UPSC STATIC QUIZ – Environment : 29 April 2024

Solution: c)

Exotic species introduced to new environments often reset the ecological conditions in that new habitat, threatening the species that exist there; this is the reason that they are also termed invasive species.

Invasive species that are closely related to rare native species have the potential to hybridize with the native species; harmful effects of hybridization have led to a decline and even extinction of native species.

Invasive species can change the food web in an ecosystem by destroying or replacing native food sources. The invasive species may provide little to no food value for wildlife.

Lakes and islands are particularly vulnerable to extinction threats from introduced species.

Solution: a)

Since each higher trophic level receives only a fraction of energy of the lower trophic levels, the energy pyramid is narrow at the top.

But, generally (barring some aquatic ecosystems) lower trophic levels have higher biomass as compared to the higher trophic levels.

Solution: a)

• Estuaries and their surrounding wetlands are bodies of water usually found where rivers meet the sea.
• Estuaries are home to unique plant and animal communities that have adapted to brackish water—a mixture of fresh water draining from the land and salty seawater.
• An ecotone is a transition area between two biomes. It is where two communities meet and integrate.
• It has some of the characteristics of each bordering biological community and often contains species not found in the overlapping communities.
• For e.g. the mangrove forests represent an ecotone between marine and terrestrial ecosystem. Other examples are grassland (between forest and desert.)

Estuaries are subject both to marine influences—such as tides, waves, and the influx of saline water—and to riverine influences—such as flows of fresh water and sediment.

The inflows of both sea water and fresh water provide high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.

The banks of many estuaries are amongst the most heavily populated areas of the world

Solution: b)

Alpha diversity

Alpha diversity describes the species diversity within a community at a small scale or local scale, generally the size of one ecosystem. When we casually speak of diversity in an area, more often than not it refers to alpha diversity.

Beta diversity

Beta diversity describes the species diversity between two communities or ecosystems. It is at a larger scale, and looks to compare the species diversity between two separate entities that are often divided by a clear geographical barrier like a river or a mountain ridge.

Gamma diversity

Gamma diversity is studied at a very large scale—a biome—where species diversity is compared between many ecosystems. It could range over areas like the entire slope of a mountain, or the entire littoral zone of a sea shore.

Example: Let’s take a mountain slope as our landscape. On this slope, there will be many different patches of forests and grasslands. Alpha diversity is the species diversity present within each forest or grassland patch of the slope. Beta diversity is represented by the species diversity between any two patches and their communities. Gamma diversity of the landscape is the species diversity along the entire range of the mountain slope.

Food web is more comprehensive than food chain.

Solution: c)

Light pollution is excessive brightness that causes visual discomfort.

• Skyglow is the brightening of the night sky over inhabited areas. It is caused by cluttered, bright, excessive and confusing groupings of light sources.
• It affects the reproductive cycles of those animals that depend on sensing light movements or seasonal movements to reproduce. Since birds migrate using star light, it can confuse them, and even disorient night-flying insects.
• Excessive blue light emitted from LEDs directly affects sleep pattern in Human by suppressing the production of the hormone melatonin, which mediates the sleep-wake cycle in humans.