Transcript Natural Causes of Extinction

 Extinction occurs when the last existing member of a
given species dies
 In other words…there aren’t any more left!
 Genetics and Demographics
 Small populations = increased risk
 Mutations
 Causes a flux in natural selection
 Beneficial genetic traits are overruled
 Loss of Genetic Diversity
 Shallow gene pools promote massive inbreeding
 Habitat Degradation
 One of the most influential
 Has many causes
 Some due to humans
 Some due to other factors
 Toxicity
 Kills off species directly through food/water
 Indirectly via sterilization
 Can occur in short spans (a single generation)
 Can occur over several generations
 Increasing toxicity
 Increasing competition for habitat resources
 Destruction of Habitat
 “Save the Rainforests!”
 Elimination of living space
 Change in habitat
 Rainforest to pasture lands
 Leads to diminishing resources
 Increases competition
 Can be caused by natural processes
 Volcanoes, floods, drought, etc…
 Predation
 Competition
 Disease
 Coextinction
 Mass Extinction
 Planned Extinction
 Introduction of predators
 Invasive alien species
 Transported by humans
 Cattle, rats, zebra muscles, etc…
 Sometimes on purpose, sometimes not
 Can eat other species
 Eat food sources
 Introduce diseases
 The loss of one species leads to the loss of another
 Chain of extinction
 Can be caused by small impacts in the beginning
 A predator looses its food source
 Affected by interconnectedness in nature
 Aka: an extinction event
 A sharp decrease in the number of species on Earth in
a short period of time
 Coincides with a sharp drop in speciation
 The process by which new biological species arise
 There have been at least 5
 Last one was 65M years ago
 Nearly 2/3rds (or more) of all animal species that ever
existed on the planet are now gone.
 With contemporary extinction being attributed to HUMAN
activity.
 Numerous factors go into the extinction of a specific
species.
 Though all point the finger to climate change.
 Began about three-million years ago (Continental
Glaciations).
 Hypotheses for initial extinction:
 Sea level depletion vs. Temperature decrease
 Though these hypotheses aren’t mutually exclusive,
they may have conspired together.
1.
2.
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5.
Cretaceous-Tertiary Extinction (65).
End Triassic Extinction (200).
Permian Triassic Extinction (250).
Late Devonian Extinction (364).
Ordovician-Silurian Extinction (440).
(#= millions of years ago)
 Human controlled
 Thought of to help humans
 Deadly viruses
 Smallpox
 Extinct in the wild
 Polio
 Near extinct (only in small parts of the world)

www.johnstonsarchive.net/spaceart/cylmaps.html
 Causes complete devastation
 Flattening and crater at
or around impact site-hundreds of
miles wide
 Reverberations felt around the world

www.iit.edu/~ipro313s/home.html
 Kills acid intolerant
species
 Can wipe out entire species
 Frog with fungus disease
 Killing frogs and other
amphibians
Natural factors usually occur at a slower
rate and therefore cause a low extinction
rate. Human activities occur at a faster
rate and cause higher extinction rates.
Human activities are mostly responsible
for the present extinction rates.
http://www.gov.mb.ca/conservation/sustain/extinct.pdf
Human Causes of
Extinction
Top Human Causes of
Extinction:
Increased human population
Destruction/Fragmentation of
habitat
Pollution
Climate change/Global warming
Based on these, and other
studies done by The
international Union for
Conservation of Nature
and Natural Resources
(IUCN), human induced
extinctions are not
necessarily a new
phenomena. However,
extinction by humans today
is becoming much more
rapid.
The rapid loss of species today is estimated by some
experts to be between 100 and 1,000 times higher than
the natural extinction rate, while others estimate rates as
high as 1,000-11,000 times higher.
Habitat Degradation
Habitat loss and degradation affect 86%
of all threatened birds, 86% of mammals and
88% of threatened amphibians
 Biodiversity is the variation of taxonomic life forms
for a given biome or ecosystem
 Boosts Ecosystem productivity
 Measure of the health of a biological system
 Food and drink
 Medicines
 Industrial materials
 Ecological services
 Leisurely, cultural, and
 aesthetic values
 Pollution
 Loss of tropical forest
 Spread of urban areas
 Warfare
 Large dam construction
 Road building
 Tourism
 Loss of traditional
lifestyles
 Loss of food
 Decrease in biomass
 Collapse of food web
 Loss of keystone species
 Reduction of ecosystem
efficiency and community
productivity
 Loss of medicinal supplies
 Increased vulnerability of
species to disease and
predation
Monoculture of crops lets the yield become susceptible
to pests or viruses
75% of crop varieties are extinct
Due to the spread of modern agriculture
 Cover 13% of Earth
 Home to 50% of all known plant and animal
species
 FAO reports 15.4 million hectares are destroyed
annually