Ecology

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Ecology

• IB Biology
• January 2007

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What is a species and how many are there?

• A species is a group of organisms that resemble
  one another in appearance, behavior, chemistry,
  and genetic make-up
• The true test to determine if two individuals are
  members of the same species is to see whether or
  not viable (fertile) offspring can be produced
  under natural conditions
• We dont know how many exist on earth
• 1.5 to 1.8 million identified
• Estimates (save bacteria) are 3 to 100 million
• Most common are insects and plants

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Each species has a niche

• Niche role in the biological community
• Includes
• range of tolerance to abiotic factors
• Types and amounts of resources it uses
• Interactions with other species
• Habitat physical location address
• Generalist species (broad niche)
• Can live in variety of habitats, eat a variety of
  things, tolerate a wide array of conditions
• Flies, cockroaches, deer, raccoons, humans
• Specialist species (narrow niche)
• Can live in only one or a few habitats, narrow
  diet, tolerate a narrow range of conditions
• More vulnerable to extinction (giant panda)

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Range of Tolerance Concept
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World Vegetation
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World Biomes
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Basic Climate Pattern
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Biotic interactions between species

• Inter vs. Intraspecific competition (-,-)
• Interbetween species
• Intrawithin species
• Strategies to avoid competitionresource
  partitioning (eg warblers)
• Predation (,-)
• Why is predation important?
• Parasitism (,-)
• Parasite usually smaller, gradually weakens host
  over time, rarely kills its host (why?)
• Mutualism (symbiosis) (,)
• Commensalism (, no effect)
• Epiphytic plants (eg. Orchids)

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Resource Partitioning in Warblers
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Mutualism/Symbiosis
Coral Reef is another great example
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Commensalism
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Biotic factor Whats causing this pattern?
High
Paramecium aurelia
Relative population density
Paramecium caudatum
Low
0
2
4
6
8
10
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16
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Days
Both species grown together
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Biotic factor Whats causing this pattern?
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Abiotic factorWhats causing this pattern?
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Energy and Matter FlowFood Chains and Food Webs

• A sequence of organisms, each of which is a
  source of food for the next, is a food chain
• Food Webnetwork of interconnected food chains
• Trophic levelfeeding level
• e.g., producers1st trophic level and primary
  consumer 2nd trophic level

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Ecosystem Components
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Food Chains in Action
Why do food chains rarely have more than four
trophic levels?
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Example of a Food Web
Note Arrows Go In Direction Of Energy Flow
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Ecological Efficiency

• Each trophic level in a food chain or web
  contains a certain amount of biomass (the dry
  weight of all organic matter)
• In a food chain/web, chemical energy stored in
  biomass is transferred from one trophic level to
  the next
• The percentage of usable energy transferred as
  biomass from one trophic level to another is
  called ecological efficiency
• Ranges between 5-20 (i.e., 95 to 80 of energy
  is lost from one level to the next)
• The more trophic levels or steps in a food chain
  the greater the cumulative loss of usable energy

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Pyramid Of Energy Flow
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Top carnivores
Decomposers/detritivores
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Carnivores
5,060
383
Herbivores
3,368
Producers
20,810
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Why you should eat veggie
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Primary and Net Productivity

• The RATE at which producers convert solar energy
  into chemical energy as biomass is the
  ecosystems gross primary productivity (GPP)
• But producers also consume energy in order to
  stay alive (metabolism)
• GPP E consumed by producer NPP (net primary
  productivity)
• NPP is available for use as food by other
  organisms in an ecosystem
• Measured in grams carbon per meter squared per
  year (gC/m2/yr) or in kilocalories per meter
  squared per year (kcals/m2/yr)

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NPP of Ecosystems
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Primary SuccessionHow is each stage different?
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Secondary SuccessionHow is this both similar and
different from primary succession?
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Early Successional Species Rabbit Quail Ringneck
pheasant Dove Bobolink Pocket gopher
Midsuccessional Species Elk Moose Deer Ruffled
grouse Snowshoe hare Bluebird
Late Successional Species Turkey Martin Hammonds
Flycatcher Gray squirrel
Wilderness Species Grizzly bear Wolf Caribou Bigh
orn sheep California condor Great horned owl
Ecological succession