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Chapter 8.1 Species Abundance and Diversity in General Biology

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  • What is biodiversity?

    Biodiversity describes the diversity of ecological entities across multiple scales, including genes, species, and communities.

  • How many species are currently described on Earth?

    About 2 million species are described, with estimates ranging from 5 to 30 million total species including unicellular organisms.

  • What is species richness?

    Species richness is the total number of species found in a community, denoted by the parameter S.

  • What does species evenness measure?

    Species evenness measures the relative abundance of each species, indicating how common or rare species are within a community.

  • How is species diversity defined?

    Species diversity combines species richness and evenness to describe the overall diversity of a community.

  • What is the Shannon Index (H')?

    The Shannon Index quantifies species diversity by combining richness and evenness; higher H' indicates greater diversity.

  • How is the Shannon Index (H') calculated?

    H' = -∑i=1S pi ln(pi), where pi is the proportion of species i and S is species richness.

  • What is a log-normal distribution in species abundance?

    A log-normal distribution shows many species with intermediate abundance, few rare species, and few dominant species in a community.

  • What is standardized sampling in ecology?

    Standardized sampling compares species abundance and diversity using the same plot size or method across different areas.

  • Why is sampling effort important in estimating species diversity?

    Increasing sample size initially increases observed species richness rapidly, but eventually reaches a plateau indicating sufficient sampling.

  • What is an indicator taxa?

    Indicator taxa are easy-to-identify groups used to estimate species diversity, but relying on a single taxa can be misleading.

  • How does species richness vary with latitude?

    Species richness generally increases at lower latitudes, showing more species and variation in composition near the equator.

  • What does a rank-abundance curve show?

    A rank-abundance curve displays species ranked by abundance, illustrating species richness and evenness in a community.

  • How does environmental complexity affect biodiversity?

    Greater environmental complexity, such as varied vegetation or elevation, generally leads to higher species diversity.

  • What did MacArthur's warblers study demonstrate?

    Higher foliage height and complexity in pine forests increased bird species diversity by providing more ecological niches.

  • What is community stability in ecology?

    Stability is a community's tendency to remain constant in structure and function over time.

  • What is community resilience?

    Resilience is the rate at which a community recovers after a disturbance.

  • How does species richness affect drought resistance in plant communities?

    Plant communities with about 15 species richness showed optimal drought resistance, with resistance increasing rapidly up to this point.

  • What is the complementarity hypothesis in diversity-function relationships?

    It predicts a linear increase in community function as species richness increases, with each species adding unique functions.

  • What is the redundancy hypothesis in diversity-function relationships?

    It suggests community function levels off after a threshold of species richness due to overlapping (redundant) species functions.

  • What is the driver and passenger hypothesis?

    Some species (drivers) have large effects on community function, while others (passengers) have smaller effects, causing a stair-step increase in function with richness.

  • Why might managers prioritize protecting rare species?

    Rare species may have unique ecological roles or conservation value, making communities with rare species higher management priorities.