Local extinction: a species is no longer found in a portion of
Ecological extinction: so few members of a population are
left that it can no longer serve its purpose in the ecosystem
Biological extinction: a species is no longer found anywhere
• Endangered: a species in danger of becoming
extinct over all or most of its natural range
• Threatened: a species in danger of becoming
endangered in the near future
• Rare: species that are limited in their
Population genetics and demographic phenomena affect the evolution,
and therefore the risk of extinction, of species. Limited geographic range
is the most important determinant of genus extinction at background
rates but becomes increasingly irrelevant as mass extinction arises.
Effects that cause or reward a loss in genetic diversity can increase the chances
of extinction of a species.
Genetic pollution is undesirable and uncontrolled gene flow into
Genetic pollution, genetic contamination or genetic swamping happens
when original set of naturally evolved (wild) region specific genes /gene
pool of wild animals and plants
become hybridized with domesticated and feral varieties or with the genes of
other nonnative wild species or subspecies from neighboring or far away regions.
Habitat degradation is currently the main anthropogenic cause
of species extinctions.
The main cause of habitat degradation worldwide is
agriculture, with urban sprawl, logging, mining and some fishing
practices close behind.
The degradation of a species' habitat may alter the fitness
landscape to such an extent that the species is no longer able to
survive and becomes extinct.
Introduction of new competitor species are also a factor in
extinction and often accompany habitat degradation, as
Sometimes these new competitors are predators and
directly affect prey species, while at other times they may
merely out-compete vulnerable species for limited
Coextinction refers to the
loss of a species due to the
extinction of another; for
example, the extinction
of parasitic insects following
Our climate is changing, both naturally and due to human exploitation. There is
already undeniable evidence that animals, birds and plants are being affected by climate
change and global warming in both their distribution and behavior.
Unless greenhouse gas emissions are severely reduced, climate change could cause a
quarter of land animals, birdlife and plants to become extinct.
• Probably 500 million species have existed over time
• “Background” rate of extinction: Amount of species that went
extinct before humans became the dominant species on earth
• With the advent of agriculture species extinctions have increased
– 8000 b.c. to a.d. 1600, one species went extinct every thousand years
– In 1985 1000 species went extinct every year
– In 2000, between 20,000 and 50,000 species are considered doomed to
extinction every year
• Extinctions will lead to ecological disaster is
e.g.: Fossil evidence shows that mass
extinctions have occurred many times
throughout the history of life.
• By the principle of “survival of the fittest”.
Life forms that cannot keep up with the rapid
changing world will always risk extinction, unless
they adapt to the new challenges.
• Economic or Medical uses
• Scientific and Ecological reasons
• Aesthetics and Recreation
• Ethical reasons
• Extinction is forever
• The future of our natural environment is becoming
uncertain as wildlife and wildlife habitats
• Every species in our world plays a unique role in
earth's intricate ecosystems.
• Plants, animals and humans live together on the
same land and water, and they are interdependent
on each other for survival in the way that we do not
• Federal Endangered Species Act
• California Endangered Species Act
• California Environmental Quality Act
• California Department of Fish and Game Code