Chapter 4 Ecosystems and Living Organisms

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Chapter 4Ecosystems and Living Organisms
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Overview of Chapter 4

• Evolution
• Natural Selection
• Domains and Kingdoms
• Biological Communities
• Primary Secondary Succession
• Symbiosis
• Mutualism, Commensalism, Parasitism
• Predation Competition
• Resource Partitioning
• Keystone Species
• Species Richness Community Stability

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Evolution

• The cumulative genetic changes that occur in a
  population of organisms over time
• Current theories were proposed by Charles Darwin,
  a 19th century naturalist
• Evolution occurs through natural selection
• Natural Selection
• Individuals with more favorable genetic traits
  are more likely to survive and reproduce
• Frequency of favorable traits increase in
  subsequent generations

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Natural Selection

• Based on four observations about the natural
  world
• Overproduction
• Each species produces more offspring than will
  survive to maturity
• Variation
• Individuals in a population exhibit variation
• Limits on Population Growth
• Resource limitations will keep population in
  check
• Differential Reproductive Success
• Individuals with most favorable traits are more
  likely to reproduce

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Natural Selection

• Darwins finches exemplified the variation
  associated with natural selection

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Domains and Kingdoms of Life
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Biological Communities

• Communities vary greatly in size and lack precise
  boundaries
• They are often nestled within each other

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Succession

• The process where a community develops slowly
  through a series of species
• Earlier species alter the environment in some way
  to make it more habitable by other species
• As more species arrive, the earlier species are
  outcompeted and replaced
• Two types of succession
• Primary succession
• Secondary succession

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Primary Succession

• Succession that begins in a previously
  uninhabited environment
• No soil is present!
• Ex bare rocks, cooled lava fields, etc.
• General Succession Pattern
• Lichen secrete acids that crumble the rock (soil
  begins to form)

Lichen mosses grasses shrubs
forests
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• Primary Succession
• Bare rock with lichen
• Grasses and shrubs
• Forest community

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Secondary Succession

• Succession that begins in an environment
  following destruction of all or part of the
  earlier community
• Ex abandoned farmland, open area after fire
• Does NOT follow primary succession!
• Even though name may imply this
• Generally occurs more rapidly than primary
  succession

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Secondary Succession of an abandoned farm field
in North Carolina
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Interactions Among Organisms

• Symbiosis
• An intimate relationship between members of 2 or
  more species
• Participants may be benefited, harmed or
  unaffected by the relationship
• Results of coevolution is the interdependent
  evolution of two interacting species. Flowering
  plants and their animal pollinators have a
  symbiotic relationship that is an excellent
  example of coevolution.
• Three types of symbiosis
• Mutualism
• Commensalism
• Parasitism

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Mutualism

• Symbiotic relationship in which both members
  benefit
• Ex Mycorrihzal fungi and plant roots
• Fungus grows around and into roots providing
  roots with otherwise unavailable nitrogen from
  soil
• Roots provide fungi with food produced by
  photosynthesis in the plant

Left root growth without fungi Right root
growth with fungi
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Commensalism

• Symbiotic relationship where one species benefits
  and the other is neither harmed nor helped
• Ex epiphytes and tropical trees

• Epiphytes anchors itself to the tree, but does
  not take nutrients from the tree
• Epiphyte benefits from getting closer to
  sunlight, tropical tree is not affected

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Parasitism

• Symbiotic relationship in which one species is
  benefited and the other is harmed
• Parasites rarely kill their hosts

• Ex Varroa mites and honeybees
• Mites live in the breathing tubes of the bees,
  sucking their blood and weakening them

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Predation

• The consumption of one species by another
• Many predator-prey interactions
• Most common is pursuit and ambush
• Plants and animals have established specific
  defenses against predation through evolution

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Pursuit and Ambush

• Pursuing prey simply means chasing it down and
  catching it
• Ex Day gecko and spider (see picture)
• Ambush is when predators catch prey unaware
• Camouflage
• Attract prey with
• colors or light

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Plant Defenses Against Predation

• Plants cannot flee predators
• Adaptations
• Spikes, thorns, leathery leaves, thick wax
• Protective chemicals that are poisonous or
  unpalatable

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Animal Defenses Against Predation

• Fleeing or running
• Mechanical defenses
• Ex quills of porcupines, shell of turtles
• Living in groups
• Camouflage
• Chemical defenses-
• poisons
• Ex brightly colored poison
• arrow frog

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Competition

• Interaction among organisms that vie for the same
  resource in an ecosystem
• Intraspecific
• Competition between individuals in a population
• Interspecific
• Competition between individuals in 2 different
  species

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Ecological Niche

• The totality of an organisms adaptations, its use
  of resources, and the lifestyle to which it is
  fitted
• Takes into account all aspect of an organisms
  existence
• Physical, chemical, biological factors needed to
  survive
• Habitat
• Abiotic components of the environment
• Ex Light, temperature, moisture

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Ecological Niche

• Fundamental niche
• Potential idealized ecological niche
• Realized niche
• The actual niche the organism occupies
• Ex Green Anole and Brown Anole

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Ecological Niche

• Green Anole and Brown Anole
• Fundamental niches of 2 lizards initially
  overlapped
• Brown anole eventually out-competed the green
  anole- reduced the green anoles realized niche

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Limiting Resources

• Any environmental resource that, because it is
  scarce or at unfavorable levels, restricts the
  ecological niche of an organism

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Interspecific Competition
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Competitive Exclusion Resource Petitioning

• Competitive Exclusion
• One species excludes another from a portion of
  the same niche as a result of competition for
  resources
• Resource Partitioning
• Coexisting species niche differ from each other
  in some way

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Keystone Species

• A species that exerts profound influence on a
  community
• More important to the community than what would
  be expected based on abundance
• The dependence of other species on the keystone
  species is apparent when the keystone species is
  removed
• Protecting keystone species is a goal to
  conservation biologists

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Species Richness

• The number of species in a community
• Tropical rainforests high species richness
• Isolated island low species richness
• Related to the abundance of potential ecological
  niches

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Ecosystem Services

• Important environmental benefits that ecosystems
  provide, such as
• Clean air to breathe
• Clean water to drink
• Fertile soil in which to grow crops

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