Ecology Exam 2 Questions

What is the density-dependent growth model?

It describes how population growth rates are influenced by population density.

What equation represents unrestricted growth?

dN/dt = rN.

Define 'Carrying Capacity' (K).

The maximum population size that the environment can sustain.

What occurs at the carrying capacity, K?

Population growth rate (r) becomes zero.

What is the intrinsic growth rate represented by in equations?

r.

How does a continuous-limited environment differ from a continuous-unlimited environment?

Continuous-limited takes into account carrying capacity, while continuous-unlimited does not.

What does the term 'logistic growth' refer to?

Population growth that initially is exponential but slows as the population reaches carrying capacity.

What impact does density-dependent competition have on population growth?

It can limit resources, decreasing growth rate as population density increases.

What is a life table?

A table that shows the survival and reproductive rates of individuals of different ages in a population.

What is meant by net reproductive rate (R0)?

The expected number of offspring produced by an average female over her lifetime.

Define 'generation time' (T).

The average period between the birth of an individual and the birth of its offspring.

What does λ represent in population studies?

The finite rate of population increase; λ > 1 means growing, λ = 1 stable, λ < 1 declining.

What is the significance of the inflection point in population growth?

It is where the rate of population growth is at its maximum.

What assumptions are made in logistic growth models?

No immigration/emigration, constant environmental conditions, no time lags, and linear relationships between birth and death rates.

What is the difference between 'r' and 'K' selection?

'r' selection prioritizes high growth rates in unstable environments, while 'K' selection focuses on stable environments near carrying capacity.

What is the role of predators in ecological systems?

They can control prey populations, affecting the structure and dynamics of communities.

Define exploitative competition.

When one species limits the availability of resources for another species.

What is interference competition?

Direct interaction between species, such as fighting or chemical warfare, influencing resource availability.

What is Gause's Competitive Exclusion Principle?

Two species competing for the same resource cannot coexist indefinitely.

What does the Lotka-Volterra model describe?

The interactions between predator and prey populations.

What are 'Zero Net Growth Isoclines' (ZNGIs)?

The resource levels at which a species neither increases nor decreases in population.

How does apparent competition differ from true competition?

It occurs when two species indirectly affect each other's population through a shared predator.

What is meant by bottom-up control in ecosystems?

When primary producers limit the population sizes of higher trophic levels.

What is a keystone species?

A species that has a disproportionate impact on its environment relative to its abundance.

What are traits of mutualisms?

Interactions where both species benefit, ranging from facultative to obligate relationships.

Define amenity value of biodiversity.

The intrinsic value that biodiversity provides in maintaining ecosystem functions.

What is the significance of interactions in community ecology?

They explain how species coexist, impact population dynamics, and affect community structure.

Explain the term 'trophic cascade.'

An ecological phenomenon triggered by the addition or removal of top predators.

What is direct effect in interspecific interactions?

When two species interact without involving intermediate species.

Describe indirect effects in ecological interactions.

When interactions between two species involve one or more intermediate species.

What are dominant species in an ecological community?

Species that are most abundant or have the highest biomass.

How do food webs differ from food chains?

Food webs depict multiple feeding relationships and energy flows, while chains depict a single linear path.

What role do microbes play in ecosystems?

They help decompose organic matter and recycle nutrients.

What is resource partitioning?

The division of limited resources by species to help avoid competition.

Explain the concept of community structure.

The composition and organization of species within an ecological community.

What effect do invasive species have on local ecosystems?

They can disrupt local species interactions and dynamics, often leading to declines of native species.

How do stable isotopes help in ecological studies?

They provide information about diet and trophic levels based on the carbon and nitrogen ratios.

What is mutualism?

A type of interaction where both species derive benefit from the relationship.

What defines a community in ecology?

An assemblage of populations of different species in a specific area that interact.

What is the role of decomposers in the ecosystem?

They break down dead organic matter, recycling nutrients back into the ecosystem.

Explain the concept of a guild in ecology.

A group of species in a community that exploit the same resources in a similar manner.

What are foundational species?

Species that have a strong role in structuring a community.

What contributes to the diversity of an ecosystem?

The variety of species and their interactions within the community.

What are density-dependent growth models?

Models that consider factors affecting population growth related to population density.

What does the Logistic Equation assume regarding immigration/emigration?

It assumes no immigration or emigration occurs.

dP/dt = rP(1 - P/K), models population growth where 'P' is the population size, 'r' is the intrinsic growth rate, and 'K' is the carrying capacity.

What characterizes r-selected species?

They maximize intrinsic growth rate, have low carrying capacity, and prioritize quantity over quality in offspring.

What is a key strategy of K-selected species?

They invest in parental care, have a lower birth rate, and maintain populations near carrying capacity.

Define Fecundity.

The number of offspring produced per reproductive event.

How do death/mortality rates and fecundity vary?

They vary with age, within and across species.

What can age-tables be used for?

To calculate accurate growth rates and population sizes.

What does Generation Time (T) represent?

The average age at which a female gives birth to offspring.

What occurs if a matrix for population remains constant over time?

The percentage of organisms at different life stages will remain constant.

What is exploitation in ecological terms?

Interaction where one species benefits at the expense of another, such as parasitism.

What is the role of predators in ecosystems?

They limit prey abundance through consumption.

How can human intervention affect unchecked non-native species?

It can help control their growth when they lack natural predators.

Define predator-prey dynamic cycling.

Oscillations in predator and prey populations that can occur over time.

What happens to prey populations when predator populations increase?

Prey populations typically decrease due to increased predation.

What is the R* model in competition?

It indicates the resource concentration level at which consumers maintain no net growth.

What happens when two species cannot coexist due to competition?

The species with the lowest R* value for a resource will outcompete the other.

What are diatoms and how do they affect the ecosystem?

Silica-using algae that grow until carrying capacity (K) of silica is reached.

What is the significance of resource supply points in competition?

They represent stable resource levels when inputs and losses are balanced.

Describe the concept of zero net growth isocline.

The resource level where a species' population remains stable.

What is competitive exclusion?

The principle that two species competing for the same resource cannot coexist indefinitely.

What is character displacement?

Differentiation of similar species to minimize competition in overlapping niches.

What is mutualism?

A symbiotic relationship where both species benefit.

What is commensalism?

A relationship where one species benefits and the other is unaffected.

Name an example of facultative mutualism.

Where species can survive without their mutualistic partners.

What are keystone species?

Species that have a disproportionately large effect on their environment.

What do food webs illustrate?

The complex interactions of different species in an ecosystem beyond just food chains.

What are the main methods of determining food webs?

Observational studies, gut content analysis, and stable isotope analysis.

What is a trophic cascade?

An indirect effect in an ecosystem where changes in one population affect multiple other populations.

What implications do disturbances have on predator-prey dynamics?

They can lead to population declines or shifts in community structure.

What is the significance of parasites in food webs?

They are crucial for maintaining healthy ecosystems and biodiversity.

What type of species are often found to outcompete others in regards to resource availability?

Species that can utilize resources more efficiently than their competitors.

What does an increase in primary production lead to in food chains?

It stimulates growth and stability in various trophic levels.

Define apparent competition.

A scenario where two species negatively affect each other indirectly through a shared predator.

What is the impact of resource overlap between two competing species?

It can lead to diminished resources for one or both species, facilitating competitive outcomes.

What is the difference between a fundamental niche and a realized niche?

A fundamental niche is the potential ecological role a species could occupy, while a realized niche is the actual role it plays, considering competition and other factors.