IELTS Academic Reading Practice Test 13

A The idea of producing meat without animals — by cultivating animal muscle cells directly in nutrient-rich liquid — moved from speculation to a fledgling commercial industry over the 2010s. The first publicly demonstrated lab-grown hamburger, presented in 2013 by Dutch scientist Mark Post, is widely said to have cost approximately $330,000 to produce and required two years of preparation. A decade later, multiple companies were producing similar products at costs measured in tens of dollars per kilogram, with the first commercial sales authorised by regulators in Singapore in 2020 and the United States in 2023. The trajectory has, in many analysts' view, resembled the early development paths of other emerging biotechnology industries, in which an initial dramatic demonstration is followed by years of incremental cost reduction.

B The motivation for cultivated meat is, in proponents' view, both environmental and ethical. Conventional livestock production accounts for approximately 14.5 percent of global greenhouse gas emissions, requires vast amounts of land and water, and supports a system in which over 70 billion animals are slaughtered for food each year. Even modest replacement of conventional meat with cultivated products could, according to industry advocates, substantially reduce emissions and land use, and would eliminate the animal-welfare concerns associated with industrial farming. The challenge has always been whether the technology can produce these benefits at competitive cost and scale.

C The biological process begins with a small sample of animal cells, generally taken by biopsy from a living animal. These cells are placed in a bioreactor containing a liquid medium that supplies nutrients, salts, growth factors, and oxygen. Under suitable conditions, the cells reportedly divide repeatedly, producing many billions of cells over several weeks. Specialised cell types are then differentiated — muscle, fat, and connective tissue — and assembled into structured tissue that approximates the texture and flavour of conventional meat. Producing minced products such as burgers and nuggets is widely considered technically straightforward; producing whole-cut products with the structure of a steak remains substantially harder. The structural problem is, in many tissue engineers' view, broadly the central technical obstacle separating cultivated meat from full substitutability with its conventional equivalent.

D The economic obstacles are widely regarded as substantial. The growth media used at laboratory scale have included fetal bovine serum — itself an animal-derived product whose cost can exceed $300 per litre — and engineered alternatives, which currently remain expensive although prices are said to be falling. Bioreactors at the scale required for commercial meat production must be much larger than those used in the pharmaceutical industry, with engineering challenges that, according to industry analysts, have not previously been solved at this size. Energy consumption is widely understood to be significant, and the carbon footprint of cultivated meat depends heavily on the source of electricity used.

E Regulatory pathways have varied widely between jurisdictions. Singapore's 2020 authorisation of GOOD Meat's cultivated chicken set an important precedent. The United States Food and Drug Administration and Department of Agriculture jointly approved Upside Foods and GOOD Meat in 2023 for limited commercial production. The European Union's regulatory framework, requiring pre-market safety assessment by the European Food Safety Authority, has progressed more slowly, with no commercial product yet approved. Israel and Australia have established pathways and are reviewing applications. The contrast between jurisdictions has been cited by industry observers as a partial determinant of where the first commercial production volumes are likely to develop.

F Consumer acceptance remains, in many analysts' view, uncertain. Survey data reportedly show varying willingness to try cultivated meat, with substantial influence from how the product is described — terms such as cultivated, cultured, lab-grown, and synthetic appear to produce different reactions. Conventional meat industry groups in several countries have lobbied for legal restrictions on using the word meat for cultivated products, with mixed legislative success. Whether cultivated meat will ultimately occupy a substantial share of global protein consumption or remain a premium niche is widely described as genuinely contested within the industry. The terminology debate is, in many writers' view, broadly a proxy for a deeper question about whether cultivated meat is to be marketed as an alternative form of the same food or as a new category in its own right.

A The photovoltaic effect — the direct conversion of sunlight into electricity — was first observed by the French physicist Edmond Becquerel in 1839, when he was only nineteen years old. Becquerel is said to have found that certain materials immersed in conductive solution produced a measurable current when exposed to light. The discovery attracted little practical attention at the time, partly because no convenient explanation was available within the physics of the era. The theoretical basis would not be available, according to most historians of science, until Einstein's 1905 paper on the photoelectric effect, which earned him the 1921 Nobel Prize in Physics. The gap of more than half a century between observation and theoretical explanation has been cited as a textbook case of how scientific progress can stall in the absence of an adequate framework for interpretation.

B The first practical solar cell was developed at Bell Laboratories in New Jersey in 1954, using crystalline silicon doped with traces of boron and phosphorus. The Bell Labs cell, with an efficiency of around 6 percent, is widely regarded as a watershed moment but its early applications were extremely limited by cost — approximately $250 per watt in 1956, equivalent to roughly $3,000 per watt today. Photovoltaic technology became practical, in researchers' view, only because of an unusual market: powering satellites in orbit, where alternative power sources were unavailable at almost any cost. The Vanguard 1 satellite, launched in 1958, is widely cited as the first to use solar cells in space, and the technology became standard for spacecraft within a decade.

C A second wave of investment in photovoltaics followed the oil crises of the 1970s. The United States government, alarmed by oil-supply disruptions, funded substantial research into terrestrial solar applications through the Department of Energy and the new National Renewable Energy Laboratory. Cell efficiencies improved steadily through the 1980s, and the first multi-kilowatt installations began appearing on remote off-grid sites — telecommunications repeaters, navigation buoys, remote homes. Costs continued to fall but remained well above grid electricity prices, and the industry was widely said to depend on niche markets and subsidy programmes for survival. The dependence on subsidy has been described by historians of energy as the defining feature of the second wave, marking the technology as commercially marginal even as its underlying performance improved.

D The fundamental transformation came, according to most industry analysts, in the 2000s. German feed-in tariffs introduced in 2000, generously paying solar electricity producers above-market rates for grid-connected generation, created a substantial guaranteed market. Chinese manufacturers, scaling crystalline silicon production aggressively, drove costs down faster than industry analysts had predicted possible. By 2010, the cost per watt of solar panels had fallen below $1, and by 2020, it was below 25 cents — amounting to a hundredfold reduction in real terms over five decades.

E Modern solar cells generally fall into several technology families. Crystalline silicon, in mono- and polycrystalline variants, accounts for over 90 percent of global production. Thin-film cells using cadmium telluride or copper indium gallium selenide typically capture most of the remainder. Perovskite cells, discovered in 2009 and improving rapidly, have demonstrated laboratory efficiencies above 25 percent but face challenges in long-term stability that have so far prevented commercial deployment. Tandem cells, stacking different materials to capture different parts of the solar spectrum, are widely said to promise efficiencies above 30 percent and are emerging in advanced commercial product lines. The diversity of cell families reflects different trade-offs among manufacturing cost, conversion efficiency, and durability.

F Solar's role in global electricity generation has, in the view of many energy analysts, grown dramatically. Global installed photovoltaic capacity passed one terawatt in 2022 — a milestone that, according to industry insiders, would have been considered fanciful only fifteen years earlier. In several markets, including parts of Australia, Spain, India, and the southwestern United States, solar electricity is now generally said to be the lowest-cost source of new generating capacity. The remaining engineering challenge is widely described as integration: matching variable solar output to continuous electricity demand through storage, transmission upgrades, and demand-response systems.

A The discovery of hydrothermal vents in the deep ocean in 1977 is widely regarded as one of the great unexpected findings of twentieth-century biology. A team of geologists aboard the submersible Alvin, surveying the Galapagos Rift in the Pacific, encountered plumes of hot mineral-rich water issuing from cracks in the sea floor at depths approaching 2,500 metres. Around the plumes, in conditions previously considered uninhabitable — total darkness, temperatures exceeding 350 degrees Celsius at the vent openings, immense pressure — they found a dense, complex community of life unlike anything previously recorded. The discovery has been described by oceanographers as a foundational moment for the modern view that life on Earth occupies a far wider envelope of physical conditions than the visible biosphere alone suggests.

B The basis of life at the vents is, in biologists' view, fundamentally different from that supporting most other ecosystems on Earth. Conventional food chains typically begin with photosynthesis: plants and algae use sunlight to fix carbon dioxide into the sugars that fuel all later life. The vent ecosystem instead depends on chemosynthesis: specialised bacteria are reported to use chemical energy from hydrogen sulphide and other reduced compounds emerging from the vents to fix carbon. These bacteria support a food chain that includes giant tube worms, vent crabs, eyeless shrimp, mussels, and various endemic fish species — none of which depend, directly or indirectly, on sunlight.

C The tube worm Riftia pachyptila, sometimes reaching two metres in length, has become the iconic vent organism. Tube worms typically have no mouth and no digestive system in adulthood. Instead, they generally host enormous populations of chemosynthetic bacteria in a specialised organ called the trophosome, which can constitute more than half the worm's body mass. The worm extracts hydrogen sulphide, oxygen, and carbon dioxide from the surrounding water through its red plume — coloured by haemoglobin uniquely adapted to bind sulphide as well as oxygen — and supplies these to its bacterial symbionts, which in return produce the organic compounds the worm needs to survive. The Riftia-bacteria partnership is considered one of the most extreme examples of obligate symbiosis in the animal kingdom.

D Hydrothermal vents are widely said to have profound implications for understanding the origin of life. The water emerging from vents contains exactly the mix of dissolved minerals — hydrogen, carbon dioxide, iron, sulphur compounds — required for the proposed early biochemical reactions of life. The presence of catalytic mineral surfaces and steep chemical gradients at vents provides what researchers describe as plausible conditions for the spontaneous emergence of metabolism, and several researchers have argued that life may have originated in such environments around four billion years ago. The hypothesis is widely considered contested but has, in many biologists' view, gained substantial support over the past two decades.

E The discovery of hydrothermal vents has also transformed astrobiology — the study of the possibility of life beyond Earth. If life can flourish in total darkness using chemosynthesis, the requirement for sunlight as a precondition for life is, in many astrobiologists' view, removed. The icy moons of Jupiter and Saturn — Europa, Enceladus, and others — are now considered serious candidates for harbouring microbial life precisely because evidence suggests they possess subsurface liquid oceans in contact with rocky cores capable of producing chemical energy analogous to terrestrial vents. The Cassini spacecraft's flybys of Enceladus between 2005 and 2017 detected molecular hydrogen in the plumes the moon ejects, consistent with active hydrothermal activity.

F Vents are also regarded as being of considerable economic interest. The chimney-like sulphide structures that build up around vents — sometimes reaching 30 metres in height before they collapse — reportedly concentrate metals including copper, zinc, lead, silver, and gold. Several mining companies have proposed extracting these massive sulphide deposits, with the first commercial trial planned in the territorial waters of Papua New Guinea before being cancelled in 2019 amid environmental concerns. The International Seabed Authority is in the process of developing regulations for deep-sea mining in international waters, with the resulting rules widely said to likely determine whether commercial-scale extraction proceeds.

G The biological communities at vents face, according to conservation scientists, their own threats. Individual vent sites are often short-lived — many endure only for years or decades before geological changes shut them down — and species must repeatedly colonise new sites to persist. Proposed deep-sea mining could destroy specific communities outright, with effects on the wider distribution of vent species regarded as poorly understood. Several international conservation organisations have argued for permanent protection of representative vent sites, but the question of how to protect ecosystems most of humanity has never seen, in waters beyond any national jurisdiction, remains widely described as genuinely unresolved.