ecology/index.php
Other interactive Labs: Ecology: http://www.learner.org/courses/envsci/interactives/index.php
Succession board game
National Climatic Data Center
National Oceanographic Data Center
Smithsonian's Ocean Planet Exhibition
Species Photographs database
Exploring the Environment interactive modules
NASA's Tracking Climate Change site
National Academy of Sciences' Climate Change Page
U.S. Census Bureau
Wildlife Rehabilitation Information Directory
Botany links
Plant Nutrition Cycles
Earth and Moon Viewer
Biodiversity and Environment Articles
Coral Reefs & Climate Change video