UPSC Essentials | Key terms of past week with MCQs

— Notably, not every geologist agrees that the Anthropocene epoch is a reality as there are disagreements within the scientific community regarding when it began, or has it already begun, or if they have enough evidence to prove its advent.

What is the Anthropocene epoch?

— The Anthropocene epoch as a term was first coined by Nobel Prize-winning chemist Paul Crutzen and biology professor Eugene Stoermer in 2000 to denote the present geological time interval, in which the Earth’s ecosystem has gone through radical changes due to human impact, especially since the onset of the Industrial Revolution.

— There are numerous phenomena associated with this epoch, such as global warming, sea-level rise, ocean acidification, mass-scale soil erosion, the advent of deadly heat waves, deterioration of the biosphere and other detrimental changes in the environment.

“Many of these changes will persist for millennia or longer, and are altering the trajectory of the Earth System, some with permanent effect. They are being reflected in a distinctive body of geological strata now accumulating, with potential to be preserved into the far future,” the AWG’s website said.

How is the Earth’s geological time divided?

— The planet’s geological time scale is divided into six broad categories: eons, eras, periods, epochs and ages. While eon is the broadest category of geological time, age is the smallest category. Each of these categories is further divided into sub-categories. For instance, Earth’s history is characterised by four eons, including Hadeon (oldest), Archean, Proterozoic, and Phanerozoic (youngest).

On what basis these categories are divided?

— According to the New York-based Paleontological Research Institution, “Most of the boundaries on the geological time scale correspond to the origination or extinction of particular kinds of fossils.” This is also related to something called the principle of faunal succession, which states that different kinds of fossils characterise different intervals of time.

As of now, at least officially, we’re in the Phanerozoic eon, Cenozoic era, Quaternary period, Holocene epoch and the Meghalayan age.

Just FYI: How has the geological time scale evolved over time?

— It has taken hundreds of years to create and evolve the geological time scale as we know it today. The roots of its origin go back to the 1500s and 1600s, when miners became interested in understanding the geological relationships of different rock units, according to a report by the University of California, Berkeley.

— The first major breakthrough came in 1669 after Danish scientist Nicolas Steno published the first laws of stratigraphy — the science of interpreting the strata, or layers of rock, in the Earth’s outer surface. He laid out two basic geologic principles: “The first stated that sedimentary rocks (formed on or near the planet’s surface, in contrast to metamorphic and igneous rocks, which are formed deep within the Earth) are laid down in a horizontal manner, and the second stated that younger rock units were deposited on top of older rock units,” the report added.

— The second principle essentially means that layers closer to the Earth’s surface must be younger than layers below them. This allowed scientists of the time to conclude that each rock layer represented a specific interval of geologic time.

— Further advancements were made when building on Steno’s principles, Italian geologist Giovanni Arduino began to name the layers. By examining the rocks of the southern Alps during the 1750s, he classified the four main layers of the Earth’s crust as Primary (the lowest metamorphic and volcanic layers), Secondary (hard sedimentary rocks), Tertiary (less hardened sedimentary rocks), and Quaternary (the most recently laid rock layer, which is quite soft in comparison to other strata).

— But there were some issues with Arduino’s classification and Steno’s principles. First, “because rocks were locally described by colour, texture, or even smell, comparisons between rock sequences of different areas were often not possible”, the University of California report stated. And without a way to compare rock layers of different parts of the world, there couldn’t have been a universal geological time scale. Second, unlike tree-ring dating, in which each ring is equivalent to one year’s growth, rock layers don’t tell the specific length of geologic time, meaning no one layer can convey how long a certain period lasted on the Earth.

— These discrepancies were finally dealt with by English surveyor William Smith, who, in the 1800s, observed that fossils could be used to characterise different intervals of time because evolution and extinction are facts of nature. For instance, a rock with a trilobite fossil upon it means that it is Paleozoic in age (541-252 million years ago) and not older or younger as trilobites flourished only in the Paleozoic era.

— Moreover, Smith came up with the principle of faunal succession, which stated that fossils are found in the same order under the Earth’s surface from place to place. “Fossil A was always found below Fossil B, which in turn was always found below Fossil C, and so on. By documenting these sequences of fossils, Smith was able to temporally correlate rock layers (or, strata) from place to place (in other words, to establish that rock layers in two different places are equivalent in age based upon the fact that they include the same types of fossils),” the New York-based Paleontological Research Institution said in a report.

— This allowed scientists to construct the first rough outlines of the geological time scale. A more evolved and precise time scale appeared with the advent of radiometric dating in the early 1900s, but fossil evidence still plays a crucial role in the division of the timeline.

(Source: Scientists say the ‘Anthropocene epoch’ began in the 1950s: What it means, significance, Advent of the Anthropocene epoch: Geological time scale, and how it has evolved over time by Alind Chauhan)

1. MCQ:

The right descending order arrangement is:

(a) Eons, eras, periods, epochs and ages. 

(b) Eons, eras, epochs, periods, and ages. 

(c) Eons, epochs, eras, periods, and ages. 

(d) Epochs, eons, eras, periods,and ages. 

Guillain-Barré Syndrome

WHY IN NEWS?

— The Peruvian government has recently declared a state of national emergency for up to three months, due to a spike in the number of cases of a rare neurological disorder called Guillain-Barré Syndrome .

— The disorder, which affects the body’s nervous system, is characterized by muscle weakness and breathing difficulties, and can even lead to total paralysis in extreme situations.

— Back in 2019, Peru faced a similar problem following an outbreak of a bacterial infection called campylobacter.

KEY TAKEAWAYS

Deutsche Welle Explains:

Aspartame

WHY IN NEWS?

— The use of aspartame, often known by the brand name Equal, in food and beverage products has long been scrutinised. The latest iteration came Thursday (July 13), when an agency of the World Health Organization declared that aspartame could possibly cause cancer and encouraged people who consume a significant number of beverages with aspartame to switch to water or other unsweetened drinks.

KEY TAKEAWAYS

— The analysis by WHO’s International Agency for Research on Cancer found the product to be “possibly carcinogenic to humans” — a categorisation generally used for things when there is either limited, but not convincing, evidence for cancer in humans or convincing evidence for cancer in experimental animals, but not both. It is the third-highest level out of the four levels in which IARC categorises carcinogens.

What exactly is aspartame?

— Chemically, aspartame is a methyl ester of the dipeptide of two natural amino acids, L-aspartic acid and L-phenylalanine. It was discovered by James M Schlatter, a chemist at the American pharmaceutical company G D Searle & Co. (which is now a subsidiary of Pfizer) in 1965, apparently by accident, when, while researching an anti-ulcer drug, he happened to lick his finger and detected a sweet taste.

— According to the US Food and Drug Administration (FDA), aspartame is about 200 times sweeter than table sugar — which makes aspartame far less sweet than other artificial sweeteners like advantame and neotame, but even then, 1 gram of aspartame has the sweetness intensity of roughly 2 teaspoons (about 8 g) of sugar.

— Aspartame is preferred by people trying to cut calories or lose weight, or by diabetics, because while 2 teaspoons (8 g) of sugar provides about 32 kcals of energy, 1 g of aspartame is only 4 kcals.

Is aspartame dangerous?

— Over more than 40 years, aspartame has been one of the most widely studied and rigorously tested chemical additives in food, including for its possible links with cancer. More than 100 studies have found no evidence of harm caused by aspartame.

— While doubts and concerns have continued to be raised by some critics and a few studies, there is a broad scientific consensus on the safety of aspartame for all groups of people except one — those suffering from phenylketonuria (PKU), a rare inherited disorder in which the patient does not have the enzyme that is needed to break down phenylalanine, one of the two amino acids in aspartame. Foods containing aspartame carry the warning “Not for phenylketonurics”.

— The USFDA permitted the use of aspartame in food in 1981, and has reviewed the science of its safety five times since then, The Washington Post report said. Aspartame is also certified as safe for human consumption by the European Food Safety Authority (EFSA), national regulators in Japan, Australia, New Zealand, and Australia, and even the WHO’s JECFA. Around 100 countries around the world, including India, permit the use of aspartame.

— The Reuters report noted that past IARC rulings have “raised concerns among consumers about their use, led to lawsuits, and pressured manufacturers to recreate recipes and swap to alternatives”. This, the report said, “has led to criticism that the IARC’s assessments can be confusing to the public.

Just FYI

Anonna Dutt Writes:

— While a World Health Organization’s (WHO) committee categorised artificial sweetener aspartame as “possibly carcinogenic to humans”, another committee simultaneously assessing the levels that can be safely consumed has said there is no need to reduce the previously established acceptable daily intake (ADI) for the sweetener.

— As per the second committee’s analysis, consuming a couple of aspartame tablets in coffee and tea is unlikely to be harmful. It is the hidden aspartame in products like diet soda and ice creams that health experts are really worried about.

*Impact Mission: These are an extension of Orbiter missions. While the main spacecraft keeps going around the Moon, one or more instruments on board make an uncontrolled landing on the lunar surface. They get destroyed after the impact, but still send some useful information about the Moon while on their way.

One of the instruments on Chandrayaan-1, called Moon Impact Probe, or MIP, was also made to crash land on the Moon’s surface in a similar way. ISRO claimed that the data sent by the MIP had presented additional evidence of the presence of water on the Moon, but these findings could not be published because of calibration errors.

*Landers: These missions involve the soft landing of the spacecraft on the Moon. These are more complicated than the Orbiter missions. In fact, the first 11 attempted lander missions had all ended in failure. The first landing on the moon was accomplished on January 31, 1966, by the Luna 9 spacecraft of the then USSR. It also relayed the first picture from the Moon’s surface.

*Rovers: These are an extension of the lander missions. The lander spacecraft, because they are bulky and have to stand on legs, remain stationary after landing. The instruments on board can carry out observations and collect data from close quarters but cannot come in contact with the Moon’s surface or move around. Rovers are designed to overcome this difficulty.

Rovers are special wheeled payloads on the lander that can detach themselves from the spacecraft and move around on the moon’s surface, collecting very useful information that instruments within the lander would not be able to obtain. The rover onboard Vikram lander in the Chandrayaan-2 mission was called Pragyaan.

*Human missions: These involve the landing of astronauts on the moon’s surface. So far only NASA of the United States has been able to land human beings on the moon. So far, six teams of two astronauts each have landed on the moon, all between 1969 and 1972. After that, no attempt has been made to land on the Moon. But with NASA’s Artemis III, currently planned for 2025, humanity is set to once again to the lunar surface in more than 50 years.

(Source: Chandrayaan-3: What are the different kinds of moon missions?)

4. MCQ:

With reference to moon missions, consider the following statements:

1. So far, six teams of two astronauts each have landed on the moon.

2. Some early examples of orbiters missions were Pioneer 3 and 4 by the United States and Luna 3 of the then USSR.

Which of the statement(s) is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

ANSWERS TO MCQs: 1 (a), 2 (c), 3 (c), 4 (a)