WEEK 8 2250

What is a community in ecological terms?

A community is a set of populations of different organisms interacting with one another in a particular ecosystem.

Define an ecosystem.

An ecosystem is a discrete unit of biotic and abiotic components interacting to form a stable system.

What are the three major changes in viewing community dynamics?

1. Stable (equilibrium) vs. Chaotic dynamics (non-equilibrium); 2. Discrete (closed) vs. Continuous systems (open); 3. Additive (predictable) vs. Non-additive interactions (emergent properties).

What does the deterministic view of community dynamics suggest?

It suggests that plant communities are highly predictable, deterministic, and converge on a stable climax community regardless of starting conditions.

Who proposed the idea that communities are artifacts of species distributions?

Henry Gleason proposed that communities are not organisms but rather artifacts responding individualistically to environmental factors.

What are the implications for conservation regarding community dynamics?

1. There is no balance of nature to right past wrongs; 2. Events in one place affect dynamics elsewhere; 3. Emergent properties complicate predictions of environmental degradation outcomes.

What is a food web?

A food web is a framework for studying community interactions.

What are two major problems with traditional trophic level pyramids?

1. They assume communities are closed systems; 2. They do not account for spatial studies and detrital shunts.

What is meant by non-additivity of species interactions?

Species have trophic density mediated interactions and non-trophic effects such as trait-mediated interactions.

What is the modern view of community dynamics?

The modern view recognizes chaotic dynamics (non-equilibrium) and continuous systems (open) rather than simplistic stable and discrete views.

What role does stochastic chance play in community assembly according to Gleason?

Stochastic chance plays a greater role, suggesting that community assembly is less deterministic.

What does the term 'emergent properties' refer to in community dynamics?

Emergent properties refer to complex interactions within communities that make predictions about environmental impacts difficult.

How does the view of communities as complex organisms differ from viewing them as artifacts?

The former sees communities as predictable and converging on a stable state, while the latter views them as coincidental and influenced by individual species' responses to the environment.

What is the significance of spatial studies in community dynamics?

Spatial studies highlight the interconnectedness of communities and how changes in one area can affect others.

What are detrital shunts?

Detrital shunts refer to the pathways through which organic matter is transferred from detritus to higher trophic levels, often overlooked in traditional models.

What does the term 'trophic density' mean?

Trophic density refers to the number of species at each trophic level and their interactions within the food web.

How do non-trophic effects influence community interactions?

Non-trophic effects, such as trait-mediated interactions, can significantly alter the dynamics and outcomes of species interactions.

What is the traditional view of community dynamics?

The traditional view sees communities as stable, discrete, and predictable systems.

What is a climax community?

A climax community is a stable and mature ecological community that has reached a steady state of development.

What does the term 'biotic components' refer to in an ecosystem?

Biotic components refer to the living organisms within an ecosystem, including plants, animals, and microorganisms.

What are abiotic components in an ecosystem?

Abiotic components are the non-living physical and chemical elements in the environment, such as water, soil, and climate.