Chapter 10 - Patterns in species richness (CHAPTER + SLIDES) Flashcards
(55 cards)
What is Species Richness?
The number of different species present in a community. It is the simplest measure of biodiversity.
What is Species Diversity?
A measure that considers both the number of species (richness) and their relative abundance.
What is Resource Availability?
The amount and range of resources available to a community can influence the number of species that can coexist.
What is Niche Breadth?
The range of resources or conditions utilized by a species. Species with narrower niches can allow for more species to coexist if resources are limited.
What is Niche Overlap?
The extent to which the resource use of different species overlaps. Greater overlap can potentially support more species if competitive exclusion is limited.
How does Predation influence species richness?
Predation can influence species richness through predator-mediated coexistence, where predation prevents competitive dominants from excluding other species.
What is Spatial Heterogeneity?
Variation in the physical structure or abiotic conditions of an environment. More heterogeneous environments often support more species.
What is Environmental Harshness?
Conditions that require specialized adaptations and are costly for organisms to tolerate. Harsh environments typically have lower species richness.
How does Climatic Variation affect species coexistence?
Seasonal or unpredictable changes in climate can influence which species can coexist. Predictable seasonality can support species adapted to different times of the year, while stable non-seasonal environments can favor specialization.
What is Disturbance in ecological terms?
Events that alter the structure and composition of a community. The intermediate disturbance hypothesis suggests that species richness is highest at intermediate frequencies and intensities of disturbance.
What is Evolutionary Age?
The length of time a community or region has existed without major disruption. Older, stable environments may be more saturated with species.
What is Island Biogeography?
The study of the factors that influence species richness on islands (or habitat islands).
What is the Species-Area Relationship?
The observation that larger areas tend to support more species. This can be due to increased habitat diversity or processes related to immigration and extinction.
What is Island Isolation?
The distance of an island from a source of colonists. More isolated islands generally have lower immigration rates and thus lower species richness.
What are Latitudinal Gradients?
The common pattern of increasing species richness from the poles towards the tropics.
What are Altitudinal Gradients?
Changes in species richness with increasing elevation. Patterns can vary (decrease, increase, or hump-shaped).
What are Depth Gradients?
Changes in species richness with increasing depth in aquatic environments.
What is the primary difference between species richness and the Shannon-Weaver diversity index?
Species richness is simply the count of different species, while the Shannon-Weaver index considers both the number of species and their relative abundance within a community.
How does the concept of niche breadth and overlap relate to the potential number of species in a community?
Communities with species that have smaller average niche breadths (more specialized) or greater average niche overlap can potentially accommodate more species along a given resource continuum.
Explain the “paradox of enrichment” and a possible explanation for it.
The paradox of enrichment is the observation that increased productivity (enrichment) can sometimes lead to a decrease in species diversity. This may occur because high productivity leads to rapid competitive exclusion of less competitive species.
How can predation intensity potentially influence species richness?
Predation can increase species richness if it prevents competitive dominant species from excluding less competitive species, creating more available space or resources.
Provide an example of how spatial heterogeneity can lead to increased species richness.
A hilly landscape, compared to a flat one, provides more varied conditions in terms of things like sunlight, moisture, and hiding places, which can support a greater variety of species.
How is environmental harshness defined in a way that avoids circular reasoning when discussing species richness?
Environmental harshness is defined by requiring organisms to possess costly, non-standard morphological or biochemical adaptations to survive there, rather than simply by low species numbers.
Contrast the potential effects of seasonal vs. non-seasonal environments on species specialization and richness.
Seasonal environments may support species adapted to different times of the year, while stable non-seasonal environments can provide opportunities for highly specialized species that require continuous availability of resources.
