Ecology Chapter on Species Interactions
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Ecology Chapter on Species Interactions

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Questions and Answers

What is the effect of intermediate levels of disturbance on species richness?

  • It increases species richness. (correct)
  • It stabilizes species richness at low levels.
  • It decreases species richness.
  • It has no effect on species richness.

    • What is a dominant species in a community?

  • A species that has a disproportionate effect on its ecosystem.
  • A species with low abundance.
  • A species that is the first to colonize an area.
  • A species that is most conspicuous or abundant. (correct)

    • What best describes a keystone species?

  • A species that competes aggressively with others for resources.
  • A highly abundant species that dominates the community.
  • A species that is rare but essential for ecosystem function. (correct)
  • A species that has no significant impact on the ecosystem.

    • Which hypothesis suggests that a species' abundance is limited by its consumers?

    <p>Top-down hypothesis.</p> Signup and view all the answers

    How is community regulation understood within ecological frameworks?

    <p>As a combination of top-down and bottom-up processes.</p> Signup and view all the answers

    What is a key factor in understanding community structure according to niche dynamics?

    <p>A multi-dimensional understanding of niches.</p> Signup and view all the answers

    What occurs during a trophic cascade?

    <p>Changes at a higher trophic level lead to changes in distributions at lower levels.</p> Signup and view all the answers

    Which of the following best describes species evenness?

    <p>The relative abundance of different species in a community.</p> Signup and view all the answers

    Which term describes the conditions within which a species can survive and thrive?

    <p>Niche</p> Signup and view all the answers

    What is the term for the niche that includes all the environmental conditions a species can potentially inhabit?

    <p>Fundamental niche</p> Signup and view all the answers

    Which of the following options represents an example of niche overlap?

    <p>Species A and B occupy the same temperature zone but different moisture levels</p> Signup and view all the answers

    What does the realized niche represent in ecological terms?

    <p>The actual conditions and resources in which a species exists</p> Signup and view all the answers

    Which concept explains the importance of certain species in maintaining the structure of an ecosystem?

    <p>Keystone species concept</p> Signup and view all the answers

    How can species richness influence community structure?

    <p>Increased species richness typically leads to greater stability in ecosystem function</p> Signup and view all the answers

    What might cause two species to have completely different niches although they live in the same environment?

    <p>Adaptations to different environmental factors</p> Signup and view all the answers

    What is the effect of niche dynamics on species interactions within an ecosystem?

    <p>They can lead to resource partitioning and coexistence</p> Signup and view all the answers

    In which type of ecosystem are keystone species most likely to have a significant impact on the community structure?

    <p>Diverse and complex ecosystems</p> Signup and view all the answers

    What is a likely ecological consequence of reduced species richness in a community?

    <p>Greater vulnerability to environmental changes</p> Signup and view all the answers

    What defines species richness in a community?

    <p>The number of species present in a community</p> Signup and view all the answers

    Which characteristic best describes communities that are species-poor?

    <p>Limited variety of species present</p> Signup and view all the answers

    What role does a dominant species play in community structure?

    <p>It is the most abundant and conspicuous species.</p> Signup and view all the answers

    Which of the following is true about keystone species?

    <p>They disproportionately affect the structure of their community.</p> Signup and view all the answers

    How do beavers influence their communities as keystone species?

    <p>They change the landscape and promote habitat diversity.</p> Signup and view all the answers

    What distinguishes a fundamental niche from a realized niche?

    <p>Fundamental niche is broader and does not account for competitors.</p> Signup and view all the answers

    What is often a characteristic of high evenness in a community?

    <p>Species are present in similar abundances.</p> Signup and view all the answers

    What usually happens to species composition upon the removal of a keystone species?

    <p>Community composition may change drastically.</p> Signup and view all the answers

    Which of the following describes a community dominated by few species?

    <p>They have low diversity and reduced resilience.</p> Signup and view all the answers

    How can a tropical rainforest be characterized in terms of species diversity?

    <p>High richness and low evenness</p> Signup and view all the answers

    What is one consequence of a community having a high species diversity?

    <p>Higher likelihood of ecosystem stability and resilience.</p> Signup and view all the answers

    What is a common misconception regarding the role of dominant species?

    <p>Their removal has no effect on the overall community balance.</p> Signup and view all the answers

    Which statement best defines the niche of an organism?

    <p>The species' interactions with both abiotic and biotic factors.</p> Signup and view all the answers

    What can be inferred about communities with low evenness?

    <p>They tend to have an unequal distribution of species.</p> Signup and view all the answers

    Study Notes

    Niche

    • G. Evelyn Hutchinson provided a formal definition about a niche: a multidimensional space of environmental factors that a species can tolerate, within which it lives, and to which it is well-adapted.
    • Hutchinson is considered the "father of American ecology".
    • A species' fundamental niche includes all the resources and conditions it can tolerate.
    • A species' realized niche is the actual resources and conditions it uses due to competition.
    • Niche is a multidimensional space of environmental factors.
    • Figure 9.18 demonstrates one dimension of the niche by showing how a species may be limited by a particular factor, such as moisture.
    • Figure 9.18 also shows how the niche can be impacted by other factors such as temperature.
    • Figure 9.18 shows the "perfect" point of a niche where a species can thrive.
    • Species may overlap closely along certain niche axes, but they are separated along others.

    Community Composition

    • Species Richness is the total number of species present in a community.
    • Evenness refers to the relative abundances of species in a community.
    • Species Diversity is a measure of both richness and evenness and integrates these two factors.
    • Tropical Rainforests are characterized by high richness and low evenness.
    • Rank Abundance is a graph that can be used to visualize evenness and includes the number of individuals from most abundant to least abundant.

    Community Structure

    • Many communities have dominant species at each trophic level.
    • A dominant species is the most conspicuous and abundant in a community often with the highest biomass.

    Keystone Species

    • Keystone species have a disproportionately large effect on community structure.
    • These species have outsides influence.
    • Keystone species are pivotal to maintaining ecological balance.
    • Removing a keystone species can significantly change community composition, resulting in the loss of other species or the unchecked growth of others.
    • They are like the capstones of an arch, crucial for holding the structure together, even though they are not the largest blocks.

    Keystone Species Examples

    • Starfish in rocky intertidal zones have been identified as a keystone species due to their ability to control muscle populations.
    • Removing starfish from the community had a significant impact on the diversity of organisms present.
    • Beavers in northern forest communities are also considered keystone species.
    • They change the landscape and create habitats for other species.

    Niche

    • Niche refers to the specific environmental factors that limit a species' distribution, growth, and reproduction.
    • Fundamental Niche is the theoretical range of conditions in which a species could survive.
    • Realized Niche is the actual range of conditions a species inhabits due to factors like competition.

    Niche (Alternative Definitions)

    • Chapter 2 describes a niche as the physical space occupied by an organism or species.
    • Charles Elton described a niche as an animal's place in the biotic environment, encompassing its relationship with food and enemies, and its status within its communities.

    Intermediate Disturbance Hypothesis

    • Intermediate Disturbance Hypothesis suggests that species diversity is highest at intermediate levels of disturbances in a community.
    • The Figure 9.32 demonstrates this hypothesis by showing how a sand-dune community can reach peak species diversity with intermediate levels of rabbit browsing.
    • With low levels of disturbance, a few dominant species may take over, while with high levels of disturbance, a diverse community is unable to establish.

    Top-down vs. Bottom-up

    • Top-Down hypothesis, or consumer control, suggests that the abundance of a species is limited by consumers.
    • A decrease in predators can lead to an increase in herbivores, leading to a decline in plants.
    • Bottom-up hypothesis, or resource control, suggests that consumer abundance is determined by resource availability.
    • A decrease in food can lead to a decrease in herbivores, and this decrease can influence predator populations.

    Trophic Cascades

    • Trophic cascades occur when changes at a higher trophic level lead to serial changes in abundance and distribution at lower levels.
    • An example might be the introduction of a predator causing changes in the prey population, ripple through the community.

    Summary of Community Ecology

    • Richness, evenness, and diversity are key measures of community composition.
    • Dominant species are important to understanding community structure.
    • Keystone species have a significant impact on community structure and diversity.
    • Understanding niches can help to understand community interactions.
    • Community structure is regulated through top-down and bottom-up processes.

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    Explore the intricate relationships and dynamics within ecological communities with this quiz. You'll delve into concepts like species richness, keystone species, and niche dynamics, enhancing your understanding of biodiversity and community structure. Perfect for students of ecology and environmental science.

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