By Samuel Viler
Mammoths fascinate scientists to the extent that they are attempting to revitalize a type of the extinct species. Scientists theorize that the mammoths evolved in Africa about seven million years ago. In time, they migrated to China and Siberia and eventually produced the woolly mammoth—an animal about the size of a modern African elephant but covered in thick, brown hair and bearing enormous tusks. They then migrated to North America by crossing a land bridge from Siberia. North American mastodons (smaller than their African cousins) were then joined by the woolly mammoths.
The last of the woolly mammoths (an isolated population of dwarf mammoths) appear to have died about 4,000 years ago on Wrangel Island, off the coast of Siberia. A number of factors could have exterminated the woolly mammoths: overhunting by humans, bone disease, and a changing climate that quickly eradicated the cool, arid grasslands preferred by the creatures.
Ironically, the present climate change may enable scientists to de-extinct the woolly mammoth; warmer temperatures are melting layers of ancient ice and uncovering well-preserved woolly mammoth carcasses. In one de-extinction effort, researchers from North-Eastern Federal University in Siberia recovered frozen tissue of woolly mammoths and sent the tissues to researchers at the Sooam Biotech Research Foundation in South Korea for analysis. The tissue may be used to clone a woolly mammoth by removing the nucleus from a frozen cell. Then, scientists would remove the nucleus from an elephant egg cell and insert the woolly mammoth nucleus. The hybrid elephant cell with a woolly mammoth nucleus would be treated to stimulate the cell to divide and form an early embryo. The embryo would be placed in the uterus of an elephant, and with any luck, this surrogate mother would give birth to a baby woolly mammoth.
Scientists proclaim many reasons as justification for a woolly mammoth revival. Some say that it is simply the right thing to do because humans helped to destroy the species. Others offer the practical excuse that useful, intact DNA of the extinct animal may be enshrouded within frozen tissue. Yet, others simply admit that they are fond of woolly mammoths. Another seemingly bizarre justification is that woolly mammoths could possibly help halt the greenhouse effect that is warming the planet. This notion is based on current changes in the arctic tundra.
The arctic tundra is sometimes referred to as a frozen desert. Lacking trees and other large plants, it has six- to 10-month-long winters with an average temperature of -30°F and possible lows around -60°F. A significant feature of the arctic tundra is permafrost (a frozen layer of ground that extends about 1,500 feet below the surface). In summer, the top layer of soil thaws and forms bogs. Global warming is causing more of the permafrost to melt and then to freeze later than usual in the fall. Within melted permafrost, bacteria decompose dead plants, releasing the greenhouse gases carbon dioxide and methane. These gases trap heat in the atmosphere and warm the planet. Some scientists estimate that melting permafrost releases an amount of greenhouse gas that is more than two times the amount that would be released by burning the world’s forests.
Repopulating the tundra with woolly mammoths could actually restore grasslands, which insulate the permafrost. As the animals wander over the land, they would fertilize the grass, as well as compress snow, and that would further insulate the permafrost. The grass would also remove carbon dioxide from the atmosphere through photosynthesis, the process by which plants use carbon dioxide to produce sugars and oxygen.
2. According to Passage 2, how would cloning mammoths help lower the greenhouse effect?
AThe mammoths would thaw more soil.
BThe mammoths would form more bogs.
CThe mammoths would melt the permafrost.
DThe mammoths would restore the grasslands.
1 answer
D. The mammoths would restore the grasslands.
According to Passage 2, repopulating the tundra with woolly mammoths could help restore grasslands, which in turn would insulate the permafrost. The grass would also absorb carbon dioxide from the atmosphere, contributing to a reduction in greenhouse gases.
