UGC NTA NET/JRF Exam, Environmental Sciences, March-2023

The first law of thermodynamics, often called the law of conservation of energy, states that energy cannot be created or destroyed in an isolated system.

The total energy within a system can change forms (from kinetic to potential energy or vice versa), but the total amount of energy remains constant.

This concept underpins many physical processes and is fundamental in understanding energy transfer and transformation in closed systems.

For instance, when we burn fuel, it doesn't disappear but is transformed from chemical energy into heat and light energy.

Similarly, when we eat, our body converts the chemical energy in food into energy that our cells can use to function and grow.

This law contrasts with concepts like conservation of mass (from which it is distinct) and conservation of momentum, which are governed by different principles.

Frontier ethics arose from the belief, especially in the 19th and early 20th centuries, that the Earth had an endless bounty of resources for humans to exploit. The first three options (a, b, c) represent this outdated and unsustainable mindset.

The idea that "Earth has an unlimited supply of resources" and that "there is always more, and it is all for human use" are obviously in conflict with modern understandings of environmental sustainability.

Similarly, viewing humans as apart from nature rather than a part of it has often led to environmental degradation. On the other hand, the fourth option, "We must understand and cooperate with nature," aligns with a sustainable and holistic perspective.

Recognizing our interdependence with nature and the need to work within ecological limits is central to creating a sustainable society.

The Tbilisi Declaration of 1977 was the outcome of the world's first intergovernmental conference on environmental education, held in Tbilisi, Georgia (then part of the USSR). Organized by UNESCO and UNEP, the conference highlighted the role of environmental education in the sustainable development of societies.

The declaration emphasized the importance of environmental education for all age groups and socioprofessional categories.

While other conferences, like the one in Stockholm in 1972, addressed environmental concerns, it was the Tbilisi conference that specifically focused on and endorsed environmental education on such a broad scale.

The average salinity of seawater in the oceans is about 3.5%. This means that for every 1,000 grams (or 1 kilogram) of seawater, there are 35 grams of salts dissolved in it, mostly in the form of sodium chloride, or common table salt. Salinity can vary depending on the location and depth in the ocean.

Factors that can increase salinity in certain areas include high evaporation rates, ice formation, and the addition of salt from underwater volcanic activity.

Factors that decrease salinity include the influx of fresh water from rivers, rainfall, and ice melting. It's essential to understand salinity because it plays a significant role in ocean circulation, marine life habitat, and the overall health of our oceans.

DDT (Dichlorodiphenyltrichloroethane) is a synthetic insecticide that gained infamy due to its environmental persistence and harmful effects on wildlife.

One of the main reasons for its persistence in the environment is its low reactivity, meaning it does not break down quickly when exposed to light, chemicals, or microbes.

Its low vapor pressure and low solubility in water further contribute to its longevity in the environment, as these properties make it less likely to evaporate or dissolve and be washed away.

However, its "high rate of evaporation" is NOT a reason for its persistence; in fact, DDT has a relatively low rate of evaporation. The concerns regarding DDT led to its ban in many countries, despite its effectiveness in controlling disease vectors like mosquitoes.

A grazing food chain represents the sequence of organisms through which energy flows in an ecosystem, starting from primary producers (like plants) and progressing through various levels of consumers.

In this context, the flow starts with the Sun, which provides energy to green plants (primary producers). Herbivores (like deer) consume these plants and become food for first-order carnivores (like foxes), which, in turn, may become prey for second-order carnivores (like eagles).

This flow represents a typical grazing food chain, with energy moving from the Sun, to plants, to herbivores, and up through higher levels of carnivores.

The species-area relationship is a wellestablished ecological principle which describes the increase in species diversity with the increase in area sampled. Specifically, as the area of a habitat or ecosystem sampled increases, the number of species observed also typically increases.

This relationship is vital for biodiversity studies and conservation efforts. It helps determine the minimum area required to sample to ensure that the maximum number of species present in an association or ecosystem is enumerated.

The relationship is commonly applied in conservation biology to prioritize areas for protection or to estimate the number of species that might be lost due to habitat destruction.

The term "Ecological Footprint" measures how much of the Earth's biologically productive land and sea areas are required to regenerate the resources a human population consumes and to absorb the corresponding waste it generates.

This includes areas for farming, grazing, forest products, fishing grounds, built-up areas, and carbon uptake to address emissions from fossil fuels.

By comparing a population's Ecological Footprint with the planet's biocapacity (its capacity to regenerate resources and absorb waste), we can assess whether humanity is living within the Earth's ecological limits or is overexploiting the planet.

If the Ecological Footprint exceeds the Earth's biocapacity, it indicates that we are depleting natural resources faster than they can be regenerated, leading to environmental degradation and depletion.