Plant Succession and Disturbance Dynamics

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Questions and Answers

What is the primary difference between primary and secondary succession?

Primary succession occurs only after volcanic eruptions, while secondary can occur after floods.

Primary succession involves faster growing species, while secondary involves slower growing species.

Primary succession starts from nutrient-rich soil, while secondary does not.

Primary succession begins after all organisms have been removed, whereas secondary involves some surviving organisms. (correct)

What role do pioneer species play in primary succession?

They stabilize the soil and enhance nutrient availability. (correct)

They compete for resources with climax species.

They are primarily photosynthetic organisms.

They contribute primarily through slow growth and nutrient absorption.

Which of the following statements about climax species is true?

Climax species tend to have faster growth rates and greater dispersal abilities.

Climax species are the first to colonize after disturbance.

Climax species are the final stable species in a mature environment. (correct)

Climax species require nutrient-poor soils to thrive.

What typically characterizes disturbances that influence ecological succession?

They can vary in frequency and magnitude. Signup and view all the answers

In which succession model does the presence of early species facilitate the colonization of later species?

Facilitation Signup and view all the answers

Which type of species is known to have a high productivity with simple food webs during early succession?

Pioneer species Signup and view all the answers

What is a key characteristic of keystone species in an ecosystem?

Their removal leads to a significant change in community composition. Signup and view all the answers

How does tree density in late-stage succession compare to middle-stage succession?

Tree density is generally lower in late-stage succession due to stronger competitors. Signup and view all the answers

What is the primary outcome of exploitation in ecological relationships?

One species gains while the other loses. Signup and view all the answers

Which of the following statements about food chain length hypotheses is true?

General hypotheses about these lengths are still relevant. Signup and view all the answers

In what context are specific names of function-response curves necessary for the final exam?

Understanding the general relationship between average prey caught and prey density suffices. Signup and view all the answers

What is primarily excluded from the final exam regarding the life cycles discussed?

Specific details of trematode life cycles. Signup and view all the answers

What type of relationships are characterized as mutualism in community dynamics?

Both species experience a gain. Signup and view all the answers

What distinguishes active transmission from passive transmission in parasites?

Passive transmission depends on the actions of the host or vector. Signup and view all the answers

Which type of ecto parasite manipulates hosts into raising their young?

Brood parasite Signup and view all the answers

What is a characteristic of endo parasites compared to ecto parasites?

They typically do not kill their host. Signup and view all the answers

Which of the following is true about microparasites?

They multiply directly within a host. Signup and view all the answers

How do hemiparasites differ from holoparasites?

Hemiparasites can perform photosynthesis. Signup and view all the answers

Which type of endo parasite typically kills its host during its immature stage?

Parasitoid Signup and view all the answers

What is a common characteristic of ecto parasites compared to endo parasites?

Ecto parasites have a free-living stage. Signup and view all the answers

Which of the following best describes macroparasites?

They release their young outside of the host's body. Signup and view all the answers

Which of the following best describes bottom-up control in an ecosystem?

Lower trophic species affect the abundance of higher trophic species. Signup and view all the answers

What is an example of bottom-up control in a freshwater ecosystem?

The amount of leaf litter affecting stream consumers. Signup and view all the answers

Which statement about community stability is accurate?

A stable community can recover from disturbances over time. Signup and view all the answers

What does the term 'resilience' refer to in the context of an ecosystem?

The speed at which an ecosystem returns to its original state after a disturbance. Signup and view all the answers

Which of the following factors is most closely related to resistance in an ecosystem?

The ability to tolerate disturbances. Signup and view all the answers

What role does indispensible mortality play in populations?

It outlines deaths that are unavoidable regardless of other factors. Signup and view all the answers

Which statement best contrasts top-down and bottom-up controls?

Top-down controls often exert greater influence in a given ecosystem. Signup and view all the answers

What impact does eutrophication generally have on aquatic ecosystems?

It lowers water oxygen levels, affecting organisms. Signup and view all the answers

What is a characteristic of Type 2 predation response?

Catch rate plateaus when prey becomes too numerous. Signup and view all the answers

Why do introduced predators tend to have a larger impact on native species compared to native predators?

Native species have adapted to native predators but not to introduced ones. Signup and view all the answers

What was a primary reason for megafauna extinctions in North America?

Overhunting by humans and climate change. Signup and view all the answers

In the middle successional stage, which type of plants predominantly characterize the community?

Shrubs and small trees. Signup and view all the answers

Which concept refers to an abiotic event that alters survival rates of one or more species?

Disturbance. Signup and view all the answers

What type of succession occurs after a disturbance that completely destroys the existing community and exposes bare land?

Primary succession. Signup and view all the answers

Which animal was specifically mentioned as having caused the extinction of bird species in Guam?

Snake. Signup and view all the answers

What often happens to species that are hunted by humans, according to the Overkill Hypothesis?

They reproduce at an earlier age and decrease in size. Signup and view all the answers

What role do parasites play in controlling invasive species?

They are often more host-specific and reduce the risk of large consequences. Signup and view all the answers

During which stage of succession do fast-growing species like herbs and grasses dominate?

Early successional stage. Signup and view all the answers

What does Community Importance (CI) indicate?

The change in a community due to the abundance of a species. Signup and view all the answers

Which type of mutualism is characterized by species that cannot survive without each other?

Obligate mutualism Signup and view all the answers

Which of the following is NOT an example of a pollinator?

Piranhas Signup and view all the answers

What is a characteristic feature of pollinator syndrome?

Plants and pollinators evolve specific traits to enhance their interactions. Signup and view all the answers

In defensive mutualism, what is typically provided by the protective species?

Protection from predators Signup and view all the answers

Which is a key benefit of resource-based mutualism?

Increased efficiency in nutrient uptake. Signup and view all the answers

What distinguishes facultative mutualism from obligate mutualism?

Both species can independently survive but benefit from each other. Signup and view all the answers

What role does the anatomical feature of a pollinator play in mutualistic relationships?

It enables efficient pollen carrying. Signup and view all the answers

Which of the following is a key component required for effective seed dispersal by animals?

Nutritional benefits from seeds. Signup and view all the answers

What advantage does seed dispersal provide compared to wind dispersal?

Effective colonization of new areas. Signup and view all the answers

What is the primary role of pioneer species in an ecosystem?

They modify the environment to support other species. Signup and view all the answers

Which succession model is characterized by early species inhibiting the growth of later species?

Inhibition Signup and view all the answers

What is most likely to increase species diversity in an ecosystem according to the intermediate disturbance hypothesis?

Medium levels of disturbance which allow coexistence. Signup and view all the answers

What distinguishes climax species from pioneer species?

Climax species are slower growing and good competitors. Signup and view all the answers

Which of the following is an example of secondary succession?

Recovery of a forest after a wildfire. Signup and view all the answers

Which trophic level relies on primary producers for energy?

Primary consumers Signup and view all the answers

How does top-down control affect food chain dynamics?

It limits the size of the levels below the top trophic level. Signup and view all the answers

What characterizes early successional species?

They have high productivity in simple food webs. Signup and view all the answers

In the context of food webs, what is the role of decomposers?

They recycle nutrients back into the soil. Signup and view all the answers

What happens to early successional species as the environment develops towards a climax community?

They are replaced by longer-lived species. Signup and view all the answers

Study Notes

Stages of Succession

Stages of plant succession involve canopy restoration and the emergence of slower-growing dominant species like trees.
Late stages (50-100+ years) see trees becoming the dominant biomass.
Tree density is lower in the later stage compared to the middle stage because strong competitors outcompete their neighbors.

Disturbances in Ecosystems

Disturbances are abiotic events that alter the survival rates of one or more species.
Disturbances can create openings and opportunities for some species, impacting resources and space.
Disturbances vary in frequency and magnitude; small-impact disturbances are most common.

Succession Types

Primary Succession: Occurs after a disturbance completely removes all organisms, exposing bare substrate.
It starts from scratch, rebuilding ecosystems from barren conditions.
Examples include fires, volcanic eruptions, glacial retreats, and floods.
Primary succession creates nutrient-poor soil, relying on primary/pioneer species to create conditions for other organisms.
Secondary Succession: Occurs after a disturbance where some organisms survive.
It builds on pre-existing conditions, balancing nutrients and progressing through succession stages.
Examples include abandoned agricultural fields.

Species Roles in Succession

Primary/pioneer species: Tolerate harsh abiotic conditions, have quick growth and reproduction, and modify the environment to benefit other species.
Often include plants with nitrogen-fixing bacteria in their roots.
Early successional species: Good dispersers, experience fast growth in high sunlight, and have high productivity with simple food webs.
Climax species: Represent the final stable species in a mature ecosystem. They exhibit slower growth, limited dispersal, and are strong competitors for nutrients and light.

Succession Models

Facilitation: Early species modify the environment (e.g. improve soil quality, alter pH, provide shade) to promote the colonization of less tolerant species.
This is common in primary succession but can also occur in secondary succession.

Community Importance and Keystone Species

Community importance measures the effect of a species' removal on the community's overall biomass.
tN = Total biomass of the original intact community
tD = Total biomass in the community after a species is removed
pI = Proportional biomass of species 'i' before removal
Keystone species have a disproportionately large impact on their community (CI > 1).

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Description

Explore the intricate stages of plant succession, from primary succession following major disturbances to the later stages dominated by mature trees. Understand how abiotic events alter ecosystem dynamics, creating opportunities for various species. This quiz covers the essential concepts of ecological succession and disturbances.