AP Environmental Science › Ecological Succession
After an event such as a fire or a tree fall in a forest, early successional species are the first to reappear. Which is an example of early successional species?
Grasses
Gorillas
Shrubs
Bears
Grasses are also early successional species because they reproduce quickly and require minimal diversity of resources to survive. Their quick reproduction and growth also categorizes them as R-selected species.
Which of the following is an accurate example of primary ecological succession?
River sediments are deposited along a waterfront consisting of barren rock, resulting in the establishment of moss and grass communities.
A wildfire burns through the underbrush of a hardwood forest, freeing up available sunlight for new understory brush.
A windstorm displaces nutrient-rich topsoil that has been heavily tilled, resulting in diminished fertility and inability for plant communities to establish themselves.
A woodland ecosystem has been overbrowsed by moose that quite enjoy low-lying willow branches and seedlings, resulting in a depletion of young willow trees. Deer soon replace moose in the woodland to graze on the abundant grasses and sedges.
Boreal forests throughout Alaska and Canada are undergoing a transition where short-lived conifer stands are slowly replaced by deciduous hardwood stands, which are characteristic of a more mature forest.
Primary succession is, by definition, the establishment of living communities in areas where life had not previously existed. A waterfront that is barren rock does not initially have the potential to support life until mineral and soil deposits allow new plant communities to establish themselves. The other answers are not correct because plant communities already exist in these examples, which is not characteristic of primary succession.
Which of the following is a structural change in a community and its nonliving environment over time that alters the ecosystem?
Succession
Adaptation
Natural selection
Evolution
Mutation
Succession is a structural change in a community and its nonliving environment over time. Community changes alter the ecosystem in ways that favor competitors, and species replace one another in a somewhat predictable manner until a stable community is reached. Examples are the changes that occur after volcanos erupt and forest fires. Adaptation is a characteristic of an organism that helps it survive and reproduce in a particular environment. The differential survival and reproduction on the basis of genetic differences among individuals is termed natural selection. Evolution is any change in the proportions of different genotpyes in a population from one generation to the next. Mutation is a change in the base sequence of DNA in a gene that is usually significant enough to alter the appearance or function of the organism.
Which of the following would NOT contribute significantly to primary succession?
Pre-existing nitrogen-fixing plant communities
Soil nutrients deposited by a nearby river
Wind-carried soil particles and nutrients
The time-consuming process of weathering the bedrock into smaller particles
Feces from wildlife populations that occupy the region
Primary succession is characterized by pioneer species establishing themselves in areas that are predominantly bedrock and devoid of organic material. The formation of organic material in these areas typically occurs with the accumulation of wind-carried soil erosion, nutrients deposited by flowing bodies of water, and erosion of bedrock. Wildlife populations are also a significant contributor of soil nutrients, with feces being rich in both nitrogen and phosphorus. In contrast, pre-existing nitrogen-fixing plants (or any pre-existing plant communities) are uncommon to nonexistent in an area with no established soil system.
Which of the following provides the most accurate example of primary succession?
Lichen and grass communities establishing themselves on a recently-formed island, resulting from an uplift in the ocean bedrock
Native grass communities forming after a wildfire burned through a meadow/woodland ecosystem
Seedlings establishing themselves in a heavily logged area where the seed-tree cutting method was employed
Lichens re-establish themselves on rocks and shallow soil beds following a tundra fire
Coral reef and aquatic wildlife communities that have re-established themselves in regions of the South Pacific that were evacuated following the nuclear tests conducted by the U.S. military
Primary succession is characterized by plants establishing themselves in areas that were initially devoid of soil (usually bedrock). Grasses establishing themselves on a newly-formed island that is mostly bedrock is the best fit for this definition.
What is the process by which ecosystems change gradually overtime?
Ecological succession
Climax community
Greenhouse effect
Pre-existing disturbance
Ecological succession is the change of the structure of an environment overtime. The environment can be changed due to a sudden disruption or small changes overtime. These changes can take place over a few decades or millions of years.
Ecosystems recover from disturbances in unique ways. A landscape ecologist observes in area right after a volcanic eruption. There is lava and dust across the landscape, and all vegetation has been removed. What is this ecosystem experiencing?
Primary succession
Secondary succession
Pioneering succesion
Climax succession
None of these
The correct response is primary succession. This represents the initial growth following a disturbance, such as a volcanic eruption. While pioneering succession involves the colonization of a location that has been affected by ecological damage, primary succession is a better answer since it refers specifically to vegetation colonizing a location in which soil is absent (such as after a volcanic eruption). Climax succession is not a term used to describe species succession over time, rather, a climax community is one that, over time, has reached a steady state.
Which of the following are least likely to be present during primary succession?
Trees
Lichen
Moss
Grass
Primary succession begins with no soil. Eventually, lichens and mosses grow and die, which creates some soil. Small plants such as grasses and some ferns use this soil and grow. It would be very unlikely for a tree to grow in this environment.
A glacier has just receded across the landscape. As the glacier retreated, it completely decimated all standing vegetation. The landscape recovers quickly because there are plenty of seeds left in the seed bank. What is this an example of?
Secondary succession
Primary succession
Tertiary succession
Quaternary succession
The correct response is secondary succession. This process occurs following some disturbance when the seedbank is still intact. For example, after an earthquake or fire all the vegetation is removed but there are still seeds in the ground. This would be an example of secondary succession because the vegetation can still recover. This is different from primary succession - primary succession occurs when there is no prior vegetation on the landscape and there is no seedbank. Tertiary and quaternary succession are made up terms.
Which of the following is an example of primary succession?
Plant communities are established in a lifeless environment, usually devoid of soil
A transition from one ecosystem type to another
A succession of larger plants (trees, shrubs, etc.) following the establishment of pioneer species
A plant community becoming simplified with fewer species and less biomass
An ecosystem diversifying, supporting more species and increases in biomass
Primary succession commonly occurs after a volcanic eruption or a glacier recedes, because these areas have been stripped of organic matter. Primary succession is the process by which pioneer species colonize an area otherwise uninhabitable for plant life and generate nitrogen for other plant communities.