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Life

What is life? Why is there life on Earth, but not on any other planets in the solar system (as far as we know…). Life on Earth occurs in a bewildering array of forms – plants, animals, fungi, protists, and bacteria, which together compose Earth’s biosphere. The biosphere is connected to the Earth System through biogeochemical cycles. Explore the links in this section to learn more about the stuff life is made of, genetics, the diversity of living things, how they coexist in ecosystems and evolve over time, and how life survives in extreme environments.

<a href="/earth/Life/autotrophs.html">Autotrophs</a> are organisms that can "make their own food" from an inorganic source of carbon (carbon dioxide) given a source of energy. Most autotrophs use sunlight in the process of <a href="/earth/Life/photosynthesis.html">photosynthesis</a> to make their own food. Alga (singular of algae) is an an autotroph because it is capable of photosynthesis.<p><small><em> Image courtesy of Corel Photography</em></small></p>

Why did the dinosaurs go <a href="/earth/past/KTextinction.html">extinct</a>? No one knows for sure, and scientists have come up with a number of theories to explain why the dinosaurs suddenly died out about <a href="/earth/past/geologic_time.html">65 million years ago</a>. It wasn't just the dinosaurs that went extinct--roughly two thirds of all of the plant and animal species on Earth disappeared, too!<p><small><em>Image courtesy of the National Science Foundation.</em></small></p>

<a href="/earth/Life/photosynthesis.html">Photosynthesis</a> is the name of the process by which <a href="/earth/Life/autotrophs.html">autotrophs</a> (self-feeders) convert <a href="/earth/Water/overview.html">water</a>, <a href="/physical_science/chemistry/carbon_dioxide.html">carbon dioxide</a>, and <a href="/sun/effect_on_earth.html">solar energy</a> into sugars and <a href="/physical_science/chemistry/oxygen_molecular.html">oxygen</a>. It is a complex chemical process by which <a href="/earth/Life/plantae.html">plants</a> and other autotrophs create the energy needed for life.<p><small><em>Image has been released into public domain (found on <a href="http://en.wikipedia.org">wikipedia.org</a>).</em></small></p>

Hydrothermal vents in the deep ocean are located at tectonic <a
href="/earth/interior/seafloor_spreading.html">spreading
ridges</a>. While most of the water in the deep ocean is close to freezing,
the water at hydrothermal vents is very hot and laden with chemicals. In
this <a
href="/earth/extreme_environments.html">extreme
environment</a>, certain species of <a
href="/earth/Life/archaea.html">Archaea</a>
and <a
href="/earth/Life/classification_eubacteria.html">Eubacteria</a>
thrive, enabling a unique <a
href="/earth/Water/life_deep.html">food
chain</a> including fish, shrimp, giant tubeworms, mussels, crabs, and clams.<p><small><em> Courtesy of NASA</em></small></p>

<a href="/earth/Life/plankton.html">Plankton</a> are a diverse set of <a href="/earth/Life/ocean_life.html">marine organisms</a>. They can live in salt and fresh water. Although some forms are able to move independently, most plankton drift with the <a href="/earth/Water/ocean_currents.html">water currents</a>. This photo shows an amphipod, a type of plankton, at high magnification.<p><small><em>Image courtesy of Uwe Kils. Creative Commons Attribution ShareAlike 3.0 License.</em></small></p>

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Explore Life

Earth's Biosphere

The biosphere is all life on our planet. This includes all the things that are living as well ...Read more

Cells: What Life Is Made Of

The Cell Theory states that all living things are made of cells, which are the basic units ...Read more

Genetics Makes Us Who We Are

Do you look a bit like your siblings? Do you and your siblings look a bit like your parents? ...Read more

Diversity and Classification of Living Things

Scientists have found and described approximately 1.75 million species on Earth according to ...Read more

Biomes and Ecosystems

Biomes are large regions of the world with similar plants, animals, and other living things ...Read more

Polar Life

All sorts of living things call Earth’s polar regions home – from tiny lichens encrusting the ...Read more

Postcards from the Field

Explore collections of Postcards from the Field, virtual postcards from scientists and educators ...Read more

The Evidence of Evolution Exploratour

This Windows to the Universe Exploratour examines the scientific evidence of biological evolution. ...Read more

Astrobiology

Take a guided tour to learn more about astrobiology, the search for life on other planets! ...Read more

News About Life

Read about current science, happenings and discoveries related to life on Earth! ...Read more

Life Image Archive

Access wonderful captioned photos and illustrations that will inspire and excite you. ...Read more

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Earth and Space Science Concept of the Day

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Riparian

xRiparian : The bank of a river or other body of water; may include the floodplains

Click on the word to find out!

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Oldest Earth Mantle Reservoir Discovered

Researchers have found a primitive Earth mantle reservoir on Baffin Island in the Canadian Arctic. Geologist Matthew Jackson and his colleagues from a multi-institution collaboration report the finding--the...Read more

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