Ecology Ch. 16

Human disturbance is widespread and comes in many forms including: increased urbanization; air and water pollution; removal of forest

Plants that are described as a vine would belong to the same life-form

Generally, there is a positive relationship, or correlation, between environmental complexity and species diversity

In tropical forest communities, the distribution of plant communities are strongly influenced by soil characteristics

One of the most ubiquitous patterns found in communities is that very few species are common; very few species are rare; most species are moderately abundant

In a tropical forest, a particular area may have many unique plant communities

Abiotic forces of disturbance would include fire; flooding

Studies by Jordan (1985) showed that in tropical Amazon forests, a change of elevation greater than 2 meters above nearby streams would have sandy well-drained soils that can cause water stress in plants

Species diversity is based on which two factors? The relative abundance of species in a community; The number of species in a community

Sousa’s work demonstrates that disturbance may allow multiple species to coexist because the disturbance prevents competitive exclusion

As a general rule, very few species are very abundant; very rare

There are many definitions of disturbance; however, most have this in common: they remove individuals or biomass; they allow for the establishment of new individuals or colonies; they are discrete physical events

The value of a rank-abundance curve lies in its ability to visually portray species richness and evenness in a two dimensional graph

Species diversity includes the number of species in community

Which are components of a community’s structure? The number of species present; The relative abundances of species; The kinds of species present

Imagine a community consisting of approximately 100 species. Considering the patterns of species abundances, one would expect to find very few of the species to be very abundant

Groups of species that live in a defined area and interact with each other are termed a community

According the IUCN in 2007, the most serious threat to species diversity is habitat loss

A discrete event that removes individuals or biomass and creates space for new individuals to become established is known as a disturbance

In a typical community, most species will be moderately abundant

Which of the following are soil characteristics important to plants? Depth to the ground water; type of soil (sand or clay); pH

The niches of plants and algae can be defined by physical characteristics such as moisture; their nutrient requirements; chemical characteristics such as pH

At similar latitudes, community A has many more species than community B. what is one possible explanation for this observation? Community A has a higher habitat heterogeneity than community B

The intermediate disturbance hypothesis that the highest level of species diversity is found in communities with continually changing conditions

In temperate grasslands, disturbances can include fire; trampling; grazing

Species evenness is also known as the relative abundance

When environmental conditions remain relatively the same over a time period, the community is said to be in equilibrium

Based on studies by MacArthur in the 1950s, communities with more complex forests contained more species of warblers than other plant communities

As nutrient levels increase in aquatic communities, plant and algae diversity decrease

The highest rates of species diversity is often associated with an intermediate level of disturbance

Tilman’s work in 1977 showed that some diatoms can coexists when the ratios of essential nutrients were correct

A rank-abundance curve with a steep curve is indicative of a community dominated by a few abundant species and lower species richness

In forest communities, the foliage height diversity varies with species richness; species evenness

Very low levels of disturbance will reduce species diversity because only the best competitors will survive

The total number of species within a community is known as the species richness

Prairie dogs create disturbance in a grassland by grazing the on the plants creating bare ground; creating burrows and depositing soil into mounds

When the number of individuals in a community are plotted by the number of species, the typical result is a lognormal distribution

Based on the figure illustrating lognormal distributions, what do forest birds and desert plants have in common? Very few species are very rare; most species have moderate coverage or abundances; very few species are abundant

A community with an H’ = 0 would have only one species

Human disturbance is a major threat to diversity because it can be frequent and or intense

The structure of a plant combined with its growth dynamics determines its life-form

When calculating the species diversity using the Shannon-Wiener index, the proportion of the i^th species is multiplied by the natural log of the proportion of the i^th species.

Based on Tilman’s work in 1977, the ratio of essential nutrients in communities can determine whether two species can coexist or exclude each other

In aquatic ecosystems, plant and algal diversity decline with increasing nutrient availability

The plot of a lognormal distribution would be bell shaped

MacArthur (1958) found that warbler diversity was correlated with foliage height

Very high levels of disturbance will reduce species diversity because few species will be able to survive the frequent and intense disturbances

Lilleskov and his colleagues found that acid-tolerant ectomycorrhizal fungi are dominant when soil nitrogen levels are high and the pH is low

Based on several surveys by Blair in 2004, avian diversity was highest in areas with an intermediate level of disturbance

High plant diversity is often correlated with high animal diversity

Species of plants with a higher percent cover and species of forest birds with higher numbers of individuals are both uncommon

In abandoned agricultural fields, nutrients and moisture do not necessarily correlate with each other creating habitat heterogeneity leading to greater plant diversity

The highest rates of species diversity found among boulders in the intertidal zone were found in areas of intermediate disturbance

By studying plant life-forms, scientists can reduce the number of species they are studying to better understand the community structure

Prairie dogs increase species diversity by creating a patchy environment with an intermediate level of disturbance

In the Park Grass Experiment, the rank-abundance curves have become steeper indicating a loss of species diversity

Worldwide urbanization has led to a homogenization of the global biota

Increases in land use intensity has led to the spread of already widespread and non-native birds species

Smaller boulders experience a higher frequency of disturbance, from this it could be predicted that species diversity would be lower on these boulders

Which community would have the highest species diversity? A community with high species richness and an abundance curve with the lowest slope

In 1980, George Sugihara proposed that the lognormal distribution of species in a community could be explained by species dividing the niches in a community

Prairie dogs create an intermediate level of disturbance that increases species diversity by allowing good colonizers and good competitors to coexist

Stream invertebrates that eat or “shred” terrestrial plant material would belong to the same guild

Nutrients in a lake such as nitrates, silicates and other nutrients can vary independently of each other over small spatial scales

In a community with very low species evenness, one would expect to encounter the same species many times before finding additional species

If two communities had the same species richness, but the rank-abundance curve for community A was much steeper than community B, then community B has a higher species diversity

Avian diversity has been found to be highest at golf courses

Under conditions of low nitrate availability, Lieskov found that fungal communities are comprised of species specialized in nitrogen uptake

Increases in land use intensity has led to a decrease in woodland bird species

Which community would have the higher species diversity? A community with 20 species with high species evenness

Varying nutrient levels in a lake creates environmental complexity leading to higher phytoplankton diversity

Animal diversity in terrestrial communities is positively correlated with plant diversity

Some ecosystems have many thousands of species, making it difficult to study the contribution of each species to the functioning of a community. Therefore, scientists may study the effects of groups of organisms on community structure by placing them into guilds

In temperate grasslands, plant diversity is highest where prairie dogs create a patchy environment

Based on Figure 16.16 illustrating the effect of fertilizing and plant diversity, it can be seen that plant diversity has decreased over time due to fertilizer use

The activities of prairie dogs help to increase plant diversity by creating bare patches of ground that facilitate colonization

A group of organisms that exploit resources in a similar way is termed a guild

In 1975, Robert May proposed that the lognormal distribution of species in a community could be explained as a statistical explanation based on many random variables

Based on Tilman’s 1977 work, two similar species of diatoms can coexist when the ratio of silicate to phosphate is low

When sampling species richness in a community, the common species will typically be found in small samples

Tilman demonstrated that Asterionella can exclude Cyclotella when the ratio of silicate to phosphate is high