Chapter 5 Ecosystems

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Chapter 5 Ecosystems Living Organisms

• Natural Selection as a mechanism of evolution
  Favorable traits (beneficial mutations) increase
  survivability of a species population. Changes
  over time due to small mutations
  microevolution.
• For natural selection and microevolution to
  proceed, the beneficial trait must be passed
  along to offspring must improve repro-ductive
  rate and/or adaptability or survivi-bility of
  offspring. Range of tolerance refers to
  organisms adaptability to changes in abiotic
  (non-living) ecosystem components.

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Ranges of tolerance as reflected in habitat and
life cycle.
Royal fern narrow range of tolerance narrow
habitat. Dormant during cold weather.
Christmas fern wide range of tolerance wide
habitat. Also, an evergreen fern.
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• When environmental changes take place
• Favorable trait must already be present
• and organisms with the favorable trait
• must be able to reproduce fast enough to
• sustain population.
• Misconceptions about evolution
• Survival of fittest in nature doesnt mean
  biggest and strongest, rather it means most
  adaptable and able to reproduce quickly.
• Humans evolved from apes. Evolution suggests
  that humans and apes had a common ancestor.
• Evolution has a goal of perfection. Some
  organisms have evolved themselves into
  extinction. Mutations are random.

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Populations are controlled by Habitat Quality
Competition w/in speciesNiche overlapChanges
w/in gene poolCarrying capacityDisease
Reproductive successMigrations (in and
out) Habitat where an organism lives. Niche
role an organism plays within its ecosystem.
Niche
overlap competition for food. Example
squirrels stealing pecans from a pecan orchard or
cheetahs, lions, leopards, and hyenas competing
for the same foods. Habitat overlap
competition for living space (see p. 95 97).
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• Gene pool - includes all of the genetic
  variations within a given species. The gene
  pool of domestic dogs would include Great Danes,
  Chihuahuas,
• Carrying capacity how many of a particular
  species can an ecosystem support? When a
  population overshoots the carrying capacity, a
  population crash occurs.
• Population all of the individuals of a given
  species interacting within a defined ecosystem
  (or area).
• Community A group of interacting populations
  within a defined ecosystem.

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Some of the Biotic Components of a Rot-ting
Log Community (Fig. 5.3, p. 85) Tempe-rature
moisture play an important role in rate of
nutrient cycling. Community Abiotic
Components Ecosystem.
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• Ecosystem boundaries are usually tran- sitional
  with some adaptable organisms migrating across
  the boundary between adjacent ecosystems.
• Succession how ecosystems change and develop
  over time.
• Primary succession when a previously
  un-inhabited area becomes available for
  colonization (lava flows, ash flows, ground
  exposed by glacial retreat, new lake bottoms,
  abandoned roads and parking lots, severely eroded
  land, new road cuts).
• Secondary succession reclamation of previously
  inhabited areas.

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• Pioneer Community on a fresh outcrop may begin
  with Rock lichens, followed by mosses drought
  resistant ferns (p. 86).

Resurrection ferns need for little soil allows
for them to grow on old hard-wood trees, as a
type of Epiphytes (see p. 91).
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Secondary Succession May include the
reclamation of an abandoned pasture or a jeep
trail in the GUC hardwood forest (below). The
colonizers include loblolly pines, sweetgums,
tulip poplars, blackberries,
April, 2002
September, 2003
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• Success of Secondary Succession depends on
  thickness and quality of O and A layers of soil.
  Relates to temperature and moisture availability
  (see discussion of soil genesis in Geology notes).

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Figure 5.5
Secondary Succession in a Temperate Deciduous
Forest Biome in North Carolina.
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• Keystone species Play a role in ecosys-tem
  management strong interactions and magnified
  modification of habitat (population control, seed
  dispersal, soil modification, disposal of
  detritus (waste).
• Examples alligators, beavers, bees,
• Indicator species species that is sensitive to
  environmental changes, e.g., freshwater clams
  (mussels) in Ga. Streams.
• Native species a species that is native to
  local conditions in the local habitat.
• Exotic (non-native) species a species not
  native to the local, regional, or continental
  ecosystem. Examples kudzu, privet,

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• Types of Interactions between Organisms
• Predation one organism consuming another.
  Strategies Pursuit or ambush. Plant Defenses
  against herbivores spines, toxins, waxy leaves.
  Animal defenses against carnivores camouflage,
  spines, toxins, stingers, teeth, claws.
• Parasitism - 1) Parasite is usually smaller than
  host 2) Remains closely assoc. with and may
  weaken host, e.g., ticks (external), viruses
  (internal) 3) Rarely kill the host.
• Competition Niche overlap, habitat overlap.
  Survival may depend on resource partitioning or
  migration, otherwise starvation may result. (see
  slide 15).

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• Mutualism Symbiosis, perhaps mutual
  exploitation, both organisms benefit. Ex. ants
  aphids, coral polyps algae.
• Commensalism One organism benefits, the other
  is not hurt (mistletoe, Resurrection ferns, other
  epiphytes).
• Details of Ecological Niches What the organism
  does and the resources it needs.
• Fundamental Niche the idealized niche that an
  organism could occupy, if not for competition
  from other species.
• Realized Niche the actual niche occupied by an
  organism, as constrained by compe-tition
  resource limits.

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• Fig. 5.13 illustrates Realized Niche decrease
  (of Green Anole lizard) due to introduction of
  aggressive Exotic Species as competition (Brown
  Anole lizard).
• Other species classifications
• Generalist species organisms with broad niches,
  i.e., they are adaptable to changes. Examples
  humans, coyotes, raccoons, rats, cockroaches,
  possums.
• Specialist species organisms with narrow
  niches, i.e., they are not well adapted to
  changes. Examples Giant pandas, Koalas, other
  endangered species.

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• Limiting Factors (p. 96) Similar to Range of
  Tolerance (of other textbooks). Refers to
  abiotic components of ecosystems.
• Competition within a given niche eventually leads
  to competitive exclusion, where one species
  dominates the other, restricting the latters
  realized niche or resource partitioning, where
  one species is forced to use different resources
  (different foods). Darwins finches are an
  example of resource partitioning, as are the
  North American warblers shown on Figure 5.16,
  which dine live in different portions of
  spruce other evergreen trees.

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• Species Richness Species diversity, generally
  contributes to ecosystem stability, i.e.,
  Resiliency, the ability to bounce back from
  disturbances. At the First Trophic Level more
  species rich-ness more food for Second Trophic
  Level more food for Third Trophic Level
• Ecosystem Services the natural benefits offered
  by different ecosystems (see Table 5.1).

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