Random Facts About Life

1. Life is broadly defined as the condition of an organism that exhibits growth through metabolism, reproduction, and adaptation to its environment. These characteristics separate living organisms from inanimate objects.ⁱ
2. The cell is the basic unit of life, and an organism must be composed of at least one cell to qualify as a living thing.ⁱ
3. The cells of every living organism contain deoxyribonucleic acid (DNA), a nucleic acid that holds the genetic instructions for the development and functioning of a life form. It is this substance that allows a living thing to grow and reproduce.ⁱ
4. DNA was first discovered in 1869 by Swiss physician Friedrich Miescher who noticed a microscopic substance in the pus on discarded bandages. The substance was later identified as DNA.ⁱ
5. A virus straddles the definition of life and, according to scientific definition, is not technically alive. It is composed simply of DNA and ribonucleic acid (RNA) strands surrounded by a protein shell and requires a host cell to metabolize and reproduce. When not within a host cell, a virus lies dormant and is nothing more than a static organic particle.ⁱ

Scientists estimate the Earth has existed for about 4.5 billions years

1. Scientists estimate the earth is about 4.5 billions years old and first began to support life forms approximately 3.7 billion years ago.^a
2. While scientists universally believe that naturally occurring amino acids were mediated by nucleic acids to create the first life forms on Earth, the question of how nucleic acids originated from inanimate matter is still being studied today. There is no definitive answer yet as to the origin of life on Earth.^g
3. Throughout history, two dominant theories of the origin of life on Earth have prevailed. Abiogenesis, a theory that is now widely discredited, holds that life was and is spontaneously generated from decaying organic matter. The theory of biogenesis, on the other hand, maintains that new life is produced from existing life forms.^g
4. The oldest living things on Earth are believed to be single-cell prokaryotes, more commonly known as bacteria. Scientists have discovered fossils of such prokaryotes from roughly 3.5 billion years ago.^a

The first plant life appeared 430 million years ago and consisted of algae-like growth

1. Plant life began on the Earth’s landforms about 430 millions years ago. The first plants were likely single-celled organisms distantly related to algae.^a
2. The first reptiles began life 300 million years ago, and modern mammals appeared roughly 75 millions years ago.^a
3. Apes originated on Earth about 35 million years ago, and the first apelike men appeared about 10 million years ago. The modern human species of Homo sapien has existed on the earth for only 100,000 years.^a
4. Scientists believe that Earth will exist for another 7.5 billion years before the sun becomes a red giant star and, in all probability, destroys the planet. Earth may cease to support life forms far before that date, however, due to increased energy output from the sun over time.^a
5. Living organisms are divided into two basic domains: prokaryotes and eukaryotes. Eukaryotes, to which humans belong, have a cellular structure with a nucleus and membrane-bound genetic information, while the cells of prokaryotes do not contain a nucleus.ⁱ
6. Today, all identified living organisms are scientifically named and categorized according to Swedish scientist Carl Linnaeus’s taxonomy. In his 1758 publication, Systema Naturae, Linnaeus divided and classified different living organisms with a ranking scale: kingdom, phylum, class, order, family, genus, and species.ⁱ
7. Scientists estimate that anywhere from five million to 100 million unique species of plants and animals currently live on Earth. However, only about two million of these species have been identified.ⁱ
8. Insect species account for 950,000 of the two million identified species on Earth.ⁱ
9. There are nearly 300,000 different species of plants currently living on Earth.ⁱ
10. Mammals make up just 5,416 of the two million identified species on Earth.ⁱ
11. The theory of evolution, which explains how living things change over time through natural selection, was first publicized by Charles Darwin in 1859. Many scientists now point to this natural phenomenon as the reason behind Earth’s great biodiversity.ⁱ
12. Worldwide, there are currently just over 6.7 billion people living in the world. The population of males is slightly higher than females (3.41 billion compared to 3.37 billion).ⁱ
13. According to the Central Intelligence Agency, average life expectancy for a person in the U.S. is 78.11 years.^e

Average life expectancy in the U.S. increased by 30 years during the twentieth century, primarily due to advances in public health care

1. During the twentieth century alone, the average life expectancy in the United States increased by more than 30 years. Officials attribute most of this increase to advances in public health care and information.ⁱ
2. According to a 2008 report, the average life expectancy in the world as a whole is 66.26 years.^f
3. The average life expectancy ranges throughout the world from a high of 84.36 years in Macau to just 31.88 years in the African nation of Swaziland. Experts attribute the low life expectancy in many African countries to high rates of HIV/AIDS infection.^{c, d}
4. The oldest documented person on record is Jeanne Calment, a Frenchwoman who lived for 122 years and 164 days. The oldest person still alive today is 114-year-old Gertrude Baines of the U.S.^b
5. The greatest verified age for any living organism is from a Great Basin Bristlecone Pine tree in Nevada called Prometheus that was measured by a ring count to be about 4,900 years old when it was cut down in 1964.^h
6. Scientists have yet to discover a sign of extraterrestrial life, but the discovery of planets outside of our solar system with habitable climates is a promising indication of life outside Earth.^a

References

^a Babcock, Loren E. 2008. Earth History. Hoboken, NJ: John Wiley & Sons, Inc.

^b Bermudez, Esmeralda. “Gertrude Baines May Be 114, but She’s Not Counting.” Los Angeles Times. January 11, 2009: A37.

^c Central Intelligence Agency. “The World Factbook – Macau.” Accessed: March 24, 2009.

^d Central Intelligence Agency. “The World Factbook – Swaziland.”  Accessed: March 24, 2009.

^e Central Intelligence Agency. “The World Factbook – United States.” Accessed: March 24, 2009.

^f Central Intelligence Agency. “The World Factbook – World.” Accessed: March 24, 2009.

^g Lahav, Noam. 1999. Biogenesis: Theories of Life’s Origin. New York, NY: Oxford University Press.

^h National Park Service. “Bristlecone Pines.” Accessed: March 26, 2009.

ⁱ Raven, Peter H., George B. Johnson, Kenneth A. Mason, Jonathan Losos, and Susan Singer. 2008. Biology. Boston, MA: McGraw-Hill Higher Education.

Related articles

• Scientists prove once and for all that there’s life on Earth [Astronomy] (io9.com)
• An Earlier Genetic Molecule May Predate DNA And RNA (medicalnewstoday.com)
• Simpler times: Did an earlier genetic molecule predate DNA and RNA? (eurekalert.org)

Places on Earth Aliens Could Thrive?

Shark Bay, Australia

For about 85 percent of the history of life on Earth, only microbes existed. The only large-scale evidence of their activities is preserved by stromatolites, ancient structural records of life on Earth that hold evidence both of the biology of the microbial mat communities that created them and the nature of the environments in which they grew. They are rocky, dome-shaped structures formed in shallow water through the trapping of sedimentary grains by communities of microorganisms.

Yellowstone National Park

What is causing the beautiful colors in this hot spring in Yellowstone National Park? Life, that’s what! Many microorganisms live in the pools there, and because the temperatures of the springs are so hot (most are well over 100 degrees F, or 37.7 degrees C), they are called extremophiles (extreme-loving). They contain molecules that absorb the damaging rays of the sun, protecting their DNA. Those same molecules are also pigments that cause the different colors we see. Different extremophiles thrive in different temperatures, so the color of a particular area is determined by which organisms are living in it. A veritable rainbow appears as the water temperature decreases as it flows further and further away from its superheated source.

Mono Lake, California

Calcium carbonate formations called tufa give California’s Mono Lake an otherworldly feel. Mountains surround the lake, forming a closed hydrological basin—water flows in, but it doesn’t flow out. Because the only way for water to leave Mono Lake is through evaporation, it is naturally hypersaline—roughly two to three times saltier than the ocean. Freshwater streams and underwater springs have brought trace amounts of minerals into the lake over the eons, including arsenic. Recently, bacteria which appear to incorporate arsenic rather than phosphorus into their basic biological molecules were found living in Mono Lake

High Lakes, South America

The highest volcanic lakes in the world are located in the Andes Mountains of South America. Their elevation and isolation make them some of the least understood lakes on Earth and excellent analogs for lakes that existed on Mars 3.5 billion years ago. Simba Lake, at an elevation of 19,265 feet (5,872 meters) in the Chilean Andes, is red because of algae that developed pigments to protect themselves against high UV radiation. They float in the water near the surface, not deep enough to use the water column as a natural protection.

Pilbara, Western Australia

Created in a shallow pool on early Earth more than three billion years ago, these stromatolites represent a record of the most ancient life on Earth. They formed because colonies of microbes, as they grew, incorporated sediments from the water to create rocky structures. Found in Western Australia, the stromatolites take several different forms, including the slightly cone-shaped ones seen here resembling an egg carton. The structures shown in this picture are each about half an inch (1.2 centimeters) high.

Rio Tinto, Spain

Cloudy with particulates and flowing along terraces made of iron oxides, the Rio Tinto in southwestern Spain stretches for more than 62 miles (100 kilometers) before reaching the Atlantic. Despite its acidic waters and high concentrations of iron and other heavy metals, the river supports an incredible diversity of extremophile microorganisms, including algae and fungi. Microbial biofilms colonize the riverbed and are covered with yellow iron oxide precipitates, seen here. Because of geological similarities with Mars, the Mars Astrobiology Research and Technology Experiment (MARTE) team tested equipment at Rio Tinto in 2005 for drilling on Mars in search of subsurface life.Svalbard, Norway

Svalbard is a remote archipelago in northern Norway, deep within the Arctic Circle. Scientists with the Arctic Mars Analog Svalbard Expedition (AMASE) traveled there to test the protocols, procedures, and equipment needed to detect traces of organic chemistry and perhaps life on Mars. Instruments that will fly onboard NASA’s Mars Science Laboratory and ESA’s ExoMars missions were tested in Svalbard by the AMASE team. With a unique combination of volcanoes, hot springs, and permafrost, the Bockfjord Volcanic Complex on Svalbard is the only place on Earth with carbonate deposits identical to those found in the famous Martian meteorite ALH84001 (aka Allan Hills).

Flinders Range, South Australia

Piece of upturned sandstone in the Flinders Range of South Australia shows ripple marks of an ancient sea bed. This area of Australia hosts fossils of the first complex, multicellular organisms, which began to emerge on Earth about 600 million years ago. The study of these early fossils, known as the Ediacaran Fauna.

Ellesmere Island, Canada

Borup Fiord Pass Glacier on Ellesmere Island in Nunavut is a site in the Canadian High Arctic where astrobiologists study the potential for life on Jupiter‘s moon Europa. Water rich in sulfur-containing compounds flows from the top of this 656-foot-thick (200-meter-thick) glacier, a chemical mix that is capable of supporting microbial life. Europa’s icy surface is similarly stained with sulfate salts.