Ecological Succession and Food Web Dynamics: Key Concepts and Models

What is ecological succession?

Change in species composition in communities over time, influenced by biotic and abiotic factors.

What are abiotic factors in ecological succession?

Non-living environmental factors such as climate, soils, nutrients, and water.

What is primary succession?

Colonization of habitats devoid of life, such as volcanic rock, which can be very slow.

What are pioneer species?

The first colonizers in primary succession that are typically stress-tolerant and transform the habitat.

What is secondary succession?

Reestablishment of a community after a disturbance where some organisms remain, such as after fires or storms.

Who studied succession on sand dunes along Lake Michigan?

Henry Cowles in 1899.

What is 'space for time substitution'?

A method used to study succession by assuming that spatial differences represent temporal changes.

What did Frederick Clements believe about plant communities?

He viewed them as 'superorganisms' working together toward a predictable climax community.

What was Henry Gleason's perspective on communities?

He believed communities are unique products of fluctuating environmental conditions and individual species interactions.

What are the three models of succession proposed by Connell and Slatyer?

Facilitation model, Tolerance model, and Inhibition model.

What does the facilitation model of succession suggest?

Early species modify the environment in ways that benefit later species, leading to a climax community.

What does the tolerance model of succession assume?

Early species modify the environment in neutral ways, allowing succession to proceed based on life-history traits.

What is the inhibition model of succession?

Early species modify conditions negatively, hindering later species until they are removed by disturbance.

What is the significance of Glacier Bay, Alaska, in studying succession?

It provides a real-world example of succession over centuries as glaciers melt.

What is the pioneer stage in Glacier Bay's succession?

The initial stage dominated by lichens, mosses, horsetails, willows, and cottonwoods.

What happens 30 years after the pioneer stage in Glacier Bay?

The Dryas (shrub) community develops, followed by the alder stage.

What occurs 100 years after the pioneer stage in Glacier Bay?

A mature Sitka spruce forest develops.

What happens 200 years later in Glacier Bay's succession?

Species richness decreases as Sitka spruce are replaced by Western hemlocks.

What are abiotic agents of change in an environment?

Disturbances and stress factors that affect growth, reproduction, or survival of species.

What role do ecosystem engineers play in community change?

They can significantly influence the structure and dynamics of communities.

What is the difference between natural and anthropogenic changes in communities?

Natural changes occur due to environmental factors, while anthropogenic changes are caused by human activities.

What is the climax community?

A stable end point in succession that changes little over time, though its existence is debated.

How do species interactions influence succession?

They can lead to species replacements and affect community structure through competition and cooperation.

What is the significance of disturbances in ecological succession?

Disturbances create opportunities for new species to colonize and can reset succession processes.

What is the role of diseases in ecological succession?

Diseases can slow growth or cause death in species, impacting community dynamics.

What is the impact of disturbance frequency and intensity on succession?

They determine the nature and pace of community changes during succession.

What is the role of spruce seeds in ecological succession?

Spruce seeds are added to each successional stage, where neighboring plants have facilitative and inhibitory effects.

What is facilitation in ecological succession?

Facilitation occurs when early-stage plants modify the habitat positively for other species, such as through soil formation and nitrogen fixation.

What negative effects do later species like alders have in succession?

Later species can inhibit the growth of subsequent species.

What drives succession according to the tolerance model?

Succession is driven by life history characteristics, with spruce dominating due to its slow growth and long life.

What distinguishes allogenic succession?

Allogenic succession is caused by environmental factors unrelated to the organisms present, such as hurricanes or climate change.

What is autogenic succession?

Autogenic succession occurs when changes in environmental conditions are caused by the biological processes of the organisms themselves.

Define autotrophic succession.

Autotrophic succession begins in a predominantly inorganic environment and is characterized by early dominance by autotrophic organisms.

What is heterotrophic succession?

Heterotrophic succession is characterized by early dominance of heterotrophic organisms in a predominantly organic environment.

What are ecological networks in ecology?

Ecological networks describe interactions among species, including consumer-resource interactions and mutualistic webs.

Who introduced food webs to ecology?

Food webs were introduced to ecology by Elton in 1927.

What was the focus of Yodzis' food web case study?

Yodzis studied the impact of culling fur seals on hake fish populations, considering both direct and indirect effects.

What are keystone species?

Keystone species have a disproportionately large effect on their community compared to their abundance.

How does the sea star Pisaster function as a keystone species?

Pisaster preys on mussels, preventing them from dominating the intertidal zone and allowing other species to coexist.

What happens when Pisaster is removed from its habitat?

Mussels dominate the intertidal zone, drastically reducing species diversity.

What did Hairston, Smith, and Slobodkin propose about food webs?

They proposed that food webs can be simplified into three interacting trophic levels: producers, herbivores, and carnivores.

What is a top-down trophic cascade?

A top-down trophic cascade occurs when predators regulate prey populations, preventing overexploitation of lower trophic levels.

What is a bottom-up trophic cascade?

A bottom-up trophic cascade is driven by energy availability at lower trophic levels, influencing higher consumer populations.

What factors regulate ecosystems according to the text?

Resource availability, primary productivity, predation pressure, and competition regulate ecosystems.

What is the relationship between primary productivity and trophic levels?

High primary productivity supports more consumers and higher trophic levels, while low productivity limits them.

What are the consequences of removing top predators from an ecosystem?

Removing top predators can lead to trophic imbalances, often resulting in overabundant prey and habitat collapse.

What is the significance of the 28 million potential interactions in the hake and seal case study?

It highlights the complexity of ecological interactions and the challenges in predicting ecological outcomes.

What is the role of competition in community structure?

Strong consumer pressure can limit prey populations and affect community structure.

What ecological concept did Oksanen et al. (1981) explore?

They explored how biomass at each trophic level changes with variations in potential primary productivity.

What is the impact of nutrient availability on ecosystem productivity?

Increases in nutrients boost producer biomass, supporting more herbivores and predators.

What is the role of shading by trees in autogenic succession?

Trees can shade and kill other plants, leading to changes in species composition.

What is the primary characteristic of heterotrophic succession?

It begins in a predominantly organic environment and is characterized by the early dominance of heterotrophic organisms.

What is the significance of ecological networks in modern ecology?

They encompass a broader range of interactions beyond simple food webs, including mutualistic and parasitic relationships.

What is the definition of a population in ecology?

A population is a group of organisms of a species living together in a particular place at a particular time.

What defines a community in ecological terms?

A community consists of all organisms of all species living together in a particular space at a particular time.

What is dispersion in ecology?

Dispersion refers to how species are distributed in space.

What are the three types of species dispersion?

Uniform, clumped, and random dispersion.

Describe uniform dispersion.

Uniform dispersion occurs in a homogeneous habitat where spacing is driven by species interactions like territoriality.

What characterizes clumped dispersion?

Clumped dispersion occurs in heterogeneous habitats with clustered resources and can be driven by social interactions.

What is random dispersion?

Random dispersion occurs in homogeneous habitats where spacing is not driven by species interactions and is the least common form.

What is stratification in aquatic systems?

Stratification refers to the presence of different thermal layers in a lake or pond system.

What are the three layers of a lentic aquatic system?

Epilimnion, metalimnion, and hypolimnion.

What is the role of the epilimnion?

The epilimnion is the upper layer of water that is warmer and more oxygenated, supporting photosynthesis.

What happens in the metalimnion?

The metalimnion is marked by a rapid transition in temperature and oxygen, acting as a barrier to nutrient and gas movement.

What characterizes the hypolimnion?

The hypolimnion is the deepest layer with low or no light and oxygen consumption, often anoxic.

What is a watershed?

A watershed is an area of land where all the water drains to a common point, such as a river, lake, or ocean.

What does the River Continuum Concept describe?

It describes the river system as a continuously integrating series of physical gradients and associated biotic adjustments from headwater to mouth.

What is a keystone species?

A keystone species is one on which other species in an ecosystem largely depend; its removal would drastically change the ecosystem.

What is the significance of intermediate disturbance in ecosystems?

Intermediate disturbances can enhance species and community diversity by creating opportunities for different species to thrive.

What is succession in ecology?

Succession is the regular change in communities over time until a self-sustaining stable community is reached.

What is the difference between primary and secondary succession?

Primary succession starts from scratch, while secondary succession occurs where a previous community existed but was lost.

What is auto-succession?

Auto-succession refers to the ability of a community to recover from disturbance.

What is diel structure in community ecology?

Diel structure refers to the variation in community composition based on time of day, such as nocturnal and diurnal patterns.

What is allochronic speciation?

Allochronic speciation occurs when breeding seasons are separated by time, allowing different species to evolve.

What is the impact of fire ecology on species diversity?

Fire ecology can accentuate species and community diversity by creating new habitats and opportunities for growth.

What is ecology?

The study of the interactions between organisms and the environment.

Define 'population' in ecological terms.

A group of interbreeding individuals of the same species, typically isolated from other groups.

What is a community in ecology?

An assemblage of spatially delimited species, often defined by a characteristic physical attribute.

What does an ecosystem consist of?

A combination of a community and its physical characteristics, including interactions among organisms and their environment.

What is the difference between 'pattern' and 'process' in ecology?

Pattern refers to what we see, while process refers to the mechanistic explanations for those patterns.

What are the four main focuses of ecological sciences?

Organismal, Population, Community, and Ecosystem ecology.

What is biodiversity?

The variety of life on Earth, measured at three levels: genetic, species, and ecosystem.

What is the significance of Hutchinson's article in ecology?

It was a pivotal moment that has driven much of the research on biodiversity in the last fifty years.

What is the relationship between populations and limiting resources?

Populations are limited by one or more limiting resources, affecting their growth.

What does natural selection depend on?

Heritable variability leading to differential reproductive success.

Define 'fitness' in ecological terms.

The genetic contribution an individual makes to the next generation relative to others in the population.

What are polymorphisms?

Multiple alleles maintained in a population, allowing for variability.

What is plasticity in ecology?

The ability of one genotype to produce multiple phenotypes in response to environmental cues.

How does selection affect species distribution?

Selection acts to maximize fitness, leading to optimal conditions that coincide with species distribution and local abundance.

What is the role of ecological data in understanding patterns?

Ecologists attempt to fit ecological data to patterns, seeking to understand the processes behind them.

What is the significance of genetic variability in populations?

Genetic variability is heritable and affects the ability to acquire resources, influencing survival and reproduction.

What are the implications of ecological science for management?

Ecological science has clear management implications, helping predict outcomes for populations and communities under specific circumstances.

What is the importance of peer review in ecological research?

It encourages objectivity and critical review, avoiding cronyism in scientific findings.

What does the term 'abiotic environment' refer to?

The non-living components of an ecosystem that affect living organisms.

Why is defining a 'species' challenging?

Due to factors like polymorphisms, plasticity, and varying definitions across different ecological contexts.

What are the main levels at which biodiversity is measured?

Genetic, species, and ecosystem levels.

What is the impact of selection forces on populations?

Selection forces can change over a gradient, affecting allele frequencies and population characteristics.

What is the role of energy flow in ecosystems?

Patterns of energy, mass, and nutrient flow are crucial for understanding ecosystem dynamics.

What is the significance of understanding ecological processes?

It allows ecologists to predict changes in populations and communities based on environmental conditions.

What is the relationship between ecological studies and biodiversity?

Ecological studies aim to understand and manage biodiversity through the examination of interactions and processes.