Ecosystem Components

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Ecosystem Components
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Autotrophs

• autotrophs (eg, plants) are of primary importance
  to ecosystems, as they are the foundation of all
  feeding chains
• photosynthesis harnesses energy from light to
  produce carbohydrates

Carbondioxide
Water
Glucose
Oxygengas
PHOTOSYNTHESIS
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Heterotrophs

• heterotrophs (eg, animals) ingest chemical energy
  (foods) as a power source
• this energy is derived from compounds of carbon,
  hydrogen, and oxygen previous synthesized by
  other organisms
• energy is then released through combination with
  oxygen (oxidation)
• basic food sources include carbohydrates, lipids,
  and proteins

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Ecosystem Controls

• for aquatic organisms, temperature, salinity, and
  depth are important controls
• on land the most important controls are
  temperature and precipitation
• temperature increases chemical reaction rates
  permitting high productivity in tropics
• most organisms cannot beyond the range of 0-50
  C but adaptations have evolved to withstand
  extreme temperatures

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Temperature and Precipitation
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Primary Productivity

• synthesis and storage of chemical energy by
  plants is known as primary production
• ecosystem productivity varies greatly
• highest primary productivity rates occur in rain
  forests, and coral reefs, and sea meadows
• measurements of productivity rates include
• grams of carbon per unit area
• vegetation index, given as a number between 0 and
  5

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Net Primary Productivity
Figure 16.5
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Habitat and Niche

• habitat physical location in which an organism
  is found (eg, pond for fish)
• niche functional role played by organism (how it
  obtains energy, influences other species, etc.)
• several species may share the same habitat, but
  few will share exactly the same niche since
  evolution will tend to favor one and weed out the
  others

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Population Distribution

• density number of individuals (or total biomass)
  per unit area, in turn limited by availability of
  energy and nutrient matter
• distribution pattern how individuals are grouped
  across the habitat, may be uniform (as in an
  orchard), clumped (most common pattern in
  nature), or random

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• Clumped dispersion is a pattern in which
  individuals are aggregated in patches

• This is the most common dispersion pattern in
  nature
• It often results from an unequal distribution of
  resources in the environment

Figure 35.2B
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• A uniform pattern of dispersion often results
  from interactions among individuals of a
  population

• Territorial behavior and competition for water
  are examples of such interactions

Figure 35.2C
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Population Growth Rate

• increase of population over given unit of time
• dependent on balance between birth rate
  (natality), death rate (mortality), and migration
• natality determined by number of fertilized eggs
  produced by females for each reproductive
  interval (millions for small fish, one for large
  mammals)
• mortality determined by number of dying due to
  disease, predation, or competition

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• Most populations are probably regulated by a
  mixture of factors

-Density-dependent birth and death rates -Abiotic
factors such as climate and disturbances
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• Among human populations the demographic
  transition is the shift from high birth and death
  rates to low birth and death rates

• During this transition, populations may grow
  rapidly until birth rates decline

Figure 35.9A
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Competition

• competition occurs where 2 species rely on a
  common resource in short supply
• the competitive exclusion principle
• populations of two species cannot coexist if
  their niches are nearly identical
• competition can only be stable if resources are
  partitioned

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Predation

• in predation an organism gains energy by feeding
  on another
• predation can maintain prey/host populations at
  levels the environment can support
• by removing weaker individuals predation can
  improve the genetic composition of the species
• predation can lead to adaptive evolutionary
  changes

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Keystone Predators

• A keystone species exerts strong control on
  community structure because of its ecological
  role
• A keystone predator may maintain community
  diversity by reducing the numbers of the
  strongest competitors in a community
• This sea star is a keystone predator

Figure 36.4A
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• Predation by killer whales on sea otters,
  allowing sea urchins to overgraze on kelp

Figure 36.4B
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Symbiotic Relationships

• two or more species that live in direct contact
• commensalism one species is benefited and the
  other not significantly affected (barnacles on
  whales)
• Mutualism both species are benefited (corals and
  coralline algae)
• Parasitism symbiotic predator/prey relationship
  the predator is usually smaller than host,
  (tapeworm, ticks)

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• Parasitism
• Flukes and tapeworms are parasitic flatworms with
  complex life cycles

Mature flukes in bloodvessels of intestine
Male
Humanhost
Female
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Sexual reproductionof flukes in
humanfertilized eggs passout in feces
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Larva penetratesskin andblood vessels
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Eggs hatchin water
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Larva thatinfects human
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Larvathatinfectssnail
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Asexual reproductionof flukes in snail
Snail host
Figure 18.6B
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Food Chains

• each community has a pattern of trophic (feeding)
  relationships through which energy and chemicals
  recycle
• these can be represented diagramatically as food
  chains
• in nature, most food chains are so complex they
  are best represented as a food web

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TROPHIC LEVEL
Quaternaryconsumers
Carnivore
Carnivore
Tertiaryconsumers
Carnivore
Carnivore
Secondaryconsumers
Carnivore
Carnivore
Primaryconsumers
Herbivore
Zooplankton
Producers
Plant
Phytoplankton
A TERRESTRIAL FOOD CHAIN
AN AQUATIC FOOD CHAIN
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Wastes anddead organisms
Tertiaryandsecondaryconsumers
Secondaryandprimaryconsumers
Primaryconsumers
Producers
Detritivores
(Plants, algae,phytoplankton)
(Prokaryotes, fungi,certain animals)
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Trophic Pyramid

• trophic pyramids show the relative amounts of
  biomass in an ecosystem
• the largest biomass and highest rates of energy
  conversion occur with the primary producers
• with each successive trophic level, energy
  conversion decreases to around a tenth of the
  preceeding level

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• A pyramid of production reveals the flow of
  energy from producers to primary consumers and to
  higher trophic levels

Tertiaryconsumers
10 kcal
Secondaryconsumers
100 kcal
Primaryconsumers
1,000kcal
Producers
10,000 kcal
1,000,000 kcal of sunlight
Figure 36.11
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• Because the production pyramid tapers so sharply,
  a field of corn or other plant crops can support
  many more vegetarians than meat-eaters

TROPHIC LEVEL
Secondaryconsumers
Humanmeat-eaters
Cattle
Primaryconsumers
Humanvegetarians
Corn
Corn
Producers
Figure 36.12
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Succession

• the change in which certain plant and animal
  communities succeed each other is known as
  succession
• primary succession occurs on a newly constructed
  mineral deposit (sand dune, lava flow)
• secondary succession occurs on a previously
  vegetated area (after fire or in old fields)

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Climax Communities

• over time, communities become increasingly dense,
  reaching a climax (steady state equilibrium)
• significant changes in ecosystem characteristics
  occur over the course of succession, so that at
  the time of climax there is
• large standing biomass (eg, a forest)
• high species diversity
• long weblike food chain

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