Ecosystems and Communities

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Ecosystems and Communities

• Chapter 4

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• The Role of Climate - Sec. 4.1
• Organisms vary in their adaptations to
  temperature, rainfall, and other environmental
  conditions.
• Species also vary in their tolerances for
  conditions outside their normal ranges.
• Weather day to day conditions of the Earths
  atmosphere at a particular place and time.
• Climate average, year to year conditions of
  temperature and precipitation in a particular
  region.

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• The Greenhouse Effect
• The atmosphere traps heat energy and maintains
  Earths temperature range.
• Top three gases carbon dioxide, methane, water
  vapor.
• Sunlight enters the atmosphere as short
  wavelength radiation and is converted to long
  wavelength heat which can not escape back out
  into space.
• Without the greenhouse effect the Earth would be
  too cold to sustain life.

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• The Effect of Latitude on Climate
• Because Earth is a sphere that is tilted on its
  axis, solar radiation strikes the surface at an
  angle that varies throughout the year.
• The further you move away from the equator the
  more solar radiation varies during the seasons.
• This divides the Earth into three main climate
  zones
• 1. Polar cold areas where light hits at low
  angle

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• 2. Temperate affected by tilt of Earth so
  seasonal change is great
• 3. Tropical near equator from 23.5 degrees
  north to 23.5 degrees south.

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• Because the sun is directly overhead year round
  at the equator climatic conditions vary very
  little.
• Heat Transport in the Biosphere
• Unequal heating of the atmosphere drives winds
  and ocean currents.
• Warm air rises and cold air sinks.
• As warm air rises it is replaced by heavier cold
  air creates prevailing winds.
• Cold water at the poles sinks and flows toward
  the equator where it warms and rises.
• These air and water movements transfer heat
  throughout the world.

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• Continents and other land masses can also affect
  winds and ocean currents.
• Winds over the oceans influence currents.
• As air rises over mountains, it cools and often
  loses its moisture as precipitation.
• This causes a dry area on the leeward side of the
  mountains Rain Shadow Effect

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• Rain Shadow Effect

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• What Shapes an Ecosystem? Sec. 4.2
• Biotic Factors
• - biological influences affecting an organism
  in its environment
• - all of the living organisms in an ecosystem
• Abiotic Factors
• - physical, or nonliving, factors that affect
  an organism in an ecosystem
• - climate, nutrient availability, soil type,
  sunlight, rainfall, etc.

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• Habitat
• where an organism lives
• Together, biotic and abiotic factors determine
  the survival and growth of an organism and the
  productivity of the ecosystem in which the
  organism lives.
• Niche
• - an organisms habitat and its role in the
  habitat
• - includes biotic and abiotic factors, its role
  in the food web, its physical tolerances, its
  reproductive methods, etc.

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• - no two species can share the same niche in
  the same habitat. Fig. 4-5
• - Many species have similar, but slightly
  different niches
• - Fundamental niche the complete niche
  that a species could occupy
• - Realized niche the niche that a species
  occupies when in competition with other
  species.

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• Community Interactions
• - refers to interactions between organisms
• A. Competition
• - occurs when organisms of the same or different
  species try to use the same resource in the same
  place at the same time.
• - Competitive Exclusion Principle
• - no two species can occupy the same niche
  in the same habitat at the same time

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• Resource partitioning in Anolis lizards.

A. distichus
A. insolitus
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• B. Predation
• - where one organism eats another
• - predator vs. prey

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• C. Symbiosis
• - relationships in which two species live
  closely together.
• A) Mutualism
• - both species benefit

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• B) Commensalism
• - one organism benefits and the other has
  no positive or negative effect
• - oxpeckers on grazers
• - barnacles on whales

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• C) Parasitism
• - one organism lives on or in another
  organism and harms it.
• - host vs. parasite

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• Ecological Succession
• - ecosystems constantly change in response to
  natural and human disturbances.
• - results in a replacement of one community of
  species by another community
• - as organisms live in an area they make the area
  better suited to other species
• - Primary Succession
• - when succession occurs where no soil
  previously exists
• - lava flows, sand dunes, bare rock, etc.
• - pioneer species first species to populate

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• - lichen are often pioneer species
• - composed of a fungus and algae
• - begin breaking down rock and forming soil
• - prepare the area for small grasses or
  herbs, which further prepare the area for
  other species
• Secondary Succession
• - when disturbance changes an existing
  community but does not remove the soil
• - after fires, cutting forests, abandoned
  farmland

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• Secondary Succession

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• Primary
• Succession

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• Alders to cottonwood

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• Spruce into Forest

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• Mount Saint Helens

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• Biomes Sec. 4.3
• complex of terrestrial ecosystems that cover a
  large area and is characterized by certain soil
  and climate conditions and particular communities
  of plants and animals.
• - organisms are adapted to certain biomes
• - an adaptation is an inherited characteristic
  that increases an organisms ability to survive
  and reproduce.
• - each species has a range of tolerance for every
  environmental factor
• - microclimate is often very important
• (insert graph of Law of Tolerances)

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• Terrestrial Biomes

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• Climatograph

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• 1. Tropical Rain Forest (pg. 100)
• 2. Tropical Dry Forest (pg. 100)
• 3. Tropical Savanna (pg. 101)
• 4. Desert (pg. 101)
• 5. Temperate Grassland (pg. 102)
• 6. Temperate Woodland and Shrubland
• 7. Temperate Deciduous Forest (pg. 103)
• 8. Northwestern Coniferous Forest (pg. 103)
• 9. Boreal Forest (Taiga) (pg. 104)
• 10. Tundra (pg. 104)

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• Aquatic Ecosystems Sec. 4.4
• - are grouped according to abiotic factors which
  affect them.
• - determined primarily by depth, flow,
  temperature, and chemistry of the water
• - depth determines light penetration
• - water chemistry refers mostly to the amount of
  dissolved chemicals in the water salts,
  nutrients, and oxygen
• - water covers approximately 75 of Earths
  surface
• -about 3 of Earth covered by fresh water

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• Aquatic Ecosystems

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• Freshwater Ecosystems
• - divided based on if water is flowing or still
• 1. Flowing-water ecosystems
• - rivers and creeks
• - change along their length
• - headwaters often cold and turbulent with
  lots of dissolved oxygen but little plant
  life (trout)
• - further down soil builds up, water slows,
  more plants grow (catfish)
• - organisms are well adapted for speed of water

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• 2. Standing-water ecosystems
• - lakes and ponds
• - still water is good habitat for plankton
• tiny, free-floating or weakly swimming
  organisms in both freshwater and saltwater
  environments
• phytoplankton single-celled algae base of
  most aquatic ecosystem food chains
• zooplankton planktonic animals which feed
  on the phytoplankton

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• Freshwater Pond

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• 3. Freshwater Wetlands
• - ecosystems in which water either covers the
  soil or is present at or near the surface of the
  soil for at least part of the year
• - often very productive
• a. bogs dominated by sphagnum moss
• - form in depressions where water
  gathers often acidic soils/water
• b. marshes shallow wetlands along rivers
• - often contain cattails, reeds, rushes

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• c. swamps water slowly flows through
• - often look like flooded forests
• Estuaries
• wetlands where rivers meet the sea
• - mixed fresh and salt water
• - affected by rise and fall of tides
• - often shallow, so they support many producers
  and are extremely productive
• - detritus feeds many of the lower levels of
  the food chains
• - important spawning and nursery areas

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• a. Salt marshes
• - temperate zone estuaries dominated by
  salt-tolerant grasses above the low-tide
  line and seagrasses below
• much of Texas Coast
• b. Mangrove swamps
• - tropical wetlands dominated by salt-
  tolerant trees called mangroves
• - seagrasses below low-tide line
• - valuable nurseries for fish and
  shellfish
• coast of Everglades N.P.

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• Estuaries

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• Marine Ecosystems pg. 109

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• Marine Ecosystems
• Photic Zone area where light penetrates
• - photosynthetic producers
• Aphotic Zone below light penetration
• - chemosynthetic producers and detritus
• 1. Intertidal zone
• - area between high and low tide
• - organisms adapted to being exposed for part
  of the day
• - clear zonation of organisms

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• Marine Ecosystems

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• 2. Coastal Ocean
• - extends from low-tide mark to outer edge of
  continental shelf
• - often all in the photic zone
• - kelp forests
• 3. Coral Reefs
• - warm, shallow tropical waters
• - coral animals hard calcium carbonate
  skeletons make up the reef base
• 4. Open Ocean
• - low productivity, but huge area makes it
  important for worldwide photosynthesis

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• 5. Benthic Zone
• - ocean floor ecosystem
• - usually depends on detritus raining down
• - benthos organisms which live on the ocean
  floor

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• Characteristics of Populations
• 1. Population Density
• - number of individuals per unit of area
• 2. Geographic Distribution
• - range
• - the area inhabited by a population
• 3. Growth Rate
• - depends on birth rates, death rates, and the
  number of individuals moving into or out of a
  population

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• Populations in nature grow in two ways
• 1. Exponential Growth
• - occurs in populations with abundant space,
  resources, and few predators or disease
• - individuals in a population reproduce at a
  constant rate.
• - at first population grows slowly, but
  steadily increases at an accelerating speed.

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• Exponential Growth Whooping Cranes

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• 2. Logistic Growth
• - after a period of exponential growth,
  resources become limited and population growth
  slows or stops.
• - slows due to decrease in birthrate, increase
  in death rate, or both
• - eventually the population reaches a maximum
  size that the environment can support Carrying
  Capacity

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• Logistic Population Growth

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• Limiting factors cause population growth to
  decrease.
• Density-Dependent Factors
• - limiting factors that depend on population size
• - become limiting only when the population
  density reaches a certain level and as population
  grows the factor becomes more limiting.
• competition, predation, parasitism, disease
• Density-Independent Factors
• - affect all populations in similar ways,
  regardless of population size
• weather, natural disasters, seasonal cycles,
  and human activities

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Human Population growth has historically been
exponential.
Age-structure diagrams give a view of what a
population is like now and what might
happen in it in the future.
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