Biodiversity refers to the variety of life on Earth, including all genes, species, and ecosystems. For billions of years, a complex web of life has evolved, with millions of species inhabiting different environments and interacting with each other. Biodiversity exists at multiple levels - genetic diversity within species, species diversity between organisms, and ecosystem diversity in biological communities interacting with their environments. Scientists estimate there are around 10 million existing species, though only a small fraction have been identified and cataloged so far. Efforts are underway to preserve samples of genetic material and biodiversity at all levels before more is lost to extinction.

1. BIODIVERSITY
Biodiversity is the extraordinary variety
of life on Earth — from genes and
species to ecosystems and the valuable
functions they perform. E.O. Wilson,
noted biologist and author who coined
the term “biodiversity,” explains it as
“the very stuff of life.”

2. For at least 3.8 billion years, a
complex web of life has been evolving
on Earth. Millions of species inhabit
land, freshwater, and ocean
ecosystems. All species, including
human beings, are intricately linked by
their interactions with each other and
the environments they live in.

3. “Biodiversity” (short for biological diversity) is
the variety of all living things and their interactions.
Biodiversity changes over time as extinction occurs
and new species evolve.
Scientists often speak of three levels of
diversity: species, genetic, and ecosystem diversity.
In fact, these levels cannot be separated. Each is
important, interacting with and influencing others.
Changes at one level can cause changes at other
levels.

4. SPECIES DIVERSITY
What Is a Species?
Species come in all shapes and sizes, from
organisms so small they can only be seen with powerful
microscopes to huge redwood trees. They include
bacteria, protozoa, fungi, flowering plants, ants,
butterflies, birds, fishes, and large animals such as
elephants, whales, and bears. Each species is a group of
organisms with unique characteristics. An individual of a
species can reproduce successfully, creating viable
offspring, only with another member of that species.

5. We are still learning about how many
species exist and how they relate to
each other and their environment.
Current estimates are of about 10 million
species on Earth, of which only about
1.9 million have been named and
catalogued. Scientists race to catalog
species before they go extinct.

6. When a new species is discovered, it is
given a name. Scientific naming follows
certain rules or conventions. A new species
is assigned to a genus based on its
relatedness to other organisms. Its unique
species name may be related to one
characteristic that makes the species
different from others, the place it was
found, or can have the name of a colleague.

7. What Is Genetic Diversity?
Biodiversity includes the genes that every
individual inherits from its parents and passes on
to the next generation. Genetic diversity is
everywhere, from the variety of songs and
feather colors of birds to the colors, tastes, and
textures of apples and other foods. Genetic
variation, which determines the extent to which
individuals can adapt to their environments, is
extremely important to their survival.

8. A genome is the complete set of genetic material
(i.e., DNA) of an organism. To preserve Earth’s genomic
diversity, scientists at the National Museum of Natural
History are collecting and freezing hundreds of thousands
of DNA samples. The collection will be used for the new
field of genomics, a discipline that sequences, assembles,
and analyzes the function and structure of genomes,
providing information into the future about plants,
animals, fungi, bacteria, and protists, even those that are
extinct. The Smithsonian's repository of DNA is just one
of many that together make up the Global Genome
Project that seeks to preserve genetic samples from
every species on Earth.

9. What Is Ecosystem Diversity?
Genes determine the traits of individuals that form
populations of a species. Individuals from different species
interact to form communities. These interact dynamically
with non-living environmental components, such as water
or minerals, to form an ecosystem. Some ecosystems such
as tropical forests and coral reefs are especially complex
and host a large number of species. Other ecosystems
such as deserts and Arctic regions have less complexity and
thus a lower number of species, but all those species are
ecologically important and some are endemic to that
ecosystem.