Organismal Interactions

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Organismal Interactions

• One way to learn how organism interact is to
  consider what happens if an organism goes extinct

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The Consequences of Extinction

• Impact on humans by extinction of non-human
  species
• The fossil record shows that it takes 5-10
  million years to replace biodiversity levels
  after a mass extinction

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The Consequences of Extinction

• Changes in biodiversity occur after a mass
  extinction
• Mass extinction of dinosaurs resulted in an
  increase of mammal species
• Consequences of the mass extinction that many
  biologists feel we are seeing today will have
  consequences for millions of years and thousands
  of generations to come

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Loss of Resources

• Extinctions result in the impoverishment of food
  source
• In addition plants with known (and potential)
  medicinal value to humans can be lost forever

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Loss of Resources
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Disruption of Ecological Communities

• Most endangered species wont affect survival of
  humans, but the effect on the biological
  community can be disastrous
• A biological community consists of all the
  organisms of different species living together in
  a particular area
• These organisms are connected by a food web the
  complex linkage among organisms within a community

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Disruption of Ecological Communities

• Biologists use the phrase web of life to
  describe food web interactions
• Analogous to a spiders web
• A disruption at one point is felt at other places
  in the web
• Some disruptions cause small damage, others
  larger damage
• Removal of strands can be devastating

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Mutualism

• Mutualism an interaction between two species
  that benefits each
• Mycorrhizae fungi improve plant roots mineral
  intake while consuming the plants sugars

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Mutualism How Bees Feed the World

• Bees are the primary pollinators of flowering
  plants
• Plant benefits by getting fertilized
• Bee benefits by getting pollen and nectar for food

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Mutualism How Bees Feed the World

• Wild bees pollinate at least 80 of all
  agricultural crops in the U.S.
• But bees have suffered dramatic declines in
  recent years, dramatically threatening humans in
  the process
• Threats to bees include parasites, competition
  from invading species, and habitat destruction

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Predation How Songbirds May Save Forests

• Predator a species that survives by eating
  another species
• Not all predators fit the common image of
  cheetahs, lions, and killer whales

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Predation How Songbirds May Save Forests

• Warblers collectively remove tons of
  tree-damaging insects from forest trees every
  summer
• Warbler populations are declining this will
  affect the growth rate of trees
• Warblers decline due to habitat destruction and
  increased attacks by human-associated predators
  (i.e. cats, raccoons)

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Predation How Songbirds May Save Forests
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Competition How a Deliberately Infected Chicken
Could Save a Life

• Competition two species of organisms both
  require the same resources in a habitat
• Competitive exclusion introduce a competitor to
  reduce numbers of specific species

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Competition How a Deliberately Infected Chicken
Could Save a Life

• Salmonella is caused by a bacterium that lives in
  eggs
• If the hens are infected with a harmless
  bacterium that is a competitor for the salmonella
  bacterium, maybe the amount of salmonella will
  decrease

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Keystone Species How Wolves Feed Bears

• As seen in a food web, most organisms have
  multiple connections
• Some single species indirectly affect more than
  one other species to the extent that if it is
  removed the community collapses (analogous to a
  keystone in an archway)
• Called keystone species

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Keystone Species How Wolves Feed Bears

• Once such keystone species is gray wolves in
  Yellowstone National Park
• Their extermination within the park by the
  mid-1920s and subsequent reintroduction in 2003
  both had profound effects on organisms as diverse
  as willow trees, elk, and beaver

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What about the bears.

• Willows were not the only plant grazed down by
  elk
• Bears feed on fruiting plants that were
  previously grazed by elk

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Changed Ecosystems

• Ecosystem all the organisms in a given area
  along with their non-biological environment
• Energy flows through an ecosystem
• Nutrients are recycled within an ecosystem

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Changed Ecosystems

• Energy flow
• Primary source of energy sun
• Through organisms
• Up trophic levels
• Nutrient cycling
• Nitrogen
• Carbon
• Other nutrients

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Changed Ecosystems

• The actions of decomposers (mostly bacteria and
  fungi) in the soil weigh heavily in the nutrient
  cycle
• Changes in soil communities can affect how well
  the nutrients are recycled
• Such changes have resulted from the introduction
  of nonnative earthworms to some ecosystems

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