Ecology And Environment

The species-area relationship describes the relationship between the area of a habitat (or part of a habitat) and the number of species found within that area. It was observed by naturalist Alexander von Humboldt.

The relationship is typically expressed by the power function:

Where:

• = Number of species
• = Area
• = Slope of the line (regression coefficient)
• = Y-intercept (a constant)

This equation describes a curve on a standard plot of S versus A.

To analyze this relationship as a straight line, it is common to plot it on logarithmic scales. Taking the logarithm (base 10 or natural log) of both sides of the equation:

Using the properties of logarithms ( and ):

This equation is in the form of a straight line on a log-log plot, where:

• (the y-intercept)
• (the slope)

Comparing this derived equation with the given options:

• log S = log C + Z log A (Matches the derived equation)
• log C = log S + Z log A
• log A = log C + Z log S
• log Z = log C + S log A

The correct equation depicting the species-area relationship in its logarithmic form is log S = log C + Z log A.

Let's evaluate each statement:

Speciation is generally a function of time:

• This statement is correct. Speciation typically occurs over long periods of time as populations become genetically distinct due to factors like natural selection, genetic drift, and geographic isolation.

Tropical environment is less seasonal, relatively more constant and predictable:

• This statement is correct. Tropical environments, especially rainforests, experience relatively constant temperatures and seasonal variations in rainfall, making them more predictable compared to temperate regions.

Solar energy contributes to high productivity:

• This statement is correct. Solar energy is the primary driver of photosynthesis, which supports the productivity of ecosystems. Regions with more sunlight typically have higher productivity.

Temperate regions have remained relatively undisturbed for millions of years:

• This statement is incorrect. Temperate regions have undergone significant changes over millions of years, including glaciations during ice ages. These regions have not remained undisturbed and have been impacted by climatic and ecological changes.

The correct answer is (C) : Only 4.

• According to David Tilman’s long-term ecosystem experiments, the total biomass in plots with more species shows less variation from year-to-year.
• This is because higher biodiversity helps stabilize ecosystem functioning, making the system more resilient to environmental fluctuations and reducing year-to-year variability in biomass.

The correct answer is (B) : Less variation from year-to-year.

Standing state (1): Refers to the amount of nutrients in the soil at a given time, as it describes the stable nutrient content in an ecosystem. This matches with q.

Pioneer species (2): These are the first species to invade a barren area and establish a presence in a new or disturbed habitat. Hence, it matches with r.

Detritivores (3): Organisms like earthworms or fungi that feed on detritus (dead organic matter) and break it down into smaller particles. This matches with s.

Standing crop (4): Refers to the mass of living material at a given time (the total biomass of plants and animals in an ecosystem). This corresponds to p.

The correct answer is (D) : 1-q, 2-r, 3-s, 4-p.